Chlorohistol is indicated for symptomatic control of all allergic conditions responsive to antihistamines, including hay fever, vasomotor rhinitis, urticaria, angioneurotic oedema, food allergy, drug and serum reactions, insect bites.

Also indicated for the symptomatic relief of itch associated with chickenpox.

Oral administration only

Do not exceed the stated dose or frequency of dosing

The minimum interval between the doses should be 4 hours.

Do not use continuously for more than two weeks without consulting a doctor.

Adults and children 12 years and over: 10mL (4mg) every 4 to 6 hourly. Maximum daily dose: 60mL (24mg) 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 12mg in any 24 hours).

Children aged 6 - 12 years: 5mL (2mg) every 4 to 6 hourly. Maximum daily dose: 30mL (12mg) in any 24 hours.

Children aged 2 - 6 years: 2.5mL (1mg) every 4 to 6 hourly. Maximum daily dose: 15mL (6mg) in any 24 hours.

Children aged 1 - 2 years: 2.5mL (1mg) twice daily. Maximum daily dose: 5mL (2mg) in any 24 hours.

Not recommended for children below 1 year

Populations

Patients with renal or hepatic impairment should seek doctor's advice prior to taking this medicine. (See Section 4.4 Special warnings and precautions for use).

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 impairment; renal impairment. Children and the elderly are more likely to experience the neurological anticholinergic effects and paradoxical excitation (e.g. Increased energy, restlessness, nervousness). Avoid use in elderly patients with confusion.

The anticholinergic properties of chlorpheniramine may cause drowsiness, dizziness, blurred vision and psychomotor impairment in some patients which may seriously affect ability to drive and use machinery.

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

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

Concurrent use with drugs which cause sedation such as anxiolytics and hypnotics may cause an increase in sedative effects, therefore medical advice should be sought before taking chlorpheniramine concurrently with these medicines.

Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrose-isomaltase insufficiency should not take this medicine.

Chlorohistol Syrup contains sucrose. This should be taken into account in patients with diabetes mellitus.

Long term use increases the risk of dental caries and it is essential that adequate dental hygiene is maintained.

Methyl paraben and propyl paraben may cause allergic reactions (possibly delayed)

Keep out of the reach and sight of children.

Concurrent use of chlorpheniramine and hypnotics or anxiolytics may cause an increase in sedative effects; concurrent use of alcohol may have a similar effect therefore medical advice should be sought before taking chlorphenamine concurrently with these medicines.

Chlorpheniramine inhibits phenytoin metabolism and can lead to phenytoin toxicity.

The anticholinergic effects of chlorpheniramine are intensified by MAOIs (see Contra-indications).

Pregnancy

There are no adequate data from the use of chlorpheniramine in pregnant women. The potential risk for humans is unknown; Use during the third trimester may result in reactions in the new-born or premature neonates. Not to be used during pregnancy unless considered essential by a physician.

Lactation

Chlorpheniramine maleate and other antihistamines may inhibit lactation and may be secreted in breast milk. Not to be used during lactation unless considered essential by a physician.

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

The following convention has been utilised for the classification of the frequency of adverse reactions: very common (>1/10), common (>1/100 to <1/10), uncommon (>1/1000 to <1/100), rare (>1/10,000 to <1/1000) and very rare (<1/10,000), not known (cannot be estimated from available data).

Adverse reactions identified during post-marketing use with chlorpheniramine are listed below. As these reactions are reported voluntarily from a population of uncertain size, the frequency of some reactions is unknown but likely to be rare or very rare:

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

Healthcare professionals are asked to report any suspected adverse reactions via:

• 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.

Symptoms and signs

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

Treatment

Management should be as clinically indicated or as recommended by the national poisons centres where available. Symptomatic and supportive measures should be provided with special attention to cardiac, respiratory, renal and hepatic functions and fluid and electrolyte balance. If overdosage is by the oral route, treatment with activated charcoal should be considered provided there are no contraindications for use and the overdose has been taken recently (treatment is most effective if given within an hour of ingestion.) Treat hypotension and arrhythmias vigorously. CNS convulsions may be treated with I.V. diazepam. Haemoperfusion may be used in severe cases.

ATC Code:  R06AB04

Chlorpheniramine is a potent antihistamine (H₁-antagonist).

Antihistamines diminish or abolish the actions of histamine in the body by competative reversible blockade of histamine H₁-receptor sites on tissues. Chlorpheniramine also has anticholinergic activity.

Antihistamines act to prevent the release of histamine, prostaglandins and leukotrines and have been shown to prevent the migration of inflammatory mediators. The actions of chlorpheniramine include inhibition of histamine on smooth muscle, capillary permeability and hence reduction of oedema and wheal in hypersensitivity reactions such as allergy and anaphylaxis.

Chlorpheniramine is well absorbed from the gastro-intestinal tract, following oral administration. The effects develop within 30 minutes, are maximal within 1 to 2 hours and last 4 to 6 hours. The plasma half-life has been estimated to be 12 to 15 hours.

Chlorpheniramine is metabolised to the monodesmethyl and didesmethyl derivatives. About 22% of an oral dose is excreted unchanged in the urine.

No additional data of relevance.

None known.

Before opening: Store below 30°C.

After opening: Store below 30°C and use within one month.

100mL Syrup in an amber glass bottle provided with aluminium/CRC cap, packed in a printed carton along with a leaflet and measuring cup.

No special requirements