Chlorpheniramine: Uses, Side Effects & Safety

What it is and what it's used for

Chlorpheniramine is an antihistamine medicine, one of the older (first-generation) antihistamines. It is used to relieve allergy symptoms such as sneezing, a runny or blocked nose, itchy and watery eyes, skin itching, rashes and hives. It is also very commonly used for the symptoms of the common cold, which is why it is an ingredient in many cold and cough syrups and tablets sold in India.

Chlorpheniramine is usually taken for short periods when symptoms are present, rather than every day for months. It is available on its own as tablets and syrup, and it is also combined with medicines such as paracetamol or a decongestant in many popular cold remedies — so it is worth checking the label, because you may already be taking it as part of a combination product.

In India, chlorpheniramine is widely available without a prescription in pharmacies, both on its own and in combination products. Even though it is easy to buy, it is a strongly sedating medicine, so it should be used with care, especially in children, older people, and anyone who drives or operates machinery.

How it works (simple language)

When the body comes into contact with something it is allergic to — such as pollen, dust, or animal fur — it releases a chemical called histamine. Histamine is what causes the sneezing, itching, runny nose and watery eyes of an allergy. Chlorpheniramine is thought to work by blocking histamine from acting on the body, which calms these symptoms down.

Because chlorpheniramine is an older antihistamine, it also affects the brain, which is why it commonly causes drowsiness. Some people actually use this sleepiness deliberately, for example taking a cold remedy at night, but the same effect makes it unsuitable during the day for anyone who needs to stay alert.

Dosage forms available in India (general info only)

Chlorpheniramine is commonly available in India as 4 mg tablets and as syrup, and it is also an ingredient in many combination cold and cough products. Brands vary, so check the label of any cold remedy you buy — chlorpheniramine maleate is often listed among its ingredients.

Never decide the dose yourself from this article. Always follow your doctor's prescription or the directions on the pack, and check with your pharmacist if you are unsure — especially for children, where the dose depends on the child's weight and age.

Side effects

Common: Drowsiness or sleepiness, dry mouth, dizziness, headache, blurred vision, constipation, nausea, and difficulty passing urine.

Serious — seek medical care: Very fast or irregular heartbeat, severe dizziness or fainting, confusion, agitation or hallucinations, seizures, difficulty breathing, swelling of the face, lips or tongue, or being unable to pass urine at all. Seek urgent medical help if any of these occur, as they may indicate a serious reaction or overdose.

Precautions and warnings

• It causes drowsiness: Chlorpheniramine can make you very sleepy, and the effect can last into the next morning. Do not drive, cycle, or operate machinery after taking it, and be careful on stairs or ladders until you know how it affects you.
• Avoid alcohol and sedatives: Alcohol, sleeping pills, and some anxiety medicines increase the drowsiness caused by chlorpheniramine and can dangerously slow your reactions and breathing. Avoid alcohol while taking it.
• Glaucoma and prostate problems: Tell your doctor if you have glaucoma, an enlarged prostate, or difficulty passing urine, as chlorpheniramine can worsen these conditions.
• Children need extra care: Chlorpheniramine should only be given to young children on a doctor's advice, and the dose must be measured carefully. In some children it can cause the opposite effect — restlessness or excitement instead of sleepiness.
• Older people are more sensitive: Older adults are more likely to feel confused, dizzy, or unsteady on chlorpheniramine, which raises the risk of falls. Use the lowest effective amount and only for as short a time as needed.
• Check combination products: Many cold remedies already contain chlorpheniramine. Taking two such products together can double the dose and increase drowsiness and side effects, so always check the ingredients on every pack.
• Do not use it to make a child sleep: Chlorpheniramine should never be given simply to sedate a child or to help them sleep; it is a medicine for allergy and cold symptoms, and misuse can be harmful.

Interactions (general)

Chlorpheniramine can interact with alcohol, sleeping pills, anxiety medicines, some antidepressants, and other sedating antihistamines, increasing drowsiness. It may also interact with medicines for Parkinson's disease and some bladder medicines. It can increase the drying effects of some other medicines, such as those for stomach cramps. Always tell your doctor about ALL medicines you take, including herbal and ayurvedic products, before taking chlorpheniramine.

Pregnancy and breastfeeding (general guidance)

Chlorpheniramine has been used for many years, but it should only be taken in pregnancy if your doctor advises it, as the evidence about its safety in pregnancy is limited. Small amounts may pass into breast milk and could make a breastfed baby drowsy or irritable, so talk to your doctor before using it while breastfeeding. Always consult your doctor first if you are pregnant, planning pregnancy, or breastfeeding.

Storage

Store chlorpheniramine tablets and syrup at room temperature, away from heat and moisture, and out of the reach of children. Keep syrup bottles tightly closed, and do not use the medicine past its expiry date.

When to see a doctor

See a doctor if: your allergy or cold symptoms do not improve within a few days, you feel excessively sleepy or confused, you have difficulty passing urine, your eyesight becomes blurred, or you develop a fast heartbeat or severe dizziness. Seek emergency care immediately for difficulty breathing, swelling of the face or lips, fainting, seizures, or signs of a severe allergic reaction.

FAQs

1. Why does chlorpheniramine make me sleepy when newer allergy medicines do not?

Chlorpheniramine is an older, first-generation antihistamine that reaches the brain and blocks histamine there as well as in the rest of the body, which causes drowsiness. Newer antihistamines such as cetirizine and loratadine act mainly outside the brain, so they are much less sedating.

2. Can I take chlorpheniramine during the day?

You can, but it may make you drowsy and slow your reactions, so it is not a good choice if you need to drive, work with machinery, or stay fully alert. Many people prefer a non-sedating antihistamine during the day and reserve chlorpheniramine for the evening or night-time, if their doctor agrees.

3. Is it safe to give chlorpheniramine to children?

It can be used in children, but only on a doctor's advice and with the dose measured exactly as directed for the child's age and weight. Never guess the dose, never give it just to help a child sleep, and watch for unusual restlessness or excitement, which can occasionally happen in children.

4. Can I take chlorpheniramine with a cold remedy?

Check the label first — many cold remedies already contain chlorpheniramine, so taking both would double the dose. If your cold remedy already lists chlorpheniramine maleate among its ingredients, do not add a separate chlorpheniramine tablet unless your doctor tells you to.