Pharmacokinetics of ceftriaxone administered by the intravenous, intramuscular or subcutaneous routes to dogs

The purpose of this study was to investigate the pharmacokinetics of ceftriaxone after single intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) doses in healthy dogs. Six mongrel dogs received ceftriaxone (50 mg/kg) by each route in a three‐way crossover design. Blood samples were collected in predetermined times after drug administration. Results are reported as mean ± standard deviation (SD). Total body clearance (Clt) and apparent volume of distribution (Vz) for the i.v. route were 3.61 ± 0.78 and 0.217 ± 0.03 mL/kg, respectively. Terminal half‐life harmonic mean (t½λ) was 0.88; 1.17 and 01.73 h for the i.v., i.m and s.c. routes, respectively. Mean peak serum concentration (Cmax) was 115.10 ± 16.96 and 69.28 ± 14.55 μg/mL for the i.m and s.c. routes, respectively. Time to reach Cmax (tmax) was 0.54 ± 0.24 and 1.29 ± 00.64 h for the i.m and s.c. routes, respectively. Mean absorption time (MAT) was 1.02 ± 0.64 and 2.23 ± 00.73 h for the i.m and s.c. routes, respectively. Bioavailability was 102 ± 27 and 106 ± 14% for the i.m and s.c. routes, respectively. Statistically significant differences were determined in Cmax, tmax, MAT and t½λ of s.c. administered ceftriaxone when compared with the i.v and i.m. routes. These findings suggest that once or twice s.c. or i.m. daily administered ceftriaxone should be adequate to treat most susceptible infections in dogs.