What medication can be given to a 9-month pregnant woman in labor for nausea and vomiting?

Antiemetic Medications for Labor-Related Nausea and Vomiting

For a pregnant woman in active labor experiencing vomiting, ondansetron or metoclopramide are the most appropriate first-line antiemetic medications, with ondansetron showing superior efficacy for severe vomiting. 1

Recommended Medications

First-Line Options

Ondansetron (5-HT3 antagonist):

• Demonstrated effectiveness for intraoperative and postoperative nausea/vomiting during cesarean delivery 1
• Superior to metoclopramide specifically for controlling severe vomiting (p = 0.042) 2
• Typical dosing: 4-8 mg IV, can be administered slowly over 1-2 minutes 3
• Important caveat: Use with caution if early labor (before 10 weeks gestation theoretically), though this is rarely relevant at 9 months; small risk of QT prolongation exists 4, 3

Metoclopramide (dopamine antagonist):

• Equally effective as ondansetron for nausea, though slightly less effective for severe vomiting 2
• Considered safe in pregnancy with large cohort data showing no increased congenital malformations 1, 4
• Typical dosing: 10 mg IV administered slowly over 1-2 minutes 5
• May cause acute dystonic reactions (treat with 50 mg diphenhydramine IM if occurs) 5

Combination Therapy for Refractory Cases

Multimodal approach is strongly recommended for optimal control: 1

• Combine 5-HT3 antagonist (ondansetron) with either dexamethasone or droperidol for significantly better efficacy than single agents 1
• Combination regimens reduce both intraoperative and postoperative nausea/vomiting more effectively 1

Corticosteroids (Adjunctive)

Dexamethasone or methylprednisolone:

• Effective for reducing intraoperative nausea and vomiting when combined with other antiemetics 1
• At 9 months gestation, the early pregnancy concerns about corticosteroids are not relevant 1, 4
• Methylprednisolone or prednisolone preferred as they are metabolized in the placenta 1, 4

Important Clinical Considerations

Address Underlying Causes First

• Maternal hypotension from regional anesthesia is the most common cause of nausea/vomiting during labor/delivery 1
• Fluid preloading with crystalloid or colloid reduces hypotension and associated nausea/vomiting 1
• IV ephedrine or phenylephrine administration prevents hypotension-related symptoms 1
• Lower limb compression (bandages, stockings, or inflatable boots) also reduces anesthesia-related hypotension 1

Medications to Avoid in Labor

• Anticholinergics (scopolamine): More effective for postoperative rather than intraoperative nausea 1
• Supplemental oxygen, IV fluids alone, acupressure/acupuncture: Not effective for reducing intraoperative nausea or vomiting 1

Safety Monitoring

• Monitor for QT prolongation with ondansetron, especially if patient has electrolyte abnormalities, congestive heart failure, or bradyarrhythmias 3
• Watch for serotonin syndrome if ondansetron used with other serotonergic drugs (SSRIs, SNRIs, fentanyl) 3
• Monitor for dystonic reactions with metoclopramide (tremor, rigidity, muscle spasms) 5

Practical Algorithm

1. Assess and correct hypotension first (fluids, vasopressors, positioning) 1
2. For mild-moderate vomiting: Metoclopramide 10 mg IV OR ondansetron 4-8 mg IV 1, 5
3. For severe vomiting: Ondansetron 8 mg IV (superior efficacy) 2
4. For refractory symptoms: Add dexamethasone 4-8 mg IV to ondansetron 1
5. If dystonic reaction occurs: Diphenhydramine 50 mg IM immediately 5