What is the recommended dose of promethazine (Phenergan) for children?

Promethazine Dosing for Children

Promethazine is contraindicated in children under 2 years of age, and for children 2 years and older, the dose is 0.5 mg per pound (approximately 1.1 mg/kg) of body weight, adjusted to age, weight, and severity of condition, not to exceed 25 mg per dose. 1

Critical Safety Warning

• Promethazine must never be used in children under 2 years of age due to the risk of fatal respiratory depression 1
• This is an FDA black box warning that supersedes all other considerations 1

Dosing by Indication

For Nausea and Vomiting

• Standard dose: 0.5 mg per pound of body weight (approximately 1.1 mg/kg), adjusted for age, weight, and severity 1
• Doses of 12.5-25 mg may be repeated every 4-6 hours as necessary 1
• Antiemetics should not be used in vomiting of unknown etiology in children and adolescents 1

For Allergies

• Initial dose: 12.5 mg taken three times daily or 6.25-12.5 mg three times daily 1
• Single 25 mg dose at bedtime may be used 1
• After initiation, adjust to the smallest amount adequate to relieve symptoms 1

For Motion Sickness

• Dose: 12.5-25 mg twice daily 1
• Initial dose should be taken 30-60 minutes before anticipated travel 1
• Repeat 8-12 hours later if necessary 1

For Sedation

• Bedtime sedation: 12.5-25 mg at bedtime 1
• Preoperative sedation: 0.5 mg per pound of body weight in combination with appropriately reduced doses of narcotic or barbiturate and atropine-like drug 1
• Postoperative sedation: 12.5-25 mg 1

Important Clinical Considerations

Adverse Effects Profile

• Promethazine has been associated with significant sedation, agitation, hallucinations, seizures, dystonic reactions, and possibly apparent life-threatening events 2
• These adverse reactions are most concerning in children under 2 years of age, who are most vulnerable 2
• If dystonic reactions occur, diphenhydramine (1-2 mg/kg or 25-50 mg parenterally) can be administered 3

Misuse Potential

• Promethazine has documented misuse and abuse potential, particularly in adolescents 4
• Misuse is often associated with concomitant opioid use and has been linked to drug-related fatalities 4
• Healthcare providers should be vigilant about potential misuse, especially since promethazine may be available over-the-counter in some formulations 4

Dosing Principles

• Always start with the smallest effective dose and adjust based on response 1
• Doses should be individualized based on the child's age, weight, and severity of condition 1
• The maximum single dose should not exceed 25 mg in most pediatric cases 1