A stability-enhanced acyclovir injection composition and a method for preparing the same

Abstract

This invention relates to the field of pharmaceutical formulation technology, and particularly to a stability-enhanced acyclovir injection composition and its preparation method. The composition comprises acyclovir, methionine, nicotinamide, glycine, proline, a pH adjuster, and water for injection. The mass-volume ratios of acyclovir, methionine, nicotinamide, glycine, and proline are 2.5–10.0 mg / ml, 0.8–1.2 mg / ml, 2.0–3.0 mg / ml, 4.0–6.0 mg / ml, and 4.0–6.0 mg / ml, respectively. The pH value of the acyclovir injection composition is 10.0–11.0. This invention utilizes four excipients—methionine, nicotinamide, glycine, and proline—in acyclovir injection. These four excipients have different molecular sizes, functional group types, and spatial configurations, enabling them to act on different stages and sites in the crystallization process. Methionine acts on the intermolecular aggregation stage, while nicotinamide acts on the heterogeneous nucleation stage.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical formulation technology, and in particular to a stability-enhanced acyclovir injection composition and its preparation method. Background Technology

[0002] Acyclovir is a synthetic purine nucleoside analog antiviral drug that selectively inhibits herpes simplex virus (HSV) and varicella-zoster virus (VZV), and is a commonly used drug in clinical practice for the treatment of viral infections. Acyclovir injection is widely used in the treatment of acute viral infections in hospitalized patients. In recent years, with the popularization of parenteral antimicrobial therapy at home, patients can bring elastomer infusion devices to complete intravenous infusions, greatly improving treatment convenience and shortening hospital stays.

[0003] Currently, commercially available acyclovir injections generally use sodium hydroxide or hydrochloric acid to adjust the pH to an alkaline range to maintain drug solubility. Besides the active pharmaceutical ingredient and pH adjuster, no other functional excipients are typically added to the formulation. This traditional formulation remains generally stable under normal storage conditions, but it reveals serious physical stability defects when used in elastomeric infusion devices. For example, patients carry large-dose infusion devices containing the medication close to their bodies. During the infusion process, which lasts for several hours, the medication remains in an environment close to body temperature. Clinical practice has shown that when acyclovir is prepared at the standard therapeutic concentration and loaded into an elastomeric infusion device, white crystalline precipitates often appear during the infusion process. These precipitates can clog the infusion tubing filter, leading to insufficient actual dosage, increased risk of treatment failure, and even the potential to induce viral resistance, indicating a stability defect. The root cause of this defect is that acyclovir molecules exhibit an anomalous negative temperature coefficient of solubility in aqueous solutions. When the temperature rises, the hydrogen bond network between acyclovir molecules is reconstructed, and the molecules approach each other through π-π stacking interactions to form dimers or even polymers. When the size of the aggregates exceeds the colloidal stability critical value, visible crystals precipitate. Traditional formulations rely solely on inorganic bases to adjust the initial pH value, completely lacking functional excipients that intervene in this crystallization process.

[0004] It is worth noting that this precipitation problem presents a significant contradiction in clinical application. For immunocompromised critically ill patients requiring high-dose antiviral therapy, the dosage concentrations required by standard clinical treatment regimens are precisely within the range where precipitation is most likely to occur. Lowering the concentration may lead to inadequate treatment, while maintaining a high concentration carries the risk of infusion blockage. Current technologies lack effective solutions to the temperature-dependent crystallization precipitation problem of acyclovir injection, particularly lacking technical means to intervene in the crystal nucleation and growth process through excipient combinations without altering the active pharmaceutical ingredient.

[0005] Therefore, there is an urgent need to provide an acyclovir injection composition that can remain physically stable in a body temperature infusion environment and does not produce crystal precipitation. Summary of the Invention

[0006] The purpose of this invention is to provide a stable acyclovir injection composition and its preparation method to solve the problem of temperature-dependent crystallization and precipitation of acyclovir injection in body temperature transport environments.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a stability-enhanced acyclovir injection composition, the composition comprising acyclovir, methionine, nicotinamide, glycine, proline, a pH adjuster, and water for injection; wherein the mass-volume ratio concentrations of acyclovir, methionine, nicotinamide, glycine, and proline are 2.5–10.0 mg / ml, 0.8–1.2 mg / ml, 2.0–3.0 mg / ml, 4.0–6.0 mg / ml, and 4.0–6.0 mg / ml, respectively; and the pH value of the acyclovir injection composition is 10.0–11.0.

[0008] Furthermore, the pH value of the acyclovir injection composition is 10.3 to 10.7, preferably 10.5.

[0009] Furthermore, the pH adjuster is selected from one or a combination of sodium hydroxide and hydrochloric acid.

[0010] Another aspect of the present invention provides a method for preparing a stability-enhanced acyclovir injection composition, comprising the following steps: S1. Take a portion of water for injection and place it in a mixing tank. Heat it to 45-55°C. Under the condition of stirring at 300-500 r / min, add methionine, nicotinamide, glycine and proline in sequence. Continue stirring for 15-30 min to completely dissolve all excipients and form a clear excipient pre-solution. S2. Cool the excipient pre-solution obtained in step S1 to 28-32°C at a cooling rate not exceeding 2°C / min. Add acyclovir in two batches while stirring at a speed of 400-600 r / min until the acyclovir is completely dissolved to form a drug mixture solution. S3. Under continuous stirring, add pH adjuster dropwise to the main drug mixture solution at a rate of 0.2 to 0.5 pH / min to obtain a solution. At the same time, use an online pH meter to monitor and adjust the pH value to 10.3 to 10.7 in real time. S4. Add the remaining water for injection to the solution obtained in step S3, continue stirring for 5-10 minutes to make the solution uniform, and pump the solution into a series three-stage filtration system for filtration to obtain the filtrate. S5. Transfer the filtrate obtained in step S4 to the hopper of the filling machine and fill it under Class 100 laminar flow protection. During the filling process, maintain the temperature at 20-30℃ and continuously introduce nitrogen into the filling pipeline for protection. The residual oxygen at the filling head should not exceed 2% of the volume percentage. Fill the drug solution into the packaging container according to the preset specifications. Immediately seal the container after filling and place the sealed product in a water bath sterilizer for final sterilization. After sterilization, immediately perform vacuum leak detection and light inspection using a vacuum leak detector to remove unqualified products and obtain a stable acyclovir injection composition. Among them, after the acyclovir injection composition was placed at a constant temperature of 37°C for 24 hours, it was tested according to the provisions of the "Visible Foreign Matter Inspection Method" under the lamp inspection method in General Chapter 0904 of the Chinese Pharmacopoeia, Part IV. No visible foreign matter was detected, and the number of insoluble particles with a particle size >10μm measured by the light obscuration method did not exceed 12 per milliliter.

