Promethazine — Drug Monograph

Brand names: Phenergan, Promethegan

Drug class: Supportive Care Agent

Mechanism of Action

Phenothiazine derivative with potent H1 antihistamine, dopamine D2 antagonist, and anticholinergic properties. Blocks dopamine receptors in the CTZ and H1 receptors in the vestibular pathway. Strong sedative due to central H1 blockade. Does not have significant 5-HT3 or NK1 antagonism.

FDA Indications

• Prevention and treatment of nausea and vomiting associated with anesthesia/surgery
• Treatment of motion sickness
• Treatment of allergic conditions
• Adjunctive sedation

Common Side Effects

• Sedation (prominent)
• Dry mouth
• Dizziness
• Blurred vision
• Constipation
• Urinary retention

Clinical Pearl

Promethazine is most useful for breakthrough nausea and opioid-induced nausea in the outpatient oncology setting due to its oral and rectal formulations and its sedative benefit in distressed patients. The IV route is absolutely contraindicated — a principle that must be reinforced with all nursing staff and trainees. IM administration into the large deltoid or gluteal muscle with adequate depth is the parenteral route of choice.

Related Therapies & Mechanisms

• Aprepitant (Emend) — Supportive Care Agent
• Avatrombopag (Doptelet) — Supportive Care Agent
• Darbepoetin Alfa (Aranesp) — Supportive Care Agent
• Defibrotide (Defitelio) — Supportive Care Agent