buserelin

General

Canada-Approved Medicine

This monograph describes a medication approved for use in Canada by the Therapeutic Products Directorate, a division of Health Canada’s Health Products and Food Branch. The medication is not approved by the United States Food and Drug Administration; however, a similar formulation carrying a different generic or brand name might be available in the US.

Pronunciation:
bue-se-rel-in

Trade Name(s)

  • Suprefact Canadian Trade name

Ther. Class.

antineoplastics

hormones

Pharm. Class.

luteinizing hormone-releasing hormone (LHRH) analogues

Indications

  • 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– Non-surgical 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 Effect(s):

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

Pharmacokinetics

Absorption: Subcut– 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 and Excretion: Metabolized in liver, kidneys and by enzymes on membranes in the pituitary gland.

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

TIME/ACTION PROFILE

ROUTEONSETPEAKDURATION
prostate cancer †7 days4 mountil discontinuation
endometriosis ‡(intranasal)unknownunknownduration of treatment
†↓ in testosterone levels.‡Symptom improvement.

Contraindication/Precautions

Contraindicated in:

  • Hypersensitivity;
  • Nonhormonal-dependent prostate cancer or previous orchiectomy;
  • Females with undiagnosed vaginal bleeding;
  • OB:  Pregnancy (avoid use);
  • Lactation: Avoid breast feeding (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).

Adverse 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 flair

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: supression of ovulation

MS: back pain

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

Risk of serious arrhythmias may be ↑ by concurrent  amiodarone,  disopyramide,  dofetilide,  flecainide   ibutilide,  propafenone   quinidine,  sotalol,  antipsychotics  (including  chlorpromazine)   antidepressants  (including  amitrypline  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

Subcut (Adults): Initial treatment– 500 mcg every 8 hr for 7 days,  Maintenance treatment– 200 mcg daily.

Intranasal (Adults): Maintenance treatment– 400 mcg (200 mcg in each nostril) 3 times daily.

 Subcut implant: (Adults): 6.3 mg every 2 mo or 9.45 mg every 3 mo.

Endometriosis

Intranasal (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)

Subcutaneous implant (depot): 6.3 mg (2–mo implant), 9.45 mg (3–mo implant)

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.

Potential Diagnoses

  • Sexual dysfunction
  • Disturbed body image

Implementation

Prostate Cancer

  • Subcut 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.
  • Intranasal 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.
  • Implant:

    Implant is inserted in subcut tissue of upper abdominal wall every 28 days. Local anesthesia may be used before injection.

    • If the implant needs to be removed for any reason, it can be located by ultrasound.

Endometriosis

  • Intranasal 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.
  • Caution both male and female patients to use contraception while taking this drug. Advise female patient to inform health care professional if pregnancy is suspected. Buserelin can be harmful to a fetus.
  • Subcut 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.
  • Intranasal 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.

Evaluation/Desired Outcomes

  • Decrease in the spread of prostate cancer.
  • Decrease in lesions and pain in endometriosis.