From the FDA Drug Label
The archival medical literature contains many informative references on the management of status epilepticus, among them the report of the working group on status epilepticus of the Epilepsy Foundation of America “Treatment of Convulsive Status Epilepticus” (JAMA 1993; 270:854-859). IM lorazepam is not preferred in the treatment of status epilepticus because therapeutic lorazepam levels may not be reached as quickly as with IV administration
The FDA drug label does not answer the question.
From the Research
There is no significant difference in efficacy between intramuscular (IM) and intravenous (IV) lorazepam for treating catatonia, with both routes being effective in resolving catatonic symptoms, as supported by the most recent and highest quality study 1. The choice between IM and IV routes should be based on practical considerations such as ease of administration, urgency of the situation, and patient factors rather than concerns about differential efficacy.
- The typical dosing for catatonia is 1-2 mg of lorazepam given every 4-6 hours, with gradual titration based on response, as seen in studies 2, 1.
- IV administration provides more rapid absorption and distribution to the brain, which may be advantageous in emergency situations requiring immediate intervention, as noted in 2.
- However, IM administration is a practical alternative when IV access is difficult or unavailable, and it still provides reliable absorption, as shown in 3.
- The therapeutic effect of lorazepam in catatonia is believed to result from enhancement of GABA neurotransmission, which reduces excessive glutamatergic activity thought to contribute to catatonic symptoms, as discussed in 4, 5.
- Once catatonia resolves, lorazepam should be continued for several days before attempting a slow taper to prevent symptom recurrence, as recommended in 1, 3.