AncillaryWell-studiedAromatase Inhibitor

Letrozole (Femara)

Aromatase Inhibitor

Also known as Femara, Letrozole

Half-life

~2 days

What is Letrozole (Femara)?

Most potent AI — reduces estrogen by 95%+. Primarily for gyno treatment emergencies.

How Letrozole (Femara) works

Potent nonsteroidal aromatase inhibitor causing profound estradiol suppression.

Benefits & uses

Common uses: Severe gynecomastia reversal, last-resort estrogen control tool.

Letrozole (Femara) dosage

Protokol doesn't recommend doses for prescription or controlled compounds. Any figures below are reference or observational reports — dosing should be set with a qualified clinician.

Reference range: Literature reports ~1–2.5 mg (often short courses); very potent — easy to crash estrogenClinical or reference range, not a personal recommendation.

Letrozole (Femara) half-life

~2 days

Letrozole (Femara) side effects

Very easy to crash estrogen. Not recommended for routine use on cycle.

Severe low-estrogen symptoms
Joint pain
Cognitive/mood effects
Fatigue/lethargy
Crashed-estrogen effects (very common at full doses)

Warnings & monitoring

Prescription medication — very potent, easy to over-suppress estrogen. Requires a doctor + bloodwork.

Monitoring: Requires estradiol bloodwork; high crash risk given potency.

Letrozole (Femara) interactions

with Anastrozole
Avoid · moderate
Both are aromatase inhibitors. Letrozole is far more potent; using together guarantees an estrogen crash.
Timing: Never combine AIs
with Anastrozole
Avoid · moderate
Both are competitive aromatase inhibitors — combining them provides no additional estrogen control and risks severe estrogen crash (joint pain, low libido, depression, bone loss). Choose one AI.
Timing: Never use two aromatase inhibitors simultaneously

Track Letrozole (Femara) in Protokol.

Log doses, model half-lives, check interactions, and line it all up against your bloodwork. Free on iPhone and Android.