Exemestane (trade names: Symex, Aromasin) is one of the most potent available **Steroidal Aromatase Inhibitors (AIs)**. It belongs to a class of compounds primarily used to lower estradiol (estrogen) levels in the blood.

How Does Exemestane Work?

Exemestane functions by **binding to and permanently deactivating** the aromatase enzyme, which is responsible for converting androgens (e.g., Testosterone) into estradiol (aromatization). This mechanism makes it unique:

• No Estrogen Rebound Risk: Since the bound enzymes are irreversibly deactivated, Exemestane eliminates any risk of a severe estrogen rebound after discontinuation, a significant advantage over non-steroidal AIs.
• High Efficacy: A dose of **25 mg daily** is highly effective at reducing circulating estrogen levels in serum by up to **85%**.

Exemestane stands out among other Aromatase Inhibitors due to its safety and effectiveness in long-term therapy:

• No Negative Impact on Lipids: As a steroidal AI, it avoids the negative impact on the lipid profile often seen with non-steroidal AIs.
• Hepatotoxicity: It is not toxic to the liver (No hepatotoxicity), allowing for safe use over an extended period.
• Ideal for PCT: It is considered an ideal drug for Post Cycle Therapy (PCT) due to its positive effect on the HPTA axis. In studies, a 25 mg daily dose **increased total Testosterone by 60% in just 10 days**.
• Increased Bioavailable Testosterone: Exemestane also lowers SHBG (Sex Hormone-Binding Globulin), which increases the bioavailability of Testosterone, enhancing cycle performance.

Although Exemestane's half-life is only about **9 hours**, its effect in eliminating aromatase enzymes (80-90% after administration) lasts up to 72 hours after a single dose. Therefore:

Dosing Guidelines:

• **Frequency:** Exemestane should be administered every 2–3 days to maintain optimal estrogen concentration.
• **Personalization:** Exact dosages are subject to individual sensitivity and **should be determined based on blood test results (estradiol levels)**.
• **Duration of Use:** It can be used throughout the duration of a steroid cycle to maintain optimal estrogen concentration.