Ticarcillin administration to the equine: Intrauterine and intramuscular

Serum levels of ticarcillin disodium, a semi-synthetic penicillin (Beecham Laboratories, Bristol, Tennessee, 37620), were measured at various time intervals up to and including 24 h after intrauterine and intramuscular administration in adult female horses. Three separate studies were conducted in Part I: in the first and second studies, serum levels were measured after intrauterine administration of 1 and 3 g of ticarcillin, respectively, and in the third study, levels were measured after intramuscular administration of 6 g of ticarcillin. In Part II, serum levels of ticarcillin were measured after intramuscular administration of ticarcillin at dosages based on body weight: 10 mg/lb (22 mg/kg) of body weight, 15 mg/lb (33 mg/kg) of body weight and 20 mg/lb (44 mg/kg) of body weight. Results showed little if any absorption of the antibiotics into the systemic circulation after intrauterine administration. All serum levels measured after administration of both intrauterine dosages of 1 and 3 g were less than 4.0 ug/ml. Peak serum concentrations, after intramuscular administration of 6 g of ticarcillin, occurred between 20 and 45 min after administration and averaged 15.97 +/- 5.0 ug/ml. Average peak serum concentrations, after intramuscular administration of 10 mg/lb (22 mg/kg) of body weight, 15 mg/lb (33 mg/kg) of body weight, 15 mg/lb (33 mg/kg) and 20 mg/lb (44 mg/kg) of body weight, were 16.12 ug/ml, 25.75 ug/ml and 50.25 ug/ml, respectively. After intramuscular administration of 6 g of ticaracilin, average serum half-life was determined to be 2.9 h.