Obstetrics & Gynaecology/Tocolytic

Tocolytics

also: nifedipine tocolysis · atosiban · preterm labour

Overview

Suppress preterm uterine contractions — used to buy ~48 hours for antenatal corticosteroids and in-utero transfer, not to prolong pregnancy indefinitely.

Mechanism

Nifedipine (a calcium-channel blocker, off-label) reduces Ca²⁺-dependent myometrial contraction. Atosiban is a competitive oxytocin-receptor antagonist, blocking oxytocin-driven contraction.

Indications

Preterm labour (to allow steroids + magnesium neuroprotection + transfer)

The agents

NifedipineCCB (off-label)

oral

NICE first-line tocolytic; cross-references the cardiovascular DHP CCB card.

Atosibanoxytocin antagonist

Alternative; fewer maternal cardiovascular effects.

Adverse effects

Nifedipine: hypotension, flushing, headachecommon

Atosiban: nausea, hyperglycaemia (better tolerated)common

Cautions & contraindications

Contraindications to prolonging pregnancyall

Chorioamnionitis, severe pre-eclampsia, significant APH, fetal compromise.

Interactions

Nifedipine + magnesium sulfate → additive hypotension/neuromuscular effects

Monitoring & kinetics

Maternal BP/pulse, fetal wellbeing (CTG)

Short course only (~48 h). Tocolysis is an adjunct to steroids, not a standalone treatment.

Source: NICE NG25 — Preterm labour & birth · BNF — Tocolytics