Rapid Tranquilization with Haloperidol and Promethazine

Pharmacological Properties

• Promethazine onset of action is within 5 minutes when given intravenously, with duration of 4-6 hours 1
• Promethazine's anticholinergic properties help counteract extrapyramidal side effects of haloperidol 1
• Haloperidol dosing should not exceed 10-15 mg as higher doses do not improve efficacy and may increase adverse effects 2

Administration and Monitoring

• The combination can be readministered after 30-60 minutes if needed for persistent agitation 3
• Monitor for hypotension, which can occur with promethazine (particularly with rapid IV administration) 1
• Be aware of potential tissue damage with extravasation of promethazine 1
• Avoid in patients with known QTc prolongation due to haloperidol's effects on cardiac conduction 1, 3

Special Patient Populations

• In elderly patients or those with comorbidities, consider reducing initial doses by 50% 3
• The combination may not be appropriate for patients with delirium due to anticholinergic properties of promethazine 3