Levonorgestrel – Effects, Uses & Side Effects
Levonorgestrel is a synthetic progestogen used in contraception and emergency contraception. It works primarily by inhibiting ovulation.
Things worth knowing about "Levonorgestrel"
Levonorgestrel is a synthetic progestogen used in contraception and emergency contraception. It works primarily by inhibiting ovulation.
What is Levonorgestrel?
Levonorgestrel is a synthetic progestogen (progesterone-like hormone) derived from natural progesterone and used in a wide range of contraceptive products as well as emergency contraception. It is one of the most widely used hormonal active ingredients in gynecological medicine worldwide.
Indications
Levonorgestrel is used for several medical purposes:
- Oral contraception: As a component of combined oral contraceptives (together with estrogen) or as a progestogen-only pill (mini-pill)
- Emergency contraception: As the so-called "morning-after pill" at a dose of 1.5 mg to prevent unintended pregnancy after unprotected intercourse
- Hormonal intrauterine systems (IUS): As a levonorgestrel-releasing intrauterine device (e.g., Mirena, Kyleena) for long-term contraception and treatment of heavy menstrual bleeding
- Treatment of endometriosis and other gynecological conditions
Mechanism of Action
Levonorgestrel acts on multiple levels within the female reproductive system:
- Inhibition of ovulation: Levonorgestrel suppresses the release of the gonadotropins LH and FSH from the pituitary gland, thereby preventing ovulation.
- Thickening of cervical mucus: The cervical mucus becomes thicker, making it more difficult for sperm to enter the uterus.
- Alteration of the endometrium: The uterine lining is changed in a way that makes implantation of a fertilized egg less likely.
When used as emergency contraception, the primary mechanism is the inhibition or delay of ovulation. Effectiveness is highest when the preparation is taken within 72 hours of unprotected intercourse.
Dosage and Usage Notes
The dosage depends on the intended application:
- Mini-pill: 30 µg levonorgestrel daily for continuous contraception
- Combined pill: 50–250 µg levonorgestrel in combination with ethinylestradiol
- Morning-after pill: A single dose of 1.5 mg levonorgestrel (or two doses of 750 µg taken 12 hours apart), taken as soon as possible after unprotected intercourse
- IUS (e.g., Mirena): Local release of 20 µg levonorgestrel per day directly within the uterus for up to 5 years
Side Effects
Like all hormonal contraceptives, levonorgestrel can cause side effects. Commonly reported side effects include:
- Changes in menstrual bleeding (spotting, absence of menstruation)
- Headaches and migraine
- Mood changes, depressive symptoms
- Nausea
- Acne and skin changes
- Breast tenderness
- Changes in libido
When used as emergency contraception, temporary lower abdominal pain, fatigue, and dizziness may also occur.
Contraindications and Interactions
Levonorgestrel should not be used in cases of:
- Known or suspected pregnancy
- Severe liver disease
- Unexplained vaginal bleeding
- Hypersensitivity to the active substance
Certain medications can reduce the effectiveness of levonorgestrel, including rifampicin, certain antiepileptic drugs (e.g., phenytoin, carbamazepine), and St. John's Wort. A healthcare professional should be consulted if these medications are taken concurrently.
References
- European Medicines Agency (EMA): Product information for levonorgestrel-containing medicinal products. www.ema.europa.eu
- World Health Organization (WHO): Medical Eligibility Criteria for Contraceptive Use, 5th Edition, 2015. www.who.int
- Glasier A.: Emergency contraception. In: New England Journal of Medicine, 363(18):1771–1773, 2010.
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