Buserelin (Suprefact)

Prescription

Buserelin acetate (brand name Suprefact, and Suprecur for some indications) is a synthetic nonapeptide GnRH agonist widely used outside the United States. It shares the class-defining position-6 substitution (D-serine(tBu)) and C-terminal ethylamide that make GnRH agonists potent and long-lasting. It is available both as a subcutaneous depot implant and as a nasal spray, giving prescribers flexibility across indications. Buserelin's mechanism is the standard GnRH-agonist paradox: continuous receptor stimulation causes an initial flare, then downregulates and desensitizes the pituitary GnRH receptor, suppressing LH and FSH and lowering sex steroids. In men with prostate cancer this produces androgen deprivation; in women with endometriosis it lowers estrogen to quiet ectopic tissue. A prominent use of buserelin is in assisted reproduction. In 'long protocol' IVF, buserelin is started before ovarian stimulation to suppress the woman's own pituitary, preventing a premature LH surge so that the fertility team can control follicle development and precisely time ovulation with an exogenous trigger. This exploits the suppression phase of the drug's action and is a different application from long-term cancer or endometriosis therapy. Buserelin is approved in the EU, UK, Canada, and Australia but is not marketed in the United States, where leuprolide, goserelin, triptorelin, and histrelin fill the same roles. Its side-effect profile matches the GnRH-agonist class — hypoestrogenic or hypoandrogenic effects, an early flare, and bone density considerations with prolonged use. Treatment is directed by an oncologist, gynecologist, or fertility specialist.