Chlorohistol is indicated for the following:

§ Acute urticaria,

§ Control of allergic reactions to insect bites and stings,

§ Angioneurotic oedema,

§ Drug and serum reactions,

§ Desensitisation reactions,

§ Hay fever,

§ Vasomotor rhinitis,

§ Severe pruritus of non-specific origin.

Adults:

The usual dose of chlorpheniramine injection for adults is 10mg to 20mg, but not more than 40mg should be given within a 24-hour period. The injection may be given by the subcutaneous, intramuscular or intravenous route.

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 chlorpheniramine 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 10mg to 20mg of chlorpheniramine injection should be given by the subcutaneous route. This can be repeated to a total of 40mg within a 24-hour period, or oral forms of chlorpheniramine may be given until the symptoms subside.

Chlorpheniramine 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 10mg.

Chlorpheniramine injection cannot, however, be relied on to prevent anaphylactic reactions in patients known to be allergic to a particular drug.

Paediatric population:

The dose for children should be calculated, based on either the child's age or their body weight, using the following table:

Age	Dose
1 month to 1 year			0.25mg/kg
1 to 5 years	2.5mg to 5mg	OR	0.20mg/kg
6 to 12 years	5mg to 10mg	OR	0.20mg/kg
12 to 18 years	10mg to 20mg	OR	0.20mg/kg

Extra care should be taken when preparing the injection for children under 1 year due to the small volumes that are required. Dilution of chlorpheniramine injection with sodium chloride intravenous infusion (0.9% w/v) should facilitate preparation. For example, diluting 0.2ml chlorpheniramine injection to 2ml with sodium chloride 0.9% injection produces a solution containing chlorpheniramine 1mg/ml.

 

 

 Hypersensitivity to the active substance, antihistamines or to any of the excipients listed in section 6.1.  Use in pre-coma states.  The anticholinergic properties of chlorpheniramine are intensified by monoamine oxidase inhibitors (MAOIs). Chlorpheniramine injection is therefore contraindicated in patients who have been treated with MAOIs within the last fourteen days.

Chlorpheniramine, 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.

Chlorohistol contains sodium. This should be considered for patients who are on a controlled sodium diet.

Concurrent use of chlorpheniramine and hypnotics or anxiolytics may potentiate drowsiness. Concurrent use of alcohol may have a similar effect.

Chlorpheniramine inhibits phenytoin metabolism and can lead to phenytoin toxicity.

The anticholinergic effects of chlorpheniramine are intensified by MAOIs (see section 4.3).

There is inadequate evidence of safety in human pregnancy. Chlorpheniramine injection should only be used during pregnancy when clearly needed and when the potential benefits outweigh the potential unknown risks to the foetus. Use during the third trimester may result in reactions in neonates.

It is reasonable to assume that chlorpheniramine may inhibit lactation and may be secreted in breast milk. The use of chlorpheniramine injection in mothers breast-feeding their babies requires that the therapeutic benefits of the drug should be weighed against the potential hazards to the mother and baby.

The anticholinergic properties of chlorpheniramine may cause drowsiness, blurred vision and psychomotor impairment, which can seriously hamper the patient's ability to drive and use machinery.

The most common side-effect is sedation varying from slight drowsiness to deep sleep. The following may also occasionally occur: inability to concentrate; lassitude; blurred vision; gastro-intestinal disturbances such as nausea, vomiting and diarrhoea.

Urinary retention; headaches; dry mouth; dizziness; palpitation; painful dyspepsia; anorexia; hepatitis including jaundice; thickening of bronchial secretions; haemolytic anaemia and other blood dyscrasias; allergic reactions including exfoliative dermatitis, photosensitivity, skin reactions and urticaria; twitching, muscular weakness and incoordination; tinnitus; depression; irritability and nightmares infrequently occur.

Paradoxical excitation in children and confessional psychosis in the elderly can occur.

Some patients have reported a stinging or burning sensation at the site of injection. Rapid intravenous injection may cause transitory hypotension or CNS stimulation.

 

To report any side effect(s):

§ Saudi Arabia:

The National Pharmacovigilance Centre (NPC):

-        Fax: +966-11-205-7662

-        SFDA Call Centre: 19999

-        E-mail: npc.drug@sfda.gov.sa

-        Website: https://ade.sfda.gov.sa/

§ Other GCC States:

Please contact the relevant competent authority.

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

Symptomatic and supportive measures should be provided with special attention to cardiac, respiratory, renal and hepatic functions, and fluid and electrolytic balance. If overdosage is by the oral route, treatment should include gastric lavage or induced emesis using syrup of ipecacuanha. Following these measures activated charcoal and cathartics may be administered to minimise absorption.

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

Pharmacotherapeutic group: Antihistamines for systemic use

ATC code: R06AB04

Antihistamines including chlorpheniramine, which is used in the treatment of allergy act by competing with histamine for H₁-receptor sites on cells and tissues. Chlorpheniramine also has anticholinergic activity.

The mechanism by which chlorpheniramine exerts its anti-emetic, anti- motion sickness and anti-vertigo effects is not precisely known but may be related to its central actions. Further, most antihistamines, including chlorpheniramine, cross the blood-brain barrier and probably produce sedation largely by occupying H₁-receptors in the brain.

Following I.V. administration, the apparent steady-state volume of distribution of chlorpheniramine is approximately 3L/kg in adults and 3.8L/kg in children.

Chlorpheniramine is approximately 70% bound to plasma proteins.

In adults with normal renal and hepatic function, the terminal elimination half-life of chlorpheniramine reportedly ranges from 12 to 43 hours.

The systemic exposure per mg dose is lower in children than adults and the elimination half-life may be shorter.

There are no pre-clinical data of relevance to the prescriber which are additional to that already included in other sections of the Summary of Product Characteristics.

Inactive Ingredients:

1.    Sodium chloride

2.    Water for injection

In the absence of incompatibility studies, this product must not be mixed with other medicinal products.

The injection should be given immediately after opening the ampoule. Once opened, any unused portion should be discarded.

24 months from the date of manufacturing.

Store below 30°C, protected from light.

5 labelled amber coloured ampoules in a printed box, along with a leaflet.

Use in the paediatric population

Due to the small volumes that are required for children under one year of age, chlorpheniramine may be diluted with sodium chloride 0.9% injection to produce a solution containing chlorpheniramine 1mg/ml. For example, 0.2ml chlorpheniramine may be diluted to 2ml with sodium chloride 0.9% injection immediately prior to administration. See information under “Posology and method of administration” for details of paediatric dosing.

The diluted solution should be inspected visually for particulate matter and discoloration prior to administration. In the event of either being observed, discard the medicinal product. Only clear solution should be used.

This medicinal product is for single use only.

If the entire reconstituted content of the ampoule is not required, any unused solution should be discarded in accordance with local requirements.