Benzoyl peroxide formulations

A 17-year-old girl, Miss EV, presents in your pharmacy with her regular prescription for Microgynon 30. Three months ago she had complained of problems of acne so you recommended that she try an over-the-counter topical benzoyl peroxide formulation. Her acne does not appear to have improved from the treatment so you recommend that she makes an appointment to see her GP. The following week she presents a new prescription for oxytetracycline tablets (500 mg b.d.). 

Apply once or twice daily, preferably after washing with soap and water. Treatment should be started with lower strength formulations. Adverse effects can include local skin irritation, such as scaling and redness, particularly on commencement of therapy. If this occurs advise the patient to reduce the frequency of application. Benzoyl peroxide formulations can also cause bleaching of clothes. 

The aqueous phase into which the monomer mix is dispersed is also prepared in a separate tank before transferring to the copolymerization ketde. It contains a catalyst, such as benzoyl peroxide [94-36-0], to initiate and sustain the polymerization reaction, and chemicals that aid in stabilizing the emulsion after the desired degree of dispersion is achieved. Careful adherence to predeterrnined reaction time and temperature profiles for each copolymer formulation is necessary to assure good physical durabiHty of the final ion-exchange product. 

It is available with or without a prescription and remains the most commonly purchased over-the-counter topical treatment for acne.12 Benzoyl peroxide is available in concentrations ranging from 1% to 10% in various formulations including creams, lotions, gels, and facial washes. 

Retinoids, which are highly effective in the treatment of acne, stimulate epithelial cell turnover and aid in unclogging blocked pores. Retinoids also exhibit anti-inflammatory properties through the inhibition of neutrophil and monocyte chemotaxis.8 Because of these comedolytic and antiinflammatory effects, topical retinoids are recommended as first-line treatment for mild to moderate comedonal and inflammatory acne.3 While success is seen with monotherapy, using a retinoid in combination with benzoyl peroxide or topical antibacterials is also an appropriate and effective therapeutic treatment option.3 Tretinoin, adapalene, and tazarotene are topical retinoids available for use in the treatment of acne. Table 62-2 describes the strengths and formulations of these agents. 

It is available as 1% or 2% concentrations in gel, lotion, solution, foam, and disposable pad formulations and is usually applied twice daily. Combination with benzoyl peroxide increases efficacy. 

It is enough to visit the clean, small production plant of Sol-Gel Technologies in Israel (Figure 8.3) to recognize that most of the value added to benzoyl peroxide entrapped in microcapsules comes from knowledge—and thus from human ingenuity—which originates the production of the microcapsules. The price at which the white water-based capsule formulation is sold to customers exceeds more than 1000 times the price of the raw materials used to prepare it. Put another way ... 

To decrease the likelihood of irritation, application should be limited to a low concentration (2.5%) once daily for the first week of therapy and increased in frequency and strength if the preparation is well tolerated. Fixed-combination formulations of 5% benzoyl peroxide with 3% erythromycin base (Benzamycin) or 1% clindamycin (BenzaClin) appear to be more effective than individual agents alone. 

Clindamycin has in vitro activity against Propionibacterium acnes this has been postulated as the mechanism of its beneficial effect in acne therapy. Approximately 10% of an applied dose is absorbed, and rare cases of bloody diarrhea and pseudomembranous colitis have been reported following topical application. The hydroalcoholic vehicle may cause drying and irritation of the skin, with complaints of burning and stinging. The water-based gel and lotion formulations are well tolerated and less likely to cause irritation. Allergic contact dermatitis is uncommon. Clindamycin is also available in a fixed-combination topical gel with benzoyl peroxide (BenzaClin). 

Mild keratolytic (exfoliating, peeling) formulations unblock pilosebaceous ducts, e.g. benzoyl peroxide, sulphur, salicylic acid, azelaic acid. 

Leyden JJ, Berger RS, Dunlap FE, Ellis CN, Connolly MA, Levy SF. Comparison of the efficacy and safety of a combination topical gel formulation of benzoyl peroxide and clindamycin with benzoyl peroxide, clindamycin and vehicle gel... 

In the most detailed studies published to date raw drug, benzoyl peroxide, its compatibility with selected excipients (see Table 1) and its presence at a range of strengths in formulated materials have been investigated (see Table 2). 

Hydrous Benzoyl Peroxide, USP. Hydrous benzoyl peroxide (Oxy-S. Oxy-IO. Vanoxide) is a while granular powder. In its pure powder form it is explosive. The compound is formulated with. 10% water to make it safer to... 

Benzoyl peroxide is available as creams, lotions, gels and washes (2.5, 5 and 10%, and a 4% cream). There is little difference in clinical response to these concentrations in terms of reducing the number of inflammatory lesions, but formulation appears to make a difference. The drying effect of an alcoholic gel base enhances the effectiveness of the active constituent, and it is more effective than a lotion of the same concentration. However, gels have a greater potential for causing skin dryness and irritation than preparations in aqueous bland bases, so water-based preparations may improve compliance. 

The BisGMA monomer is polymerized by either of two free-radical mechanisms a thermally induced peroxide initiation or a photoinduced a,b-diketone initiation. Many of the initiator formulations are proprietary to their respective manufacturers, but a typical peroxide initiator is benzoyl peroxide, which forms free radicals when the temperature is raised. The a,b-diketone initiator responds to incident light energy to form free radicals. 

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