Azithromycin therapy of papillomatosis in dogs: a prospective, randomized, double-blinded, placebo-controlled clinical trial

Azithromycin, an azalide subclass macrolide antibiotic, is an effective, well-tolerated and safe therapeutic option for treatment of papillomatosis in humans. This study reports the clinical and histopathological results from a prospective, randomized, double-blinded, placebo-controlled trial of 17 dogs of various breeds with diagnosis of oral (n = 12) and cutaneous papillomatosis (n = 5) treated with azithromycin. Papillomas appeared as whitish, verrucous, hyperkeratotic papules 1-2.7 mm in size. The cases were randomly assigned to azithromycin (n = 10) and placebo treatment groups (n = 7). Both owners and investigators were blinded to the allocation to the groups. Azithromycin (10 mg/kg) was administered per os every 24 h for 10 days. Clinical evaluations were done by the same investigator throughout the trial. Azithromycin treatment significantly decreased clinical scores (P < 0.001), whereas there was no change seen in the placebo group. In the azithromycin treatment group, skin lesions disappeared in 10-15 days. One case in the placebo had spontaneous regression of its papillomas by day 41, but lesions were still evident at day 50 in the remaining six cases. There was no recurrence of papillomatosis in the azithromycin treated dogs (follow up 8 months). No adverse effects were seen in either group. In conclusion, azithromycin appears to be a safe and effective treatment for canine papillomatosis.