What anti-emetics are safe for use during pregnancy?

Safe Anti-Emetics for Pregnancy

Ondansetron, metoclopramide, and certain steroids are considered safe and effective for treating nausea and vomiting during pregnancy, with metoclopramide and ondansetron being first-line options after non-pharmacological approaches. 1

First-Line Approaches

Non-Pharmacological Options

• Diet and lifestyle modifications:
  • Small, frequent, bland meals
  • BRAT diet (bananas, rice, applesauce, toast)
  • High-protein, low-fat meals
  • Avoiding spicy, fatty, acidic, and fried foods
  • Identifying and avoiding specific triggers 1

First-Line Pharmacological Options

1. Vitamin B6 (Pyridoxine)

   • Dosage: 10-25 mg every 8 hours 1
   • Safe and effective for mild nausea

2. Ginger

   • Dosage: 250 mg capsule 4 times daily 1
   • Natural option with good safety profile

3. H1-Receptor Antagonists

   • Doxylamine: FDA-approved for pregnancy nausea
   • Combination of doxylamine and pyridoxine (10 mg/10 mg or 20 mg/20 mg)
   • Promethazine and dimenhydrinate also considered safe 1

4. Metoclopramide

   • Dosage: 5-10 mg orally every 6-8 hours
   • Meta-analysis of 33,000 first-trimester exposures showed no significant increase in congenital defects (OR 1.14,99% CI 0.93-1.38) 1
   • Should be used as second-line therapy due to risk of extrapyramidal effects 2

Second-Line Options

1. Ondansetron

   • Safe and effective for moderate to severe nausea/vomiting
   • Small increased risk of orofacial clefts (0.03% absolute increase) and ventricular septal defects (0.3% absolute increase) 1
   • Benefits often outweigh risks in moderate-severe cases 2
   • FDA pregnancy data: "Available postmarketing data have not identified a drug associated risk of miscarriage or adverse maternal outcomes" 3

2. Corticosteroids

   • Safe after 10 weeks of gestation (palate formation complete)
   • Preferred options: methylprednisolone or prednisolone (metabolized in placenta)
   • Avoid betamethasone or dexamethasone (nearly 100% placental passage) 1
   • Increased risk of oral clefts if used before 10 weeks gestation 1

Treatment Algorithm Based on Severity

Mild Nausea and Vomiting (PUQE score ≤6)

1. Start with non-pharmacological approaches
2. Add vitamin B6 (pyridoxine) and/or ginger
3. If ineffective, add doxylamine (alone or in combination with pyridoxine)

Moderate Nausea and Vomiting (PUQE score 7-12)

1. Combination of doxylamine and pyridoxine
2. If ineffective, add metoclopramide
3. Consider ondansetron if above treatments fail

Severe Nausea and Vomiting/Hyperemesis Gravidarum (PUQE score ≥13)

1. May require IV hydration (0.9% NaCl with potassium chloride) 2
2. Ondansetron 8 mg every 4-6 hours
3. Consider methylprednisolone or prednisolone (after 10 weeks)
4. Thiamine supplementation (100 mg three times daily) for women with prolonged vomiting 2

Important Considerations and Cautions

• Combination therapy may be needed for refractory cases
• Monitor for adverse effects and discontinue medication if they occur
• Neurokinin-1 antagonists (aprepitant): Limited human data, FDA pregnancy class B, but avoid injection formulation (contains ethanol) 1
• Second-generation antipsychotics (olanzapine): Linked to increased risk of ventricular and septal defects 1
• Early intervention is key to prevent progression to hyperemesis gravidarum 1

The safety of anti-emetics in pregnancy should be balanced against the risks of untreated severe nausea and vomiting, which can lead to dehydration, weight loss, electrolyte imbalances, and poor maternal and fetal outcomes.