Diphencyprone is not detectable in serum or urine following topical application.

Diphencyprone is a potent contact sensitizer in widespread use for treatment of alopecia areata. It is currently not known whether this compound is absorbed following topical application. This is important, since little is known regarding potential toxicity. We therefore analysed serum and urine samples following application of at least 0.5 ml of a 1% solution of diphencyprone to the scalp of patients under treatment for alopecia areata. Serum samples were obtained over 8 h following treatment and 24-h urine collections were performed. The threshold for detection was 2 ng, and the assay gave an accurate linear response for samples of serum and urine containing known concentrations of diphencyprone. Blood and/or urine samples were obtained from a total of 18 subjects. Diphencyprone was not detected in any sample of serum or urine from the subjects. These data suggest that diphencyprone is not absorbed following application to the skin.