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 β ), 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  μ g/mL, achieved at 0.25 (0.25–0.50) and 0.25 (0.25–1.00) h, the t 1/2 β 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  μ g/mL), t 1/2 β (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.