[0011] Furthermore, in step S1, the portion of water for injection is 80% to 90% of the final prepared amount.

[0012] Further, in step S2, the specific operation of adding acyclovir in two batches is as follows: add half the mass of acyclovir in the first batch and stir for 10-15 minutes to dissolve; then add the remaining half the mass of acyclovir and continue stirring for 15-30 minutes.

[0013] Further, in step S3, the pH adjuster includes one or a combination of a sodium hydroxide solution with a concentration of 0.5 to 2.0 mol / L and a hydrochloric acid solution with a concentration of 0.5 to 1.0 mol / L. The cumulative volume of the hydrochloric acid solution used for pH value correction does not exceed 2.0 ml / L, the number of corrections does not exceed 2, and the chloride ion concentration in the solution after correction does not exceed 2.0 mmol / L.

[0014] Furthermore, in step S4, the three-stage filtration system is composed of filter elements with pore sizes of 1.2μm, 0.45μm and 0.22μm connected in series, and the pressure difference between each stage of the filter is controlled to be no greater than 0.3MPa, and the filtration temperature is maintained at 20-30℃.

[0015] Furthermore, in step S5, the packaging container is a borosilicate glass infusion bottle or a polyolefin infusion bag; The filling specifications are 25ml, 50ml or 100ml.

[0016] Furthermore, in step S5, the final sterilization is performed by sterilizing at 121°C for 12-15 minutes, or by using an over-sterilization method of sterilizing at 115°C for 25-35 minutes. The vacuum leak detection is performed at a vacuum level of -70~90KPa for 4~6 minutes, with an illuminance of 1800~2200lx for lamp inspection, and 20~40 seconds of inspection under both black and white backgrounds.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention incorporates four excipients—methionine, nicotinamide, glycine, and proline—in acyclovir injection. These four excipients differ in molecular size, functional group type, and spatial configuration, enabling them to act on different stages and sites of the crystallization process. Methionine acts on the intermolecular aggregation stage, nicotinamide on the heterogeneous nucleation stage, and glycine and proline on the crystal growth stage, thus synergistically intervening in the nucleation and growth processes at different levels. The composition of this invention exhibits excellent physical stability in a body temperature infusion environment, fundamentally solving the problem of crystal precipitation and tubing blockage caused by elevated temperatures in high-concentration acyclovir in elastomeric infusion devices. The preparation method provided by this invention avoids degradation or microcrystal formation of acyclovir during dissolution due to local pH fluctuations or supersaturation. Furthermore, this invention directly uses the prescription and clinical concentrations of commercially available acyclovir, without requiring changes to the dosing regimen and dosage, resulting in low clinical switching costs. It provides a safe, effective, and stable dosing regimen for immunocompromised patients requiring high-dose antiviral therapy, reducing the risk of phlebitis and improving patient comfort and compliance during infusion. It is particularly suitable for patients requiring long-term or multiple infusions. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0019] Unless otherwise specified, those skilled in the art may select from the following post-processing operations such as "mixing", "vacuum", "heating", "cooling", and "stirring" according to actual conditions, without further limitation.

[0020] The raw materials and preparation tools used in the following preparation examples, embodiments and comparative examples are all commercially available industrial products, including: acyclovir, with a purity >99.5%, and quality standards conforming to the 2020 edition of the Chinese Pharmacopoeia, Part II, purchased from Hubei Keyi Pharmaceutical Co., Ltd. or Sigma-Aldrich (Shanghai) Trading Co., Ltd. Methionine, CAS No. 59-51-8, purity ≥99.0%, injection grade, quality standard conforms to the 2020 edition of the Chinese Pharmacopoeia, Part II, purchased from Tianjin Tianyao Pharmaceutical Co., Ltd. or Sigma-Aldrich (Shanghai) Trading Co., Ltd. Nicotinamide, purity ≥99.5%, injection grade, quality standard conforms to the 2020 edition of the Chinese Pharmacopoeia, Part II, purchased from Shanghai Mairui Biochemical Technology Co., Ltd. or Zhejiang Xinhecheng Co., Ltd.; Glycine, purity ≥99.0%, injection grade, quality standard conforms to the 2020 edition of the Chinese Pharmacopoeia, Part II, purchased from Beijing Jinming Biotechnology Co., Ltd. or Wuxi Jinghai Amino Acid Co., Ltd. Proline, with a purity of 98%, injection grade, and quality standards conforming to the 2020 edition of the Chinese Pharmacopoeia, Part II, was purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd. or Wuxi Jinghai Amino Acid Co., Ltd. Sodium hydroxide, pharmaceutical grade, content ≥99.0%, quality standard conforms to the 2020 edition of the Chinese Pharmacopoeia, Volume IV, purchased from Shanghai Keyi Chemical Technology Co., Ltd. or Hunan Ercon Pharmaceutical Co., Ltd. Hydrochloric acid; pharmaceutical grade, content 36-38%, quality standard conforms to the 2020 edition of the Chinese Pharmacopoeia, Part IV, purchased from Hunan Ercon Pharmaceutical Co., Ltd. Nitrogen gas, with a purity of ≥99.999% and conforming to the quality standard GB / T 8979-2008, was purchased from Beijing Praxair Practical Gases Co., Ltd. The series-connected three-stage filtration system was purchased from Shanghai Shangsan Environmental Protection Equipment Co., Ltd. The water bath sterilizer was purchased from Zhangjiagang Huanyu Pharmaceutical Equipment Co., Ltd. Water for injection was purchased from Thermo Fisher Scientific.

