What is the recommended dose of vitamin B6 for nausea?

Vitamin B6 Dosing for Nausea

For pregnancy-related nausea, start with 10-25 mg of vitamin B6 orally every 8 hours (three times daily), which can be titrated based on symptom severity and response. 1

Recommended Dosing Algorithm

For Pregnancy-Related Nausea and Vomiting

Initial therapy:

• Start with 10 mg orally every 8 hours (three times daily) for mild to moderate symptoms 1, 2
• If inadequate response after 24-48 hours, increase to 25 mg every 8 hours (three times daily) 1, 2
• Maximum recommended dose is 25 mg three times daily (75 mg total daily) 1

Treatment escalation if monotherapy insufficient:

• Add doxylamine (H1-receptor antagonist) to vitamin B6 for combination therapy, which is FDA-approved and recommended by the American College of Obstetricians and Gynecologists 1
• The combination of 40 mg vitamin B6 with 40 mg doxylamine daily has established safety in pregnancy 3

Evidence Supporting Efficacy

Vitamin B6 demonstrates clear benefit for pregnancy nausea:

• In patients with severe nausea (visual analogue scale >7), vitamin B6 at 25 mg every 8 hours significantly reduced nausea scores compared to placebo (mean difference 4.3 vs 1.8, p<0.01) 2
• Vitamin B6 significantly reduced vomiting episodes, with only 8 of 31 patients experiencing vomiting after 3 days of therapy compared to 15 of 28 in the placebo group (p<0.05) 2
• Meta-analysis of 13 trials showed overall reduction in nausea from anti-emetic medication including vitamin B6 (odds ratio 0.17,95% CI 0.13-0.21) 4

Safety Considerations

Established safety profile:

• Harmlessness of oral vitamin B6 during pregnancy has been established for doses up to 40-60 mg/day 3
• The recommended daily intake for adults is 1.3-1.7 mg/day, with an upper tolerable limit of 100 mg/day 5
• Doses used for pregnancy nausea (30-75 mg/day) are well below the toxicity threshold 1, 3

Important caveat on toxicity:

• Chronic intake exceeding 100 mg/day can cause sensory neuropathy 6
• Toxicity primarily occurs with prolonged use of doses >100 mg/day, not with the therapeutic doses recommended for nausea 7

Monitoring Response

Use objective assessment:

• The Motherisk Pregnancy-Unique Quantification of Emesis (PUQE) score can objectively assess severity: mild (≤6), moderate (7-12), or severe (≥13) 1
• Reassess symptoms after 3-4 days of therapy to determine if dose escalation or combination therapy is needed 1, 2

Alternative Dosing Schedules

Some guidelines suggest four times daily dosing:

• An alternative regimen is 10 mg four times daily (40 mg total daily), which may be used alone or in combination with doxylamine 3
• This schedule provides more frequent dosing intervals but similar total daily dose to the three-times-daily regimen 3