Cyproheptadine tablets
Periactin
Peer reviewed by Dr Colin Tidy, MRCGPLast updated by Michael Stewart, MRPharmSLast updated 27 Apr 2023
Meets Patient’s editorial guidelines
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Cyproheptadine is an antihistamine. It is taken for allergic conditions.
Make sure you follow the dosage directions on the label.
The most common side effects are feeling tired or sleepy. This may affect your ability to drive.
At a glance
Cyproheptadine is an antihistamine used to relieve allergic conditions like hay fever and skin rashes.
It works by blocking histamine, a chemical that triggers allergic symptoms.
Common side effects include feeling tired or sleepy, blurred vision, headache, and dry mouth.
Avoid driving or operating machinery if you feel drowsy or have blurred vision.
Do not drink alcohol while taking cyproheptadine as it can worsen drowsiness.
Tell your doctor or pharmacist if you are pregnant, have liver or kidney problems, or are taking other medicines.
Cyproheptadine is usually for short-term use, especially for allergy symptoms.
In this article:
Video picks for Allergy medicines
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Overview
Type of medicine | An antihistamine |
Used for | Allergic conditions, such as hay fever and skin rashes |
Also called | Periactin® |
Available as | Tablets |
What is cyproheptadine used for?
Back to contentsCyproheptadine is a type of antihistamine that is used to relieve allergies, such as hay fever and some allergic skin conditions.
You can buy cyproheptadine tablets without a prescription at a pharmacy.
Continue reading below
How does cyproheptadine work?
Back to contentsCyproheptadine works by blocking the effect of histamine.
Exposure to substances such as pollen, pet fur, house dust, or insect bites can cause some people to produce an excess of a chemical called histamine.
This triggers allergic symptoms, which can include skin rashes, sneezing, watery eyes, and a runny or blocked nose.
Cyproheptadine blocks the effects of histamine by preventing it from binding to its receptors in the body, helping to relieve allergic symptoms.
Side effects of cyproheptadine
Back to contentsCommon side effects of cyproheptadine are:
Feeling tired or sleepy.
Blurred vision.
Headache.
Difficulty peeing (passing urine).
Dry mouth.
You will find a full list in the manufacturer's information leaflet supplied with your medicine.
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How to manage cyproheptadine side effects
Back to contentsThe unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any continue or become troublesome.
Cyproheptadine side effects | What can I do if I experience this? |
Feeling tired or sleepy, blurred vision | Do not drive and do not use tools or machines until you feel better. Do not drink alcohol |
Headache | Drink plenty of water and ask your pharmacist to recommend a suitable painkiller. If the headaches continue, let your doctor know |
Difficulty passing urine | Speak with your doctor if this becomes troublesome |
Dry mouth | Try sucking sugar-free sweets or chewing sugar-free gum |
If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist for further advice.
Who should not take cyproheptadine?
Back to contentsTo make sure that this is the right treatment for you, before you start taking cyproheptadine it is important that you discuss the treatment with a doctor or pharmacist if:
You are pregnant, trying for a baby or breastfeeding.
You have a problem with the way your liver works, or if you have a problem with your kidneys.
You have a condition which causes increased pressure in your eyes, such as glaucoma.
You have prostate problems, or if you have been experiencing any difficulty passing urine.
You know you have a stomach ulcer or a blockage in your small intestines.
You have epilepsy.
You have a rare inherited blood condition known as porphyria.
You are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.
You have ever had an allergic reaction to a medicine.
How to take cyproheptadine
Back to contentsRead the manufacturer's printed information leaflet from inside your pack. It will give you more information about cyproheptadine tablets and will provide a full list of the side effects.
Take cyproheptadine exactly as your doctor or pharmacist tells you to. The usual recommended doses are:
For adults: one tablet (4 mg) three times daily.
For children aged 7-14 years: one tablet (4 mg) two or three times daily.
For children aged 2-6 years: half a tablet (2 mg) two or three times daily.
You can take cyproheptadine before or after meals. Some people find it helps to swallow the tablets with a drink of water.
If you forget to take a dose, take the next dose when it is due and then continue as before. Do not take two doses together to make up for a forgotten dose.
Most people only need to take an antihistamine for a short while when they have symptoms. You should stop taking cyproheptadine once your symptoms have eased.
Getting the most from your treatment
Back to contentsCyproheptadine can make you feel drowsy (sleepy). If this happens, do not drive or use tools or machinery. Avoid alcohol, as it can make drowsiness worse.
If you are having surgery, medical tests, or allergy tests, tell the healthcare professional that you are taking cyproheptadine. You may need to stop it for a short time before some tests.
Cyproheptadine can make your skin more sensitive to sunlight. Use a sunscreen with at least SPF 15 and UVA protection, especially in strong sunlight. Do not use sunbeds.
Always check with a pharmacist before taking any new medicines. Some medicines can interact with cyproheptadine and increase side effects.
How to store cyproheptadine
Back to contentsKeep all medicines out of the reach and sight of children.
Store in a cool, dry place, away from direct heat and light.
Frequently asked questions
Back to contentsHow quickly does cyproheptadine work?
Cyproheptadine usually starts working within a few hours for allergy symptom relief.
If used for appetite stimulation, increased hunger may develop within a few days, although this varies between individuals.
Can cyproheptadine be taken long term?
Cyproheptadine is generally intended for short-term or intermittent use, especially for allergy symptoms.
Long-term use may be considered in specific cases (such as appetite stimulation), but only under regular medical supervision due to side effects such as sedation and increased appetite.
Can I drink alcohol while taking cyproheptadine?
It is best to avoid alcohol while taking cyproheptadine. Alcohol can significantly increase drowsiness and impair coordination, making side effects more intense and potentially dangerous.
Does cyproheptadine cause weight gain?
Weight gain can occur as a side effect due to increased appetite and sedation-related reduced activity. This effect varies widely between individuals and is not guaranteed.
Important information about all medicines
Back to contentsImportant information about all medicines
Never take more than the recommended dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.
This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.
If you have any questions about this medicine ask your pharmacist.
Report side effects to a medicine or vaccine
If you experience side effects, you can report them online through the Yellow Card website.

