Relative Bioavailability of Liquid and Tablet Formulations of the Antiparasitic Moxidectin

The antiparasitic agent moxidectin is under development for the treatment of onchocerciasis. As the first-in-human study of moxidectin used a liquid formulation but other trials used tablets, a study was performed to determine the relative bioavailability of the 2 formulations and to gain more information about the pharmacokinetics of moxidectin. Fifty-eight healthy male participants were randomized to receive open-label moxidectin (10 mg) as a tablet (n = 29) or liquid (n = 29) formulation. The mean +/- SD pharmacokinetic parameters observed following administration of the tablet were peak concentration (C-max) 67.1 +/- 27.4 ng/mL, time to peak concentration (t(max)) 3.2 +/- 1.4 hours, area under the concentration time curve (AUC) 4403 +/- 2360 ng.h/mL, apparent volume of distribution 3635 +/- 1720 L, oral clearance 2.83 +/- 1.25 L/h, and elimination half-life 1032 +/- 502 hours. The C-max and AUC observed following administration of the liquid formulation were 28.6% and 28.8% higher, respectively, and t(max) 0.9 hours shorter compared with tablets. No serious adverse events (AEs) were observed. The most commonly reported AEs were headache, infection, diarrhea, asthenia, myalgia, and dizziness during the inpatient phase and flu syndrome, headache, and infection during the 6-month outpatient phase. There was no difference in reporting of these AEs between formulations.