Histafen (discontinued in the UK)

How does it work?

Terfenadine belongs to a group of medicines called non-sedating antihistamines. Histamine is a chemical produced by the body. It is stored in cells (mast cells) in almost all tissues of the body. When the body reacts to a foreign substance (an allergen e.g. flower pollen), the mast cells release their stores of histamine. Histamine may then bind to receptors (H-1 receptors) in many areas of the body causing an increase in blood flow to the area of the allergy and the release of other chemicals that add to the allergic response. This stimulates the symptoms of an allergic reaction such as inflammation of the skin, airways or tissues, rashes, itching of the skin, eyes or nose, nasal congestion or narrowing of the airways. Terfenadine acts by blocking the binding of histamine to receptors in the body and so preventing or relieving the typical symptoms of an allergic reaction. Histamine may be released from and act in a small (localised) area of the body e.g the nose. Alternatively, histamine can result in a serious or complete body reaction e.g. anaphylactic reaction. Terfenadine is only useful for the prevention or relief of localised or less serious allergies such as hay fever or itchy rash (rather than very serious allergic reactions). Terfenadine is called a non-sedating anti-histamine as it does not enter the brain in significant quantities and is therefore unlikely to cause drowsiness. However, drowsiness may very rarely occur.

What is it used for?

Allergic conjunctivitis

Allergic skin conditions such as itch and/or rash

Inflammation of the nasal lining due to allergies

Warning!

Unless your doctor or pharmacist tells you otherwise, you should avoid drinking grapefruit juice while taking this medicine, as it may affect the level of this medicine in your blood.

This medicine may cause drowsiness. If affected do not drive or operate machinery.

If terfenadine fails to provide relief of symptoms, do not exceed the maximum recommended dose or add in another antihistamine. It is recommended to seek advice from your doctor.

If dizziness, fainting or noticeable abnormal heart beats occur, stop taking terfenadine and notify your doctor immediately.

This medicine may interact with many other medicines, resulting in serious side-effects. It is important to tell your doctor and/or pharmacist you are taking this medicine before buying any other medicines.

Use with caution in

Significantly decreased kidney function

Not to be used in

A type of irregular heart beat (QT prolongation arrhythmia)

Any illness that may cause an imbalance of the salts in the blood e.g. loss of appetite, vomiting or diarrhoea

Breastfeeding

Children less than 12 years of age or weighing less than 50kg

Heart disease

History of symptomatic irregular heart beats (symptomatic arrhythmias)

Imbalance of the salts in the blood, particularly low blood potassium levels (hypokalaemia) or low blood magnesium levels (hypomagnesemia)

People taking medicine(s) that may cause an imbalance of salts in the blood (such as diuretics)

Pregnancy

Significantly decreased liver function

Slow heart rate (bradycardia)

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. 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.

This medicine should not be used during pregnancy. Seek medical advice from your doctor.

This medicine passes into breast milk. It is recommended that mothers should avoid using this medicine while breastfeeding. Seek medical advice from your doctor.

Side effects

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. Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

Drowsiness

Confusion

Blood disorders

Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain

Visual disturbances

Abnormal heart beats (arrhythmias)

Abnormal production of breast milk (galactorrhoea)

Increased need to pass urine

Breathing difficulties due to a narrowing of the airways (bronchospasm)

Skin reactions such as rash and itch

Liver disorders

Hair thinning/loss

Disorders of the menstrual cycle

Dry mouth, nose and throat

The side effects listed above may not include all of the side effects reported by the drug'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.

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