Health Centres - Pollenase antihistamine tablets
How does it work?
Pollenase anthistamine tablets contain the active ingredient chlorphenamine maleate (previously spelt chlorpheniramine in the UK), which is a type of medicine called a sedating antihistamine. (NB. Chlorphenamine is also available without a brand name, ie as the generic medicine.) Chlorphenamine works by preventing the actions of histamine.
Histamine is a substance produced by the body as part of its defence mechanisms. It is stored in cells called mast cells, in almost all tissues of the body. When the body reacts to a foreign substance (known as an allergen, eg flower pollen), the mast cells are stimulated by the allergen and release their stores of histamine.
The released histamine then binds to its receptors (H1 receptors), causing a chain reaction that results in allergic symptoms. It causes an increase in blood flow to the area of the allergy, and the release of other chemicals that add to the allergic response.
All this results in the symptoms of an allergic reaction. In hayfever, this causes inflammation of the nose, eyes, skin or airways and results in itchy watery eyes, a runny nose, sneezing and nasal congestion. Histamine is also responsible for the symptoms of allergic and itchy rashes, and allergic reactions to foods, medicines or insect bites. It can also cause more severe allergic reactions such as angioneurotic oedema, which involves severe swelling of the eyes, lips, tongue or throat.
Chlorphenamine works by blocking histamine H1 receptors. It does not prevent the actual release of histamine from mast cells, but prevents it binding to its receptors. This in turn prevents the release of other allergy chemicals and increased blood supply to the area, and provides relief from the typical symptoms of allergies.
Chlorphenamine is called a sedating antihistamine because it enters the brain in significant quantities and causes drowsiness.
The antihistamine action and the fact that it causes drowsiness also make chlorphenamine useful for relieving itching caused by chickenpox. It may be especially helpful for itching that is worse at night. This is often the case in children, who notice itching less during the day when they are active, but are bothered by it at night when they are still and have nothing else to focus on.
What is it used for?
- More serious allergic reaction causing swelling of the eyes, lips, tongue or throat
- Itching associated with chickenpox
Warning!
- This medicine may cause drowsiness, blurred vision or dizziness. If affected do not drive or operate machinery. Children should avoid potentially hazardous activities such as riding bikes or climbing trees if affected. Alcohol should be avoided.
- If you are due to have any skin prick tests to diagnose allergies you should stop taking your antihistamines at least 48 hours before the tests. This is because antihistamines can prevent or lessen the skin reactions that indicate an allergy, and so can make the test results unreliable.
- If symptoms persist despite treatment, seek medical advice from your doctor or pharmacist.
Use with caution in
- Elderly people
- Children
-
Asthma
-
Bronchitis
- Widening of the airways which may be hereditary or due to infection (bronchiectasis)
-
Enlarged prostate gland
-
Epilepsy
-
Glaucoma
- Liver disease
-
Severe cardiovascular disease
-
Very high blood pressure
-
Overactive thyroid gland.
Not to be used in
- People who have taken a type of medicine called a monoamine oxidase inhibitor (MAOI), eg antidepressants such as phenelzine, in the last 14 days.
- Pollenase antihistamine tablets are not recommended for children under six years of age. A syrup form of chlorphenamine is more suitable for this age group.
This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
Pregnancy and Breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- The safety of this medicine during pregnancy has not been established. It should be avoided during pregnancy, unless the potential benefits to the mother outweigh any possible risk to the developing baby. This is particularly important during the first and third trimesters. As with all medicines, seek medical advice from your doctor before using this medicine if you are pregnant.
- This medicine may pass into breast milk. It should be avoided by breastfeeding mothers unless the potential benefits to the mother outweigh any possible risk to the nursing infant. As with all medicines, seek medical advice from your doctor before using this medicine if you are breastfeeding.
Label warnings
- This medication may cause drowsiness. If affected do not drive or operate machinery. Avoid alcoholic drink.
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