Examest Drug Interactions

The drug is metabolised through cytochrome P450 (CYP)3A4 and aldo-keto reductases and does not inhibit any of the major CYP isoenzymes. The specific inhibition of CYP 3A4 by Ketoconazole showed no significant effects on the pharmacokinetics of Exemestane.
Although administration of Rifampicin, a potent CYP3A4 inducer, significantly decreased Exemestane systemic exposure (C_max and AUC), the suppression of plasma estrogen levels (estrone sulfate) produced by Exemestane was not influenced. Therefore, Exemestane can be given concomitantly with inducers of CYP3A4 without dosage adjustment.
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 oesterogen-containing medicines as these would negate its pharmacological action.
In an interaction study with Rifampicin, a potent CYP450 inducer, at a dose of 600 mg daily and a single dose of Exemestane 25 mg. 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.