Topical Application of Tacrolimus Ointment Did Not Alter the Cutaneous Pigmentation of Yucatan Micropigs

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Abstract
Tacrolimus is a potent immunosuppressant marketed for the prevention of rejection in liver and kidney transplantation. Topical tacrolimus has been shown to be effective in the treatment of atopic dermatitis, a disease with an immunologic basis, and is currently being developed for this indication. The objective of the current study was to determine whether repeated topical application of tacrolimus ointment could result in hypopigmentation at the application site(s). Each of 10 Yucatan miniature pigs received topical application of 0.03%, 0.1%, and 0.3% tacrolimus ointment, positive control (a combination of 2% 4-hydroxyanisole and 0.01% all-trans-retinoic acid, 4-HAArRA), and a negative control (vehicle placebo) to five test sites (approximately 12.5 cm2) along either side of the dorsal midline (10 sites per animal). Tacrolimus and controls were randomly assigned to the test site on each animal and were applied unoccluded twice daily for 8 weeks at a dose volume of 0.1 ml per site for tacrolimus and vehicle control and 0.025 ml per site for the positive control. Topical application of tacrolimus ointment in concentrations of up to 0.3% for 8 weeks had no effect on the cutaneous pigmentation of Yucatan miniature swine. In contrast, the application of 4-HAArRA produced a statistically significant (P<.05) induction of hypopigmentation from week 4 through the end of the study application.