Intramuscular Treatment for Acute Psychosis
For acute psychotic agitation requiring immediate IM treatment, use either haloperidol 2-5 mg IM or olanzapine 10 mg IM as monotherapy, or combine haloperidol 5 mg IM with lorazepam 2 mg IM for more rapid sedation. 1, 2, 3
First-Line IM Options
Conventional Antipsychotic Monotherapy
- Haloperidol 2-5 mg IM is FDA-approved for prompt control of acutely agitated psychotic patients with moderately severe to very severe symptoms. 2
- Subsequent doses may be given as often as every hour, though 4-8 hour intervals are typically satisfactory. 2
- If rapid sedation is specifically required, consider droperidol over haloperidol (though droperidol carries FDA black box warning for QT prolongation). 1
Atypical Antipsychotic Monotherapy
- Olanzapine 10 mg IM is an effective alternative with better tolerability than conventional antipsychotics. 3, 4
- Atypical antipsychotics cause fewer extrapyramidal symptoms, which is critical for future medication adherence. 5, 6
Benzodiazepine Monotherapy
- Lorazepam or midazolam IM are effective as monotherapy for undifferentiated acute agitation. 1
- This approach is particularly useful when the etiology of psychosis is unclear or when avoiding antipsychotic side effects is paramount. 1
Combination Therapy for Faster Control
- The combination of haloperidol 5 mg IM plus lorazepam 2 mg IM may produce more rapid sedation than monotherapy in acutely agitated psychiatric patients. 1, 7
- This combination addresses both psychotic symptoms and agitation simultaneously. 7
Critical Transition Strategy
- Switch to oral medication as soon as practicable—within 12-24 hours following the last parenteral dose. 2
- For oral transition, use the parenteral dose administered in the preceding 24 hours as an initial approximation of total daily oral dose. 2
- Oral risperidone 2 mg plus lorazepam 2 mg is as effective as IM haloperidol plus lorazepam for cooperative patients and should be considered first-line to avoid IM administration entirely. 1, 7, 6
When IM Treatment is NOT Appropriate
- Long-acting injectable antipsychotics should NOT be used for acute treatment—oral or short-acting IM medications are preferable when dosage flexibility is needed. 1
- LAI treatment should only begin after improvement of acute symptoms. 1
Common Pitfalls to Avoid
- Avoid excessive initial dosing—large doses don't hasten recovery but significantly increase side effects, particularly extrapyramidal symptoms that compromise future adherence. 8, 5
- Don't use typical antipsychotics as first-line when atypical options are available, as extrapyramidal side effects reduce long-term medication acceptance. 5, 6
- Rule out organic causes before administering antipsychotics—in atropine-like drug psychosis or certain organic psychoses, antipsychotics should be avoided entirely. 9
- Monitor QTc interval when feasible, especially with droperidol or when combining multiple agents that prolong QT. 1, 10