Toxicology & Substance Use · Topic 17 of 17

Substance Use Disorders: Screening & Other Withdrawals

Addiction · screening and withdrawal

Substance Use Disorders: Screening & Other Withdrawals

Ask every adult about alcohol and drugs, intervene briefly and refer — and never stop a benzodiazepine abruptly in a dependent patient.

Key numbers

AUDIT-C positive: ≥ 4 men, ≥ 3 women≥ 4 men / ≥ 3 women

Taper benzodiazepines 5–10% every 2–4 weeks5–10% q2–4 wk

01 · The ruleScreen every adult: alcohol and drugs

USPSTF (grade B): screen all adults 18 and older, including pregnant patients, for unhealthy alcohol use, with brief counseling for risky drinking, and ask about drug use when treatment can be offered or referred.

02 · The ruleSBIRT: screen, intervene, refer

SBIRT: screening rapidly assesses severity of use; a brief intervention builds insight and motivation to change; referral to treatment links patients who need more to specialty care — usable in hospitals, EDs and trauma centers.

03 · AvoidNever stop benzodiazepines abruptly

Do not stop benzodiazepines abruptly in a physically dependent patient — withdrawal can cause seizures and status epilepticus; restart the agent or substitute a long-acting benzodiazepine (diazepam, chlordiazepoxide), then taper.

The rules

Know these

Taper benzodiazepines 5–10% every 2–4 weeksTaper long-term benzodiazepines gradually — start with 5–10% dose reductions every 2–4 weeks, generally no faster than 25% every 2 weeks — adjusting to symptoms and adding CBT.

Barbiturate withdrawal: hospitalize for seizures, deliriumBarbiturate withdrawal resembles alcohol withdrawal: symptoms start 8–12 hours after a short-acting barbiturate, with seizures and delirium possible within 16 hours; nearly every patient stopping abruptly should be hospitalized.

Confirm urine drug screens; immunoassays cross-reactUrine immunoassays cross-react (pseudoephedrine, TCAs and quetiapine can read as amphetamines), and opioid panels detect natural and semisynthetic opioids — fentanyl and methadone need their own tests. Confirm positives with a confirmatory assay.

Presentation

What you'll see

Stimulant withdrawal: fatigue, hunger, depressionCocaine or amphetamine withdrawal ('crash') begins within 24 hours: fatigue, hypersomnia or insomnia, increased appetite, dysphoria and anxiety; it can precipitate major depression and needs close supervision.

Cannabis withdrawal: irritability, insomnia, poor appetiteCannabis withdrawal after heavy use is mild: insomnia, irritability, depression, nausea and anorexia, starting about 12 hours after last use, peaking at 2–3 days and lasting up to 7 days.

Diagnosis & monitoring

Work-up

AUDIT-C positive: ≥ 4 men, ≥ 3 women must knowAUDIT-C — 3 questions on drinking frequency, typical amount and heavy-drinking occasions — is among the most accurate brief alcohol screens; positive at ≥ 4 in men or ≥ 3 in women.

Single question: heavy-drinking days past yearNIAAA single question: "How many times in the past year have you had 5 (men) or 4 (women, anyone over 65) or more drinks in a day?" — one or more is positive.

TAPS tool screens tobacco, alcohol and drugsTAPS: a 4-item past-12-month screen (tobacco, alcohol, prescription misuse, illicit drugs), then a past-3-month assessment; per substance, ≥ 1 flags problem use and ≥ 2 suggests a possible substance use disorder.

Short-acting benzodiazepine withdrawal begins in 1–2 daysBenzodiazepine withdrawal starts 1–2 days after a short-acting agent and several days to a week after a long-acting one: tachycardia, tremor, hyperreflexia, confusion, seizures; alprazolam withdrawal can cause hallucinations.

Red flags & don'ts

Avoid harm

Cannabinoid hyperemesis: haloperidol or topical capsaicin complicationCannabinoid hyperemesis syndrome — cyclic vomiting in frequent cannabis users — is treated with IV fluids, antiemetics, haloperidol and topical capsaicin to the abdomen (anecdotal evidence).

Avoid flumazenil in benzodiazepine-dependent patients avoidFlumazenil can precipitate seizures in benzodiazepine-dependent patients (about 1 in 5 with a seizure disorder) and in co-ingestion of TCAs or antiseizure drugs; it is mainly diagnostic, and sedation recurs within about an hour.

Benzodiazepine or stimulant withdrawal?

Commonly confused

Onset	1–2 days (short-acting) to a week (long-acting)
Main features	Tremor, tachycardia, hyperreflexia, confusion
Main danger	Seizures, status epilepticus
Management	Restart or substitute a long-acting benzodiazepine, then taper

More detail

Reference

Show 5 reference facts

CAGE detects alcohol dependence but misses the wider spectrum of unhealthy use; drug screens include the NIDA Quick Screen (4 questions) and the 8-item ASSIST.

Brief behavioral counseling after a positive alcohol screen reduces heavy drinking episodes and drinking above recommended limits at 6–12 months.

A urine cocaine screen detects benzoylecgonine, so a positive result is not a cross-reaction — unlike most other immunoassays.

Many people who misuse benzodiazepines also drink heavily, and a delayed benzodiazepine withdrawal can complicate alcohol withdrawal.

Reassess benzodiazepine risks and benefits within 1 month of a new prescription — physical dependence can develop quickly; use shared decision-making and tailor the taper to the patient's response.

Pearl

Screen, intervene, refer: a positive screen opens a brief conversation about change, not a lecture.

Sources · USPSTF — Unhealthy Alcohol Use in Adolescents and Adults: Screening and Behavioral Counseling Interventions (2018) · USPSTF — Unhealthy Drug Use: Screening (2020) · Bradley KA et al. AUDIT-C as a brief screen for alcohol misuse in primary care. Alcohol Clin Exp Res 2007;31(7):1208–1217 · SAMHSA — Screening, Brief Intervention, and Referral to Treatment (SBIRT) · NIDA Data Share — Tobacco, Alcohol, Prescription Medication, and Other Substance Use (TAPS) Screening · Merck Manual Professional — Benzodiazepines and Barbiturates · Brunner E et al. Joint Clinical Practice Guideline on Benzodiazepine Tapering: Considerations When Risks Outweigh Benefits. J Gen Intern Med 2025;40(12):2814–2859 · McNeely J et al. Performance of the TAPS Tool for Substance Use Screening in Primary Care Patients. Ann Intern Med 2016;165(10):690–699 · Merck Manual Professional — Amphetamines · Merck Manual Professional — Cocaine (Jun 2026) · Merck Manual Professional — Marijuana (Cannabis) · Merck Manual Professional — Drug Testing · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).