Consumer medicine information

1 Name of Medicine

Promethazine hydrochloride.

2 Qualitative and Quantitative Composition

Chemists' Own Antihistamine for Allergy Relief tablets come in two strengths and contain either 10 mg or 25 mg of promethazine hydrochloride.
Excipients with known effect. contains sugars as lactose.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

Chemists' Own Antihistamine for Allergy Relief 10 mg tablets are round, white to off-white, flat faced, bevelled-edged tablets, debossed 10 on one side and plain on the reverse side.
Chemists' Own Antihistamine for Allergy Relief 25 mg tablets are round, white to off-white, flat faced, bevelled-edged tablets, debossed 25 on one side and plain on the reverse side.

4 Clinical Particulars

4.9 Overdose

Symptoms of severe overdosage are variable. They are characterised in children by various combinations of excitation, ataxia, incoordination, athetosis and hallucinations, reversible intellectual disability and cognition deficit in children less than 6 years of age, while adults may become drowsy and lapse into coma. Convulsions may occur in both adults and children: coma or excitement may precede their occurrence. Tachycardia may develop. Cardiorespiratory depression is uncommon. The chief sign of acute poisoning from ingestion of an overdose of promethazine hydrochloride is unconsciousness which is commonly delayed. In addition, convulsions, hallucinations, delirium, acute anxiety, psychotic reactions, extreme hyperaesthesia and hyperalgesia with extensor plantar responses may occur. Anticholinergic action may cause tachycardia, flushed skin, dry mouth and sometimes mydriasis and urinary retention.
In adults, CNS depression is more common, with drowsiness, coma, convulsions, progressing to respiratory failure or cardiovascular collapse.
High doses can cause ventricular arrhythmias including QT prolongation and torsade de pointes (see Section 4.8 Adverse Effects (Undesirable Effects)).
In infants and children, CNS stimulation predominates over CNS depression causing ataxia, excitement, tremors, psychoses, hallucinations, convulsions and possibly hyperpyrexia, which may be followed by deepening coma and cardiorespiratory collapse.
Treatment. Similar to that of other phenothiazines. In the event of overdose of promethazine, take all appropriate measures immediately. Symptomatic supportive therapy is indicated and maintenance of adequate ventilation should be instituted if necessary.
For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.3 Preclinical Safety Data

Genotoxicity. No data available.
Carcinogenicity. No data available.

6 Pharmaceutical Particulars

6.7 Physicochemical Properties

Promethazine hydrochloride is a white or faintly yellow, practically odourless, crystalline powder. It is very soluble in water, freely soluble in alcohol and in chloroform, and practically insoluble in ether.
Chemical structure. Its structural formula is:
https://stagingapi.mims.com/au/public/v2/images/fullchemgif/CSPROHYD.gif CAS number. CAS: 58-33-3.

7 Medicine Schedule (Poisons Standard)

S3 - Pharmacist Only Medicine.

Summary Table of Changes

https://stagingapi.mims.com/au/public/v2/images/fulltablegif/CHOAARST.gif