Salicylic acid formulations

A variety of formulations of salicylic acid have been used as peeling agents. These include 50% ointment formulations (Table 6.1) [2,3], as well as 10, 20 and 30% ethanol formulations (Table 6.2) [4,6]. More recently, commercial formulations of salicylic acid have become available (BioGlan Pharmaceuticals Company, Malvern, PA Bionet Esthetics, Little Rock, AR). 

Table 6.1 Formulations of salicylic acid salicylic acid ointment...

Salicylism, or salicylic acid toxicity, is characterized by rapid breathing, tinnitus, hearing loss, dizziness, abdominal cramps, and central nervous system reactions. It has been reported with 20% salicylic acid applied to 50% of the body surface, and it has also been reported with use of 40 and 50% salicylic acid paste preparations [7]. The author has peeled more than 1,000 patients with the current 20 and 30% marketed ethanol formulations and has observed no cases of salicylism. 

Ethanol formulations of salicylic acid (20 and 30%) are used for combination peeling (see salicylic acid section). Trichloroacetic acid is prepared as an aqueous solution, since ethanol solutions do not penetrate the skin. It is prepared by mixing the appropriate concentration of crystals with up to 100 cc of distilled water. Ten and fifteen percent TCA is prepared by mixing 10 or 15 g of crystals in up to 100 cc of total volume, respectively. Aqueous solutions of TCA remain stable for up to 6 months unless contaminated. Other methods have been used to formulate TCA peeling solutions however, the weight/volume methods appear to be the most reliable formulation [5]. Premixed TCA solutions are available from a variety of medical... 

Erdmann et al. (2000) report the fabrication of devices for the localized delivery of salicylic acid from the poly(anhydride-co-ester)s mentioned in Section II.C. A unique feature of this drug delivery system is that the drug compound is part of the polymer backbone. Devices were implanted intraorally and histopathology was reported (Erdmann et al., 2000). Chasin et al. (1990) review fabrication and testing of implantable formulations for other drugs including angiogenesis inhibitors for treatment of carcinomas and bethanechol for the treatment of Alzheimer s disease. 

Fig. 12 Plot of the mean integrated intensity of the salicylic acid peaks as a function of the weight percent of salicylic acid in the hydrogel formulations. (O) Peak I contains lines with d-spacings of 3.58, 3.53, and 3.52 A ( ) peak II contains lines with d-spacings of 2.95,2.91, and 2.88 A. (Reproduced with permission of the copyright owner, Elsevier, from Ref. 58.)...

As the following pages of this section will show, there is hardly a new method of analysis which is not immediately tried for the determination of aspirin as such, or in formulations and biological fluids. The analysis of aspirin is intricately interwoven with that of salicylic acid, its precursor and degradation product. From the very first, residual salicylic acid was determined by the convenient reaction with ferric salts — typical for phenols — which give a violet complex with salicylic acid. 

Bioactive compounds from Blumea gariepina salicin, salicylic acid, tenoxicam, ketorolac, piroxicam, tolmetin, naproxen, flurbiprofin, diclofenac, and ibuprofen in pharmaceutical formulations and biological samples ... 

There are oral formulations that deliver drug to the lower intestine. In mesalazine 5-amino-salicylic acid is formulated in a polymer-coated oral preparation. Olsalazine is a dimer of 5-aminosalicylate linked by an azo bond. Balsalazide is delivered to the colon where it is cleaved by bacterial azoreduction to release equimolar quantities of mesalazine and 4-aminobenzoyl-/i-alanine. The newer 5-ASA preparations were shown to be superior to placebo and tended towards therapeutic benefit over sulfasalazine. However, considering their relative costs, a clinical advantage to using the newer 5-ASA preparations in place of sulfasalazine appears unlikely. 

Salicylic acid USP, EP, and other pharmacopeia grades are used medically as antiseptic, disinfectant, antifungal, and keratolytic agents. Salicylic acid is formulated in lotion or ointment formulations for the treatment of dandruff, eczema, psoriasis, and various parasitic skin diseases. Because the keratolytic property of this aromatic acid has use in the safe removal of dead skin cells from the surface of healthy skin, the acid is used in concentrated salicylic acid solutions or suspensions to remove warts and corns. In more dilute form, salicylic acid preparations have found use in dandruff and eczema treatment. Salicylic acid has been considered and found effective by the Advisory Committees to the FDA in various over-the-counter (OTC) drug regulated uses. Among these are acne products, dermatitis, dry skin, dandruff and psoriasis products, and foot care products (24). 

Drugs that contain 5-aminosalicylic acid (5-ASA) have been used successfully for decades in the treatment of inflammatory bowel diseases (Figure 62-8). 5-ASA differs from salicylic acid only by the addition of an amino group at the 5 (meta) position. Aminosalicylates are believed to work topically (not systemically) in areas of diseased gastrointestinal mucosa. Up to 80% of unformulated, aqueous 5-ASA is absorbed from the small intestine and does not reach the distal small bowel or colon in appreciable quantities. To overcome the rapid absorption of 5-ASA from the proximal small intestine, a number of formulations have been designed to deliver 5-ASA to various distal segments of the small bowel or the colon. These include sulfasalazine, olsalazine, balsalazide, and various forms of mesalamine. 

Gloor, M., et al. 2001. Clinical effect of salicylic acid and high dose urea applied in standardized NRF formulations. Pharmazie 56 810. 

Salicylic acid can be helpful as a monotherapy. Witman reported that it is most commonly used in combination with corticosteroids, enhancing their penetration. Concentration of salicylic acid used for this purpose is 2 to 10%.2 Such combinations require compounding by a pharmacist and carry the risk of imprecise formulations that are potentially unstable, unsafe, or ineffective.2... 

Gabard, B., P. Treffel, F. Schwarb, C. Surber, and E. Bieli, S. Liidi, Salicylic acid release from topical formulations does not predict in vitro skin absorption. Dermatology, 1997, 195 198. 

Schwarb, F., B. Gabard, G. lost, Th. Rufli, and C. Surber, Percutaneous absorption of salicylic acid in man following topical administration of different formulations. Dermatology, 1997, 195 129. 

Nook, T.H., In vivo measurement of the keratolytic effect of salicylic acid in three ointment formulations. Br. J. Dermatol., 1987, 117 243-5. 

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