Chlorphenamine, the active ingredient in Piriton, belongs to a group of medicines known as sedating antihistamines. It is used to relieve allergies (such as hay fever, food and drug allergies, and allergic skin reactions), and to relieve itching caused by infections such as chickenpox.
Exposure to substances such as pollen, pet fur, peanuts, shellfish or insect bites can cause some people to produce an excess of a chemical called histamine. This causes allergic symptoms which can include swelling, skin rashes, sneezing, watery eyes, and a runny or blocked nose. Chlorphenamine blocks the effects of histamine, so it helps relieve allergic symptoms like these.
Chlorphenamine is available on prescription, or you can buy it without a prescription at pharmacies.
Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The manufacturer's leaflet will give you more information about chlorphenamine and will provide a full list of the side-effects which you may experience from taking it.
Take chlorphenamine exactly as your doctor, dentist or pharmacist tells you to. The usual recommended doses for adults and children over 12 years: 4 mg every 4-6 hours. Do not take more than six doses (24 mg) a day if you are under 65 years of age, or more than a total of three doses (12 mg) a day if you are over 65 years.
You can take chlorphenamine before or after food. Some people find it helps to swallow the tablets with a drink of water.
Most people only need to take an antihistamine for a short while when they have symptoms. You should stop taking chlorphenamine once your symptoms have eased.
If you forget to take a dose, don't worry, just 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.
Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. Children and people over 65 years of age may be more prone to side-effects from chlorphenamine. You will find a full list of side-effects in the manufacturer's information leaflet supplied with your medicine but the table below contains the most common ones. The 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.
Common chlorphenamine side-effects
- Feeling dizzy or sleepy, and blurred vision
- Dry mouth
- Lack of concentration, upset stomach, difficulty passing urine, feeling unco-ordinated, irritability (in children)
If you experience any other symptoms which you think may be due to this medicine, speak with your doctor, dentist or pharmacist for further advice.
To make sure that this is the right treatment for you, before you (or your child) start taking chlorphenamine it is important that you discuss the treatment with a doctor or pharmacist if:
- You are pregnant or breast-feeding.
- You have a problem with the way your liver works.
- You have glaucoma, a condition which causes increased pressure in your eyes.
- You have prostate problems, or if you have been experiencing any difficulty passing urine.
- You know you have a blockage in your small intestines.
- You have epilepsy.
- 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.
The patient information leaflet (PIL) is a leaflet containing specific information about medical conditions, doses and side effects. You can download a copy of the PIL here:
Patient Info Leaflet