How does it work?
Zaditen tablets and elixir contain the active ingredient ketotifen hydrogen fumarate, which is a type of medicine called a sedating antihistamine.
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 house dust mites, pet fur), the mast cells stimulated by the allergen 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. For example, in hay fever, histamine causes inflammation of the nose, resulting in a runny nose, sneezing and nasal congestion.
Ketotifen is thought to work in a number of ways. It prevents the release of histamine from mast cells and also blocks H1 receptors, so that any histamine that is released is prevented from having an effect.
By blocking the actions of histamine, ketotifen helps prevent your body from reacting to allergens that would normally cause your allergic symptoms.
Ketotifen is called a sedating antihistamine because it enters the brain in significant quantities and causes drowsiness.
What is it used for?
- Relieving symptoms of allergic conditions such as allergic rhinitis (eg hay fever) or allergic conjunctivitis in adults and children aged three years and over.
How do I take it?
- Zaditen tablets and elixir should be taken with or after food.
- Adults should take one Zaditen tablet twice a day, OR one 5ml spoonful Zaditen elixir twice a day, when needed to relieve symptoms. If this doesn't relieve your symptoms you can increase the dose to two tablets OR two 5ml spoonfuls taken twice a day.
- Children aged three years and over should be given one Zaditen tablet twice a day, OR one 5ml spoonful Zaditen elixir twice a day, when needed to relieve symptoms. Do not exceed this dose.
- People who are usually very susceptible to sedating effects of medicines should start by taking half to one Zaditen tablet, OR half to one 5ml spoonful Zaditen elixir, at night for the first few days.
- You can continue to take this medicine to relieve your symptoms for as long as you are exposed to the allergen, for example throughout the pollen season. Follow the instructions given by your doctor.
- If your symptoms don't improve despite taking this medicine, seek medical advice from your doctor or pharmacist.
- This medicine may cause drowsiness, especially during the first few days of starting treatment. If affected you should not perform potentially hazardous tasks such as driving or operating machinery. Children who are affected should not do potentially hazardous activities such as riding bikes or horses, or climbing trees.
- You should avoid drinking alcohol while taking this medicine, because it is likely to make any drowsiness worse.
- If you are due to have any skin prick or patch tests to diagnose allergies you should stop taking your antihistamines at least 48 hours before the tests. This is because antihistamines can prevent or reduce the skin reactions that indicate an allergy, and so can make the test results unreliable.
Use with caution in
- People with a history of epilepsy.
- Hereditary blood disorders called porphyrias.
- Liver disease.
Not to be used in
- Children under three years of age.
- Zaditen tablets contain lactose and should not be taken by people with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption.
- Zaditen elixir contains maltitol and should not be taken by people with rare hereditary problems of fructose intolerance.
This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.
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 for use during pregnancy has not been established. The manufacturer states that it is not recommended for women who are pregnant. Seek further medical advice from your doctor.
- This medicine passes into breast milk. The manufacturer states that it is not recommended for mothers who are breastfeeding. Seek further medical advice from your doctor.
- This medicine should be taken with or after food.
- This medication may cause drowsiness. If affected do not drive or operate machinery. Avoid alcoholic drink.
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.
Common (affect between 1 in 10 and 1 in 100 people)
- Drowsiness, particularly when you start treatment. This usually improves in a few days.
- Difficulty sleeping (insomnia), particularly in children.
- Excitability, irritability or nervousness, particularly in children.
Uncommon (affect between 1 in 100 and 1 in 1000 people)
- Dry mouth.
- Bladder inflammation, commonly caused by infection (cystitis).
Rare (affect between 1 in 1000 and 1 in 10,000 people)
Very rare (affect fewer than 1 in 10,000 people)
- Inflammation of the liver (hepatitis).
- Severe blistering skin reaction affecting the tissues of the eyes, mouth, throat and genitals (Stevens-Johnson Syndrome).
- Severe skin rash (erythema multiforme).
The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.
For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.
How can this medicine affect other medicines?
You should tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.
There may be an increased risk of drowsiness if this medicine is taken with any of the following (which can also cause drowsiness):
- antipsychotic medicines, eg chlorpromazine, haloperidol
- barbiturates, eg phenobarbital
- benzodiazepines, eg diazepam, temazepam
- other sedating antihistamines, eg chlorphenamine, brompheniramine, hydroxyzine
- sleeping tablets, eg zopiclone
- strong opioid painkillers, eg morphine, codeine, dihydrocodeine
- tricyclic antidepressants, eg amitriptyline.
A few people taking this medicine in combination with antidiabetic tablets have experienced a reversible fall in the number of blood cells called platelets in their blood. The manufacturer recommends that this medicine should be avoided in people taking antidiabetic tablets, for example metformin.
Antihistamines may oppose the effect of histamine (used to treat leukaemia) and are not recommended for people having this treatment.
Antihistamines may also oppose the effect of betahistine (used to treat Ménière's disease).
Other medicines containing the same active ingredient