Which uterotonic is contraindicated in a patient with a history of asthma?

Carboprost (15-Methyl-PGF2α) is Contraindicated in Asthma

Carboprost, a prostaglandin F2α analogue used as a uterotonic agent for postpartum hemorrhage, is contraindicated in patients with asthma due to its potent bronchoconstriction effects. 1

Evidence from Clinical Practice

Real-world data from over 5.6 million delivery hospitalizations demonstrates that carboprost is used significantly less frequently in patients with asthma compared to those without asthma (11.4% vs 18.0%), reflecting clinical awareness of this contraindication. 1 In adjusted analysis, the presence of asthma was associated with a 32% decrease in likelihood of carboprost use (adjusted risk ratio 0.68,95% CI 0.62-0.74). 1

Mechanism of Contraindication

Carboprost is a prostaglandin analogue that can trigger severe bronchospasm in asthmatic patients through direct effects on airway smooth muscle. 1 Patients with asthma have hyperresponsive airways, making them particularly vulnerable to prostaglandin-induced bronchoconstriction, which can precipitate life-threatening asthma exacerbations. 2

Alternative Uterotonic Agents for Asthmatic Patients

When managing postpartum hemorrhage in patients with asthma, the following alternatives should be prioritized:

First-Line Alternatives

• Oxytocin remains the safest first-line uterotonic agent, as it does not cause bronchoconstriction and is the WHO-recommended standard (10 IU intramuscular or intravenous). 3
• Carbetocin is a safe alternative with high-certainty evidence showing similar effectiveness to oxytocin without increased side effects, including no bronchospasm risk. 3

Combination Therapy Options

• Ergometrine plus oxytocin reduces PPH ≥ 500 mL compared to oxytocin alone (RR 0.76,95% CI 0.64 to 0.90), though it may increase nausea, vomiting, and hypertension. 3 Importantly, ergometrine does not cause bronchoconstriction and can be used cautiously in asthmatic patients. 3
• Misoprostol plus oxytocin probably reduces PPH ≥ 500 mL (RR 0.70,95% CI 0.57 to 0.87), though it increases gastrointestinal side effects and fever. 3 Misoprostol does not cause bronchospasm and is safe for asthmatic patients. 3

Critical Clinical Caveat: Beta-Blockers

While not a uterotonic, intravenous labetalol (a beta-blocker used for hypertensive disorders in pregnancy) should also be used with extreme caution in asthmatic patients. 1 The same database study found that IV labetalol use was associated with significantly increased risk of status asthmaticus compared with other antihypertensive medications (6.5 vs 1.7 per 1,000 delivery hospitalizations, P<0.01). 1 Beta-blockers can precipitate severe bronchospasm in asthmatic patients, even beta-1 selective agents, particularly in the setting of active bronchospasm. 2

Practical Management Algorithm

1. Avoid carboprost entirely in any patient with a documented history of asthma, regardless of current control status. 1
2. Use oxytocin as first-line for both prophylaxis and treatment of postpartum hemorrhage. 3
3. If additional uterotonics are needed, choose from ergometrine, misoprostol, or their combinations with oxytocin—all avoid bronchospasm. 3
4. Screen for concurrent beta-blocker use and consider alternative antihypertensives if treating preeclampsia. 1
5. Have bronchodilators immediately available (albuterol, ipratropium) if any respiratory symptoms develop during uterotonic administration. 2, 4