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Nafarelin Acetate

Pronunciation: NAFF-uh-RELL-in ASS-uh-TATE
Class: Gonadotropin-releasing hormone

Trade Names

Synarel
- Nasal solution 2 mg/mL (as nafarelin base)

Pharmacology

Initially causes synthesis and release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). With continued use (more than 4 wk) suppresses secretion of LH and FSH.

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Pharmacokinetics

Absorption

Nafarelin acetate is rapidly absorbed into system circulation after intranasal administration. T max is 10 to 40 min, C max is 0.6 to 1.8 ng/mL, and serum bioavailability is 2.8%.

Distribution

Plasma protein binding is 80%.

Elimination

Nafarelin acetate is eliminated in urine (3% as unchanged) and feces. Serum t 1/ 2 is about 3 h (adults), 2.5 h (children), and 85.5 h (metabolites).

Indications and Usage

Treatment of endometriosis, central precocious puberty in children of both sexes.

Contraindications

Hypersensitivity to gonadotropin-releasing hormone (GnRH); or GnRH-agonist analogs; undiagnosed abnormal vaginal bleeding; pregnancy; lactation.

Dosage and Administration

Endometriosis
Adults

Intranasal 400 mcg/day (200 mcg [1 spray] in 1 nostril in morning and 200 mcg [1 spray] in other nostril in evening. For long-term suppression, 800 mcg/day (1 spray in each nostril twice daily) may be necessary.

Central Precocious Puberty
Children

Intranasal 1,600 mcg/day (400 mcg [2 sprays] in each nostril in morning and 400 mcg [2 sprays] in each nostril in evening). In some patients 1,800 mcg/day (3 sprays in alternating nostrils 3 times daily) may be necessary.

General Advice

  • When treating endometriosis, begin treatment between days 2 and 4 of menstrual cycle.
  • Administer intranasally with metered-spray pump. Tilt patient's head back slightly.
  • If administering more than 1 spray per nostril, wait 30 sec between sprays.

Storage/Stability

Store container upright at controlled room temperature (59° to 86°F). Protect from light.

Drug Interactions

None well documented.

Laboratory Test Interactions

Diagnostic tests of pituitary gonadotropic and gonadal function during treatment and 4 to 8 wk after discontinuation of treatment may be misleading.

Adverse Reactions

CNS

Headaches; insomnia; depression.

Dermatologic

Acne; seborrhea.

EENT

Nasal irritation.

Genitourinary

Vaginal dryness.

Miscellaneous

Hot flushes; decreased libido; emotional lability; myalgia; reduced breast size; edema; weight gain; hirsutism; decreased bone density.

Precautions

Pregnancy

Category X .

Lactation

Do not use in lactating women.

Bone density loss

May be small loss in bone density during therapy, some of which may not be reversible. Risk is greater in patients who smoke or have osteoporosis and in alcoholics.

Intercurrent rhinitis

If patient must use topical nasal decongestant during nafarelin therapy, should be used at least 2 h after nafarelin dosing to decrease possibility of reduced absorption.

Menstruation

Should stop with effective doses.

Noncompliance

Irregular or incomplete doses may result in stimulation of pituitary-gonadal axis.

Ovarian cysts

Have occurred in first 2 mo of therapy.

Patient Information

  • Caution patient that this medication must not be taken during pregnancy or when pregnancy is possible. Advise patient to use nonhormonal form of birth control while taking this drug.
  • Advise patient regarding proper administration techniques and storage information.
  • Tell patient to begin treatment between days 2 and 4 of menstrual cycle if being treated for endometriosis.
  • Instruct patient not to blow nose, and to avoid sneezing immediately after administration.
  • Tell patient using topical nasal decongestant to use 2 h after nafarelin has been administered.
  • Advise patient that each bottle contains about 60 sprays and plan refills accordingly.
  • Explain side effects of medication and instruct patient to report the following symptoms to health care provider: bleeding/menses continues, breakthrough bleeding or adverse/side effects.

Copyright © 2009 Wolters Kluwer Health.

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