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Side effects of Histop, Piriton (Chlorpheniramine) tablets and syrup

Updated on October 16, 2015


Piriton and Histop are popular brand names of an over the counter generic drug Chlorpheniramine. This medicine is a first generation antihistamine. It is used for symptomatic relief of allergies such as colds, cough, allergy, hay fever and allergic rhinitis. Chlorpheniramine is a common ingredient in common cough medicines. It is also used for the emergency treatment of anaphylaxis.

This medicine is available in tablet and liquid form for children. Side effects are more with the children and the elderly.

How Histop/Piriton works?

Histop works by blocking histamine (H1) receptors in the body. It passes through the brain to cause sedation and drowsiness. Drowsiness is usually tolerable in time. In addition, Histop increases several neurotransmitter levels in the brain.

If you have kidney disease, liver disease, enlarged prostate, glaucoma, epilepsy then do not to take this medication without consulting a doctor. You should not use this drug, if you are pregnant or breastfeeding, unless prescribed by a doctor.

Side effects of Histop

What are the most common side effects?

Drowsiness is the most common side effect of Histop/Piriton. Headaches, urinary retention and blurred vision are also common side effects. Nasopharyngitis, fatigue, and dry mouth are common side effects as well. gastrointestinal symptoms such as nausea may occur in some patients. If you take Histop, it is important to avoid operating machinery, driving, having excess alcohol or taking other CNS depressant medications.

The general advice to avoid the side effects

Take this medication at the recommended dose and it should not exceed the dose. This medication should be taken with a full glass of water. Do not crush medicines before using. Do not eat food high in fat at the time of the drug. High-fat meal reduces the blood concentrations of Histop.

What are other side effects that are not so common?

Fatigue, and reduce energy consumption reported. Sometimes a patient may have low blood pressure, elevated heart rate, cardiac arrhythmias, and abnormal movements. Dizziness, confusion and depression can occur in some patients. Sleep problems are another annoying side effect that may occur rarely. Very rarely, patients may get tremors and convulsions (fits).

Rarer side effects that are specific to Histop are exforliative dermatitis (skin peeling off), tinnitus, short-term drop in blood pressure, and abnormal central nervous system stimulation.

Use of Histop/Piriton during pregnancy

While there are no evidence of fetal harm, the manufacturer's advice to avoid using Hitop during pregnancy. Especially in the first three months.

Use of Histop/Piriton during lactation

Histop secretes into the breast milk in significant amounts, therefore it should not be used during nursing.


British National Formulary

AHFS Drug Information


Even though the author of this article is a Medical doctor, contents of this article are for information only. You should always consult your doctor, before starting or stopping Histop. In addition, medical information can change over time.

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