Phenobarbital for Alcohol Withdrawal: Bedside Teaching Guide

1. First question: how likely is severe withdrawal?

Use PAWSS up front.

PAWSS ≥ 4
or prior DTs
or withdrawal signs despite positive EtOH level
        ↓
HIGH-RISK withdrawal pathway

PAWSS < 4
and >2 days since last drink
        ↓
MODERATE-RISK withdrawal pathway

The order set uses PAWSS questions such as prior withdrawal, withdrawal seizures, delirium tremens, blackouts, recent intoxication, alcohol plus sedatives, alcohol plus other substances, BAL >200, and autonomic signs like HR >120, tremor, sweating, agitation, or nausea.

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2. Second question: how likely is respiratory compromise?

Before choosing the dose, sort the patient into a sedation/respiratory-risk bucket.

Minimal respiratory risk
- Age <65
- No recent benzodiazepines
- No recent opioids
- Not requiring supplemental oxygen
- No major pulmonary/liver issue

Moderate respiratory risk
- Age ≥65
- Received benzodiazepines or opioids
- On supplemental O2
- Liver disease
- Pneumonia
- Chest tubes
- Other respiratory vulnerability

High respiratory risk
- Very frail or tenuous respiratory status
- Significant hypoventilation risk
- Multiple sedating exposures
- Concerning pulmonary disease/oxygenation

The order set specifically calls out age ≥65, benzodiazepine/opioid exposure, supplemental oxygen requirement, liver disease, pneumonia, and chest tubes as reasons to lower the phenobarbital dose.

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3. Dosing map

High-risk withdrawal: PAWSS ≥4 / prior DTs / withdrawal with positive EtOH

HIGH withdrawal risk
        ↓
Assess respiratory/sedation risk
        ↓
Minimal risk      → 15 mg/kg IV IBW
Moderate risk     → 10 mg/kg IV IBW
High risk         →  6 mg/kg IV IBW

Withdrawal risk	Respiratory/sedation risk	Initial phenobarbital dose
High	Minimal	15 mg/kg IV IBW
High	Moderate	10 mg/kg IV IBW
High	High	6 mg/kg IV IBW

The draft order set lists consideration ranges of 12–15 mg/kg, 10–12 mg/kg, and 6–10 mg/kg respectively for these high-withdrawal-risk categories.

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Moderate-risk withdrawal: PAWSS <4 and >2 days since last drink

MODERATE withdrawal risk
        ↓
Assess respiratory/sedation risk
        ↓
Minimal risk      → 10 mg/kg IV IBW
Moderate risk     →  8 mg/kg IV IBW
High risk         →  5 mg/kg IV IBW

Withdrawal risk	Respiratory/sedation risk	Initial phenobarbital dose
Moderate	Minimal	10 mg/kg IV IBW
Moderate	Moderate	8 mg/kg IV IBW
Moderate	High	5 mg/kg IV IBW

The order set lists consideration ranges of 10–12 mg/kg, 8–10 mg/kg, and 5–8 mg/kg respectively in the moderate-withdrawal-risk pathway.

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4. Bedside mental model

Alcohol withdrawal risk tells you whether the patient needs a bigger hammer.

Respiratory risk tells you how hard you can safely swing it.

So the dose is not based only on withdrawal severity.

A patient can have:

Severe withdrawal risk + low respiratory risk
        → larger load is reasonable

Severe withdrawal risk + high respiratory risk
        → still treat withdrawal, but lower initial dose and monitor closely

Lower withdrawal risk + high respiratory risk
        → conservative dose, close reassessment

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5. Safety checklist after ordering phenobarbital

Before / during administration:
□ Use ideal body weight dosing
□ IVPB in NS 50 mL
□ Hang over 15 minutes
□ Do not exceed 60 mg/min
□ Place on capnography / ETCO2 monitoring
□ Watch for respiratory depression
□ Contact MD if HR <55

The order set requires capnography monitoring, monitoring for respiratory depression, avoiding infusion rates above 60 mg/min, and contacting the physician for HR <55. It also includes a communication order to place the patient on ETCO₂ monitoring.

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6. Practical bedside diagram

Patient with alcohol withdrawal risk
        ↓
Calculate PAWSS
        ↓
 ┌───────────────────────────────┐
 │ PAWSS ≥4 / prior DTs /         │
 │ withdrawal + positive EtOH     │
 └───────────────────────────────┘
        ↓
 HIGH-RISK withdrawal pathway
        ↓
Choose dose by respiratory risk:
15 mg/kg  → minimal risk
10 mg/kg  → moderate risk
 6 mg/kg  → high risk


 ┌───────────────────────────────┐
 │ PAWSS <4 and >2 days           │
 │ since last drink               │
 └───────────────────────────────┘
        ↓
 MODERATE-RISK withdrawal pathway
        ↓
Choose dose by respiratory risk:
10 mg/kg  → minimal risk
 8 mg/kg  → moderate risk
 5 mg/kg  → high risk

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7. Summary

“Phenobarbital dosing here is two-step: first PAWSS tells us withdrawal severity, then respiratory/sedation risk tells us how much to load. High withdrawal risk gets 15, 10, or 6 mg/kg based on respiratory risk; moderate withdrawal risk gets 10, 8, or 5 mg/kg. Everyone needs capnography and respiratory monitoring.”