Acne vulgaris is an almost ubiquitous condition. When antimicrobials are used alone, there is a risk of creating widespread, multidrug resistance of P. acnes as well as other skin flora such as Staphylococcus aureus (2,5,30). This potential resistance can be limited by combining agents that act on different steps in the mechanism of acne pathogenesis. When topical retinoids are used in combination with oral or topical antimicrobials, excessive ductal cornification, P. acnes proliferation, and inflammation can be simultaneously targeted for increased efficacy, faster onset of effects, decreased total antibiotic use and risk of resistance, and shorter overall duration of treatment (2). The combination tretinoin with topical or oral antibiotics has been shown to be superior to either alone in decreasing lesion count, increasing rate of improvement, and decreasing levels of P. acnes and free fatty acids (8,14). Similarly, the combination of adapalene with topical doxycycline or clindamycin shows increased efficacy in improving total, inflammatory, and noninflammatory lesions including a faster onset of action without an augmentation in side effects (17). In addition, combination use of adapalene offers an anti-inflammatory benefit, which minimizes the increased risk of irritation that occurs upon increasing the number of topical treatments (17).
Similar results were found upon combining retinoic acid and antibiotics, with a reduction in the initial retinoid-induced flare of lesions through the antibiotic use (3). When combined with a benzoyl peroxide oxidizing wash—which demonstrates an effective bacteriostatic concentration after only 20 seconds of use—tretinoin 0.1% micro gel decreased P. acnes counts without increasing irritation (6,31).
With long-term use, however, overall improvement is similar with combination therapy as compared with topical retinoid use alone (14,23,32). Increased reductions in open and closed comedones, papules, and pustules were demonstrated when tazarotene or tretinoin creams were combined with clindamycin/ benzoyl peroxide as compared to either retinoid alone (14,32).
Finally, it has been shown that combining topical retinoid therapy with oral antibiotics for inflammatory acne is more cost-effective than using an oral retinoid alone when accounting for pretreatment and treatment laboratory tests, pregnancy tests, and diagnostic fetal tests after a potential unintended pregnancy (33).
A new combination clindamycin 1%/tretinoin 0.025% gel, Velac, has demonstrated greater and faster treatment success in initial clinical trials when compared to clindaymycin or tretinoin gel alone and provides a convenient means of application, which may improve patient adherence (12). The side effect profile of Velac was similar to that of tretinoin gel alone, with only slightly higher irritancy than clindamycin gel alone (12).
And as previously discussed, the use of topical retinoid in combination with oral antibiotics can decrease time of use of antibiotics, decreasing risk of resistance, adverse response, or drug interaction.
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