Pharmacokinetics of repeated oral administration of tramadol hydrochloride in Hispaniolan Amazon parrots (Amazona ventralis)

Abstract

To determine the pharmacokinetics of tramadol hydrochloride (30 mg/kg) following twice-daily oral administration in Hispaniolan Amazon parrots (Amazona ventralis). 9 healthy adult Hispaniolan Amazon parrots. Tramadol hydrochloride was administered to each parrot at a dosage of 30 mg/kg, PO, every 12 hours for 5 days. Blood samples were collected just prior to dose 2 on the first day of administration (day 1) and 5 minutes before and 10, 20, 30, 60, 90, 180, 360, and 720 minutes after the morning dose was given on day 5. Plasma was harvested from blood samples and analyzed by high-performance liquid chromatography. Degree of sedation was evaluated in each parrot throughout the study. No changes in the parrots' behavior were observed. Twelve hours after the first dose was administered, mean ± SD concentrations of tramadol and its only active metabolite M1 (O-desmethyltramadol) were 53 ± 57 ng/mL and 6 ± 6 ng/mL, respectively. At steady state following 4.5 days of twice-daily administration, the mean half-lives for plasma tramadol and M1 concentrations were 2.92 ± 0.78 hours and 2.14 ± 0.07 hours, respectively. On day 5 of tramadol administration, plasma concentrations remained in the therapeutic range for approximately 6 hours. Other tramadol metabolites (M2, M4, and M5) were also present. On the basis of these results and modeling of the data, tramadol at a dosage of 30 mg/kg, PO, will likely need to be administered every 6 to 8 hours to maintain therapeutic plasma concentrations in Hispaniolan Amazon parrots.