Comparative study on the circulatory and respiratory effects of buprenorphine and methadone

A comparative study on the effects on circulation and respiration of buprenorphine and methadone was performed on a group of four healthy volunteers in a double blind way. Both drugs were given by continuous slow i.v. infusion. Before and after administration of the drugs, the subjects breathed in an open, resp. closed system, gas mixtures of 50% O2 / 50% N2 resp. 50% O2 / 43% N2 / 7% CO2. After each breathing/rebreathing period pupil diameters were measured photographically. The effects on respiration were calculated as shifts in vol. % CO2 necessary to obtain a standard respiratory minute volume. Analysis of variance showed a dose-independent inhibition of respiration of buprenorphine and a dose-dependent inhibition of methadone. Both drugs caused a weakly dose-dependent miosis. There were no significant dose-dependent effects on circulation and both drugs caused a similar side effect profile.