Promethazine teoclate

How it works

It antagonises histamine H1 receptors and has central antimuscarinic and anti-emetic actions, dampening vestibular and chemoreceptor trigger zone input that drives nausea.

Prescribing in practice

• It causes marked drowsiness and has antimuscarinic effects, so use cautiously in the elderly and avoid in those for whom sedation or anticholinergic burden is hazardous.
• Avoid in patients with significant prostatic hypertrophy, urinary retention, narrow-angle glaucoma or pyloroduodenal obstruction owing to its antimuscarinic activity.
• For motion sickness it is more effective taken before travel, and the teoclate salt is favoured for its longer duration of anti-emetic effect.

Monitoring

Routine monitoring is not generally needed, but assess for excessive sedation, anticholinergic effects and confusion, particularly in older patients.

Counselling the patient

• Warn the patient that the medicine causes drowsiness and to avoid driving or operating machinery.
• Advise avoiding alcohol while taking it.
• For travel sickness, recommend taking it before the journey begins.

Evidence & guidelines

Promethazine teoclate is a well-established anti-emetic and antihistamine, with use for nausea and motion sickness supported by its SPC and long clinical experience.