Phenobarbital Dosing for Alcohol Withdrawal Syndrome
For alcohol withdrawal syndrome, phenobarbital should be administered at an initial IV/SC bolus dose of 1-3 mg/kg followed by a maintenance infusion of 0.5 mg/kg/hour, with a usual maintenance dose of 50-100 mg/hour. 1
Initial Dosing Strategies
Phenobarbital can be administered using two main approaches for alcohol withdrawal:
Front-Loading Strategy
- Loading dose: 10 mg/kg IV infusion over 30 minutes 2
- This approach is associated with significantly lower mechanical ventilation rates and reduced need for continuous sedative infusions
- Particularly useful for benzodiazepine-resistant alcohol withdrawal
Intermittent Dosing Strategy
- Initial dose: 1-3 mg/kg IV/SC bolus 1
- Followed by: Starting infusion of 0.5 mg/kg/hour
- Usual maintenance dose: 50-100 mg/hour 1
Oral Dosing for Withdrawal Management
For patients who can tolerate oral medications or for gradual withdrawal:
- Substitution approach: 30 mg phenobarbital for each 100-200 mg of barbiturate the patient has been taking 3
- Total daily dose: Divided into 3-4 doses, not to exceed 600 mg daily 3
- If withdrawal symptoms appear on first day, a loading dose of 100-200 mg IM may be administered 3
Tapering Protocol
After stabilization:
- Standard taper: Decrease total daily dose by 30 mg per day as long as withdrawal proceeds smoothly 3
- Alternative taper: Decrease daily dosage by 10% if tolerated by patient 3
- If withdrawal symptoms appear, maintain dosage at that level or increase slightly until symptoms disappear 3
Monitoring Parameters
- Vital signs, especially respiratory rate and blood pressure
- Level of consciousness and sedation
- Signs of withdrawal (tremors, agitation, hallucinations)
- Watch for paradoxical excitement in elderly patients 1
- Monitor for adverse effects: hypotension, nausea, vomiting, Stevens-Johnson syndrome, angioedema, rash, agranulocytosis, thrombocytopenia 1
Important Considerations
- Phenobarbital shows a strong linear correlation between dose and plasma concentration, making dosing relatively predictable 4
- Phenobarbital may be particularly useful in benzodiazepine-resistant alcohol withdrawal 5
- Recent evidence suggests phenobarbital protocols may result in lower rates of delirium compared to benzodiazepine-based protocols 6
- Thiamine (100-300 mg/day) should be administered concurrently to prevent Wernicke's encephalopathy 1
Cautions
- Lethal dose of barbiturates is far less if alcohol is also ingested 3
- Respiratory depression is a potential concern, though front-loaded phenobarbital has not shown increased rates of respiratory failure compared to intermittent dosing 2
- Barbiturates do not have analgesic effects; opioids may be necessary for patients with pain 1
Alternative Approach for Severe Cases
For benzodiazepine-resistant severe alcohol withdrawal:
- Initial dose of 260 mg IV push
- Followed by 130 mg IV push every 15 minutes as needed 2
This evidence-based approach to phenobarbital dosing provides effective management of alcohol withdrawal while minimizing complications such as respiratory depression and the need for mechanical ventilation.