Over an eight-week period, three treatments for moderately severe acne were compared in groups of adolescents: (1) 0.05% daily vitamin A acid (retinoic acid) alone; (2) demeclocycline hydrochloride alone, 600 mg a day for the first three weeks, 300 mg thereafter; (3) a combination of the two. In addition to clinical assessment, subjects in each group were studied with regard to the relationship of free fatty acids (FFA) to the density of Corynebacterium acnes.
The combination therapy produced the swiftest and greatest effect on all three factors: therapeutic benefit, decreased FFA, and reduction in the anaerobic microflora.
It was postulated that vitamin A potentiated the effect of demeclocycline by bringing about an increased tissue concentration of the antibiotic.
Mills OH, Marples RR, Kligman AM. Acne VulgarisOral Therapy With Tetracycline and Topical Therapy With Vitamin A. Arch Dermatol. 1972;106(2):200-203. doi:10.1001/archderm.1972.01620110036009