Pharmacokinetics and bioavailability of spectinomycin after i.v., i.m., s.c. and oral administration in broiler chickens

A pharmacokinetic and bioavailability study of spectinomycin was conducted in healthy broiler chickens following administration of a single (50 mg/kg bw) intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) dose and oral doses of 50 and 100 mg/kg bw. Following i.v. administration, the elimination half-life (t(1/2 beta)), mean residence time (MRT), volume of distribution at steady-state (V-d(ss)), volume of distribution based on the terminal phase (V-d(z)) and total body clearance (Cl-B) were 1.46 +/- 1.10 h, 1.61 +/- 1.05 h, 0.26 +/- 0.009 L/kg, 0.34 (0.30-0.38) L/kg and 2.68 +/- 0.017 mL/min/kg respectively. After i.m. and s.c. dosing, the C-max was 152.76 +/- 1.08 and 99.77 +/- 1.04 mu g/mL, achieved at 0.25 (0.25-0.50) and 0.25 (0.25-1.00) h, the t(1/2 beta) was 1.65 +/- 1.07 and 2.03 +/- 1.06 h and the absolute bioavailability (F) was 136.1% and 128.8% respectively. A significant difference in C-max (5.13 +/- 0.10, 14.26 +/- 1.12 mu g/mL), t(1/2 beta) (3.74 +/- 1.07, 8.93 +/- 1.13 h) and Cl-B/F (22.69 +/- 0.018, 10.14 +/- 0.018 mL/min/kg) were found between the two oral doses (50 and 100 mg/kg bw respectively), but there were no differences in the t(max) [2.00 (2.00-4.00), 2.00 (2.00-2.00) h] and V-d(z)/F [6.95 (6.34-9.06), 7.98 (4.75-10.62) L/kg). The absolute bioavailability (F) of spectinomycin was 11.8% and 26.4% after oral administration of 50 and 100 mg/kg bw respectively.