Inhibition of Oxytocin‐Induced Uterine Activity in Midpregnancy by Combined Adrenergic α‐Blockade and β‐Stimulation

Arrest of imminent premature labour by β‐adrenergic stimulation often fails, due to undesirable side effects or lack of effectiveness. Inhibition of oxytocin release from the neurohypophysis by ethanol also has disadvantages. α‐adrenergic stimulation in pregnant and non‐pregnant women increases uterine contractions, while blocking of α‐receptors in non‐pregnant patients has been shown to reduce uterine activity. A combination of adrenergic α‐blockade followed by β‐stimulation therefore might be more effective than β‐stimulation alone in the treatment of premature labour. This combined regimen was used in 6 women at 16–20 weeks of pregnancy. The response to oxytocin‐induced uterine contractions was measured. In mid‐pregnancy, blockade of α‐receptors did not reduce oxytocin‐induced activity, β‐stimulation reduced the uterine activity; this reduction seemed to be independent of α‐blockade. The combination of α‐blockade and β‐stimulation did not seem to be superior to β‐stimulation alone.