Résumé
AIM To evaluate bioavailability, biocompa- tibility and biodegradability of an injectable microsphere sustained release preparation of naltrexone(NTX) in 4 dogs. METHODS Pharmacokinetic data of NTX and remained NTX in microspheres in injection site were studied using high performance liquid chromatography(HPLC)-electrochemical detection with naloxone(NLX) as internal standard. Biocompatibility of the microspheres was assayed by histological examination. RESULTSPharmacokinetics of NTX after an intramuscular dose of 0.5 or 1.0 mg*kg-1 NTX indicated a plasma clearance range of 0.66 to 0.73 L*min-1 and a t1/2β range of 60.0 to 67.2 min. After a 1-week washout period without medication, NTX microspheres injection period about 4 weeks followed. After injection of 1.0 g of microspheres containing (296.5±2.1)mg of NTX, mean blood concentrations of NTX exceeded 1 μg*L-1 for 26-28 d, and cmax per dose (mg*kg-1) was only 1% of that after NTX dosing. It was estimated that approximately (93.0±4.1)% of the administered dose was absorbed after microspheres injection in 4 dogs. There were no serious adverse effects other than light tissue irritation. CONCLUSIONThis NTX microspheres preparation provides a safe, complete and sustained release of the drug for about one month.