Therapy with β2-adrenoreceptor-agonists in case of postponing delivery is controversial because of the range of adverse effects. A well-known β2-agonist is fenoterol which is administered via infusion or injection. All labour inhibitors are effective in decreasing uterus contractions or even stop them. However, the delivery is only postponed for several hours or days. This extra time gives the opportunity to increase the fetal condition by giving corticosteroids.
β2-agonists have their main adverse effects on the circulatory system: tremors in hand and feet, transpiration, nervous feeling. Other side effects involve nausea and vomiting. Pulse and blood pressure need to be monitored frequently. The fetus can display tachycardia.
Why are pulse and blood pressure monitored with β2-agonists in pregnancy?
Extra info: β2-agonists act the opposite of β-blockers: where the β-blockers’ main action is that of decreasing heart rate, β2-agonists increase it. β-blockers also cause vasoconstriction, which is an unwanted effect for hypertensive patients. In practice, this vasoconstriction is relatively small and doesn’t pose danger for the patient.