Buserelina (POSADA) is a gonadotropin-releasing hormone agonist (GnRH agonist). The drug's effects are dependent on the frequency and time course of administration. GnRH is released in a pulsatile fashion in the postpubertal adult. Initial interaction of any GnRH agonist, such as buserelin, with the GnRH receptor induces release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) by gonadotrophes. Long-term exposure to constant levels of buserelin, rather than endogenous pulses, leads to downregulation of the GnRH receptors and subsequent suppression of the pituitary release of LH and FSH.
Like other GnRH agonists, buserelin may be used in the treatment of hormone-responsive cancers such as prostate cancer or breast cancer, estrogen-dependent conditions (such as endometriosis or uterine fibroids), and in assisted reproduction.
It is normally delivered via a nasal spray, but is also available as an injection.
Buserelin is also marketed under the brand name Metrelef. Metrelef is approved to treat patients with endometriosis by suppression of ovarian hormone production. In ovulation induction It is used as a pituitary blockade as an adjunct to gonadotrophin administration.
