Terbutaline
Brethine
Selective β2-adrenergic agonist (tocolytic / bronchodilator)
β2 agonism → uterine + bronchial smooth-muscle relaxation.
Indications
- •Acute uterine TOCOLYSIS (fetal distress/tachysystole, uterine hyperstimulation, external version, intrauterine resuscitation)
- •Bronchospasm
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Acute tocolysis | 0.25 mg SC or 0.1–0.25 mg IV | — |
Pharmacokinetics
Onset minutes (SC/IV). Short duration.
Hemodynamic effects
Maternal tachycardia, palpitations; the expected β2 effects.
Side effects
- !Maternal tachycardia, arrhythmia, pulmonary edema (esp. with prolonged use + fluids + magnesium)
- !Hyperglycemia, hypokalemia
- !FDA warning against prolonged use for preterm labor
Contraindications
- ×Maternal cardiac disease/tachyarrhythmia
- ×Prolonged use for preterm labor (FDA warning — maternal deaths)
Clinical pearls
- ★The go-to acute intrauterine-resuscitation tocolytic (tachysystole/fetal distress) — relaxes the uterus in seconds to buy time.
- ★Expect maternal tachycardia; avoid prolonged/repeated use (pulmonary edema, cardiac events).
Other drugs in OB / GYN Related
- Oxytocin
Stimulates uterine smooth muscle contraction (uterine OXTR receptors). ADH-like action at high doses.
- Carboprost (Hemabate)
15-methylated synthetic analog of prostaglandin F2α. Binds prostaglandin F receptors on uterine smooth muscle → potent contraction. Also constricts pulmonary smooth muscle → BRONCHOSPASM (contraindication in asthma).
- Methylergonovine (Methergine)
Direct uterine smooth muscle stimulant — potent + sustained contraction. Also vasoconstrictor (especially coronary + cerebral arteries) → CONTRAINDICATED in HTN, preeclampsia, CAD.
- Misoprostol (Cytotec)
Synthetic PGE1 analog. Binds prostaglandin E receptors on uterine smooth muscle → contraction. Also: cytoprotective gastric mucosa (original indication for NSAID-induced ulcers); cervical ripening; GI motility.
Browse all classes: /reference/drugs
Suggested reading
- •Miller's Anesthesia, 9e
- •FDA package insert
