Professional reference. Rapid tranquillisation must follow local policy, with the least restrictive approach first and appropriate monitoring afterwards. Check compatibility in your institution’s references (for example Trissel’s, the King Guide, the Australian Injectable Drugs Handbook) for the exact products you stock.
Quick reference
- Compatible in syringe: haloperidol lactate 5 mg/mL + lorazepam 2 mg/mL, drawn up together immediately before IM injection (commonly 5 mg + 2 mg).
- Not compatible: haloperidol decanoate (oily depot) with anything; don’t mix in a syringe.
- Don’t combine IM olanzapine with parenteral benzodiazepines within a short time (risk of cardiorespiratory depression).
Background
Combining an antipsychotic with a benzodiazepine can calm severe agitation faster than either alone, and giving them in one syringe means one injection instead of two for a distressed patient. In US emergency departments, the combination of haloperidol 5 mg and lorazepam 2 mg, sometimes with diphenhydramine 50 mg to reduce extrapyramidal side effects (“B52”), has long been used. UK NICE guidance on rapid tranquillisation recommends IM lorazepam alone, or haloperidol combined with promethazine, considering the person’s history and ECG; haloperidol alone is not recommended because of dystonia risk.
Compatibility details
| Combination |
Syringe compatibility (commonly reported) |
Notes |
| Haloperidol lactate + lorazepam |
Compatible for short periods |
Lorazepam is viscous (propylene glycol/PEG vehicle); mix gently |
| Haloperidol lactate + diphenhydramine |
Compatible |
Part of “B52” |
| Haloperidol lactate + promethazine |
Compatible |
NICE-recommended combination |
| Haloperidol decanoate + any |
Incompatible (oily) |
Never mix |
| IM olanzapine + lorazepam |
Don’t mix or give close together |
Separate by at least 1 hour per product guidance |
Compatibility data apply to specific concentrations, manufacturers and contact times. Use the shortest possible time between drawing up and injection (minutes), inspect for cloudiness or precipitate, and label the syringe with both drugs and doses.
Administration and monitoring
- Use a large muscle (deltoid or ventrogluteal/thigh per policy) and an appropriate needle length; total volume is typically about 2 mL.
- Monitor pulse, blood pressure, respiratory rate, oxygen saturation, temperature and level of consciousness, typically every 15 minutes for the first hour, then hourly, per protocol.
- Watch for respiratory depression (benzodiazepine; have flumazenil available per policy), hypotension, acute dystonia (treat with an anticholinergic), and QT prolongation/arrhythmia (haloperidol; obtain an ECG when possible).
- Take extra care in older adults, people with alcohol or other sedative intoxication, respiratory disease, Parkinson’s disease or Lewy body dementia (avoid haloperidol).
- Lorazepam injection is usually stored refrigerated; check expiry and storage.
Other compatibility and preparation notes are in the clinical pharmacy notes.
Frequently asked questions
Can Haldol and Ativan be given IV together?
Haloperidol lactate is not licensed for IV use in some countries, and IV administration requires ECG monitoring because of QT risk. Follow local policy; IV combinations are usually given separately with flushes.
How long is a mixed syringe stable?
Draw up immediately before use. Don’t prepare in advance or store mixed syringes.
Why not haloperidol alone?
Haloperidol alone carries a higher risk of acute dystonia and akathisia; guidelines pair it with promethazine, a benzodiazepine or an anticholinergic.
Sources and further reading
CanforaMedicine Guide
