Nomegestrol acetate is a synthetic progestin, a medication chemically similar to the natural hormone progesterone. It is used in various hormonal therapies and functions by interacting with the body’s hormonal pathways. This prescription medication is administered orally, either alone or combined with an estrogen.
Medical Uses of Nomegestrol Acetate
The primary application of nomegestrol acetate is as a hormonal contraceptive to prevent pregnancy. It is an ingredient in combined oral contraceptives, often paired with an estrogen like estradiol. One such product, sold under the brand name Zoely, combines 2.5 mg of nomegestrol acetate with 1.5 mg of estradiol. This combination is taken daily to regulate the menstrual cycle and inhibit conception.
Beyond contraception, nomegestrol acetate is used in hormone replacement therapy (HRT) for postmenopausal individuals. It helps manage symptoms associated with menopause by supplementing the body’s declining hormone levels. It is also prescribed for various gynecological disorders. These include managing menstrual disturbances such as heavy or irregular bleeding (menorrhagia) and treating endometriosis, where tissue similar to the uterine lining grows outside the uterus.
The dosages for these applications differ. For gynecological treatments, a dose might be 3.75-5 mg daily, whereas its use in HRT involves lower doses. Its effectiveness in treating endometriosis-related pain has been demonstrated in studies where it reduced chronic pelvic pain.
How Nomegestrol Acetate Functions in the Body
Nomegestrol acetate works by mimicking progesterone, which allows it to influence the menstrual cycle. Its principal function in contraception is the suppression of ovulation. It achieves this by inhibiting the mid-cycle surge of gonadotropin hormones, specifically luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are necessary for an egg to be released from the ovary.
Another way it prevents pregnancy is by altering the cervical mucus. The medication causes the mucus to become thicker and more viscous. This change creates a physical barrier that makes it more difficult for sperm to travel through the cervix and reach an egg.
The drug also affects the endometrium, the lining of the uterus. It causes the endometrium to become thinner, creating an environment that is unfavorable for a fertilized egg to implant. Endometrial thickness has been observed to remain below 8 mm, which is insufficient to support a pregnancy.
Common and Serious Side Effects
Like other hormonal medications, nomegestrol acetate is associated with a range of potential side effects. The most common are changes in menstrual bleeding patterns, which can include irregular bleeding, spotting between periods, or the complete absence of a period (amenorrhea). Users may also experience acne, headaches, breast tenderness, and mood swings. Some individuals report changes in weight or libido.
While many of these side effects are mild, there are less frequent but more serious risks. A significant concern with combined hormonal contraceptives is an increased risk of venous thromboembolism (VTE), which is the formation of blood clots in the veins. The risk of VTE is present for all women taking combined hormonal contraceptives and may be higher for those with underlying risk factors.
It is important to recognize the warning signs of a blood clot and seek immediate medical attention. Symptoms can include sudden or severe pain in the leg, shortness of breath, chest pain, or sudden changes in vision. Blood clots can lead to serious health events like a pulmonary embolism. Discussing your personal and family medical history with a healthcare provider can help assess the level of risk.
Contraindications and Precautions
Certain pre-existing conditions make the use of nomegestrol acetate unsafe. Individuals with a personal or family history of venous thromboembolism (VTE), such as deep vein thrombosis or pulmonary embolism, should not use this medication. It is also contraindicated for those with known hormone-sensitive cancers, including certain types of breast cancer, as the medication could stimulate cancer growth.
Other contraindications include severe liver disease, as the liver is responsible for metabolizing the hormones in the medication. Anyone with undiagnosed abnormal vaginal bleeding should also avoid this drug until a cause is determined. It is important to provide a complete medical history to a healthcare provider before starting treatment.
Certain medications can interact with nomegestrol acetate and reduce its effectiveness as a contraceptive. These include some drugs used to treat epilepsy, such as carbamazepine and phenytoin, as well as certain antibiotics like rifampicin. The herbal supplement St. John’s wort can also interfere with its function. When taking these substances, an additional barrier method of contraception, like a condom, may be necessary.