BMA Concise Guide to Medicine & Drugs

Chlorphenamine (Chlorpheniramine)

Brand names Allercalm, Boots Allergy Relief, Piriton

Used in the following combined preparations Galpseud Plus, Haymine

QUICK REFERENCE

Drug group Antihistamine

Overdose danger rating Medium

Dependence rating Low

Prescription needed No (tablets and liquid); yes (injection)

Available as generic No

GENERAL INFORMATION

Chlorphenamine has been used for over 30 years to treat allergies such as hay fever, allergic conjunctivitis, urticaria (hives), insect bites and stings, and angioedema (allergic swellings). It is included in several over-the-counter cold remedies.

Like other antihistamines, it relieves allergic skin symptoms such as itching, swelling, and redness. It also reduces sneezing and the runny nose and itching eyes of hay fever. Chlorphenamine also has a mild anticholinergic action, which suppresses mucus secretion.

Chlorphenamine may also be used to prevent or treat allergic reactions to blood transfusions or X-ray contrast material, and can be given with epinephrine (adrenaline) injections for acute allergic shock (anaphylaxis).

INFORMATION FOR USERS

Follow instructions on the label. Call your doctor if symptoms worsen.

How taken/used Tablets, liquid, injection.

Frequency and timing of doses 4–6 x daily (tablets, liquid); single dose as needed (injection).

Dosage range Adults 12–24mg daily (by mouth); up to 40mg daily (injection). Children Reduced dose according to age and weight.

Onset of effect Within 60 minutes (by mouth); within 20 minutes (injection).

Duration of action 4–6 hours (tablets, liquid, injection).

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug Can be safely stopped as soon as you no longer need it.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause drowsiness or agitation, seizures, or heart problems. Notify your doctor.

POSSIBLE ADVERSE EFFECTS

Drowsiness is the most common adverse effect of chlorphenamine; other side effects are rare. Some of these, such as dry mouth, blurred vision, and difficulty in passing urine, are due to its anticholinergic effects. Gastrointestinal irritation may be reduced by taking the tablets or liquid with food or drink. Discuss with your doctor if these symptoms become severe or if the drug causes severe headaches. If you develop a rash, or if a child taking the drug becomes unusually excitable, stop the drug and consult your doctor.

INTERACTIONS

Anticholinergic drugs All drugs, including some drugs for parkinsonism, that have an anticholinergic effect are likely to increase the anticholinergic effect of chlorphenamine.

Phenytoin The effects of phenytoin may be enhanced by chlorphenamine.

Monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants These drugs may increase the side effects of chlorphenamine.

Sedatives All drugs with a sedative effect are likely to increase the sedative properties of chlorphenamine.

SPECIAL PRECAUTIONS

Be sure to consult your doctor or pharmacist before taking this drug if:

· You have a long-term liver problem.

· You have had epileptic seizures.

· You have glaucoma.

· You have urinary difficulties.

· You are taking other medicines.

Pregnancy Safety in pregnancy not established. Discuss with your doctor.

Breast-feeding The drug passes into the breast milk and may cause drowsiness and poor feeding in the baby. Discuss with your doctor.

Infants and children Reduced dose necessary.

Over 60 Reduced dose may be necessary. Increased likelihood of adverse effects.

Driving and hazardous work Avoid such activities until you have learned how chlorphenamine affects you because the drug can cause drowsiness, dizziness, and blurred vision.

Alcohol Avoid. Alcohol may increase the sedative effects of this drug.

PROLONGED USE

No problems expected.