CHLORPHENAMINE

Posology Adults The usual dose of chlorphenamine injection for adults is 10 mg to 20 mg, but not more than 40 mg should be given within a 24-hour period. When a rapid effect is desired, as in anaphylactic reactions, the intravenous route is recommended in addition to emergency therapy with adrenaline (epinephrine), corticosteroids, oxygen and supportive therapy as required.

In this case chlorphenamine injection should be injected slowly over a period of one minute, using the smallest adequate syringe. Any drowsiness, giddiness or hypotension which may follow is usually transitory. In the event of a blood transfusion reaction, a dose of 10 mg to 20 mg of chlorphenamine injection should be given by the subcutaneous route.

This can be repeated to a total of 40 mg within a 24-hour period, or oral forms of chlorphenamine may be given until the symptoms subside. Chlorphenamine injection may be helpful in the prevention of delayed reactions to penicillin and other drugs when given separately by intramuscular injection immediately prior to administration of the other drug.

The usual dose is 10 mg. Chlorphenamine injection cannot, however, be relied on to prevent anaphylactic reactions in patients known to be allergic to a particular drug. 20 mg/kg Extra care should be taken when preparing the injection for children under 1 year due to the small volumes that are required.

9% w/v) should facilitate preparation. 9% injection produces a solution containing chlorphenamine 1 mg/ml. The diluted product should be used immediately. Method of administration Intramuscular Subcutaneous Intravenous When administered intravenously the injection should be given slowly over a period of one minute in order to avoid hypotension or central nervous system stimulation.

The following effects have been reported and are listed below by system organ class: System Organ Class (SOC) Frequency Adverse Event Blood and lymphatic system disorders Not known* Haemolytic anaemia and other blood dyscrasias Cardiac disorders Not known* Palpitations Ear and labyrinth disorders Not known* Tinnitus Eye disorders Not known* Blurred vision Gastrointestinal disorders Not known* Nausea, vomiting, diarrhoea, dry mouth, painful dyspepsia General disorders and administration site conditions Not known* Irritability, lassitude, stinging or burning sensation at the site of injection Hepatobiliary disorders Not known* Hepatitis including jaundice Immune system disorders Not known* Hypersensitivity, anaphylactic reaction Metabolism and nutrition disorders Not known* Anorexia Musculoskeletal and connective tissue disorders Not known* Twitching, muscular weakness, incoordination Nervous system disorders Not known* Headaches, dizziness, inability to concentrate, sedation (most common side effect varying from slight drowsiness to deep sleep), CNS stimulation (as a result of rapid intravenous injection) Psychiatric disorders Not known* Depression, nightmares, paradoxical excitation in children, confusional psychosis in the elderly Renal and urinary disorders Not known* Urinary retention Respiratory, thoracic and mediastinal disorders Not known* Thickening of bronchial secretions Skin and subcutaneous tissue disorders Not known* Exfoliative dermatitis, photosensitivity, skin reactions, urticaria Vascular disorders Not known* Transitory hypotension (as a result of rapid intravenous injection) * cannot be estimated from the available data Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important.

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Chlorphenamine, in common with other drugs having anticholinergic effects, should be used with caution in epilepsy; raised intra-ocular pressure including glaucoma; prostatic hypertrophy; severe hypertension or cardiovascular disease; bronchitis; bronchiectasis and asthma; hepatic disease and thyrotoxicosis.

Children and the elderly are more likely to experience the neurological anticholinergic effects. This medicine contains less than 1 mmol sodium (23 mg) per ml, that is to say essentially 'sodium-free'.

1. The anticholinergic properties of chlorphenamine are intensified by monoamine oxidase inhibitors (MAOIs). Chlorphenamine injection is therefore contraindicated in patients who have been treated with MAOIs within the last fourteen days.