Plasma concentration and disposition of buprenorphine after intravenous and intramuscular doses to baboons.

Buprenorphine is a newly-developed strong analgesic. A selected ion monitoring method has been developed to measure its plasma levels over the concentration range 20-3000ng ml-1. Six baboons each received intravenous and intramuscular doses of buprenorphine hydrochloride at a level of 5mg/kg in a cross-over study. The mean peak plasma concentrations (+/-standard deviation) were 2290 +/- 357ng ml-1 and 805 +/- 416ng ml-1 respectively and the corresponding times to the peak levels were 4.0 +/- 1.5 minutes and 30.3 +/- 24.6 minutes suggesting the rapid release of the drug from intramuscular sites. Comparison of areas under the plasma concentration versus time curves to 24 hours after dosing showed the mean bioavailability of buprenorphine from the intramuscular doses was 70% of that from the reference intravenous doses.