Brand names Calimal, Piriton, Rimarin.
Used in the following combined preparations Contac 400, Dristan, Expulin,
Haymine, Lemsip, and others.
GENERAL INFORMATION
Chlorpheniramine, an antihistamine that has been given for over 30 years, is used to treat allergies such as hay fever, allergic conjunctivitis, urticaria (hives), 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. Chlorpheniramine also has a mild anticholinergic action,
which suppresses mucus secretion.
Chlorpheniramine may also be used to prevent or treat allergic reactions to blood transfusions or X-ray contrast material, and is added to epinephrine (adrenaline) injections for acute allergic shock (anaphylaxis).
QUICK REFERENCE
Drug group Antihistamine
Overdose danger rating Medium
Dependence rating Low
Prescription needed No
Available as generic Yes
INFORMATION FOR USERS
Follow instructions on the label. Call your doctor if symptoms worsen.
How taken
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
4-8 hours (tablets, liquid, injection).
POSSIBLE ADVERSE EFFECTS
Diet advice
None.
Storage
Keep in a closed container in a cool, dry place 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. Notify your doctor.
Drowsiness is the most common adverse effect of chlorpheniramine; other side
effects are rare. Some of these, such as dryness of the mouth, blurred vision,
and difficulty passing urine, are due to its anticholinergic effects.
Gastrointestinal irritation may be reduced by taking tablets or liquid with food
or drink.
INTERACTIONS
Sedatives All drugs with a sedative effect are likely to enhance the sedative
effect of chlorpheniramine.
Phenytoin The effects of Phenytoin may be enhanced by chlorpheniramine.
Anticholinergic drugs All drugs, including certain drugs for parkinsonism, that
have an anticholinergic effect are likely to increase the anticholinergic effect
of chlorpheniramine.
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 fits. You have glaucoma.
You have urinary difficulties.
You are taking other medications.
Pregnancy
Safety in pregnancy not established. Discuss with your doctor.
Breast-feeding
The drug passes into the breast milk, but at normal doses adverse effects on the
baby are unlikely. 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 chlorpheniramine 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
The effect of the drug may become weaker with prolonged use over a period of
weeks or months as the body adapts. Transfer to a different antihistamine may be
recommended.