[0021] Example 1 A stability-enhanced acyclovir injection composition, per 1000 ml, comprises acyclovir, methionine, nicotinamide, glycine, proline, a pH adjuster, and water for injection; wherein the mass-volume ratio concentrations of acyclovir, methionine, nicotinamide, glycine, and proline are 5 mg / ml, 1 mg / ml, 2.5 mg / ml, 5 mg / ml, and 5 mg / ml, respectively; the pH value of the acyclovir injection composition is 10.5, and the water for injection is added to a final volume of 1000 ml. The pH adjuster uses 1.0 mol / L sodium hydroxide solution to adjust the pH to 10.5 ± 0.2. During the adjustment process, if the pH exceeds 10.7, 0.5 mol / L hydrochloric acid solution is used to adjust it back to pH 10.5.

[0022] A method for preparing a stability-enhanced acyclovir injection composition includes the following steps: S1. Take 850 ml of water for injection, place it in a mixing tank, heat it to 50°C, and add 1.0 g of methionine, 2.5 g of nicotinamide, 5.0 g of glycine and 5.0 g of proline in sequence (add them in the above order, and add the next one after each excipient is completely dissolved). Continue stirring for 20 min to completely dissolve all excipients and form a clear excipient pre-solution. S2. Cool the excipient pre-solution obtained in step S1 to 30°C at a cooling rate of 1.5°C / min. Under the condition of stirring at 500 r / min, first add half of 2.5 g of acyclovir and stir for 12 min to dissolve. Then add the remaining 2.5 g of acyclovir and continue stirring for 20 min to dissolve completely, forming a drug mixture solution. S3. Under continuous stirring, add 1.0 mol / L sodium hydroxide solution dropwise to the main drug mixture at a rate of 0.3 pH / min to obtain a solution. At the same time, use an online pH meter to monitor and adjust the pH value in real time until it reaches 10.5. Stop adding the solution and continue stirring for 5 minutes to stabilize the pH value. Repeat the pH value test. If the pH value is in the range of 10.3 to 10.7, if the pH value is outside the range, use 0.5 mol / L hydrochloric acid solution at the same rate to adjust the pH value back to 10.5 in a small amount. S4. Add water for injection to the solution obtained in step S3 to a final volume of 1000 ml, and continue stirring for 8 minutes to ensure uniformity. Then, pump the solution sequentially into a series three-stage filtration system for filtration to obtain the filtrate. The series three-stage filtration system includes a first-stage filter element with a pore size of 1.2 μm (polypropylene), a second-stage filter element with a pore size of 0.45 μm (polyethersulfone), and a third-stage filter element with a pore size of 0.22 μm (polyvinylidene fluoride). The filtration temperature is controlled at 25°C, and the pressure difference between each filter stage is 0.20 MPa. S5. Transfer the filtrate obtained in step S4 to the hopper of the filling machine and fill it under Class 100 laminar flow protection. During the filling process, the mass flow meter controls the filling accuracy to ±2%, maintains the temperature at 25℃, and continuously introduces nitrogen into the filling pipeline for protection. Use an online oxygen analyzer to monitor the residual oxygen at the filling head. The residual oxygen at the filling head should not exceed 1.5% of the volume percentage. Fill the drug solution into borosilicate glass infusion bottles according to the preset specification of 50ml. Place the filled product in a water bath sterilizer and sterilize it at 121℃ for 15 minutes for final sterilization. Cool it down to 40℃ and immediately perform vacuum leak detection with a vacuum degree of -80kPa for 5 minutes and light inspection at 2000lx under black and white backgrounds for 30 seconds each. Remove unqualified products (products with poor sealing or visible foreign matter) to obtain a stable acyclovir injection composition.

[0023] Example 2 A stability-enhanced acyclovir injection composition, per 1000 ml, comprises acyclovir, methionine, nicotinamide, glycine, proline, a pH adjuster, and water for injection; wherein the mass-volume ratio concentrations of acyclovir, methionine, nicotinamide, glycine, and proline are 2.5 mg / ml, 0.8 mg / ml, 2.0 mg / ml, 4.0 mg / ml, and 4.0 mg / ml, respectively; the pH value of the acyclovir injection composition is 10.3, and the water for injection is added to a final volume of 1000 ml.

