Promethazine

Provider Level

RN/Paramedic

Class

Phenothiazine antiemetic and antihistamine

Mechanism of Action

Competitively blocks histamine H1 receptors. Exhibits central anticholinergic and sedative effects. Suppresses the chemoreceptor trigger zone to produce antiemetic effects.

Indications

Prevention and treatment of nausea and vomiting. Treatment of motion sickness. Adjunct in allergic reactions. Sedation.

Contraindications

Hypersensitivity to phenothiazines. Comatose states or profound CNS depression. Children under 2 years of age due to potential for fatal respiratory depression. Intra-arterial or subcutaneous administration.

Routes

PO, IM, IV, IO

Onset / Duration

Onset: IV 3 to 5 minutes IM 20 minutes. Duration: 2 to 8 hours.

Adverse Effects

Sedation confusion extrapyramidal symptoms including dystonia and akathisia respiratory depression severe tissue damage from extravasation hypotension tachycardia blurred vision dry mouth.

Precautions & Interactions

Use with extreme caution IV due to risk of severe tissue injury. Dilution and administration through a large patent vein is strongly recommended if IV route must be used. Synergistic CNS depression with alcohol and other sedatives. Lower seizure threshold.

Special Considerations

Carries FDA Black Box Warnings for fatal respiratory depression in children under 2 and severe tissue injury including gangrene from perivascular extravasation. Deep IM is the preferred parenteral route. Immediately halt administration if patient reports burning or pain during injection.