Cyproheptadine hydrochloride

How it works

It antagonises histamine H1 receptors and serotonin (5-HT) receptors, producing antihistamine, antipruritic, appetite-stimulating and antimigraine effects.

Prescribing in practice

• It is markedly sedating with antimuscarinic effects, so avoid in narrow-angle glaucoma, urinary retention and prostatic enlargement, and use caution in the elderly because of confusion and falls.
• Additive sedation and antimuscarinic burden occur with alcohol, other antihistamines, tricyclics and anticholinergics.
• Its appetite-stimulant and weight-gain effect can be useful in selected patients but is undesirable in others.

Monitoring

Routine laboratory monitoring is not required; review for sedation, anticholinergic effects and, where relevant, weight change.

Counselling the patient

• Expect drowsiness and avoid driving or operating machinery until you know how it affects you.
• Avoid alcohol while taking it.
• Report difficulty passing urine, dry mouth or blurred vision.

Evidence & guidelines

Cyproheptadine is a long-established antihistamine whose sedative and antiserotonergic properties underpin its varied uses.