How to Administer Promethazine (Avomine)
Deep intramuscular injection is the preferred and safest route for promethazine administration, as intravenous administration carries significant risks of severe tissue injury, gangrene, and requires strict precautions. 1
Route Selection and Safety Priorities
Preferred Route: Deep Intramuscular (IM)
- Deep IM injection is the FDA-preferred route due to lower risk of catastrophic complications 1
- This route avoids the severe tissue injury risks associated with IV administration 1
Intravenous Administration (Use Only When Necessary)
If IV administration is required, follow these critical safety measures:
Dilution and Rate Requirements:
- Maximum concentration: 25 mg/mL 1
- Maximum infusion rate: 25 mg per minute 1
- Preferably inject through tubing of a functioning IV infusion set 1
Critical Safety Precautions:
- Never give intra-arterially - this causes severe arteriospasm and gangrene requiring amputation 1
- Stop injection immediately if patient complains of pain to evaluate for arterial injection or extravasation 1
- Aspiration of dark blood does NOT exclude intra-arterial placement, as blood discolors upon contact with promethazine 1
- Perivascular extravasation can cause tissue necrosis, gangrene, and may require fasciotomy, skin grafts, or amputation 1
Contraindicated Route
- Subcutaneous injection is absolutely contraindicated due to tissue necrosis risk 1
Dosing by Indication
Nausea and Vomiting
- Standard dose: 12.5-25 mg IV or IM 2, 1
- Frequency: Every 4-6 hours as needed 2, 3
- Lower doses (6.25 mg) are equally effective with fewer adverse effects 4, 5
- Do not repeat more frequently than every 4 hours 1
Sedation (Hospitalized Adults)
- Nighttime sedation: 25-50 mg 1
- As adjunct to procedures: 25-50 mg combined with reduced doses of analgesics 2, 1
Allergic Conditions
Preoperative/Postoperative Use
- Dose: 25-50 mg combined with reduced doses of analgesics and anticholinergics 1
Special Population Considerations
Pediatric Patients - Critical Restrictions
- Absolutely contraindicated in children under 2 years of age due to fatal respiratory depression risk 1
- For children ≥2 years: Use lowest effective dose and avoid concomitant respiratory depressants 1
- Postmarketing fatalities have occurred in children under 2 years 1
Elderly Patients
- Start with 6.25 mg IV, which is as effective as higher doses with significantly fewer adverse effects 5
- The 6.25 mg dose had lower median ADR frequency compared to 12.5 mg (P = 0.048) 5
Obstetric Use
- Early labor: 50 mg for sedation 1
- Established labor: 25-75 mg (average 50 mg) with reduced narcotic dose 1
- Maximum 100 mg total in 24 hours during labor 1
Monitoring and Adverse Effect Management
Respiratory Monitoring
- Respiratory depression is a major risk, especially with concomitant CNS depressants 1
- Avoid in patients with compromised respiratory function, COPD, or sleep apnea 1
- Monitor oxygen saturation continuously 2
Common Adverse Effects
- Hypotension (particularly with rapid IV administration) 2, 3
- CNS depression and sedation occur frequently 3
- Dizziness, blurred vision, dry mouth 3
Serious Adverse Effects Requiring Vigilance
- Extrapyramidal symptoms and dystonic reactions 2, 3
- Neuroleptic malignant syndrome (hyperpyrexia, muscle rigidity, altered mental status) 2, 1
- Seizure threshold lowering 1
Drug Interactions and Dose Adjustments
- Reduce doses of concomitant analgesics, barbiturates, and sedatives when using promethazine 1
- Avoid combination with other respiratory depressants in pediatric patients 1
- Enhanced CNS depression occurs with alcohol, benzodiazepines, opioids, and tricyclic antidepressants 1