Exetas 25 Drug Interactions

In vitro evidence showed that the drug is metabolised through Cytochrome P450 (CYP) 3A4 and aldoketoreductases and does not inhibit any of the major CYP isoenzymes. In a clinical pharmacokinetic study, the specific inhibition of CYP 3A4 by ketoconazole showed no significant effects on the pharmacokinetics of Exemestane.
In an interaction study with rifampicin, a potent CYP450 inducer, at a dose of 600mg daily and a single dose of Exemestane 25 mg, the AUC of Exemestane was reduced by 54% and Cmax by 41%. Since the clinical relevance of this interaction has not been evaluated, the co-administration of drugs, such as rifampicin, anticonvulsants (e.g. phenytoin and carbamazepine) and herbal preparations containing hypericum perforatum (St John's Wort) known to induce CYP3A4 may reduce the efficacy of Exemestane.
Exemestane should be used cautiously with drugs that are metabolised via CYP3A4 and have a narrow therapeutic window. There is no clinical experience of the concomitant use of Exemestane with other anticancer drugs.
Exemestane should not be co-administered with oestrogen containing medicines as these would negate its pharmacological action.