Medications and Drugs
Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD
GENERIC NAME: nafarelin
BRAND NAME: Synarel
DRUG CLASS AND MECHANISM: Nafarelin is a synthetic (man-made) protein that
blocks the effects of the natural gonadotropin-releasing hormone (GnRH), a
hormone that regulates the output of gonadotropins (a class of hormones) by the
pituitary gland (a small gland located at the base of the brain). Gonadotropins
(follicle stimulating hormone or FSH and luteinizing hormone or LH) are hormones
that cause estrogen production by the ovaries. When nafarelin (known
scientifically as a GnRH analog) is administered continuously to women in their
reproductive years, the pituitary output of FSH, LH, and the production of
estrogen by the ovaries are suppressed. Suppression of estrogen production
causes menstruation to stop, resulting in a temporary (but reversible) state of
"menopause." This temporary state of menopause results in shrinkage of the lining of the
uterus, known as the endometrium.
Endometriosis is a condition whereby the cells
that normally form the endometrium inside of the uterus are instead found
outside of the uterus. These abnormally located cells (called endometrial
implants) are most commonly found on the ovaries, Fallopian tubes, outer surfaces of the uterus or intestines,
and on the surface lining of the pelvic cavity. Like the normal endometrium,
implants respond to the hormones of the menstrual cycle, i.e., they build up
during the month, then break down and bleed during menstruation. However, unlike
normal endometrium, the implants bleed internally. (blood from implants cannot
exit the body like blood from the uterus can.) The internal bleeding, followed
by tissue inflammation and subsequent scarring, is believed to be responsible
for the symptoms of pain and infertility in women with endometriosis. Nafarelin
has been found to be effective in relieving the pain of endometriosis and
shrinking the endometrial implants.
FSH and LH also control the onset of puberty in boys and girls. Therefore,
administration of nafarelin blocks the puberty-promoting effects of FSH and LH,
reducing the development of secondary sexual characteristics (such as pubic
hair) and skeletal development in boys and girls with abnormally early puberty
(central precocious puberty) due to problems in the brain that result in high
levels of FSH and LH. The FDA approved nafarelin in February 1991.
PRESCRIPTION: Yes
GENERIC AVAILABLE: No
PREPARATIONS: Nasal spray: 200µg/spray
STORAGE: Nafarelin should be stored at room temperature, 15 to 30 C (59 to 86
F).
PRESCRIBED FOR: Nafarelin is prescribed for the management of endometriosis,
to relieve pain and shrink endometrial implants. It also is used for managing
central precocious puberty.
DOSING: For treatment of endometriosis nafarelin is given as one spray (200
µg) into one nostril in the morning and one spray in the other nostril in the
evening for 6 months. The first dose of nafarelin should be taken between the
second and fourth day after menstrual bleeding begins. After the first two
months of nafarelin treatment, most women can expect a decrease in menstrual
flow, and menstruation may stop altogether. For women who continue to experience
normal menstrual cycles after two months of treatment, the daily dose may be
increased to 800 µg daily.
Central precocious puberty is treated with 1600-1800 µg daily administered as
four sprays in alternating nostrils twice daily or three sprays in alternating
nostrils three times daily. Thirty seconds should elapse between sprays.
For optimal effectiveness and safety, nafarelin has to be given continuously
without interruption. Missing one or more doses can cause vaginal bleeding.
Missing successive doses can cause release of an egg from the ovary (ovulation)
and result in pregnancy, unless proper contraceptive measures have been
followed. Since birth control pills cannot be used with nafarelin, it is
important to use non-hormonal methods of contraception (such as a
diaphragm with
contraceptive jelly, IUD, or condoms) while taking nafarelin.
Absorption of nafarelin is not affected by a cold or runny nose. If nasal
decongestant sprays are needed, they should be taken at least 2 hours before or
after using nafarelin.
DRUG INTERACTIONS: Nasal decongestant sprays (for example, Afrin) may interfere with
the absorption of nafarelin. If nasal decongestant sprays are needed, they
should be used at least 2 hours before or after using nafarelin.
PREGNANCY: Nafarelin should not be used in
pregnancy or in women who may
become pregnant while receiving the medication because it might harm the fetus.
Safe use of nafarelin in pregnancy has not been established. Pregnancy must be
excluded before starting treatment with this medication, and a non-hormonal
method of contraception should be used during treatment.
NURSING MOTHERS: Nafarelin should not be used by
nursing mothers because its
safety has not been evaluated.
SIDE EFFECTS: Side effects of nafarelin are mostly related to the low
estrogen state. Side effects include hot flashes, vaginal dryness,
headaches,
mood changes, and decreased interest in sex. Some patients may experience acne,
muscle pain, reduced breast size, and irritation of the tissue inside the nose.
These side effects should disappear after stopping the medication.
The low estrogen state and the temporary menopause induced by nafarelin can
cause a small amount of bone thinning, which may only partially recover after
stopping treatment. Patients should discuss this possibility with their doctors
and alert their doctors to conditions that they may have that could increase the
risk of bone thinning. These conditions include chronic
tobacco use, excessive
use of alcohol, family history of osteoporosis, and taking other medications
that can cause bone thinning (such as anticonvulsants or corticosteroids).
Reference: FDA Prescribing Information
Last Editorial Review: 9/2/2009
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
- Drug Interactions - Learn about potential drug interactions you may be exposed to. Drug interactions can occur with prescription drugs, OTC medication, vitamins, herbs, and supplements.
- Endometriosis - Lern about endometriosis symptoms like pelvic pain, infertility, diarrhea, constipation, lower back pain, abdominal pain, irregular or heavy menstrual bleeding, and even blood in the urine.
- Drugs: What You Should Know About Your Drugs - Find out what you should know about your drugs such as side effects, warnings and precautions, storage information, and if a generic version is as good as the brand name.
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