Apo-Anastrozole Drug Interactions

Antipyrine and cimetidine clinical interaction studies indicate that the co-administration of anastrozole with other drugs is unlikely to result in clinically significant drug interactions mediated by cytochrome P450.
A review of the clinical trial safety database did not reveal evidence of clinically significant interaction in patients treated with anastrozole who also received other commonly prescribed drugs. There were no clinically significant interactions with biphosphonates (see Pharmacology: Pharmacodynamics under Actions).
Oestrogen-containing therapies should not be co-administered with anastrozole as they may counteract the goal of achieving estrogen suppression.
Tamoxifen should not be co-administered with anastrozole, as this may diminish its pharmacological action (see Contraindications). Co-administration of anastrozole and tamoxifen in breast cancer patients reduced anastrozole plasma concentration by 27% compared to those achieved with anastrozole alone; however, the co-administration did not affect the pharmacokinetics of tamoxifen or N-desmethyltamoxifen.