Inj. Lorazepam IM (Ativan)

Drug Class & Mechanism

Pharmacokinetics (IM Route)

Note: Diazepam IM is painful and unreliably absorbed - lorazepam IM is preferred when IV access is unavailable. Midazolam peaks faster (30 min IM).

• Morgan & Mikhail's Clinical Anesthesiology, 7e

Indications for IM Use

1. Acute Agitation / Psychiatric Emergency

• Monotherapy: 2-4 mg IM - equivalent efficacy to haloperidol 5 mg
• Combination (most common): Haloperidol 5 mg + Lorazepam 2 mg IM - produces faster sedation than either agent alone; this is the classic "B52" or similar combination used in psychiatric emergencies
• American College of Emergency Physicians: Level B recommendation supports monotherapy with lorazepam for acute agitation
• Useful across diagnoses: mania, schizophrenia, delirium, substance-induced states

2. Status Epilepticus (when IV access unavailable)

• Lorazepam is the most effective benzodiazepine for status epilepticus and treatment of choice for acute seizure control (Harrison's, 2025)
• IV preferred; IM can be used when IV not available
• Dose: 0.1 mg/kg IV (max 4 mg); repeat in 5 min if needed - Rosen's Emergency Medicine
• For SE in adults: 2-4 mg/min IV to total 10-15 mg - Adams & Victor's Neurology
• Always follow with a maintenance anticonvulsant: fosphenytoin, valproate, or levetiracetam

3. Alcohol Withdrawal Seizures

• Lorazepam 2 mg IV/IM; may need repeated doses
• Preferred in liver disease patients (no active metabolites)

4. Preoperative Premedication

• 0.05 mg/kg orally; IM route also used

5. Neuroleptic Malignant Syndrome (NMS)

• IM lorazepam has been used as adjunctive management after antipsychotic withdrawal
• Maudsley Prescribing Guidelines, 15e

Dosage Summary

Adverse Effects

Ventilation must be monitored in all patients receiving benzodiazepines IV; resuscitation equipment and airway-trained personnel must be present.

• Morgan & Mikhail's Clinical Anesthesiology, 7e

Contraindications / Precautions

• Absolute: Acute narrow-angle glaucoma, severe respiratory insufficiency (unless intubated), hypersensitivity to benzodiazepines
• Caution: Hepatic impairment (dose reduction), elderly (prolonged effect), co-administration with opioids or other CNS depressants (synergistic respiratory depression)
• Pregnancy: Use minimal effective dose; avoid if possible
• COPD / Obstructive sleep apnea: High risk of respiratory depression

Drug Interactions

• Opioids: Marked synergistic respiratory depression and hypotension
• CNS depressants (alcohol, barbiturates, antipsychotics): Additive sedation
• Cimetidine: Inhibits hepatic metabolism, prolongs effect
• Volatile anesthetics: Lorazepam reduces minimum alveolar concentration by up to 30%

Reversal

• Flumazenil (competitive benzodiazepine antagonist): reverses sedation and respiratory depression
• Caution: short duration of action (may need repeated doses); can precipitate withdrawal seizures in chronic users
• Miller's Anesthesia, 10e

Key Clinical Points

1. Lorazepam IM is reliably absorbed - unlike diazepam IM
2. Onset slower than midazolam IM (90 min vs. 30 min peak) - prefer midazolam if very rapid effect needed
3. No active metabolites - safer in liver disease than diazepam
4. Clinical duration is often prolonged despite moderate half-life, due to high receptor affinity
5. For status epilepticus, always follow with a long-acting anticonvulsant (fosphenytoin, VPA, levetiracetam)
6. In delirium, benzodiazepines can worsen cognitive dysfunction - dexmedetomidine preferred for non-alcohol/non-withdrawal ICU delirium