Exemestane

A steroidal aromatase inhibitor that permanently deactivates every aromatase molecule it touches. The community calls this the suicidal mechanism, and it is the key difference from anastrozole: once exemestane binds, that enzyme copy is gone, and your body needs to synthesize new aromatase to bring estrogen back up. That takes days, which means no rebound spike when you stop. The steroidal structure also gives exemestane weak androgenic activity.

The clinical evidence base mirrors anastrozole’s: deep in breast cancer, absent for the community use case. The head-to-head trial showed them equivalent for cancer outcomes. The community reaches for exemestane when it wants a cleaner transition off cycle or a lower rebound risk heading into PCT.

Deep oncology data, thin community data. The dosing-flexibility finding is the one that matters most for how people actually run it:

Take exemestane with a meal that has some fat in it. Absorption is meaningfully better with food, and skipping this is the most common rookie mistake with exemestane. On a standard aromatizing cycle, 12.5 mg every other day is the starting point and where most people stay. The phase 2b data confirms that three-times-weekly dosing still suppresses estrogen meaningfully, which supports the less-than-daily approach the community runs. If estrogen is still running hot on bloodwork, move to 12.5 mg daily. Past that, the cycle dose is the problem.

In PCT, exemestane at 12.5 mg every other day pairs with a SERM to cover both sides: the SERM restarts the axis while exemestane keeps estrogen from climbing during the transition. Because the inhibition is irreversible, you do not need to taper. When you stop, estrogen rises gradually as new enzyme is built rather than spiking the way it can with anastrozole.

The suicidal mechanism is a double-edged advantage. If you crash your estrogen, recovery is slower: