Buserelin
Buserelin is a synthetic GnRH agonist with a D-Ser(tBu)6 substitution and C-terminal ethylamide modification, approximately 40x more potent than native GnRH. Marketed as Suprefact and Suprecur, it is used clinically for prostate cancer, endometriosis, and IVF downregulation, with wider adoption in Europe, Canada, and Australia than the United States.
Overview
Buserelin was developed in the 1970s-1980s as part of the wave of GnRH superagonists designed to exploit the paradoxical downregulation of the pituitary-gonadal axis by sustained GnRH receptor stimulation. Its dual structural modifications — the D-amino acid at position 6 preventing endopeptidase cleavage, and the C-terminal ethylamide enhancing receptor binding — produce a molecule approximately 40 times more potent than native GnRH. Buserelin is distinguished clinically by its intranasal formulation, which provides a non-injection option for patients, and by its significant veterinary applications in aquaculture (particularly salmon spawning induction). While it shares the same mechanism and clinical indications as other GnRH agonists (leuprolide, goserelin, triptorelin), regional prescribing patterns have made buserelin the dominant GnRH agonist in several non-US markets.
Mechanism of Action
Buserelin binds the GnRH receptor (GnRHR) on anterior pituitary gonadotroph cells with substantially higher affinity than native GnRH. Like all GnRH agonists, it produces a biphasic hormonal response. During the initial 1-2 weeks of continuous administration, buserelin stimulates LH and FSH release (the flare phase), transiently elevating testosterone in men and estradiol in women. With sustained receptor occupancy, GnRHR undergoes internalization, downregulation of receptor mRNA, and uncoupling of intracellular Gq/11 signaling cascades. By 2-4 weeks, gonadotropin secretion is suppressed to castrate levels, and sex steroid production falls correspondingly. The 40x potency advantage over native GnRH allows effective pituitary desensitization at relatively low doses, enabling intranasal delivery despite the limited bioavailability of the nasal route.
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Research
IVF Downregulation
Buserelin is widely used in European IVF centers for pituitary downregulation in the long protocol. Subcutaneous buserelin (500 mcg daily, reduced to 200 mcg daily after downregulation is confirmed) or intranasal buserelin (900 mcg/day) starting in the mid-luteal phase suppresses endogenous gonadotropin surges during controlled ovarian stimulation. Daya (2000) reviewed outcomes of GnRH agonist long protocols, demonstrating improved IVF success rates through prevention of premature LH surges.
Veterinary Aquaculture
Buserelin has significant veterinary applications, particularly in salmonid aquaculture where it is used to induce ovulation and spermiation. The peptide is administered by injection to broodstock fish, triggering gonadotropin release and gamete maturation. This application exploits the conserved GnRH system across vertebrates and represents a major commercial use of buserelin outside human medicine.
Prostate Cancer
Buserelin was among the first GnRH agonists evaluated for medical castration in advanced prostate cancer. Borgmann et al. (1982) demonstrated that subcutaneous buserelin achieved castrate testosterone levels equivalent to bilateral orchiectomy. Subsequent large-scale trials confirmed long-term efficacy and established buserelin as standard androgen deprivation therapy in European oncology practice. Intranasal buserelin (900 mcg/day in three divided doses) provided a non-injection alternative, though compliance with TID nasal dosing was a recognized limitation.
Endometriosis
Intranasal buserelin (900 mcg/day) effectively induces a hypoestrogenic state causing regression of endometriotic implants and relief of pelvic pain, dysmenorrhea, and dyspareunia. Fedele et al. (1989) compared buserelin nasal spray to danazol, showing comparable efficacy with fewer androgenic side effects (weight gain, acne, hirsutism). Treatment is typically limited to 6 months due to bone density concerns.
Prostate cancer androgen deprivation
Buserelin is a synthetic nonapeptide GnRH agonist. After an initial gonadotropin flare, sustained administration down-regulates pituitary GnRH receptors, producing medical castration. Randomized comparisons found it equivalent to orchiectomy for testosterone suppression and survival in metastatic prostate cancer, and superior to estrogens for symptom control. Co-administration of an antiandrogen mitigates the initial testosterone-surge flare. It is approved in Europe and Canada but not the United States.
- Equivalent to orchiectomy for castration and survival
- Superior to estrogens for performance status and symptom relief
- Flare mitigated by concurrent antiandrogen therapy
Gynecologic hypoestrogenic therapy
By suppressing ovarian estrogen production, buserelin induces a reversible hypoestrogenic state used to treat endometriosis, uterine fibroids and endometrial hyperplasia, and for pituitary down-regulation in IVF. Multicenter studies support efficacy in endometriosis, with hypoestrogenic side effects limiting treatment duration.
- Reduces endometriotic lesions and pain over 6 months
- Used for pituitary down-regulation in assisted reproduction
- Hypoestrogenic effects (hot flashes, bone loss) constrain duration
Safety Profile
Buserelin shares the class-wide safety profile of GnRH agonists. Primary adverse effects result from the intended hypogonadal state: hot flashes (60-80%), decreased libido, sexual dysfunction, mood changes, and fatigue. Long-term use causes bone mineral density loss (2-5% per year), metabolic syndrome risk, and potential cardiovascular effects. The initial flare phase (days 1-14) can cause transient disease worsening in prostate cancer, managed with anti-androgen cover. Intranasal-specific adverse effects include nasal irritation, rhinitis, epistaxis, and nasal mucosal dryness in 10-20% of patients. Nasal decongestant use can alter absorption and should be avoided within 30 minutes of buserelin administration. All hormonal effects are reversible upon discontinuation, with recovery typically within 2-4 months.
