Topical product formulations containing strontium for reducing skin irritation

Abstract

Topical formulations containing aqueous-soluble divalent strontium cation in a suitable topical formulation vehicle, and methods of using these formulations to inhibit skin irritation, are disclosed.

Description

[0001]This application is a continuation of Ser. No. 09 / 992,491, filed Nov. 21, 2001, Ser. No. 09 / 871,576, filed May 31, 2001, Ser. No. 09 / 149,886, filed Sep. 8, 1998, which is a continuation of Ser. No. 08 / 666,978, filed Jun. 20, 1996, and issued as U.S. Pat. No. 5,804,203, which is a continuation-in-part of Ser. No. 08 / 362,100, filed Dec. 21, 1994, and issued as U.S. Pat. No. 5,716,625. The present application claims the benefit of the filing date of Ser. No. 08 / 362,100 (Dec. 21, 1994), as well as the benefit of all intervening applications, pursuant to 35 U.S.C. § 120 and other applicable law, and the entire disclosures of all of these applications are incorporated herein by reference in their entirety.BACKGROUND[0002]Many substances are applied topically to the skin or mucous membranes of humans or animals (hereinafter “skin”) in order to alter the subject's appearance, to protect the subject from the environment, or to produce a biological change in the skin or other tissue for...

AI Technical Summary

Benefits of technology

[0034]The present invention is directed to topical product formulations containing the divalent cation strontium (Sr2+) and aqueous-soluble salts thereof as ingredients to provide fast-acting, efficient and safe topical skin anti-irritant effects. It is one object of the present invention to provide topical formulations and ingredients which can suppress skin irritation due to chemical or environmental exposure, or due to tissue inflammation, injury or other skin pathology. The invention is particularly useful for preventing, reducing or eliminating the potential irritation caused by topical application of products containing irritating ingredients, including especially cosmetics such as hydroxy acid or other exfoliant containing products, facial peels, shaving products, sunscreen products, deodorants and other cosmetics as described above, as well as topical drug / therapeutic products containing irritating active ingredients or vehicles, and other products such as cleansing products, including soaps, detergents, solvents and the like which are either applied topically or are topically exposed to the body. Thus, the present invention meets a clear need for formulations and ingredients that will prevent or reduce the potential skin irritation caused by topical products. The formulations of the present invention may be topically applied simultaneously with, prior and / or subsequent to application of irritating topical products, such as those described above. Alternatively, such cosmetic, therapeutic, cleansing and other irritating topical products themselves may be formulated to comprise divalent strontium cation, which would act to inhibit or suppress the skin irritating properties of other various ingredients in these formulations.

[0038]In one preferred embodiment, the strontium cation is combined in a topical product formulation further comprising a potentially irritating ingredient, the cation being present in a total amount effective to reduce or eliminate irritation due to the irritant ingredient.

Problems solved by technology

In a large number of cases, topical products contain chemicals which may produce irritation or inflammation when applied to the skin or mucosa.

Many ingredients used in topical products are known irritants or are potentially irritating, especially to people with “sensitive skin”.

Additionally, many topical product active ingredients, including chemicals that may also be classified as drugs, produce irritation when applied to the skin.

Furthermore, chemical ingredients may react with one another, or in the environment of the skin, to form new chemicals which are irritating.

The vehicles in which the active drug ingredients are formulated may also produce irritation in sensitive people, especially in drugs such as topical corticosteroids.

In addition to chemicals which directly trigger skin irritation, some chemicals indirectly cause the skin to become more sensitive to other chemicals or environmental conditions which would not normally cause irritation.

Extremes of humidity, for example, can greatly increase irritation from topically-applied products.

Normal processes such as sweating may also increase the ability of irritant materials, such as antiperspirants, deodorants or sunscreens, to penetrate the skin through pores or glands, thus exacerbating the potential for irritation.

Similarly, the skin may become sensitized or inflamed due to infection, shaving abrasion, repeated or excessive washing or bathing, sun exposure, or other mechanical abrasion or injury, resulting in sensory irritation responses upon subsequent application of underarm deodorants, after-shaves or other topical products.

People with respiratory allergies, for example, tend to have excessively dry skin which facilitates increased absorption of potentially irritating chemicals.

The excessively dry skin which accompanies atopic dermatitis, for example, predisposes patients with this condition to irritation from many topically-applied products.

In any event, it is often not feasible or practical to identify or eliminate all of the irritating chemical(s), particularly when the irritating chemical(s) are the active ingredient of the product or are required for formulation, preservative or other functional reasons.

Hydroxy acids, in concentrations high enough to exfoliate, are well known often to cause skin irritation and rashes.

The danger of irritation is even higher for persons that have sensitive skin.

Such methods have the reported drawback of reducing the ability of the resulting hydroxy acid salt to penetrate the skin and thus compromising the beneficial effects (particularly anti-acne or anti-“dry skin” effects) of the hydroxy acid.

Thus, the cation may alter the ability of epidermal nerve cells to depolarize or repolarize, as for example by blocking or interfering with ion channel or pump operation or by altering the transmembranal action potential, or the cation may interfere with the transmission of nerve impulses from one nerve cell to another (as by suppressing neurotransmitter release).

While laboratory studies such as these using cultured single cells or microelectrode single-cell electrophysiological techniques have done much to advance the understanding of nerve activity, distinct challenges are presented in the clinical setting.

A number of factors make it difficult to predict what effects, if any, particular agents (cationic or otherwise) may have on nerve activity and sensation in intact animal bodies.

In addition, the mechanisms underlying sensory stimulation and perception in the animal body are diverse and exceedingly complex.

Such factors lead to considerable clinical uncertainty as to how various agents may affect such nervous responses.

In the final analysis, the Markowitz and Kim group concluded that it is difficult to explain the clinical desensitizing effects of the available ionic desensitizing dentrifices (which require several weeks of treatment) in terms of a direct nerve cell membrane function, and that studies undertaken with exposed nerves may not reflect the pain-induction mechanisms observed clinically (Markowitz & Kim, above).

The human skin presents a sensory and structural environment that is much more complicated than that of the tooth.

Agents which are effective to combat one source of sensory stimulus—for example steroidal agents to treat skin inflammation—are ineffective against other sensory stimuli such as pressure, heat, or the transitory sting or itch caused by an applied skin care product.

Conversely, local anesthetic agents which are effective to depress all sensory or even motor activity in a treated region are not desirable if only a single sensation—for example a transitory sting or itch—is sought to be eliminated.

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