[0024] A method for preparing a stability-enhanced acyclovir injection composition includes the following steps: S1. Take 850 ml of water for injection, place it in a mixing tank, heat it to 45°C, and add 0.8 g of methionine, 2.0 g of nicotinamide, 4.0 g of glycine and 4.0 g of proline in sequence (add them in the above order, and add the next one after each excipient is completely dissolved). Continue stirring for 30 min to completely dissolve all excipients and form a clear excipient pre-solution. S2. Cool the excipient pre-solution obtained in step S1 to 28°C at a cooling rate of 1.5°C / min. Under the condition of stirring speed of 400r / min, first add half of 1.2g of acyclovir and stir for 10min to dissolve it. Then add the remaining 1.3g of acyclovir and continue stirring for 15min to dissolve it completely, forming the active pharmaceutical ingredient mixture solution. S3. Under continuous stirring, add 1.0 mol / L sodium hydroxide solution dropwise to the main drug mixture at a rate of 0.2 pH / min to obtain a solution. At the same time, use an online pH meter to monitor and adjust the pH value in real time until it reaches 10.3. Stop adding the solution and continue stirring for 5 minutes to stabilize the pH value. Repeat the pH value test. If the pH value is in the range of 10.3 to 10.7, if the pH value is outside the range, use 0.5 mol / L hydrochloric acid solution at the same rate to adjust the pH value back to 10.3 in a small amount. S4. Add water for injection to the solution obtained in step S3 to a final volume of 1000 ml, and continue stirring for 8 minutes to ensure uniformity. Then, pump the solution sequentially into a series three-stage filtration system for filtration to obtain the filtrate. The series three-stage filtration system includes a first-stage filter element with a pore size of 1.2 μm (polypropylene), a second-stage filter element with a pore size of 0.45 μm (polyethersulfone), and a third-stage filter element with a pore size of 0.22 μm (polyvinylidene fluoride). The filtration temperature is controlled at 25°C, and the pressure difference between each filter stage is 0.20 MPa. S5. Transfer the filtrate obtained in step S4 to the hopper of the filling machine and fill it under Class 100 laminar flow protection. During the filling process, the mass flow meter controls the filling accuracy to ±2%, maintains the temperature at 20℃, and continuously introduces nitrogen into the filling pipeline for protection. Use an online oxygen analyzer to monitor the residual oxygen at the filling head. The residual oxygen at the filling head should not exceed 1.5% of the volume percentage. Fill the drug solution into borosilicate glass infusion bottles according to the preset specification of 50ml. Place the filled product in a water bath sterilizer and sterilize it at 121℃ for 15 minutes for final sterilization. Cool it down to 40℃ and immediately perform vacuum leak detection with a vacuum degree of -70kPa for 6 minutes and light inspection at 1800lx under black and white backgrounds for 40 seconds each. Remove unqualified products (products with poor sealing or visible foreign matter) to obtain a stable acyclovir injection composition.

[0025] Example 3 A stability-enhanced acyclovir injection composition, per 1000 ml, comprises acyclovir, methionine, nicotinamide, glycine, proline, a pH adjuster, and water for injection; wherein the mass-volume ratio concentrations of acyclovir, methionine, nicotinamide, glycine, and proline are 10.0 mg / ml, 1.2 mg / ml, 3.0 mg / ml, 6.0 mg / ml, and 6.0 mg / ml, respectively; the pH value of the acyclovir injection composition is 10.7, and the water for injection is brought to 1000 ml.

[0026] A method for preparing a stability-enhanced acyclovir injection composition includes the following steps: S1. Take 850 ml of water for injection, place it in a mixing tank, heat it to 55°C, and add 1.2 g of methionine, 3.0 g of nicotinamide, 6.0 g of glycine and 6.0 g of proline in sequence (add in the above order, and add the next one after each excipient is completely dissolved). Continue stirring for 15 min to completely dissolve all excipients and form a clear excipient pre-solution. S2. Cool the excipient pre-solution obtained in step S1 to 32°C at a cooling rate of 1.5°C / min. Under the condition of stirring speed of 600r / min, first add half of 5g acyclovir and stir for 15min to dissolve it. Then add the remaining 5g acyclovir and continue stirring for 30min to dissolve it completely, forming the active pharmaceutical ingredient mixture solution. S3. Under continuous stirring, add 1.0 mol / L sodium hydroxide solution dropwise to the main drug mixture at a rate of 0.2 pH / min to obtain a solution. At the same time, use an online pH meter to monitor and adjust the pH value in real time until it reaches 10.7. Stop adding the solution and continue stirring for 5 minutes to stabilize the pH value. Repeat the pH value test. If the pH value is in the range of 10.3 to 10.7, if the pH value is outside the range, use 0.5 mol / L hydrochloric acid solution at the same rate to adjust the pH value back to 10.7 in a small amount. S4. Add water for injection to the solution obtained in step S3 to a final volume of 1000 ml, and continue stirring for 10 minutes to ensure uniformity. Then, pump the solution sequentially into a series three-stage filtration system for filtration to obtain the filtrate. The series three-stage filtration system includes a first-stage filter element with a pore size of 1.2 μm (polypropylene), a second-stage filter element with a pore size of 0.45 μm (polyethersulfone), and a third-stage filter element with a pore size of 0.22 μm (polyvinylidene fluoride). The filtration temperature is controlled at 25°C, and the pressure difference between each filter stage is 0.20 MPa. S5. Transfer the filtrate obtained in step S4 to the hopper of the filling machine and fill it under Class 100 laminar flow protection. During the filling process, the mass flow meter controls the filling accuracy to ±2%, maintains the temperature at 300℃, and continuously introduces nitrogen into the filling pipeline for protection. Use an online oxygen analyzer to monitor the residual oxygen at the filling head. The residual oxygen at the filling head should not exceed 1.5% of the volume percentage. Fill the drug solution into borosilicate glass infusion bottles according to the preset specification of 50ml. Place the filled product in a water bath sterilizer and sterilize it at 121℃ for 15 minutes for final sterilization. Cool it down to 40℃ and immediately perform vacuum leak detection with a vacuum degree of -90kPa for 4 minutes and light inspection at an illumination of 2200lx under black and white backgrounds for 20 seconds each. Remove unqualified products (products with poor sealing or visible foreign matter) to obtain a stable acyclovir injection composition.

[0027] Example 4 A stability-enhanced acyclovir injection composition and its preparation method are described below. The specific implementation method is the same as that in Example 1, except that the raw materials of the composition are any one of combination A, combination B, combination C, combination D, combination E or combination F, acyclovir with a mass-volume ratio concentration of 5.0 mg / ml, a pH adjuster to adjust the pH value of the composition to 10.5, and water for injection added to 1000 ml. Combination A consists of methionine and nicotinamide: 1.0 mg / ml methionine and 2.5 mg / ml nicotinamide. Combination B consists of methionine and glycine: 1.0 mg / ml methionine and 5.0 mg / ml glycine; Combination C consists of methionine and proline: 1.0 mg / ml methionine and 5.0 mg / ml proline; Combination D consists of nicotinamide and glycine: 2.5 mg / ml nicotinamide and 5.0 mg / ml glycine; Combination E consists of nicotinamide and proline: 2.5 mg / ml nicotinamide and 5.0 mg / ml proline; Combination F consists of glycine and proline: 5.0 mg / ml glycine and 5.0 mg / ml proline.