Pharmacokinetic Profile
Buserelin — Pharmacokinetic Curve
Intranasal spray, Subcutaneous injection, IM depotQuick Start
- Route
- Intranasal spray, Subcutaneous injection, IM depot
Molecular Structure
- Formula
- C60H86N16O13
- Weight
- 1299.5 Da
- CAS
- 57982-77-1
- PubChem CID
- 50225
- Exact Mass
- 1238.6560 Da
- LogP
- -0.1
- TPSA
- 441 Ų
- H-Bond Donors
- 15
- H-Bond Acceptors
- 15
- Rotatable Bonds
- 33
- Complexity
- 2450
Identifiers (SMILES, InChI)
InChI=1S/C60H86N16O13/c1-7-64-57(87)48-15-11-23-76(48)58(88)41(14-10-22-65-59(61)62)69-51(81)42(24-33(2)3)70-56(86)47(31-89-60(4,5)6)75-52(82)43(25-34-16-18-37(78)19-17-34)71-55(85)46(30-77)74-53(83)44(26-35-28-66-39-13-9-8-12-38(35)39)72-54(84)45(27-36-29-63-32-67-36)73-50(80)40-20-21-49(79)68-40/h8-9,12-13,16-19,28-29,32-33,40-48,66,77-78H,7,10-11,14-15,20-27,30-31H2,1-6H3,(H,63,67)(H,64,87)(H,68,79)(H,69,81)(H,70,86)(H,71,85)(H,72,84)(H,73,80)(H,74,83)(H,75,82)(H4,61,62,65)/t40-,41-,42-,43-,44-,45-,46-,47+,48-/m0/s1
CUWODFFVMXJOKD-UVLQAERKSA-NResearch Indications
Approved Indications
GnRH agonist producing medical castration; available as depot and intranasal formulations (Suprefact/Profact).
Induces hypoestrogenic state to reduce endometriotic lesions and pain (Suprecur).
Other / Investigational Uses
Used to shrink fibroids and control bleeding via estrogen suppression.
Employed for pituitary down-regulation in controlled ovarian stimulation.
Research Protocols
subcutaneous Injection
Subcutaneous buserelin (500 mcg daily, reduced to 200 mcg daily after downregulation is confirmed) or intranasal buserelin (900 mcg/day) starting in the mid-luteal phase suppresses endogenous gonadotropin surges during controlled ovarian stimulation. Clinical Research Protocols Subcutaneous Initiati
| Goal | Dose | Frequency | Duration |
|---|---|---|---|
| General Research Protocol | 500 mcg, 200 mcg, 900 mcg, 300 mcg, 50 mg, 5 mg, 6.3 mg | Daily | 2-4 weeks(Route: Subcutaneous Injection, Intranasal) |
intranasal Injection
Buserelin is distinguished clinically by its intranasal formulation, which provides a non-injection option for patients, and by its significant veterinary applications in aquaculture (particularly salmon spawning induction). The 40x potency advantage over native GnRH allows effective pituitary desen
| Goal | Dose | Frequency | Duration |
|---|---|---|---|
| General Research Protocol | 500 mcg, 200 mcg, 900 mcg, 300 mcg, 50 mg, 5 mg, 6.3 mg | Daily | 2-4 weeks(Route: Subcutaneous Injection, Intranasal) |
Interactions
Peptide Interactions
Combining buserelin with bicalutamide or flutamide provides combined androgen blockade, suppressing both testicular and adrenal androgen action. The anti-androgen also serves as flare protection during the first 2-4 weeks of buserelin initiation.
What to Expect
What to Expect
Effects begin within hours of administration based on half-life of ~80 minutes (SC); effective duration depends on formulation
Subcutaneous injection provides near-complete bioavailability (>95%) with Tmax of 1-2 hours.
Buserelin 500 mcg SC three times daily for 7 days (loading phase), then transition to maintenance: either SC 200 mcg daily or intranasal 900 mcg/day...
Testosterone monitoring at baseline, 1 month, and 3-month intervals.
Buserelin acetate depot implant (6.3 mg) provides sustained release over 2 months.
Quality Indicators
Caution
- Short half-life may require frequent dosing
Frequently Asked Questions
References (12)
- [7]
- [8]Shore et al — Oral GnRH antagonist relugolix versus injectable GnRH agonists: a shifting paradigm Lancet Oncol. (2024)
- [9]Ferrero et al — GnRH agonists for endometriosis: intranasal vs. depot formulations Reprod. BioMed. Online (2023)
- [2]
- [5]
- [10]Neven et al — Long-term safety of GnRH agonists in central precocious puberty Hum. Reprod. Update (2022)
- [1]Borgmann V et al Sustained suppression of testosterone by the long-acting GnRH agonist buserelin Urol Int (1982)
- [3]
- [4]Daya S Gonadotropin releasing hormone agonist protocols for pituitary desensitization in IVF Hum Reprod (2000)
- [10]Danish Buserelin Study Group The effect of Buserelin versus conventional antiandrogenic treatment in patients with T2-4NXM1 prostatic cancer: a prospective, randomized multicentre phase III trial (Danish Buserelin Study Group) Scandinavian Journal of Urology and Nephrology (1996)
→ In 140 men with metastatic prostate cancer, buserelin suppressed testosterone and improved performance status comparably to orchiectomy, and better than estrogens.
- [11]et al. Treatment of endometriosis with the GnRH agonist buserelin (Suprecur): a multicenter study Geburtshilfe und Frauenheilkunde (1994)
→ In 430 women, intranasal buserelin 3x300 mcg/day for 6 months reduced endometriosis in a multicenter phase III evaluation.
- [12]et al. Intranasal buserelin in the treatment of advanced prostatic cancer: a phase II trial Cancer (1987)
→ Among 31 evaluable men with advanced prostate cancer, 25 responded (2 complete, 12 partial, 11 improved) to intranasal buserelin.
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