Abstract: The pharmacokinetics and absolute bioavailability of the sublingual naloxone tablet were studied with HPLC-electrochemical detection. Eight male dogs received single 5 mg dose of naloxone intravenously, the plasma concentration-time curves could be fitted to two-compartment open model, with 12.0 min of t1/2α, 143.4 min of t1/2β and 7.92 mg·min/L of AUC. The same eight dogs received 5 mg dose of the sublingual naloxone tablet after an interval of a week. The main pharmacokinetic parameters were: t1/2ka = 11.0 min, t1/2α = 15.4 min, t1/2β = 164.1 min, Tmax = 27.7 min, Cmax = 34.2 ng/ml, and AUC = 6.79 mg·min/L, respectively. The plasma concentration-time curves were fitted to the first order absorption two-compartment open model also. The mean absolute bioavailability of the sublingual naloxone tablet was 86.8(10.9%. No statistically significant differences were found with t1/2α, t1/2β, and between the two routes of administration. These results indicated that the course of disposition for naloxone in dogs was similar for the two routes of administration, and the absolute bioavailability of the sublingual naloxone tablet was high. Thus satisfactory clinical effects could be expected.

Key words: Naloxone, Sublingual tablet, Bioavailability, Dog, HPLC-ED