CIPI-M, chlorpheniramine

CHLORMINE (Chlorphenamine Tablets BP 4mg)

Chlorphenamine Maleate is a potent antihistamine (H1-receptor antagonist) and acts by blocking the action of histamine in the body by competitive reversible blockade of histamine H1-receptor sites on tissues. Thereby mediates the contraction of smooth muscle and the dilation and increased permeability of the capillaries and hence reduction of oedema and wheal in hypersensitivity reactions such as allergy and anaphylaxis.

Pharmacokinetic

Absorption: Chlorphenamine maleate is well absorbed from the gastrointestinal tract after oral dosing with extensive first-pass effect. The effects develop within 30 minutes and maximum within 1 to 2 hours and last 4 to 6 hours.

Distribution: It is highly bound to plasma proteins. It is distributed widely in the body. It enters the brain and cross the placenta. Antihistamines pass into the milk at low concentrations

Metabolism: The plasma half-life has been estimated to be 12 to 15 hours. Chlorphenamine is metabolized to the monodesymethyl and didesmethyl derivatives.

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Excretion: it is slowly excreted via urine and bile. About 22% of an oral dose is excreted unchanged in the urine. Only trace amounts have been found in the feces.

Indications

To relieve the symptoms of allergic conditions such as hay fever (seasonal allergic rhinitis), urticaria, pruritis, food allergy, drug and serum reactions, insect bite or sting reactions, allergies to foods or medicines and angioneurotic oedema.

Contraindications

Hypersensitivity to chlorphenamine or to any of the excipients. Hypersensitivity to antihistamines.

Patients in coma or patients with brain damage

Patients on monoamine oxidase inhibitor therapy within the previous 14 days.

Special precautions and warning

Use with caution in epilepsy, raised intra-ocular pressure including glaucoma, prostatic hypertrophy, severe hypertension or cardiovascular disease, thyrotoxicosis, urinary retention, bronchitis, bronchiectasis or asthma, hepatic impairment.

Children and the elderly are more likely to experience the neurological effects and paradoxical excitation (e.g. increased energy, restlessness, nervousness)

The effect of alcohol may be increased and therefore concurrent use should be avoided

Should not be used with other antihistamines containing products, including antihistamines containing cough and cold medicines

Patients with a rare hereditary problem of galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine

Keep out of sight and reach of children.

Pregnancy: Category B. Safety for use during pregnancy has not been established.

Lactation: may inhibit lactation and may be secreted in breast milk. Not to be used during lactation unless considered essential by a physician.

Dosage and directions for use

Do not exceed the stated dose or frequency of dosing

Adults and children over 12 years: 1 tablet 4 to 6 hourly. Maximum daily dose; 6 tablets (24mg in total) in any 24 hours

Elderly: The elderly are more likely to experience neurological anticholinergic effects. Consideration should be given to using a lower daily dose (e.g. a maximum of 3 tablets (12 mg in total) in any 24 hours, taken 1 tablet 4 to 6 hourly

Children aged 6-12 years: ½ tablet 4 to 6 hourly. Maximum daily dose: 3 tablets (12 mg in total) in any 24 hours

Not recommended for children under the age of 6 years.

Adverse effects

Nervous system disorders: sedation varying from slight drowsiness to deep sleep, somnolence, dizziness, headache and concentration ability impaired, incordination

Eye disorders: blurred vision

Gastrointestinal disorders: nausea, dry mouth, vomiting, diarrhea, abdominal pain, dyspepsia and anorexia.

General disorders and administration site conditions: lassitude, dizziness, tightness of chest and irritability.

Drug interactions
  • Chlorphenamine inhibits phenytoin metabolism and can lead to phenytoin toxicity.
  • Alcohol potentiates sedation due to chlorphenamine.
  • The risk of antimuscarinic side effects is increased when antihistamines are given with antimuscarinics.
  • Antidepressant increase the sedative and antimuscarinic effects of antihistamines
  • Concurrent use of chlorphenamine and hypnotic or anxioliytics may cause an increase in sedative effects.
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  • The anticholinergic effects of chlorphenamine are intensified by MAOIs
  • Lopinavir may increase the plasma concentration of chlorphenamine.
Overdosage

Estimated lethal dose of chlorphenamine is 25-50mg/kg body weight. Symptoms and signs include sedation, paradoxical stimulation of CNS, toxic psychosis, seizures, apnoea, convulsions, anticholinergic effects, dystonic reactions and cardiovascular collapse including arrhythmias.

Treatment includes gastric lavage or emesis using syrup of ipecac. Following these measures the activated charcoal and cathartics may be administered to minimize absorption. Other symptomatic and supportive measures should be provided with special attention to cardiac, respiratory, renal and hepatic functions and fluid and electrolyte balance.

Treat hypotension and arrhythmias vigorously. CNS convulsions may be treated with IV diazepam or phenytoin. Haemoperfusion may be used in severe cases.

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