Is intramuscular administration of Ativan (lorazepam) appropriate when oral or intravenous routes are unavailable, and what are the recommended adult dosing and precautions, especially for elderly or hepatic‑impaired patients?

Intramuscular Lorazepam Administration

Yes, intramuscular administration of Ativan (lorazepam) is appropriate and FDA-approved, with complete absorption (96-100% bioavailability) and rapid onset, making it a suitable alternative when oral or IV routes are unavailable. 1, 2

FDA-Approved Dosing

Preanesthetic Use

• Standard adult dose: 0.05 mg/kg IM up to a maximum of 4 mg 1
• Must be administered at least 2 hours before the anticipated procedure for optimum amnestic effect 1
• Doses of other CNS depressants should be reduced when used concomitantly 1

Status Epilepticus (When IV Unavailable)

• IM lorazepam is not the preferred route for status epilepticus because therapeutic levels are not reached as quickly as IV administration 1
• However, when an IV port is unavailable, the IM route may prove useful 1
• Pediatric guidelines recommend 0.2 mg/kg IM (maximum 6 mg per dose) for seizure management when IV access is unavailable, repeatable every 10-15 minutes 3

Acute Agitation/Delirium

• Standard dose: 1 mg IM for delirium management 3
• Reduced dose for elderly/frail/COPD patients: 0.25-0.5 mg IM instead of standard doses 3
• Combination with antipsychotics is frequently recommended by experts for acute agitation 3

Pharmacokinetic Advantages Over Diazepam

Lorazepam is strongly preferred over diazepam for IM administration because: 3, 4

• Fast onset of action with rapid and complete absorption 3
• No active metabolites 3
• Peak plasma levels reached at approximately 1.15 hours after IM injection 2
• Absolute bioavailability averages 95.9% (essentially complete) 2

In contrast, diazepam should NOT be used IM due to erratic and unreliable absorption, plus risk of tissue necrosis 4

Special Population Dosing

Elderly Patients

• No dosage adjustment needed for acute dosing in elderly patients 1
• However, use reduced doses (0.25-0.5 mg) for frail elderly to minimize adverse effects 3
• Increased fall risk necessitates careful monitoring and environmental safety measures 3

Hepatic Impairment

• No dosage adjustment needed for patients with hepatic disease 1
• This is a significant advantage, as lorazepam undergoes glucuronidation (not oxidative metabolism) 1

Renal Impairment

• No adjustment needed for acute dose administration 1
• Caution with frequent doses over short periods in renal disease patients 1

Critical Safety Precautions

Respiratory Monitoring (Highest Priority)

• Equipment to maintain a patent airway must be immediately available prior to administration 1
• Continuous oxygen saturation monitoring required, especially when combined with other sedatives 3
• Significant risk of respiratory depression, particularly when combined with antipsychotics, other sedatives, or opioids 3

Common Adverse Effects

• Delirium and drowsiness 3
• Paradoxical agitation 3
• Local irritation at injection site 3
• Increased fall risk 3

Drug Interactions

• Reduce doses of other CNS depressants when used concomitantly 1
• Particular caution when co-administered with antipsychotics in elderly or frail patients 3

Clinical Pearls

Absorption characteristics: IM lorazepam demonstrates slightly more rapid uptake than oral administration, with similar plasma levels achieved by 2 hours regardless of route 5. The absorption half-life for IM administration averages 14.2 minutes, significantly faster than oral routes 2.

Duration considerations: The drug should not be used in outpatient settings or in patients with expected hospital stays less than 72 hours due to prolonged duration of action 6. Approximately one-third of peak concentration remains in blood at 24 hours 5.

Benzyl alcohol warning: The FDA label notes that lorazepam injection contains benzyl alcohol and requires special consideration in pediatric use 1.