Benzodiazepines ranked by half-life

Every benzodiazepine used in psychiatry ranked by half-life, from ultra-short-acting midazolam to long-acting diazepam and clonazepam. Half-life determines onset, duration, withdrawal difficulty, and clinical use case.

Medically reviewed by Shariq Refai, MD, MBA Last reviewed: July 2026

Ranking (shortest to longest effective half-life)

Ultra-short (half-life under 6 hours):

Midazolam (Versed): 1.5 to 3 hours. IV/IM for procedural sedation, seizure aborting. Not used for chronic anxiety or sleep.
Triazolam (Halcion): 1.5 to 5 hours. Sleep initiation only. Rarely first-line due to anterograde amnesia and rebound insomnia risk.

Short (6 to 12 hours):

Alprazolam (Xanax): 6 to 12 hours (parent), 12 to 15 hours (extended-release). Anxiety and panic. Notoriously difficult to taper because of interdose withdrawal.
Oxazepam (Serax): 4 to 15 hours. Anxiety and alcohol withdrawal. No active metabolites; preferred in hepatic impairment.

Intermediate (12 to 24 hours):

Lorazepam (Ativan): 10 to 20 hours. Anxiety, alcohol withdrawal, procedural sedation, catatonia. No active metabolites; preferred in hepatic impairment and older adults.
Temazepam (Restoril): 8 to 22 hours. Sleep maintenance. No active metabolites.
Estazolam (ProSom): 10 to 24 hours. Sleep. Rarely used.

Long (24 to 100 hours effective):

Clonazepam (Klonopin): 30 to 40 hours. Anxiety, panic disorder, seizure disorders. Long half-life makes tapering easier than shorter-acting drugs.
Diazepam (Valium): parent 20 to 100 hours; active metabolite desmethyldiazepam 30 to 200 hours. Anxiety, alcohol withdrawal, muscle spasm, seizures. Standard reference drug for benzodiazepine equivalence.
Chlordiazepoxide (Librium): parent 5 to 30 hours; active metabolites extend effective half-life to 40 to 100 hours. Alcohol withdrawal, anxiety.
Flurazepam (Dalmane): parent 2 to 3 hours; active metabolite N-desalkylflurazepam 40 to 250 hours. Sleep. Rarely used due to very long active metabolite.
Clorazepate (Tranxene): prodrug converted to desmethyldiazepam. Effective half-life 30 to 200 hours. Anxiety.
Quazepam (Doral): parent 25 to 41 hours; active metabolites longer. Sleep. Rarely used.

What half-life predicts clinically

Onset speed: Roughly inverse to half-life. Ultra-short-acting drugs (midazolam, triazolam) reach peak concentration fastest. Diazepam is also relatively fast onset despite long half-life. Clonazepam is intermediate. Oxazepam is slower.

Duration of therapeutic effect: Roughly proportional to half-life. Alprazolam wears off in 4 to 6 hours; clonazepam lasts 8 to 12+ hours; diazepam effectively lasts days after a single dose.

Interdose withdrawal risk: Short-acting benzodiazepines cause dips in plasma level between doses, producing rebound anxiety, insomnia, and physical symptoms in the hours before the next dose. Alprazolam and lorazepam are notorious for this. Long-acting drugs (diazepam, clonazepam) have stable levels and minimal interdose withdrawal.

Withdrawal difficulty: Short-acting drugs are harder to taper because the interdose withdrawal makes every dose reduction acute. Standard clinical practice is to convert short-acting drugs to diazepam or clonazepam equivalents before tapering. See the benzodiazepine equivalents calculator.

Accumulation with chronic use: Long-acting drugs accumulate to higher steady-state levels, particularly in older adults and hepatic impairment. Diazepam and its metabolite desmethyldiazepam can persist for days.

Cognitive effects in older adults: Long-acting drugs cause more cognitive slowing and fall risk in older adults due to accumulation. Beers Criteria specifically flag long-acting benzodiazepines in older adults.

Clinical use by half-life category

Ultra-short and short-acting: procedural sedation, acute anxiety attacks, sleep initiation, seizure aborting. Not appropriate for maintenance anxiety treatment due to interdose withdrawal and dependence risk.

Intermediate: alcohol withdrawal management (lorazepam, oxazepam), anxiety in older adults or hepatic impairment (lorazepam, oxazepam), catatonia (lorazepam is first-line).

Long-acting: alcohol withdrawal management (diazepam, chlordiazepoxide), maintenance anxiety treatment when a benzodiazepine is indicated (clonazepam), status epilepticus (diazepam, lorazepam), muscle spasm (diazepam).

Common questions

Which benzodiazepine has the longest half-life? Diazepam and its active metabolite desmethyldiazepam have the longest effective half-life, up to 200 hours (about 8 days). Flurazepam's active metabolite N-desalkylflurazepam is similar. This is why diazepam accumulation in older adults is a real clinical concern.

Which has the shortest half-life? Midazolam and triazolam at 1.5 to 5 hours. Midazolam is used almost exclusively for procedural sedation. Triazolam is rarely used now due to rebound insomnia risk.

Why is alprazolam so hard to stop? Its half-life (6 to 12 hours for immediate release) is short enough that plasma levels dip between doses, producing interdose withdrawal that patients often interpret as returning anxiety. This drives escalation. Alprazolam has the highest abuse liability and treatment difficulty among benzodiazepines. Standard tapering approach is to convert to clonazepam or diazepam equivalents before reducing dose.

Why is lorazepam preferred in older adults? Lorazepam has no active metabolites and moderate half-life (10 to 20 hours). Older adults and patients with hepatic impairment can clear it via glucuronidation (which is preserved with aging) rather than hepatic oxidation. This produces predictable pharmacokinetics without accumulation. Oxazepam and temazepam share this metabolic advantage.

Which benzodiazepine is best for sleep? Depends on the sleep problem. Sleep initiation: short-acting (triazolam, zolpidem, zaleplon, though the last two are not technically benzodiazepines). Sleep maintenance: intermediate-acting (temazepam, estazolam). Not first-line for chronic insomnia; CBT-I is first-line.

Which benzodiazepine is best for panic disorder? Clonazepam is the most commonly used long-term due to its longer half-life (30 to 40 hours) and lower interdose withdrawal than alprazolam. First-line for panic disorder is an SSRI or SNRI; benzodiazepine augmentation or short-term use may be considered.

Are benzodiazepines dangerous long-term? Chronic benzodiazepine use is associated with cognitive impairment, falls, motor vehicle accidents, dependence, and cognitive decline in older adults. Risk-benefit is usually poor for chronic use. Short-term or intermittent use for specific situations is often reasonable. See the anticholinergic burden and discontinuation syndromes pages.

Sources

Ashton CH. The Ashton Manual: Benzodiazepines: how they work and how to withdraw. Newcastle University, 2002.
FDA prescribing information for each benzodiazepine via DailyMed.
American Geriatrics Society 2023 Updated AGS Beers Criteria. J Am Geriatr Soc. 2023;71(7):2052-2081.
Griffin CE, Kaye AM, Bueno FR, Kaye AD. Benzodiazepine pharmacology and central nervous system-mediated effects. Ochsner J. 2013;13(2):214-223.

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