Promethazine Administration and Safety

Adult Dosing and Pharmacokinetics

The standard adult dose of promethazine is 12.5-25 mg intravenously, infused slowly to minimize hypotension risk, as recommended by the American Gastroenterological Association 1, 2, 3, 4, 5
The total adult dose range is 25-100 mg, which may be used as an adjuvant to narcotics and benzodiazepines, according to the American Gastroenterological Association 1, 3, 4
The onset of action of promethazine is within 5 minutes of IV administration, with a duration of 4-6 hours and a plasma half-life of 9-16 hours, as reported by the American Gastroenterological Association 1, 2, 3, 4

Promethazine can cause hypotension, particularly with rapid infusion, as well as neuroleptic malignant syndrome and extrapyramidal effects, according to the American Gastroenterological Association 1, 2, 3, 4, 5
Local tissue damage, including burning, pain, thrombophlebitis, tissue necrosis, and gangrene, can occur with inadvertent perivascular extravasation, intra-arterial injection, or intraneuronal/perineuronal infiltration, as reported by the American Gastroenterological Association 2, 5