Short answer: Leuprolide has a half-life of about 3 hours (after an IV dose). Levels peak 2 to 4 hours after a depot injection after a dose. People vary, so treat these as estimates.
Leuprolide (leuprolide acetate, also called leuprorelin) is a synthetic version of GnRH, the brain hormone that tells the pituitary to release LH and FSH. Given continuously, it shuts that signal down and lowers testosterone in men and estrogen in women. It is sold as Lupron Depot, a long-acting injection given by a healthcare provider for advanced prostate cancer, endometriosis and fibroids, and as Lupron Depot-PED for early puberty in children.
Also known as: Lupron Depot, leuprorelin, leuprolide acetate.
For prostate cancer, Lupron Depot comes as 7.5 mg (one injection every 4 weeks), 22.5 mg (every 12 weeks), 30 mg (every 16 weeks) and 45 mg (every 24 weeks). For endometriosis and fibroids it comes as 3.75 mg (monthly) and 11.25 mg (every 3 months). Lupron Depot-PED for children comes in 1-, 3- and 6-month strengths. Each kit is a prefilled two-chamber syringe: the powder is mixed with the liquid in the other chamber and injected into muscle all at once. The labels say not to use part of a kit or combine kits, because the strengths release the drug differently.
The Lupron Depot labels approve leuprolide for advanced prostate cancer (7.5, 22.5, 30 and 45 mg), for endometriosis and, with iron, for anemia from fibroids before surgery (3.75 and 11.25 mg), and, as Lupron Depot-PED, for central precocious puberty (early puberty) in children. It must be given by a healthcare provider. For endometriosis, one course is up to 6 months, and the total is capped at 12 months, with retreatment only alongside norethindrone acetate "add-back" tablets, because it causes bone loss that may not fully reverse.
The prostate cancer label warns that testosterone first rises to about 50% above baseline in the first weeks, which can briefly worsen symptoms (the "flare"). It also warns about high blood sugar, diabetes and high blood fats, a reported higher risk of heart attack, sudden cardiac death and stroke in men taking GnRH agonists, QT prolongation, seizures, severe skin reactions, and harm to an unborn baby. The 3.75 mg label says it is not used in pregnancy or with undiagnosed abnormal uterine bleeding.
WADA bans GnRH agonists, naming leuprorelin, as testosterone-stimulating peptides in males (S2.2.1), in and out of competition. See also goserelin and triptorelin.
The Lupron Depot labels give a terminal half-life of about 3 hours after a 1 mg IV dose in healthy men. After a depot injection, levels peak within hours (at 4 hours for the 22.5 mg and 3.75 mg kits, and 2 hours for the 45 mg kit), then settle into a steady release from about the third week that lasts the whole dosing interval. That slow release, not the half-life, is why one injection lasts 1 to 6 months.
Numbers shown are taken from the source above. Half-life varies from person to person.
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