Comparison of the stability of topical isotretinoin and topical tretinoin and their efficacy in acne.

After 4 hours of exposure to incandescent light, 80% of 0.05% topical isotretinoin and 60% of 0.05% topical tretinoin preparations remained in their original form. In contrast, after 2 hours of exposure to fluorescent light only 25% of topical tretinoin and possibly 60% of topical isotretinoin remained in their original forms. Longer exposure to fluorescent light did not result in further breakdown, and the final breakdown of both preparations was similar. A 12-week, double-blind clinical trial comparing isotretinoin (0.05%) with tretinoin (0.05%) applied topically to patients with moderate acne was carried out. Both preparations caused significant reductions in papules and pustules. However, neither treatment was significantly superior to the other in the reduction of acne lesions. This may be because both preparations are rapidly broken down to similar products when exposed to fluorescent light.