Unsure about mixing medicines?
Check for possible interactions between medicines, supplements and foods before taking them together.
Frequently asked questions
Can I take cyproheptadine if I have a stomach ulcer or bowel obstruction?
No, you should discuss this with a doctor or pharmacist first. Cyproheptadine should not be taken if you know you have a stomach ulcer or a blockage in your small intestines.
Are there any medicines that should not be taken with cyproheptadine?
Yes, interactions can occur. You should always check with a pharmacist before taking any new medicines, including those bought without a prescription, and herbal or complementary medicines, as some can interact with cyproheptadine and increase side effects.
How should I store cyproheptadine tablets?
Cyproheptadine tablets should be stored in a cool, dry place, away from direct heat and light. Always keep all medicines out of the reach and sight of children.
Continue reading below
About the authorView full bio

Michael Stewart, MRPharmS
Medicine Leaflet Review Manager – Contractor, Pharmacist
BPharm (Hons), MRPharmS
Michael is a community pharmacist practicing in the Midlands and South Yorkshire with more than 20 years’ experience advising on medicines and medical conditions. He has a strong background in healthcare training, having produced and delivered training courses for pharmacy teams and staff of residential care settings, including nurses. He has also contributed to pharmacy advisory boards for the management of low acuity conditions in the community.
About the reviewerView full bio

Dr Colin Tidy, MRCGP
General Practitioner, Medical Author
MBBS, MRCGP, MRCP (Paediatrics), DCH
Dr Colin Tidy is an NHS Doctor, based in Oxfordshire.
Article history
The information on this page is written and peer reviewed by qualified clinicians.
Next review due: 25 Oct 2027
27 Apr 2023 | Latest version

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