In patients with cannabinoid‑hyperemesis syndrome who have persistent vomiting and poor oral intake, should prophylactic thiamine be administered and what is the recommended dosing regimen?

Thiamine Prophylaxis in Cannabinoid Hyperemesis Syndrome

Yes, prophylactic thiamine should be administered to patients with cannabinoid hyperemesis syndrome who have persistent vomiting and poor oral intake, using 200-300 mg IV daily until vomiting resolves and oral intake is adequate. 1

Rationale for Thiamine Administration in CHS

Patients with CHS experiencing persistent vomiting and poor oral intake meet multiple high-risk criteria for thiamine deficiency that mandate prophylactic supplementation:

• Prolonged vomiting is an established indication for thiamine supplementation, with guidelines specifically recommending 200-300 mg daily for patients with prolonged vomiting or dysphagia at risk of thiamine deficiency. 1

• Thiamine stores deplete rapidly—within just 20 days of inadequate intake—making CHS patients with persistent vomiting and poor oral intake critically vulnerable to developing Wernicke's encephalopathy. 1

• The hyperemetic phase of CHS can last days, during which patients have essentially zero oral intake combined with increased metabolic demands from repeated vomiting, creating a perfect storm for thiamine depletion. 2

Recommended Dosing Regimen

Intravenous Route (Preferred During Active Vomiting)

• Administer 200-300 mg IV thiamine daily for patients with active persistent vomiting and poor oral intake, continuing until vomiting resolves and adequate oral intake is established. 1

• The IV route is mandatory during active vomiting because oral absorption is unreliable when patients cannot tolerate oral intake or are actively vomiting. 1

• Thiamine must be given BEFORE any glucose-containing IV fluids to prevent precipitating acute Wernicke's encephalopathy, as glucose administration in thiamine-depleted patients can trigger irreversible neurological damage. 1, 3

Transition to Oral Therapy

• Transition to oral thiamine 100-300 mg daily once the patient can tolerate oral intake adequately, vomiting has ceased, and there is no severe dysphagia compromising absorption. 3

• Continue oral thiamine for 2-3 months after resolution of symptoms to fully replenish tissue stores, as standard multivitamins containing only 1-3 mg are inadequate for recovery. 1

Clinical Context and Risk Stratification

The CHS population has several overlapping risk factors that amplify thiamine deficiency risk:

• Many CHS patients have concurrent alcohol use or poor nutritional habits, with 30-80% of alcohol-dependent individuals showing thiamine deficiency. 1

• The cyclic nature of CHS means repeated episodes of vomiting, with each episode potentially depleting thiamine stores further if not adequately repleted between cycles. 2

• CHS patients often present to emergency departments multiple times before diagnosis, meaning cumulative vomiting episodes across presentations create compounding deficiency risk. 2, 4

Critical Timing Considerations

• Initiate thiamine immediately upon presentation with persistent vomiting and poor oral intake—do not wait for laboratory confirmation, as treatment is safe, inexpensive, and potentially life-saving. 1

• For patients requiring IV dextrose for hypoglycemia or dehydration, administer thiamine concurrently with or immediately before glucose-containing fluids. 1, 3

• The first 3-4 days are most critical for preventing Wernicke's encephalopathy in high-risk patients with persistent vomiting. 3

Safety Profile

• Thiamine has no established upper limit for toxicity, with excess simply excreted in urine, making prophylactic administration extremely safe. 1, 3

• High IV doses (>400 mg) may cause mild nausea, anorexia, or mild ataxia, but anaphylaxis is rare. 1, 3

• The benefit-risk ratio is overwhelmingly favorable even in the absence of confirmed deficiency, given the catastrophic consequences of untreated Wernicke's encephalopathy versus minimal adverse effects. 1

Common Pitfalls to Avoid

• Do not rely on standard IV multivitamins (containing only 2-6 mg thiamine) as adequate prophylaxis in high-risk CHS patients with persistent vomiting—this dose is insufficient. 1

• Do not wait for thiamine levels before treating—red blood cell thiamine diphosphate (ThDP) is the only reliable test, but empiric treatment should begin immediately as results take days and deficiency can cause irreversible damage within that timeframe. 1

• Do not assume oral thiamine is adequate during active vomiting—absorption is unreliable and IV administration is mandatory until vomiting ceases. 1

• Do not discontinue thiamine too early—continue for 2-3 months after symptom resolution to fully replenish tissue stores, as premature discontinuation is the most common cause of relapse. 1

Monitoring and Follow-Up

• Clinical improvement is the best indicator of adequate response—resolution of confusion, weakness, or neurological symptoms suggests adequate repletion. 3

• If laboratory confirmation is needed, measure red blood cell or whole blood thiamine diphosphate (ThDP), not plasma thiamine, as this is the only reliable marker unaffected by inflammation. 1, 3

• Reassess nutritional status and thiamine supplementation needs at each CHS episode, as recurrent vomiting creates ongoing risk. 1