Adults

1 mg (5 mL syrup) twice daily (morning and evening) with food. May be increased to 2 mg (10 mL syrup) twice daily in severe cases or if required.

Elderly

No specific dosage adjustment required, but caution is advised in elderly patients with impaired organ function.

Renal_impairment

No specific dosage adjustment recommended, but use with caution in severe impairment.

Onset

Full therapeutic effect for asthma prophylaxis may take several weeks (e.g., 2-4 weeks). Antihistaminic effects may be seen earlier.

Excretion

Primarily via urine, with about 1% excreted unchanged. About 60-70% of a dose is excreted in urine and 10% in faeces within 48 hours.

Half life

Plasma half-life is approximately 12 hours (biphasic elimination with a shorter initial half-life of 3-5 hours and a terminal half-life of 21 hours for metabolites).

Absorption

Rapidly absorbed from the GI tract. Absolute bioavailability is about 50% due to first-pass metabolism.

Metabolism

Extensively metabolized in the liver, primarily by N-demethylation and glucuronidation. The major metabolite is ketotifen-N-glucuronide.

Antihistamines

Potentiation of sedative effects. Concurrent use should be avoided or used with caution.

Oral Antidiabetics

Concurrent use may cause a reversible decrease in platelet count, therefore, co-administration is contraindicated.

CNS Depressants (Alcohol, Sedatives, Hypnotics)

Increased CNS depression, drowsiness, and impaired psychomotor function.