What is Exemestane?
Exemestane (brand name Aromasin) is a steroidal, irreversible aromatase inhibitor - a so-called suicide inhibitor. Unlike reversible anastrozole, exemestane binds aromatase permanently and shuts the enzyme molecule down completely. The body has to make new aromatase to restore activity.
This information is for research and educational purposes only. No medical advice.
How it works
As a suicide inhibitor, exemestane binds aromatase irreversibly and deactivates it for good. That has a practical advantage: after stopping there is no estrogen rebound (no sudden estradiol spike) as can occur with reversible AIs. Exemestane also has a mildly androgenic structure itself and tends to affect lipids more favorably than non-steroidal AIs.
Exemestane vs anastrozole
- Exemestane (steroidal, irreversible): no rebound after stopping, tends to be more lipid-friendly.
- Anastrozole (non-steroidal, reversible): finer control in small steps, larger experience base in AAS research.
Dosing
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What the research shows
The Intergroup Exemestane Study (Coombes et al., NEJM 2004) showed that switching to exemestane after 2-3 years of tamoxifen improved disease-free survival in postmenopausal breast cancer. That confirms the strong and reliable estrogen lowering.
Side effects
- Too-low estradiol: joint pain, libido loss, fatigue.
- Watch bone density with long-term use.
- Tends to be more lipid-friendly than non-steroidal AIs.
Storage
Store dry and protected from light. Out of reach of children.