Topical preparations

Different performanee eriteria are laid down for injeetable and ophthahrtic preparations, topical preparations and oral hquid preparations. Inhibition of the challenge organism is determined by viable coimting teehniques. The British Pharmacopoeia (1993) should be eonsulted for full details of the experimental procedures to be used. 

Topical mesalamine products provide a more rapid response than oral preparations. Improvement in symptoms may be seen in as little as 2 days, but 2 to 4 weeks of treatment may be necessary for maximal response. Response rates of up to 90% after 4 weeks of topical therapy have been reported, compared to 45% to 62% response rates with oral therapy.6,18 Oral and topical mesalamine preparations may be used together to provide maximal effect. Oral mesalamine may also be used for patients who are unwilling to use topical preparations. 

Carbonic anhydrase inhibitors decrease aqueous humor production by inhibition of the carbonic anhydrase isoenzyme II located in the ciliary body. In the eye, carbonic anhydrase catalyzes the conversion of water and carbon dioxide to bicarbonate and hydrogen ion, which is a significant step in aqueous humor production. Carbonic anhydrase inhibitors are available in systemic and topical preparations.10,13,14... 

Topical preparations, like all other dosage forms, must be formulated, manufactured, and packaged in a manner that assures that they meet general standards of bioavailability, physical (physical system) stability, chemical (ingredient) stability, freedom from contamination, and elegance. Like all other pharmaceuticals, these factors must remain essentially invariant over the stated shelf life of the product and they must be reproducible from batch to batch. 

Evaluation of the cosmetic elegance of topical preparations can be accomplished scientifically, but it is questionable whether physical experiments on system rheology and the like offer appreciable advantage over the subjective evaluations of the pharmacist, the formulator, or other experienced people. Persons who use cosmetics are particularly adept and helpful as evaluators. 

Many topical preparations containing arnica are commercially available. Arnica is most commonly prepared as a tincture that can also be used as the base for creams, ointments, compresses, and poultices. Arnica oil may also be used in topical preparations. 

Lazzaro C, Calaciura C, Spitalieri S, Lazzaro GC Treatment of pyogenic skin infections Results of a controlled trial with a new topical preparation (in Italian). Aggiornamenti Med Chir(Rome) 1989 13 1—11. 

The present chapter deals with calculations involving isotonicity, pH, and buffering of topical preparations. The discussion presented here is also relevant to the dosage forms for other routes of administration including parenteral routes. 

Mueller-Goymann, C.C., and Frank, S.G., Interaction of lidocaine and lidocaine-hydrochloride with the liquid crystal structure of topical preparations, Int. J. Pharm., 29 147-159 (1986). 

Topical preparations for the treatment of acne include the use of azelaic acid, salicylic acid, benzoyl peroxide and triclosan. Clindamycin is an antibacterial preparation available for use in the treatment of acne both topically and systemically. 

Rubefacients act by counter-irritation produced as a result of local vasodilation, resulting in a warm sensation that masks the pain. Counter-irritants should not be applied on broken skin or before or after taking a hot shower. Examples of counter-irritants include salicylates, nicotinates, capsicum, menthol and camphor. Ketoprofen is an example of a non-steroidal anti-inflammatory drug that is available as a topical preparation indicated in painful musculoskeletal conditions. 

Topical application of corticosteroids may lead to spreading of local skin infections, striae and thinning of the skin. Topical preparations containing corticosteroids should not normally be applied for more than 7 days. 

Benzoyl peroxide promotes the shedding of keratinised epithelial cells on the skin and is therefore a keratolytic agent. In the treatment of acne it is indicated as a first-line agent in the form of topical preparations. Benzoyl peroxide is mildly irritant, particularly during the early stages of treatment and hence a low strength is chosen to initiate treatment. Moreover aqueous preparations are preferred over alcoholic preparations, to avoid irritation. 

Tacrolimus is used in situations where cyclosporine has been shown to be ineffective or cannot be used because of toxicity or otherwise. It is also used in a topical preparation in the treatment of severe atopic dermatitis, severe refractory uveitis after bone marrow transplants and in vitiligo. 

There are many retinol containing preparations to treat vitamin deficiency states. Retinoids are also used to treat dermatological diseases like acne, psoriasis, Darier s disease, and ichthyosis. Tretinoin, all-trans-retinoic acid, is a topical preparation while isotretinoin or 13-cis-retinoic acid, and etretinate are available for oral administration. 

EMLA cream (lidocaine 2.5% and prilocaine 2.5%) consists of a eutectic mixture of focal anesthetics. It is used to provide topical anesthetic to intact skin. Other topical preparations are effective only on mucosal surfaces. EMLA has been shown to reduce pain on venipuncture and provide substantial anesthesia for skin graft donor sites. No significant local or systemic toxicity has been demonstrated. 

Topical preparations usually contain relatively insoluble steroids, such as clobetasol propionate, triamcinolone acetonide, or triamcinolone diacetate. Side effects of this mode of drug application are usually milder and more transient than those seen after systemically administered steroids. However, potent topical corticosteroids, such as clobetasol propionate (Temovate), can suppress adrenal function when used in large amounts for a long time, especially when the skin surface is denuded or when occlusive dressings are employed. Since the high potency topical preparations carry a higher risk of local side effects, their use should be held in reserve. 

Androgens come in oral, injectable, implantable, and topical preparations. Because of the toxicity of the oral preparations and the inconvenience of the injectable forms, the transdermal gels have been a major clinical advance for treatment of hypogonadal males. 

Discontinue topical preparation if irritation or redness develops... 

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