[0028] Example 5 A stability-enhanced acyclovir injection composition and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that the preparation process parameters of combinations A to F in Example 4 are adjusted respectively, specifically as follows: Combination A: In step S1, the heating temperature is increased from 50℃ to 55℃, and in step S2, the cooling rate of 1.5℃ / min is adjusted to natural cooling. Combination B: In step S1, the heating temperature is increased from 50℃ to 45℃, and in step S2, the cooling rate is changed from 1.5℃ / min to 1.0℃ / min. Combination C: Adjust the cooling rate in step S2 from 1.5℃ / min to 3.0℃ / min; In combination D, the cooling rate in step S2 of 1.5℃ / min is adjusted to natural cooling, and the cooling rate in step S3 of 0.3pH / min is adjusted to 0.6pH / min. Combined with E, adjust the cooling rate in step S2 from 1.5℃ / min to natural cooling, and adjust the pressure difference between each stage of the filter in step S4 from 0.20MPa to 0.45MPa; Combine F, adjust the cooling rate of 1.5℃ / min in step S2 to natural cooling, and adjust the continuous nitrogen gas supply for protection in step S5 to protection without nitrogen gas supply.

[0029] Comparative Example 1 A conventional acyclovir injection solution without excipients and its preparation method, comprising 5.0 g acyclovir added to 1000 ml of water for injection, wherein sodium hydroxide is used to adjust the pH of the acyclovir injection solution to approximately 10.5; The general preparation method for conventional acyclovir injection is as follows: Take 900 ml of water for injection (90% of the total volume) and place it in a mixing tank, controlling the water temperature at 25±2℃; Add 5.0g of the prescribed amount of acyclovir at a stirring speed of 400r / min and stir for 5min to achieve initial dispersion; Add 1.0 mol / L sodium hydroxide solution dropwise at a rate of 0.3 pH / min, while monitoring with an online pH meter. Stop adding the solution when the pH reaches 10.5, and continue stirring for 15 min to completely dissolve the acyclovir. Retest the pH to confirm that it is within the range of 10.4-10.6. Add water for injection to a final volume of 1000 ml, and continue stirring for 5 minutes to ensure homogeneity. The solution was filtered sequentially through microporous membranes of 0.45 μm and 0.22 μm. The solution was filled into 50ml borosilicate glass infusion bottles under Class 100 laminar flow protection and then sealed. Final sterilization was performed at 121℃ for 15 minutes to obtain conventional acyclovir injection.

[0030] Comparative Example 2 An enhanced stability acyclovir injection composition and its preparation method are disclosed. The specific component dosages and implementation methods are the same as in Example 1, except that only a single excipient, glycine, is added, and the components of methionine, nicotinamide, and proline are missing.

[0031] Comparative Example 3 An enhanced stability acyclovir injection composition and its preparation method are disclosed. The specific component dosages and implementation methods are the same as in Example 1, except that only the single excipient proline is missing, and methionine, nicotinamide and glycine are added.

[0032] The compositions prepared in the above examples and comparative examples were subjected to performance tests: (1) Physical stability test (crystallization and insoluble particles): Take 50 ml of the composition and dispense it into an elastomer infusion device (Easypump II type, capacity 100 ml). Place the device in a constant temperature water bath at 37℃±0.5℃ to simulate the human infusion environment. Take it out every 30 min to observe the appearance of the drug solution and record the time when visible crystal precipitation first appears, i.e. crystallization induction time. According to the "Insoluble Particle Test Method" (light obscuration method) of General Chapter 0903 of Part IV of the Chinese Pharmacopoeia 2020 Edition, samples were taken at 24 h time points to detect insoluble particles, including the number of particles with a particle size ≥10 μm and ≥25 μm. According to the "pH Value Determination Method" of General Chapter 0631 of Part IV of the Chinese Pharmacopoeia 2020 Edition, the changes of the composition at the initial and 24 h were measured using a calibrated pH meter.

[0033] (2) Chemical stability test (acyclovir content and related substances): The initial acyclovir content and initial total related substances were determined by high performance liquid chromatography. Chromatographic conditions: octadecylsilane-bonded silica gel was used as the packing material, C18 column (4.6 mm × 250 mm, 5 μm), mobile phase was methanol-water (10:90), detection wavelength was 254 nm, flow rate was 1.0 mL / min, column temperature was 30 °C. At the same time, the chromatogram was recorded until twice the retention time of the main component peak. Impurity A (guanine) and impurity H (epoxyguanine) were calculated by external standard method. Other individual impurities and total related substances were calculated by self-comparison method. In accordance with the "Guiding Principles for Stability Testing of Active Pharmaceutical Ingredients and Preparations" in General Chapter 9001 of Part IV of the 2020 edition of the Chinese Pharmacopoeia, the composition was placed in a constant temperature and humidity chamber at 40℃±2℃ and 75%RH±5% for 6 months, and samples were taken to test each index after 6 months of accelerated testing. The composition was then placed at 25±2℃ and 60RH±5% for 18 months, and samples were taken to test each index.

[0034] (3) Osmolarity and vascular irritation test (osmolar concentration): Osmolar concentration was determined using the freezing point depression method osmolarity test according to the "Determination of Osmolar Concentration" in Section IV, General Chapter 0632 of the 2020 edition of the Chinese Pharmacopoeia. Vascular irritation was assessed using a multi-group rabbit marginal ear vein infusion model: Six rabbits were infused with the composition (50 mg acyclovir per kilogram of body weight, infusion rate of 2 mg per kilogram of body weight per minute). The rabbits were observed for 72 hours after infusion to determine vascular irritation and assess whether the clinical use requirements were fully met. The scoring criteria were based on the scoring system in the "Technical Guidelines for Drug Irritation, Allergy and Hemolysis Studies".

[0035] Each embodiment and comparative example was tested according to the above method as required, and the test results are shown in Tables 1-3.

