Is Ativan (lorazepam) 2 mg intramuscularly (IM) effective?

Lorazepam 2 mg IM: Efficacy and Clinical Use

Yes, Ativan (lorazepam) 2 mg intramuscularly is effective for acute seizure management and sedation, though it is not the preferred route for status epilepticus when IV access is available. The FDA-approved dosing for preanesthetic sedation is 0.05 mg/kg IM up to a maximum of 4 mg, making 2 mg a standard and effective dose for most adults 1.

Approved Indications and Efficacy

For Status Epilepticus:

• IM lorazepam is not preferred for status epilepticus because therapeutic levels are not reached as quickly as with IV administration 1
• However, when IV access is unavailable, the IM route may prove useful as an alternative 1
• The WHO recommends IV lorazepam as preferred over diazepam when IV access is available; IM phenobarbital may be considered when rectal diazepam is not possible 2
• Historical data shows lorazepam controls status epilepticus in 88% of patients (22 of 25) at doses of 4-8 mg IV, with plasma concentrations between 30-100 ng/mL providing good seizure control 3

For Preanesthetic Sedation:

• The standard IM dose is 0.05 mg/kg up to a maximum of 4 mg, making 2 mg appropriate for a 40 kg (88 lb) adult or as a conservative dose for larger patients 1
• IM lorazepam should be administered at least 2 hours before the anticipated procedure for optimum effect 1
• Following IM administration, lorazepam is completely and rapidly absorbed, reaching peak concentrations within 3 hours 1
• A 4 mg IM dose provides a maximum concentration (Cmax) of approximately 48 ng/mL 1

Pharmacokinetic Considerations

Absorption and Onset:

• IM lorazepam is completely absorbed with peak levels at 3 hours, which is significantly slower than IV administration (initial concentration ~70 ng/mL immediately) 1
• This delayed absorption is why IM is not preferred for acute seizure emergencies requiring rapid control 1
• Research confirms that IM administration of diazepam has erratic absorption, but lorazepam has more reliable IM absorption 2

Duration of Action:

• Lorazepam has a longer duration of anticonvulsant action (up to 72 hours) compared to diazepam (<2 hours) or midazolam (3-4 hours) 4
• The intended effects of recommended doses usually last 6-8 hours 1
• This longer duration means repetitive injections are typically not required for continuing seizure control 3

Dosing Adjustments

Special Populations:

• Elderly patients (>50 years): The standard 2 mg IV dose should not be exceeded; similar caution applies to IM dosing 1
• Hepatic disease: No dosage adjustment needed 1
• Renal disease: No adjustment needed for acute dosing, though caution with frequent repeated doses 1
• Drug interactions: Reduce dose by 50% when coadministered with probenecid or valproate 1

Safety Profile and Adverse Effects

Respiratory Depression:

• This is the most clinically relevant adverse effect, occurring in 0-18% of patients across studies 5
• Moderate-quality evidence shows lorazepam is associated with significantly fewer occurrences of respiratory depression compared to diazepam (RR 0.72,95% CI 0.55 to 0.93) 5
• Equipment to maintain a patent airway should be immediately available 1

Other Adverse Effects:

• Sedation and drowsiness are expected dose-related effects 1
• Enhanced sensitivity to CNS depressants and alcohol may persist beyond 24 hours in rare cases with higher doses 1
• Upper airway obstruction has occurred in rare instances with excessive dosing and oversedation 1
• Paradoxical agitation occurs in approximately 10% of patients treated with benzodiazepines 2

Clinical Context and Alternatives

Comparison to Other Routes:

• For acute agitation, IM midazolam 5 mg is preferred over lorazepam due to more rapid onset (1-2 minutes vs. hours) and shorter duration (15-80 minutes) 6
• For seizures without IV access, intranasal lorazepam appears as effective as IV lorazepam (RR 0.96,95% CI 0.82 to 1.13) with faster administration 5
• Sublingual lorazepam solution (1 mg median dose) stopped prolonged seizures within 5 minutes in 70% of patients and prevented further repetitive seizures in 66% 7

Important Caveats:

• Regular use can lead to tolerance, addiction, depression, and cognitive impairment 2
• Infrequent, low doses of agents with short half-lives are least problematic for chronic use 2
• The 2 mg dose is below the maximum 4 mg limit, providing a safety margin 1
• When combining with antipsychotics for agitation, reduce the benzodiazepine dose to minimize oversedation risk 2, 6