Alcohol Content in Promethazine-Dextromethorphan Formulations and Clinical Significance

Drug Interactions and CNS Depression

• Promethazine's hypnotic and sedative effects are significantly increased when combined with alcohol or other CNS depressants such as benzodiazepines and opioid narcotics 1
• The American Gastroenterological Association warns that promethazine can cause respiratory depression, particularly when combined with other CNS depressants including alcohol 2
• Diphenhydramine (a related antihistamine) demonstrates increased hypnotic effects when given in combination with alcohol, a property likely shared by promethazine given their similar pharmacologic profiles 1

Patient Populations Requiring Caution

• The American Geriatrics Society recommends caution with dextromethorphan/quinidine combinations in older adults due to limited efficacy and increased fall risk 3