[0036] Table 1 - Results of Physical Stability Tests

[0037] Note: >24* in Comparative Example 3 indicates that the substance was basically clear upon visual inspection after 24 hours, but trace amounts of crystals were visible under a microscope.

[0038] Table 2 - Results of Chemical Stability Tests

[0039] Table 3 - Results of Osmolarity and Vascular Irritation Tests

[0040] Note: Examples 4-5 were not included in the chemical stability test and osmotic pressure and vascular irritation test. This is because Example 4 was to verify whether the synergistic effect of the four excipients was superior to any combination of two excipients, while Example 5 was to verify the boundary feasibility of each key process parameter in the preparation method, focusing on the physical stability of the crystallization inhibition effect and the impact of process parameters on product quality, rather than chemical stability or long-term storage performance. Furthermore, conducting chemical stability tests and osmotic pressure and vascular irritation tests on Examples 4-5 would incur significant testing costs and time. Additionally, the existing data from the physical stability test results support a preliminary judgment that the product cannot meet the clinical use requirements of the elastomer infusion device, and therefore further evaluation is neither necessary nor required.

[0041] Analysis of Test Results: Based on the performance test results in Tables 1-3 above, firstly, analyzing the physical stability test results, the crystallization induction time of Example 1 exceeded 24 hours. This means that under the constant temperature condition of 37°C simulating the human infusion environment, the drug solution remained clear and transparent for 24 hours without any crystal precipitation. After being placed at 37°C for 24 hours, the number of particles with a diameter ≥10μm was 9 / ml, far below the limit stipulated in the Chinese Pharmacopoeia (not exceeding 25 / ml). This indicates that under the synergistic protection of the four excipients, there were almost no particle aggregates of detectable size in the drug solution, indicating excellent product quality. Example 2, with the lower limit ratio of components, also showed a crystallization induction time exceeding 24 hours. The induction time demonstrated that within the lower limit range of the components, the four excipients still produced an effective crystallization inhibition effect, with a particle count of 12 / ml. Although slightly higher than in Example 1, it was still within the pharmacopoeia limit, proving that the lower limit ratio also met the quality requirements. Example 3 was a high-concentration acyclovir formulation, and its crystallization induction time was exactly 24 hours, meeting the basic requirements for clinical use. However, since the acyclovir concentration was increased to 10 mg / ml, the crystallization risk increased slightly, and the safety margin was slightly lower than in Example 1. The crystallization induction time of the six pairwise excipient combinations (AF) in Example 4 was all in the range of 4-7 hours, significantly inferior to the more than 24 hours of the four-excipient combination. Among them, the best-performing combination F (glycine + proline) showed the best crystallization induction time. The time was 7 hours, still far below the clinically required 24 hours, and the particle count of each pair of combinations was in the range of 132-285 particles / ml, significantly exceeding the pharmacopoeia limit. This strongly demonstrates that the synergistic effect of the four excipients is superior to the crystallization inhibition effect of any two excipient combinations, and the difference in effect is extremely significant. In Example 5, the crystallization induction time of each process parameter adjustment group showed obvious parameter dependence. The crystallization induction time of combination C (cooling rate 3℃ / min) was shortened to 16 hours, indicating that the excessively rapid cooling rate causes acyclovir to form microcrystal memory during dissolution. These microcrystals become crystal seeds for crystal growth under subsequent body temperature conditions, accelerating the crystallization precipitation process. Combinations A, B, D, E, and F all maintained a crystallization induction time of more than 24 hours. The crystallization induction time of h and the number of particles in each group all meet the pharmacopoeia requirements, which proves that the product quality has good robustness within the process parameters defined by this invention. The crystallization induction time of Comparative Example 1 is only 4h, which means that under body temperature, the traditional acyclovir injection can only maintain a clear state for 4h, after which crystals begin to precipitate. This means that when patients use elastomer infusion devices for home treatment, the tubing may be blocked by crystals before the infusion is completed, resulting in a serious underdose. Its particle number is as high as 2150 particles / ml, which exceeds the pharmacopoeia limit by 85 times. This means that after 4h of body temperature exposure, a large number of fine crystals and aggregates have formed in the drug solution, making it completely unusable for clinical infusion.Comparative Example 2 showed a crystallization induction time extended to 12 hours, a significant improvement over Comparative Example 1, but still insufficient to cover the complete 24-hour infusion cycle. Furthermore, its particle count of 620 particles / ml remained far above the pharmacopoeia limit, indicating that while glycine alone can delay crystallization to some extent, its effect is limited and cannot achieve the complete inhibition level required clinically. Comparative Example 3 showed a crystallization induction time exceeding 24 hours. Visual inspection revealed no visible precipitate, but microscopic observation revealed trace amounts of fine crystals. The number of insoluble particles (≥10μm: 58 particles / ml) was also significantly higher than in Example 1 (9 particles / ml). This result reveals the unique function of proline: as a crystal habit modifier, proline can adsorb onto specific crystal faces of acyclovir crystals, altering their growth morphology and rate. In the absence of proline, although no visible precipitate is observed macroscopically, microcrystals still exist at the microscopic scale. These microcrystals may gradually aggregate during infusion to form visible precipitates or directly enter the pulmonary circulation, causing microembolism. The risk of infection further confirms the irreplaceable role of proline in inhibiting microcrystal formation; and the number of ≥25μm particles in Examples 1 and 2 was 0 / ml, indicating that there were no large visible foreign objects in the product. Comparative Example 1 had a high number of ≥25μm particles of 186 / ml, Comparative Example 2 had 42 / ml, and Comparative Example 3 had 5 / ml. This further proves that the complete combination of the four excipients can inhibit particle nucleation and growth at the source, enabling the product to reach the highest physical cleanliness standard. Regarding pH changes, in Example 1, after 24 hours of body temperature exposure, the pH value dropped from 10.5 to 10.3, a change of only 0.2 units, indicating that the four excipients formed an effective buffer system that could resist the pH decrease caused by carbon dioxide absorption and acyclovir hydrolysis. In contrast, the pH value of Comparative Example 1 plummeted from 10.5 to 8.2, a change of 2.3 units. This drastic pH drop not only accelerates the hydrolytic degradation of acyclovir but may also cause chemical irritation to the vascular endothelium.

