buserelin

REMS

Subcutaneous injection: Initial and maintenance palliative treatment of advanced hormone-dependent prostate cancer (usually given with an anti-androgen).
Nasal solution: Maintenance palliative treatment of advanced hormone-dependent prostate cancer (usually given with an anti-androgen).
Nasal solution: Nonsurgical treatment of endometriosis (course of treatment 6–9 mo).

Action ⬆ ⬇

Acts as a synthetic analog of endogenous gonadotropin-releasing hormone (GnRH/LHRH). Chronic use results in inhibited secretion of gonadotropin release and gonadal steroid production. The overall effect is due to down-regulation of pituitary LHRH receptors. In males, testosterone synthesis and release is decreased. In females, secretion of estrogen is decreased.

Therapeutic effects:

Decreased spread of advanced prostate cancer.
Decreased sequelae of endometriosis (pain, dysmenorrhea).

Pharmacokinetics ⬆ ⬇

Absorption: SUBQ: 70%; intranasal: 1–3%; implant: drug is slowly absorbed over 2–3 mo.

Distribution: Accumulates in liver, kidneys and anterior pituitary lobe; enters breast milk in small amounts.

Metabolism/Excretion: Metabolized in liver, kidneys and by enzymes on membranes in the pituitary gland.

Half-Life: SUBQ: 80 min; intranasal: 1–2 hr; implant: 20–30 days.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
prostate cancer ‡	7 days	4 mo	until discontinuation
endometriosis ‡(intranasal)	unknown	unknown	duration of treatment

‡↓in testosterone levels.

‡Symptom improvement.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Nonhormonal-dependent prostate cancer or previous orchiectomy;
Females with undiagnosed vaginal bleeding;
OB: Pregnancy (avoid use);
Lactation: Avoid breastfeeding (small amounts enter breast milk; injection contains benzyl alcohol).

Use Cautiously in:

Prostate cancer with urinary tract obstruction or spinal lesions;
Pedi: Safety and effectiveness not established (injection contains benzyl alcohol).

Adv. Reactions/Side Effects ⬆ ⬇

CNS: depression, dizziness

CV: hypertension

Endo: glucose intolerance

Hemat: anemia

Local: injection site reactions

MS: osteoporosis (long-term use)

Misc: transient exacerbation of metastatic prostate cancer or endometriosis

Prostate cancer

CNS: headache (nasal solution)

EENT: nasal irritation (nasal spray)

GU: ↓libido, impotence

Derm: hot flushes

Endo: gynecomastia, testosterone flare

MS: bone pain

Endometriosis

CNS: headache, weakness, insomnia

CV: edema

GI: constipation, gastrointestinal disorders, nausea

GU: ↓libido, vaginal dryness, menorrhagia

Derm: hot flushes, acne

Endo: suppression of ovulation

MS: back pain

Interactions ⬆ ⬇

Drug-drug:

Risk of serious arrhythmias may be ↑ by concurrent amiodarone, disopyramide, dofetilide, flecainide ibutilide, propafenone quinidine, sotalol, antipsychotics (including chlorpromazine) antidepressants (including amitriptyline and nortriptyline), opioids (including methadone), macrolide anti-infectives (including azithromycin, erythromycin and clarithromycin), fluoroquinolones (including moxifloxacin), azole antifungals, 5-HT3 antagonists (including ondansetron), beta-2 receptor agonists (including salbutamol), pentamidine, and quinine.

Route/Dosage ⬆ ⬇

Prostate cancer

SC (Adults ): Initial treatment: 500 mcg every 8 hr for 7 days, Maintenance treatment: 200 mcg daily.
(Adults ): Maintenance treatment: 400 mcg (200 mcg in each nostril) 3 times daily.

Endometriosis

(Adults ): 400 mcg (200 mcg in each nostril) 3 times daily. Treatment is usually continued for 6 mo; not to exceed 9 mo.

Availability ⬆ ⬇

Solution for subcutaneous injection (contains benzyl alcohol): 1000 mcg/mL
Intranasal Solution: 1000 mcg/mL (delivers 100 mcg per actuation)

Assessment ⬆ ⬇

Cancer: Monitor patients with vertebral metastases for increased back pain and decreased sensory/motor function.
Monitor intake and output ratios and assess for bladder distention in patients with urinary tract obstruction during initiation of therapy.
Endometriosis: Assess for signs and symptoms of endometriosis before and periodically during therapy. Amenorrhea usually occurs within 8 wk of initial administration and menses usually resume 8 wk after completion.

Lab Test Considerations:

Monitor serum testosterone levels every 3 mo during treatment with male patients. When treatment begins, testosterone levels can temporarily markedly ↑ and patients may need another medication to ↓ levels.
- Monitor blood glucose in patients with diabetes frequently; may affect blood glucose levels.
- Verify negative pregnancy test before starting therapy for women.

Implementation ⬆ ⬇

Prostate Cancer

SC: Only use syringes that come with kit for accurate dose. Inject into fatty tissue of abdomen, arm, or leg 3 times/day for 7 days; then daily during maintenance.
When used as maintenance, begin nasal spray in each nostril 3 times daily. If patient also receives decongestant nasal spray, wait 30 min to give buserelin spray before or after the decongestant.

Endometriosis

One spray in each nostril 3 times daily for 6–9 mo.

Patient/Family Teaching ⬆ ⬇

Inform male patients that they may experience breast swelling and tenderness, decreased libido, hot flashes and sweats, impotence and weight gain. Notify health care professional if these symptoms occur.
Inform female patients that they may experience decreased libido, constipation, painful sexual intercourse, menopausal symptoms, changes in hair growth. Notify health care professional if these symptoms occur.
Rep: Caution both male and female patients to use contraception while taking this drug. Advise females of reproductive potential to inform health care professional if pregnancy is suspected. Buserelin may cause fetal harm.
SC: Instruct patient in proper technique for self-injection, care and disposal of equipment. Use only syringes included in kit. Instruct patients that syringes may only be used once, and then discarded.
Instruct patient on proper nasal spray technique. Prime pump before use.
Advise patients that the nasal spray can cause nose bleeds, and may change smell and taste senses.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