Pharmacokinetics of maropitant citrate in New Zealand White rabbits (Oryctolagus cuniculus)

OBJECTIVE To determine the pharmacokinetics and adverse effects of maropitant citrate after IV and SC administration to New Zealand White rabbits (Oryctolagus cuniculus). ANIMALS 11 sexually intact (3 males and 8 females) adult rabbits. PROCEDURES Each rabbit received maropitant citrate (1 mg/kg) IV or SC. Blood samples were collected at 9 (SC) or 10 (IV) time points over 48 hours. After a 2-week washout period, rabbits received maropitant by the alternate administration route. Pharmacokinetic parameters were calculated. Body weight, food and water consumption, injection site, mentation, and urine and fecal output were monitored. RESULTS Mean +/- SD maximum concentration after SC administration was 14.4 +/- 10.9 ng/mL and was detected at 1.25 +/- 0.89 hours. Terminal half-life after IV and SC administration was 10.4 +/- 1.6 hours and 13.1 +/- 2.44 hours, respectively. Bioavailability after SC administration was 58.9 +/- 13.3%. Plasma concentration at 24 hours was 2.87 +/- 1.69 ng/mL after IV administration and 3.4 +/- 1.2 ng/mL after SC administration. Four rabbits developed local dermal reactions at the injection site after SC injection. Increased fecal production was detected on the day of treatment and 1 day after treatment. CONCLUSIONS AND CLINICAL RELEVANCE Plasma concentrations of rabbits 24 hours after SC and IV administration of maropitant citrate (1 mg/kg) were similar to those of dogs at 24 hours. Reactions at the SC injection site were the most common adverse effect detected. Increased fecal output may suggest an effect on gastrointestinal motility. Additional pharmacodynamic and multidose studies are needed.