Which fast‑acting medication is appropriate for acute anxiety in an adult without contraindications such as severe respiratory disease, uncontrolled glaucoma, pregnancy, substance‑use disorder, or severe hepatic impairment for short‑term use?

Fast-Acting Anxiety Medication for Acute Use

For acute anxiety in adults without contraindications, lorazepam 2-4 mg IM/IV is the first-line fast-acting medication, offering rapid onset within 15-30 minutes, predictable absorption, and no active metabolites. 1, 2

Primary Recommendation: Lorazepam

Lorazepam is preferred over other benzodiazepines for acute anxiety because it has fast onset of action, rapid and complete absorption, and no active metabolites. 1 The American Academy of Emergency Medicine specifically recommends lorazepam 2-4 mg IM/IV as first-line treatment for acute agitation and anxiety. 2

Key Advantages of Lorazepam:

• Rapid onset: Achieves therapeutic effect within 15-30 minutes 1
• Predictable absorption: Complete absorption via IM or oral routes, unlike diazepam which has erratic IM absorption 1, 3
• No active metabolites: Reduces risk of prolonged sedation and drug accumulation 1
• Therapeutic for withdrawal: If anxiety stems from alcohol or benzodiazepine withdrawal, lorazepam is therapeutic rather than merely symptomatic 2

Dosing Strategy:

• Standard dose: 2-4 mg IM/IV for acute episodes 2
• Oral alternative: 1-2 mg orally for cooperative patients 4
• Duration: Intended for short-term use only (less than 4 months) 4

Alternative: Midazolam for Faster Onset

Midazolam 5 mg IM achieves sedation significantly faster than lorazepam (18.3 minutes vs 32.2 minutes), representing a clinically meaningful 14-minute advantage when rapid control is critical. 2 However, midazolam has a shorter duration of action (82 minutes to arousal vs 217 minutes for lorazepam), requiring more frequent reassessment. 2

Choose midazolam when:

• Speed is paramount (severe acute anxiety requiring immediate control) 2
• Shorter duration of sedation is desirable for frequent reassessment 2
• Patient has seizure history (midazolam provides seizure prophylaxis) 2

Choose lorazepam when:

• Longer duration of anxiolysis is acceptable or desired 2
• Substance use disorder is suspected (covers withdrawal syndromes) 2
• More predictable pharmacokinetics are needed 1

Critical Safety Warnings

Black Box Warnings from FDA:

Lorazepam carries serious risks including respiratory depression, coma, and death when combined with opioids, alcohol, or other CNS depressants. 4 Patients must be warned not to drive or operate machinery until effects are known. 4

Dependence and Withdrawal:

Physical dependence can develop even with prescribed use, and sudden discontinuation causes serious withdrawal symptoms including seizures, psychosis, and suicidal thoughts. 4 Withdrawal symptoms can persist for weeks to over 12 months, including anxiety, insomnia, tremor, and perceptual disturbances. 4, 5

Contraindications:

• Absolute: Allergy to benzodiazepines 4
• Relative cautions: Severe respiratory disease (COPD, sleep apnea), pregnancy (may harm fetus), breastfeeding (passes into breast milk), liver/kidney impairment, history of substance abuse 4

When NOT to Use Benzodiazepines Alone

Benzodiazepines have no antidepressant or analgesic effects and should not be used as monotherapy for anxiety with comorbid depression. 5 For chronic anxiety disorders, SSRIs (sertraline, paroxetine) or SNRIs (venlafaxine) are more appropriate long-term treatments, as benzodiazepines lack evidence for long-term efficacy beyond 4 months. 1, 6

For anxiety with psychotic features, combine lorazepam 2 mg with an antipsychotic (haloperidol 5 mg or olanzapine 10 mg) for more rapid sedation than benzodiazepine monotherapy. 1, 3

Monitoring Requirements

After administration, monitor vital signs and sedation level every 5-15 minutes during the first hour. 2 Watch for:

• Respiratory depression (shallow or slowed breathing) 4
• Excessive sedation 4
• Paradoxical agitation (occurs in 10% of patients, especially elderly and young children) 3

Common Pitfalls to Avoid

• Do not use diazepam IM: Erratic absorption makes it unreliable for acute management 3, 7
• Avoid long-acting benzodiazepines for acute anxiety: Drugs like diazepam cause prolonged hangover effects and unpredictable duration 5, 7
• Do not prescribe beyond short-term need: Risk of dependence increases with duration, and efficacy for chronic anxiety is unproven 4, 5, 7
• Elderly patients require dose reduction: Start at lower doses (0.5-1 mg) due to increased sensitivity and risk of oversedation, tremor, ataxia, and confusion 5