Promethazine for sedation is used two ways during moderate sedation: as an antiemetic for nausea, or, at low doses, as an adjunct that adds mild sedative and antihistamine effect alongside the primary sedation medications.
Dosage:
One time dose: 12.5- 50 mg
Onset of action: 2-5 minutes
Peak effect: Unknown
Duration of effect: More than 120 minutes
⚠ FDA boxed warnings: IV promethazine can cause severe tissue injury including gangrene on extravasation — deep IM is the preferred route; if IV is used, dilute and administer slowly through a running line. Contraindicated in children under 2 years (risk of fatal respiratory depression).
Reversal Agent:
None
Promethazine in Moderate Sedation
Because of the FDA boxed warning on tissue injury, the route matters as much as the dose: deep IM is preferred, and if IV is used it must be well diluted and given slowly into a running, free-flowing line — never as a direct push and never if there is any doubt about line placement. At sedative-adjunct doses, promethazine adds to the respiratory depression and sedation of the other medications on board, so monitoring stays continuous through its more-than-two-hour duration, longer than most of the sedation medications it is paired with. It is never given to children under two, where it carries a risk of fatal respiratory depression. There is no reversal agent; recovery is monitored, not reversed. As with any medication given during moderate sedation, administration follows the facility’s sedation policy and the provider’s scope of practice.
Educational reference for sedation providers, relocated from the previous version of this site — not a substitute for the current package insert, your facility protocols, or clinical judgment. Verify all doses against current references before clinical use.