[0042] Then, based on the analysis of the chemical stability test results, the acyclovir content in Example 1 was 97.8% after 6 months of accelerated aging, a decrease of only 2.4 percentage points, indicating that the product has good chemical stability under simulated accelerated aging conditions. Furthermore, the impurity A content in Example 1 was 0.45%, significantly lower than the 1.20% in Comparative Example 1. Impurity A (guanine) is a hydrolysis product of acyclovir and carries potential genotoxic risks. The ICH M7 guidelines stipulate strict limits on its acceptable intake. This application, through the synergistic protection of four excipients, controls the formation of impurity A at a low level, reducing the long-term medication risk for patients. The content in Comparative Example 1 decreased to 92.5%, a decrease of 7.8 percentage points, with a degradation rate approximately three times that of Example 1. The content decreases in Comparative Example 2 (96.2%) and Comparative Example 3 (97.2%) were both greater than that in Example 1, demonstrating that the synergistic antioxidant effect of the four excipients is superior to that of a single excipient or a three-excipient combination lacking proline. Moreover, the impurity A content in Comparative Example 2 was 0.68%, and in Comparative Example 3 it was 0.50%. The percentages were all higher than in Example 1, indicating that the antioxidant capacity of glycine alone is limited. Although the lack of proline had little impact on chemical stability, it still led to a slight increase in impurities. The content of Example 3 (high concentration) decreased to 97.0%, slightly lower than that of Example 1, but still met the quality standard requirements. This indicates that the high concentration formulation is comparable to the conventional concentration in terms of chemical stability, but its physical stability safety margin is lower. After 18 months of long-term treatment, the acyclovir content of Example 1 was 98.2%, a decrease of only 2.0 percentage points, which is consistent with the trend of the data after 6 months of accelerated treatment (the content was 97.8% after 6 months of accelerated treatment). The content of Comparative Example 1 after 18 months was 93.8%, which is close to the lower limit of content (90%), indicating that the traditional formulation has a high risk of failure during long-term storage. Specifically, acyclovir degrades in alkaline aqueous solution mainly through two pathways: first, the hydrolysis of the purine ring to generate guanine (impurity A); second, oxidative degradation to generate epoxide guanine (impurity H). In the composition of this application, the thiol group of methionine can capture free radicals in solution and interrupt the oxidative chain reaction; nicotinamide, as a light stabilizer, can produce a UV shielding effect, reducing photoinduced degradation; glycine... Proline stabilizes the microenvironment of the solution, reduces conformational fluctuations of the acyclovir molecule, and lowers the rate of hydrolysis. The four excipients in this compound work together to protect the acyclovir molecule from different levels, achieving chemical stability superior to existing technologies. As for impurity H (epoxyguanine), it is an oxidative degradation product of acyclovir, and its formation is closely related to the dissolved oxygen and free radical levels in the solution. The impurity H in Example 1 is 0.35%, which is significantly lower than the 0.85% in Comparative Example 1. This difference is mainly attributed to the free radical scavenging ability of methionine and the nitrogen protection during the filling process.

[0043] Finally, analysis of the osmotic pressure and vascular irritation test results showed that the normal plasma osmolality in the human body is approximately 285-310 mOsm / kg. When the osmotic pressure of the injection solution differs significantly from that of plasma, it can cause permeability damage to vascular endothelial cells, manifesting as phlebitis, pain, and tissue edema. The osmotic pressure of Example 1 was 328 mOsm / kg, which is considered a slightly hyperosmolar state (approximately 6-15% higher than the upper limit of plasma), clinically acceptable. Furthermore, its phlebitis score in rabbits was 0.33 (0 points for no reaction, 1 point for slight redness and swelling), indicating that this osmotic pressure level has good vascular compatibility. The osmotic pressure of Example 2 was 305 mOsm / kg. The concentration of 0.5 mOsm / kg is close to isotonic (falling within the normal range of plasma), making it the formulation with the least vascular irritation. However, its excipient concentration is at the lower limit, and its physical stability (12 particles / ml) is slightly inferior to Example 1. Under the premise of ensuring safety, Example 1 has better physical stability. Therefore, the phlebitis scores of Examples 1 and 2 are 0.33 and 0.17 respectively, indicating that the composition of the present invention has good vascular compatibility. The osmotic pressure of Example 3 is 395 mOsm / kg, which is a significantly hypertonic state (approximately 27% higher than the upper limit of plasma). Its phlebitis score in rabbits is 1.33, showing obvious redness and swelling reaction. The results indicate that the infusion rate needs to be strictly limited or diluted when using this concentration formulation; the osmotic pressure of Comparative Example 1 was 385 mOsm / kg, comparable to Example 3, but its phlebitis score (1.17 points) was slightly lower than that of Example 3 (1.33 points) due to the absence of any excipients. This may be because some components in the excipients (such as glycine and proline) have cytoprotective effects and can improve the tolerance of vascular endothelial cells to hyperosmolar environments; the phlebitis score of Comparative Example 2 was 0.83 points, which was better than Comparative Example 1, but still worse than Example 1, proving that although glycine alone has a certain protective effect, its effect is not as good as the synergistic combination of four excipients; the traditional formulation In Comparative Example 1, sodium hydroxide was used to adjust the pH. Sodium ions are the main contributor to osmotic pressure. In this application, by introducing four amino acid excipients and utilizing their amphoteric electrolyte properties to construct a buffer system, the amount of sodium hydroxide used was reduced, thereby lowering the osmotic pressure. At the same time, the amino acid excipients (especially glycine and proline) act as osmotic pressure protectants, which can stabilize the cell membrane structure and improve the tolerance of endothelial cells to changes in osmotic pressure. This is why the osmotic pressure (328) of Example 1 is higher than that of Example 2 (305), but the phlebitis score (0.33) is the same. Therefore, the higher excipient concentration in Example 1 provides a stronger cell protection effect.

