What is the recommended dose of thiamine for a pregnant woman with hyperemesis gravidarum?

Thiamine Dosing for Hyperemesis Gravidarum in Pregnancy

For pregnant women with hyperemesis gravidarum, administer thiamine 200-300 mg daily orally, or 100 mg intravenously/intramuscularly if unable to tolerate oral medication or if clinical suspicion of acute deficiency exists. 1, 2

Assessment of Severity

Severity of hyperemesis gravidarum can be assessed using:

• Weight loss >5% of pre-pregnancy weight
• Dehydration
• Electrolyte abnormalities
• Ketonuria (though not an indicator of dehydration) 3

Thiamine Dosing Algorithm

Mild-Moderate Hyperemesis (Outpatient Management)

• Oral thiamine 200-300 mg daily 1, 2
• Plus vitamin B co strong 1-2 tablets three times daily 1
• Continue until vomiting resolves

Severe Hyperemesis (Requiring Hospitalization)

• If unable to tolerate oral medication or with clinical suspicion of acute deficiency:
  • Intravenous thiamine 100 mg daily 4, 5
  • Continue until able to tolerate oral supplements

Critical Cases (Neurological Symptoms Present)

• For patients with signs of Wernicke's encephalopathy (mental confusion, oculomotor disturbances, ataxia):
  • Immediate intravenous thiamine 500 mg or higher daily 5, 6
  • Continue high-dose therapy for several days, then transition to maintenance dose

Rationale and Evidence

Thiamine supplementation is crucial in hyperemesis gravidarum to prevent Wernicke's encephalopathy, which can develop rapidly in pregnant women due to:

• Increased thiamine demand during pregnancy
• Rapid depletion with persistent vomiting (typically after 7 weeks of vomiting) 5
• Risk of exacerbation when glucose is administered without thiamine 5

The American Association for the Study of Liver Diseases and American Gastroenterological Association both recommend immediate thiamine supplementation for women with hyperemesis gravidarum 1, 2.

Warning Signs Requiring Escalation of Care

Escalate to IV thiamine if any of the following occur:

• Persistent vomiting >2 weeks
• Weight loss >5% of pre-pregnancy weight
• Inability to tolerate oral medications
• Neurological symptoms (double vision, blurred vision, confusion, ataxia) 5
• Before administering IV glucose solutions 5

Common Pitfalls to Avoid

1. Inadequate thiamine dosing (subtherapeutic dosing occurred in 63.6% of reported Wernicke's encephalopathy cases) 5
2. Administering IV glucose without thiamine (can precipitate or worsen Wernicke's encephalopathy) 5
3. Delaying thiamine supplementation until neurological symptoms appear
4. Failing to recognize the rapid progression of thiamine deficiency in pregnancy compared to non-pregnant states 6

Early and adequate thiamine supplementation is essential to prevent serious complications including chronic cognitive disorders (65.4% of untreated cases), pregnancy loss (50%), and maternal death (5%) 5.