A sedating antihistamine
Cyproheptadine
An older sedating antihistamine that also stimulates appetite and is sometimes used for allergic symptoms and migraine.
What is Cyproheptadine?
Cyproheptadine is a sedating (first-generation) antihistamine. As well as easing allergic symptoms such as itch and hives, it tends to cause drowsiness and can increase appetite, which is sometimes used deliberately. It is generally a second-line choice because newer non-drowsy antihistamines are usually preferred.
Education and reference only. This is a plain-language guide to Cyproheptadine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Cyproheptadine is a first-generation antihistamine, meaning it crosses into the brain and tends to cause drowsiness. In the UK it is used much less than modern non-drowsy antihistamines, but it still has a few specific roles: relieving itchy allergic skin conditions and hives, and, because it can boost appetite, it is sometimes used where appetite stimulation is wanted. It has also been used for some types of headache and migraine.
How it works
Cyproheptadine blocks histamine H1 receptors, which calms the itch, redness and swelling that histamine drives in allergic reactions. Because it is an older antihistamine, it also passes into the brain (causing sedation) and blocks other receptors, including serotonin receptors — an action linked to its appetite-stimulating and headache effects.
Company & origin
Originated / developed by: Merck (originator).
An older, first-generation antihistamine introduced in the 1960s and still occasionally used in the UK.
Practical use
How to take Cyproheptadine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it as your prescriber or pharmacist directs, with or without food.
- It commonly causes drowsiness, so avoid driving or using machinery until you know how it affects you.
- Avoid alcohol, which adds to the drowsiness.
- If you are using it for appetite, take it as advised and review with your prescriber whether it is helping.
- If you miss a dose, take it when you remember unless it is nearly time for the next one — do not double up.
Weighing it up
Advantages & disadvantages of Cyproheptadine
Advantages
- Eases allergic itch and hives, and the night-time drowsiness can help sleep when symptoms are troublesome.
- Can stimulate appetite, which is occasionally the reason it is prescribed.
- An inexpensive, long-established medicine with familiar effects.
Disadvantages
- Causes drowsiness, so it is unsuitable when you need to be alert and can impair driving.
- Anticholinergic effects (dry mouth, blurred vision, constipation, urinary difficulty) are common, especially in older people.
- Weight gain from increased appetite may be unwanted, and modern non-drowsy antihistamines are usually preferred for everyday allergy.
Practical use
Good to know
Because it makes most people drowsy, it is best taken when you do not need to drive or operate machinery, and it can be useful at night. The drowsiness and appetite increase are sometimes the reason it is chosen, and sometimes an unwanted nuisance. Older people are more sensitive to its sedating and anticholinergic effects (dry mouth, constipation, confusion), so it is used cautiously in this group and is not suitable for sedating very young children.
Who should not take it / use with caution
- Used cautiously in older people, who are more prone to drowsiness, confusion and falls.
- Avoided in people with closed-angle glaucoma, urinary retention or significant prostate enlargement, and in severe heart, liver or stomach-outlet problems.
- Not used to sedate very young children; check suitability in pregnancy or breastfeeding with a clinician.
Monitoring
- Whether allergic symptoms or appetite improve as intended.
- Daytime drowsiness, and anticholinergic effects in older people.
- Weight, if appetite stimulation is a concern.
Side effects
- Drowsiness and a 'hangover' feeling the next morning.
- Dry mouth, blurred vision, constipation and sometimes difficulty passing urine.
- Increased appetite and weight gain; occasionally dizziness or, in some people, restlessness.
Key interactions
- Alcohol and other sedating medicines (sleeping tablets, strong painkillers, some antidepressants) add to drowsiness.
- Other anticholinergic medicines increase dry mouth, constipation and confusion.
- Monoamine-oxidase inhibitor (MAOI) antidepressants should not be combined with it.
Available as: Tablets, and an oral solution.
Answers
Cyproheptadine: frequently asked questions
Will cyproheptadine make me drowsy?
Usually yes — it is a sedating antihistamine, so drowsiness is common. Take it when you do not need to drive or concentrate, and avoid alcohol, which makes the drowsiness worse.
Why is it sometimes used to increase appetite?
As well as blocking histamine, it acts on serotonin receptors, an effect that can stimulate appetite. This is occasionally used on purpose, though any benefit should be reviewed with your prescriber.
Can children take it?
It is sometimes used for allergic symptoms in children under medical advice, but it is not recommended for sedating very young children. Always follow a clinician's guidance on suitability.
Is it safe for older people?
It is used with caution because older people are more sensitive to its drowsiness and anticholinergic effects, such as confusion, constipation and falls. A non-drowsy antihistamine is often preferred.
Can I drink alcohol with it?
It is best to avoid alcohol, because both alcohol and cyproheptadine cause drowsiness and the combination can leave you very sleepy or unsteady.
The wider class
About Antihistamines
Cyproheptadine belongs to the antihistamines class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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