Aqueous suspension with good redispersibility

Abstract

The aqueous suspension can be prepared by incorporating, in an aqueous suspension of a hardly soluble drug, a water-soluble polymer within the concentration range from the concentration at which the surface tension of the aqueous suspension of the drug begins to decrease up to the concentration at which the reduction in surface tension ceases. The resulting aqueous suspension shows ready redispersibility and will not undergo aggregation of dispersed particles or caking. Because of its good redispersibility, the suspension is useful as a parenteral preparation, eye drops, nasal drops, a preparation for oral administration, a lotion or the like.

Description

[0001] The present invention relates to an aqueous suspension with good redispersibility.[0002] In preparing, for instance, an ophthalmic preparation, nasal preparation or parenteral preparation containing a medicinal compound hardly soluble in water, it is presumable that the drug be suspended in an aqueous medium to give an aqueous suspension. When such aqueous suspension is stored for a long period, the drug occurring as dispersed particles (hereinafter sometimes referred to merely as dispersed particles) tends to undergo aggregation, resulting in increases in size of dispersed particles or sedimentation of dispersed particles and further in secondary aggregation of the dispersed particles that have settled, for example caking. Therefore, efforts have been devoted to prevent the aggregation or sedimentation of dispersed particles as far as possible or, when such aggregation or sedimentation cannot be prevented, to obtain suspensions capable of readily regaining their original sta...

AI Technical Summary

Benefits of technology

[0009] As will be shown later herein in Test Example 1, the surface tension of an aqueous suspension begins to decrease with the increase in the amount of a water-soluble polymer added thereto. Upon continuation of the addition, the reduction in surface tension ceases and, thereafter, a substantially constant surface tension is maintained. On the contrary, the redispersibility of the dispersed particles of an aqueous suspension becomes good at the point at which the surface tension of the aqueous suspension begins to decrease as a result of addition of the water-soluble polymer, and the good redispersibility is maintained until the reduction in surface tension ceases. Thereafter, as the reduction in surface tension ceases and the surface tension becomes constant, the redispersibility of the dispersed particles becomes gradually worsened.

[0023] The aqueous suspension of the invention has good redispersibility without involving aggregation or caking of dispersed particles and, therefore, can be used with advantage as, for example, an ophthalmic preparation, a preparation for nasal application, an injection, a preparation for oral administration or a lotion.

Problems solved by technology

For supplying these in the form of aqueous preparations such as ophthalmic, nasal, parenteral and other preparations, it is unavoidable in many instances to employ the aqueous suspension form.

However, the prior art aqueous suspensions have a redispersibility problem; in many instances, it is difficult to restore suspensions uniform in concentration without a long time of shaking to effect redispersion.

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