Trauma is a common sequela to agonistic social encounters in rhesus macaques (Macaca mulatta), and veterinarians often prescribe antibiotics as part of a balanced treatment plan. Long-acting, single-dose, injectable antibiotics for use in rhesus macaques are unavailable currently. Ceftiofur crystalline free acid (CCFA) is a long-acting, single-dose, injectable third-generation cephalosporin that provides at least 7 d of ceftiofur therapeutic plasma concentrations in swine (Sus scrofa domesticus). We hypothesized that CCFA would achieve similar therapeutic concentrations (≥ 0.2 μg/mL) in rhesus macaques. We describe the pharmacokinetic profile of CCFA in healthy, adult male rhesus macaques ( n = 6) in this 2-period, 2-treatment crossover study of 5 and 20 mg/kg SC administered once. Plasma ceftiofur metabolite concentrations were determined prior to and for a maximum of 21 d after administration. Noncompartmental pharmacokinetic analysis was performed. The 5-mg dose achieved a maximal plasma concentration of 2.24 ± 0.525 μg/mL at 2.59 ± 1.63 h, an AUC of 46.9 ± 17.6 h/μg/mL, and a terminal elimination half-life of 56.5 ± 21.7 h; for the 20-mg/kg dose, these parameters were 9.18 ± 4.90 μg/mL at 1.82 ± 1.30 h, 331 ± 84.4 h/μg/mL, and 69.7 ± 8.86 h, respectively. No adverse effects were noted after either dose. Macaques maintained plasma ceftiofur concentrations of 0.2 μg/mL or greater for at least 2 d after 5 mg/kg SC and at least 7 d after 20 mg/kg SC
