Variation in comedonal antibiotic concentrations following application of topical tetracycline for acne vulgaris.
A miniaturized sensitive bioassay was used to detect tetracycline in open comedones following topical twice daily application of 0.22% tetracycline hydrochloride for a minimum of 4 weeks to the facial skin of patients with mild to moderate acne. The lower limit of detection was 4.8 +/- 0.8 ng per comedone or per 10 microliters. Using this method, 111 of 155 open comedones from 15 patients were found to contain a detectable amount of tetracycline, ranging from 1.8 to 156.9 ng per comedone, and between 4.5 and 1140.1 ng per mg comedonal material. There was a significant effect of comedone weight on tetracycline content, with smaller comedones containing proportionately more tetracycline. The Spearman rank correlation coefficient was -0.5619 (P < 0.001). All 111 comedones in which tetracycline was detected contained sufficient drug to inhibit fully antibiotic-sensitive propionibacteria. However, conditions favourable to the selection and overgrowth of highly tetracycline-resistant strains (MIC > or = 32 micrograms/ml) prevailed in at least 18.7% (29 of 155) of the comedones tested.
Gardner
K J
KJ
Department of Dermatology, Leeds General Infirmary, U.K.
Cunliffe
W J
WJ
Eady
E A
EA
Cove
J H
JH
D000152:Acne Vulgaris / Q000188:drug therapy / Q000378:metabolism*; D000279:Administration, Cutaneous; D001681:Biological Assay; D004334:Drug Administration Schedule; D006801:Humans; D011424:Propionibacterium / Q000187:drug effects; D012627:Sebaceous Glands / Q000737:chemistry* / Q000382:microbiology; D013752:Tetracycline / Q000008:administration & dosage / Q000032:analysis*
D013752:Tetracycline