[0044] In summary, the stability-enhanced acyclovir injection composition prepared in this application, through the addition of four excipients—methionine, nicotinamide, glycine, and proline—synergistically intervenes in the nucleation and growth process of crystallization at different levels. Specifically, methionine forms competitive hydrogen bonds with acyclovir molecules through its thiol groups, preventing intermolecular π-π stacking; nicotinamide complexes trace metal ions involved in crystallization through its amide groups, eliminating heterogeneous nucleation sites; glycine and proline act as crystal habit modifiers, adsorbing onto specific crystal faces to alter the crystal growth morphology and rate, achieving zero crystallization physical stability at body temperature; the thiol groups of methionine act as free radical scavengers, interrupting the oxidation chain reaction and inhibiting the generation of impurity H; and nicotinamide's ultraviolet absorption provides a shielding effect. The four excipients work synergistically to protect acyclovir molecules from three levels: antioxidant, photoprotective, and microenvironmental stabilization. This ensures chemical stability, reduces the generation of toxic degradation products, and improves the safety of long-term use. Furthermore, the four amino acid excipients partially replace sodium hydroxide as a pH buffer, reducing the introduction of sodium ions and thus lowering osmotic pressure. Glycine and proline, as osmolarity protectants, stabilize the vascular endothelial cell membrane structure, improve cell tolerance to hyperosmolar environments, reduce the risk of phlebitis, and enhance patient comfort and compliance during infusion, making them particularly suitable for patients requiring long-term or multiple infusions.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A stability-enhanced acyclovir injection composition, characterized in that, The composition comprises acyclovir, methionine, nicotinamide, glycine, proline, a pH adjuster, and water for injection; wherein the mass-volume ratio concentrations of acyclovir, methionine, nicotinamide, glycine, and proline are 2.5–10.0 mg / ml, 0.8–1.2 mg / ml, 2.0–3.0 mg / ml, 4.0–6.0 mg / ml, and 4.0–6.0 mg / ml, respectively; and the pH value of the acyclovir injection composition is 10.0–11.

0.

2. The stability-enhanced acyclovir injection composition according to claim 1, characterized in that, The pH value of the acyclovir injection composition is 10.3 to 10.

7.

3. The stability-enhanced acyclovir injection composition according to claim 1, characterized in that, The pH adjuster is selected from one or a combination of sodium hydroxide and hydrochloric acid.

4. A method for preparing a stability-enhanced acyclovir injection composition according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Take a portion of water for injection and place it in a mixing tank. Heat it to 45-55°C. Under the condition of stirring at 300-500 r / min, add methionine, nicotinamide, glycine and proline in sequence. Continue stirring for 15-30 min to completely dissolve all excipients and form a clear excipient pre-solution. S2. Cool the excipient pre-solution obtained in step S1 to 28-32°C at a cooling rate not exceeding 2°C / min. Add acyclovir in two batches while stirring at a speed of 400-600 r / min until the acyclovir is completely dissolved to form a drug mixture solution. S3. Under continuous stirring, add pH adjuster dropwise to the main drug mixture solution at a rate of 0.2 to 0.5 pH / min to obtain a solution. At the same time, use an online pH meter to monitor and adjust the pH value to 10.3 to 10.7 in real time. S4. Add the remaining water for injection to the solution obtained in step S3, continue stirring for 5-10 minutes to make the solution uniform, and pump the solution into a series three-stage filtration system for filtration to obtain the filtrate. S5. Transfer the filtrate obtained in step S4 to the hopper of the filling machine and fill it under Class 100 laminar flow protection. During the filling process, maintain the temperature at 20-30℃, continuously introduce nitrogen gas into the filling pipeline for protection, and ensure that the residual oxygen at the filling head does not exceed 2% by volume. Fill the drug solution into the packaging container according to the preset specifications, seal it immediately after filling, and place the sealed product in a water bath sterilizer for final sterilization. After sterilization, immediately perform vacuum leak detection and light inspection using a vacuum leak detector, and remove unqualified products to obtain a stable acyclovir injection composition.

5. The method for preparing the stability-enhanced acyclovir injection composition according to claim 4, characterized in that, In step S1, the portion of water for injection is 80% to 90% of the final prepared amount.

6. The method for preparing the stability-enhanced acyclovir injection composition according to claim 4, characterized in that, In step S2, the specific operation of adding acyclovir in two batches is as follows: add half the mass of acyclovir in the first batch and stir for 10-15 minutes to dissolve; then add the remaining half the mass of acyclovir and continue stirring for 15-30 minutes.

7. The method for preparing the stability-enhanced acyclovir injection composition according to claim 4, characterized in that, In step S3, the pH adjuster includes one or a combination of sodium hydroxide solution with a concentration of 0.5 to 2.0 mol / L and hydrochloric acid solution with a concentration of 0.5 to 1.0 mol / L.

8. The method for preparing the stability-enhanced acyclovir injection composition according to claim 4, characterized in that, In step S4, the three-stage filtration system consists of filter elements with pore sizes of 1.2μm, 0.45μm and 0.22μm connected in series, and the pressure difference between each stage of the filter is controlled to be no greater than 0.3MPa, and the filtration temperature is maintained at 20-30℃.

9. The method for preparing the stability-enhanced acyclovir injection composition according to claim 4, characterized in that, In step S5, the packaging container is a borosilicate glass infusion bottle or a polyolefin infusion bag; The filling specifications are 25ml, 50ml or 100ml.

10. The method for preparing the stability-enhanced acyclovir injection composition according to claim 4, characterized in that, In step S5, the final sterilization is performed by sterilizing at 121°C for 12-15 minutes, or by using an over-sterilization method by sterilizing at 115°C for 25-35 minutes. The vacuum leak detection is performed at a vacuum level of -70~90KPa for 4~6 minutes, with an illuminance of 1800~2200lx for lamp inspection, and 20~40 seconds of inspection under both black and white backgrounds.

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