Pharmacokinetics of parenteral morphine sulfate and oral sustained release morphine sulfate in dogs

The objectives of the research were (1) to develop a suitable assay for measurement of therapeutic morphine concentrations in canine serum, (2) to examine the pharmacokinetics of MS administered intravenously (IV) and IM in two clinically relevant dosages to dogs, and (3) to examine the pharmacokinetics of OSRMS at two dosages in dogs.A radioimmunoassay (RIA) for morphine in canine serum was developed from a commercial kit for human serum morphine detection (Diagnostic Products Corporation, Los Angeles). Human serum calibrators were replaced with equivalent standards prepared in canine serum. The limit of sensitivity was 2.0 ng/mL, the intraassay coefficient of variation was 5.4%, and the interassay coefficient of variation was 14.6%. Manufacturer's estimates of (percent) crossreactivity with morphine metabolites were morphine-3-glucuronide (0.035%), morphine-6-glucuronide (0.16%), codeine (0.06%), and normorphine (9.2%).It was concluded that the IM route of administration is an effective method for rapid and complete delivery of a dosage of MS into the systemic circulation in dogs. (Abstract shortened by UMI.).Source: Masters Abstracts International, Volume: 30-03, page: 0661