Azelaic Acid Esters Do Not Depigment Pigmented Guinea Pig Skin

To the Editor.—  Azelaic acid (1,7-heptanedicarboxylic acid) is a naturally occurring dicarboxylic acid produced by Malassezia furfur, which has been postulated to cause the hypopigmentation seen in tinea versicolor.¹ Some authors maintain that azelaic acid has selective inhibition of only hyperproliferative melanocytes.^2-3 Other authors maintain that it does not cause significant depigmentation or inhibition of growth of melanocytes at physiologic levels.⁴ Azelaic acid was recently compared with several other known depigmenting agents, and was found to produce weak depigmentation compared with the other compounds studied.⁴Since the intensity of the depigmenting effect of azelaic acid varies from laboratory to laboratory, we thought that drug delivery could be important. We postulated that if azelaic acid is indeed able to depigment by inhibition of melanogenesis via inhibition of tyrosinase,¹ then its depigmenting activity could be increased by modification of the rather hydrophilic molecule to a more lipophilic