PHARMACOKINETICS, EFFICACY, AND SAFETY OF VORICONAZOLE AND ITRACONAZOLE IN HEALTHY COTTONMOUTHS (AGKISTRODON PISCIVORUS) AND MASSASAUGA RATTLESNAKES (SISTRURUS CATENATUS) WITH SNAKE FUNGAL DISEASE

Author: 

Lindemann DM, Allender MC, Rzadkowska M, Archer G, Kane L, Baitchman E, Driskell EA, Chu CT, Singh K, Hsiao SH, Sykes JM 4th, Cox S
J Zoo Wildl Med. 2017 Sep;48(3):757-766

Abstract: 

Snake fungal disease (SFD; Ophidiomyces ophiodiicola) is posing a significant threat to several free-ranging populations of pitvipers. Triazole antifungals have been proposed for the treatment of mycoses in reptiles; however, data are lacking about their safety and efficacy in snakes with SFD. Study 1 investigated in vitro susceptibility, and identified that plasma concentrations >250 ng/ml (voriconazole) and >1,000 ng/ml (itraconazole) may be effective in vivo for SFD. In Study 2, the pharmacokinetics after a single subcutaneous voriconazole injection were assessed in apparently healthy free-ranging cottonmouths (Agkistrodon piscivorus). Based on pilot-study results, four snakes were administered a single injection of voriconazole (5 mg/kg). One pilot snake and three full-study snakes died within 12 hr of voriconazole administration. All surviving snakes maintained plasma concentrations >250 ng/ml for 12-24 hr. In Study 3, two Eastern massasaugas (Sistrurus catenatus) and a timber rattlesnake (Crotalus horridus horridus) diagnosed with SFD were treated with voriconazole delivered by subcutaneous osmotic pumps. The timber rattlesnake (12.1-17.5 mg/kg/hr) reached therapeutic concentrations, whereas the massasaugas (1.02-1.6 mg/kg/hr) did not. In Study 4, the pharmacokinetics of a single 10-mg/kg per-cloaca dose of itraconazole (Sporanox®) was evaluated in seven apparently healthy free-ranging cottonmouths. Similarly, the plasma and tissue concentrations did not meet therapeutic concentrations based on in vitro data. The data presented in this report serve as an initial step toward understanding the pharmacokinetics, efficacy, and safety of triazole antifungals in pitviper species with SFD. Further study is needed to determine the appropriate dose and route of administration of triazole antifungals in pitviper species.