---
title: "Barbiturates and Benzodiazepines"
url: https://mghmclean.org/residents/handbk/part2a/barb.htm
description: "Barbiturates and Benzodiazepines - a chapter of the MGH/McLean Residency Training Program in Psychiatry manual."
published: 2026-08-10
updated: 2026-08-10
---

# Barbiturates and Benzodiazepines

Published 2026-08-10

PART 3 / CH 26

Siobhan O’Neill

|  | Barbiturates/Sedative-hypnotics | Benzodiazepines |
|---|---|---|
| Urine Levels | >200ng/ml detectable | >200ng/ml detectable |
| Duration of (+) result | 2-20 days after use | 1-14 days after use |
| Serum Levels | variable | variable |
| Duration of (+) result |  | Depends on half-life. Shortest triazolam 1.5-5.5 hours;longest diazepam, clorazepate, flurazepam (20-100h) |
| Acute intoxication | Sustained vertical and horizontal nystagmus, slurred speech, ataxia.Elevated mood, euphoria; labile mood; increased energy and self-confidence, irritability | Somnolence,slurred speech |

| (cont.’d) | Barbiturates | Benzodiazepines |
|---|---|---|
| Treatment of acute intoxication oroverdose | Respiratory support, restraint if needed. | Respiratory support, restraint if needed. Flumazenil reversal is possible but sz risk.Bdz + EtOH can cause life threatening respiratory depression |
| Chronic use | Physiologic dependence, tolerance. | Physiologic dependence, tolerance. |
| Withdrawal:signs/sx | Onset at 12-24h up to 3-4d, based on half-life.Anxiety, tremors, nightmares, insomnia, anorexia, nausea, vomiting, postural hypotension, seizures, delirium hyperpyrexia. | Onset at 1-8d, based on half-life.**Low dose benzo:**anxiety, agitation, tachycardia, palpitations, anorexia, blurred vision, muscle cramps/spasms, insomnia, nightmares, confusion, psychosis, increased sensitivity to light and noise, paresthesias.**High dose benzo:**(supratherapeutic)as above, plus seizures, hyperpyrexia. |
| Treatment of withdrawal | phenobarbital taper | clonazepam tapermonitor vital signs |