Respiratory effects and tolerability of Mr 2264 Cl. A new opiate partial agonist in comparison with morphine and placebo.

In this double-blind, randomised, placebo-controlled cross-over study the respiratory effects of M(r) 2264 Cl 2 x 5 mg i.v., a new partial opiate receptor agonist, were investigated and compared with the respiratory effects of morphine 2 x 10 mg i.v. and placebo. As primary end-points, the slope of the rebreathing curve (dV'/dPCO2ET) and V55 (ventilation at PCO2ET = 55 mm Hg) were determined by Read's rebreathing method. The incidence of adverse events was also documented and compared. The respiratory depression after the intravenous administration of 5 mg and 10 mg M(r) 2264 Cl was comparable to the decreased sensitivity of the respiratory centre after the 20 mg morphine i.v. In contrast to morphine, a ceiling effect of M(r) 2264 Cl was found. The tolerability of M(r) 2264 Cl was comparable to that of morphine.