CARDIOVASCULAR AND METABOLIC RESPONSES TO 2 RECEPTOR-SELECTIVE OPIOIDAGONISTS IN PREGNANT SHEEP

OBJECTIVE: Our purpose was to assess the effects of an intravenous dos e of a highly selective mu-(DALDA) and delta-(DPDPE) opioid peptide to determine which class of peptide has the best clinical potential. STU DY DESIGN: Chronically instrumented pregnant ewes received a 0.3 mg/kg intravenous bolus of each peptide with and without opioid receptor bl ockade by means of a randomized prospective design. RESULTS: Intraveno us DALDA produced only mild hypertension and a loss of heart rate vari ability, whereas DPDPE produced respiratory depression, maternal hyper tension, and a fall in heart rate in both mother and fetus. Uterine bl ood flow, oxygen uptake, and glucose uptake were unchanged with both d rugs. The effects of DALDA but not DPDPE were reversed by opioid recep tor blockade. CONCLUSION: The delta-selective agonist had multiple non opioid adverse effects, whereas the mu-selective agonist was well tole rated by the pregnant ewe, suggesting that mu-selective agonists have better potential for clinical use as an analgesic in pregnancy.