Comprehensive Pharmacological and Clinical Monograph: Buserelin (DB06719)

Executive Summary

Buserelin is a potent synthetic analogue of gonadotropin-releasing hormone (GnRH), classified as a GnRH superagonist. Its mechanism of action is biphasic: an initial, transient stimulation of the pituitary-gonadal axis results in a surge of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and consequently, sex steroids (testosterone and estradiol). This is followed by a profound and sustained downregulation of pituitary GnRH receptors with chronic administration, leading to a state of medical castration characterized by a 95% reduction in sex hormone levels. This reversible suppression of the hypothalamic-pituitary-gonadal axis is the cornerstone of its therapeutic utility.

Buserelin is indicated for a range of hormone-dependent conditions. In oncology, it is a key component of androgen-deprivation therapy for advanced, hormone-sensitive prostate cancer and is also used for premenopausal breast cancer. In gynecology, it is effective in treating endometriosis, uterine fibroids, and endometrial hyperplasia by inducing a hypoestrogenic state. Furthermore, it plays a critical role in assisted reproductive technologies (ART) by providing precise control over the menstrual cycle for ovarian stimulation protocols.

The drug's pharmacokinetic profile dictates its formulation and administration. With negligible oral bioavailability, it is administered via subcutaneous injection, depot implant, or nasal spray. The high bioavailability of subcutaneous routes makes them suitable for long-term, consistent suppression in cancer therapy, while the lower bioavailability and short half-life of the nasal spray allow for flexible dosing and rapid cessation of effect, which is advantageous in ART.