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Peptide Plug is a research and organization tool intended for adults 18 years of age or older. By continuing, you confirm you are at least 18.

Reference only · Not medical advice · For adults 18+ · No dosing information is published here
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Aromatase Inhibitors

Letrozole — reference

Potent non-steroidal aromatase inhibitor for hormone-receptor-positive breast cancer.

Regulatory statusFDA-Approved (labeled use)
Published half-life~2 days (terminal, longer with repeated dosing)
Evidence levelFDA label
CategoryAromatase Inhibitors

Regulatory status

FDA-Approved (labeled use). FDA-approved for breast cancer. Any use in men is off-label.

Reported cautions

⚠ Worth knowing. Substantially more potent than anastrozole and correspondingly easier to over-suppress estradiol with. Bone density loss is a documented long-term effect.

Pharmacokinetics

Published figures give an elimination half-life of ~2 days (terminal, longer with repeated dosing). FDA label (Femara); accumulates somewhat with chronic daily dosing.

This figure is tagged FDA label in our evidence system. This figure appears in an approved product's prescribing information, which is the strongest tier in our system — a regulator-reviewed number for a specific approved product. You can see the shape this implies between doses in the Half-Life Visualizer, and compare it against every other compound in the Half-Life Data Table. Our sourcing page explains what each tier means.

Remember that an estimated curve is a model built from a population figure, not a measurement of your blood. Individual clearance varies, and for depot injections the figure describes release from the injection site rather than the compound clearing. Half-life explained →

What Peptide Plug does and does not publish

This page carries regulatory status, general context and published pharmacokinetics. It carries no dose, frequency or cycle information — that is a deliberate editorial line, because dosing is a clinical decision rather than reference data. We also do not sell, supply, source or link to vendors for any compound.

Frequently asked

Is Letrozole FDA-approved?
FDA-Approved (labeled use). FDA-approved for breast cancer. Any use in men is off-label.
What is the half-life of Letrozole?
Published figures give ~2 days (terminal, longer with repeated dosing). FDA label (Femara); accumulates somewhat with chronic daily dosing.
How reliable is that half-life figure?
It is tagged “FDA label” in our system. This figure appears in an approved product's prescribing information, which is the strongest tier in our system — a regulator-reviewed number for a specific approved product.
What cautions are associated with Letrozole?
Substantially more potent than anastrozole and correspondingly easier to over-suppress estradiol with. Bone density loss is a documented long-term effect.
Does Peptide Plug publish dosing for Letrozole?
No. This library publishes regulatory status, general context and pharmacokinetics only. Dose, frequency and cycle information is deliberately absent from these public pages — those are clinical decisions, not reference data.
Does Peptide Plug sell Letrozole?
No. We do not sell, supply, source or link to vendors for any compound, and we have no affiliate arrangements with suppliers. Peptide Plug is a tracking and calculation tool.

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Reference information, not medical advice. This page describes regulatory status and published pharmacokinetics. It does not tell you whether to use this compound, how much to use, how often, or whether it is safe for you. Peptide Plug does not sell, supply or source any compound. Those decisions belong to you and a licensed clinician.

Part of the Peptide Plug research library · How we source our figures