The effects of opioids on isolated human pregnant uterine muscles.
We determined the effects of fentanyl, sufentanil, morphine, and meperidine on the spontaneous contractility of isolated human pregnant uterine muscle strips. Uterine specimens were obtained from normal full-term parturients undergoing elective lower-segment cesarean delivery. Longitudinal muscle strips were prepared and mounted vertically in tissue chambers to record their isometric tension. Opioid concentration-response curves were constructed after rhythmic contractions were established. The responses were also examined in the presence of opioid receptor blocker, nitric oxide synthase inhibitor, beta-adrenoceptor blocker, or cyclooxygenase inhibitor. Fentanyl and meperidine inhibited uterine contractility in a concentration-dependent manner, their concentration that inhibited 50% being 2.3 x 10(-6) and 1.0 x 10(-3)M, respectively. Sufentanil and morphine had no significant effects on uterine contractility. Pretreatment with either naloxone, N(G)-nitro-L-arginine methyl ester, atenolol, or indomethacin did not affect the uterine responses to opioids. These results demonstrate that fentanyl and meperidine may have direct inhibitory effects on the contractility of the human uterus, though at supraclinical concentrations.


CONCLUSIONS
Opioids do not have a significant effect on spontaneous contractions of gravid human uterine muscle at their clinically relevant concentrations.
Yoo
K Y
KY
Department of Anesthesiology, Chonnam National University Medical School, Kwangju, South Korea. kyyoo@chonnam.ac.kr
Lee
J
J
Kim
H S
HS
Jeong
S W
SW
D000701:Analgesics, Opioid / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011247:Pregnancy; D014599:Uterus / Q000187:drug effects*
D000701:Analgesics, Opioid