What medications can be prescribed for nausea during the first trimester of pregnancy?

From the Guidelines

For nausea during the first trimester of pregnancy, the most effective and safest medication to prescribe is a combination of Vitamin B6 (pyridoxine) and doxylamine, as recommended by the American College of Obstetricians and Gynecologists (ACOG) 1. This combination has been shown to be effective in managing nausea and vomiting of pregnancy (NVP) and has a well-established safety profile.

• Vitamin B6 (pyridoxine) can be prescribed at a dose of 10-25mg every 8 hours,
• while doxylamine can be prescribed at a dose of 12.5mg at night or 12.5mg three times daily. Before starting medication, it is essential to try dietary modifications like eating small, frequent meals, avoiding spicy or fatty foods, and staying hydrated.
• Other options, such as promethazine (Phenergan) 12.5-25mg every 4-6 hours, metoclopramide (Reglan) 5-10mg three times daily, or ondansetron (Zofran) 4-8mg every 8 hours, may be used if the initial treatment is insufficient, but they should be used with caution and under close monitoring due to potential side effects and risks, as reported in recent studies 1. It is crucial to note that most morning sickness resolves by 12-16 weeks of pregnancy, so medication is typically needed only temporarily during the first trimester.
• A study published in 2023 found that metoclopramide 5-10 mg orally, every 6-8 h, is commonly used by pregnant women to treat nausea and vomiting of pregnancy, and the risk of major congenital defects was not significantly increased 1.
• Another study published in 2024 recommended a step-up approach for patients who do not respond to first-line therapy, with metoclopramide and ondansetron as second-line therapies 1.

From the Research

Medications for 1st Trimester Nausea

The following medications can be prescribed for nausea during the first trimester of pregnancy:

• Doxylamine succinate-pyridoxine hydrochloride (Diclegis) 2, 3, 4, 5
• Pyridoxine (Vitamin B6) alone or in combination with doxylamine 3, 6
• Antihistamine (H(1)) blockers 3
• Phenothiazines 3

Safety and Efficacy

These medications have been shown to be safe and effective for the treatment of nausea and vomiting in pregnancy:

• Doxylamine succinate-pyridoxine hydrochloride (Diclegis) has been approved by the US Food and Drug Administration (FDA) for the treatment of nausea and vomiting in pregnancy and has a substantial amount of safety data accumulated over the years 2
• Pyridoxine (Vitamin B6) has been established as harmless during pregnancy for doses up to 40-60mg/day, mainly in combination with doxylamine 6
• Antihistamine (H(1)) blockers and phenothiazines have been shown to be safe and effective, but the magnitude of effect may differ among individual agents 3

Dosage and Administration

The dosage and administration of these medications may vary:

• Doxylamine succinate-pyridoxine hydrochloride (Diclegis) is typically taken as a delayed-release combination pill, 2-4 times per day, depending on symptoms 2, 4
• Pyridoxine (Vitamin B6) can be taken orally, 10mg four times a day, alone or in combination with doxylamine 6