Myfembree (relugolix/estradiol/norethindrone) is a prescription medication used in premenopausal women to manage heavy menstrual bleeding due to uterine fibroids and moderate to severe pain associated with endometriosis. While Myfembree can provide relief from these conditions, it is essential to be aware of its potential side effects. This article provides a comprehensive overview of Myfembree's side effects, ranging from common to severe, and offers guidance on managing them effectively.
What is Myfembree?
Myfembree is a relatively new oral medication, approved since 2021, combining three active ingredients: relugolix, estradiol, and norethindrone. Relugolix helps modulate hormone production, while estrogen and progestin provide a gentle way to manage pain associated with uterine fibroids and endometriosis. It is typically prescribed for premenopausal women who wish to avoid surgery for managing heavy bleeding and pain.
How Myfembree Works
The medication is taken orally once daily, with or without food. Most patients experience symptom relief after a few months of regular use. Relugolix, the primary active ingredient, blocks instructions from the brain that signal the ovaries to produce hormones like progesterone and estrogen. While these hormones are crucial for overall health and menstrual cycle function, excessive production can lead to problems. The inclusion of estrogen in Myfembree helps mitigate unwanted side effects like hot flashes or bone loss, which can occur when estrogen is fully suppressed.
Many patients report improvements in symptoms, particularly bleeding, within the first 4 to 8 weeks of starting Myfembree. The full benefits may take up to 3 months. If you are not satisfied with your experience after this period, consult your healthcare team for further evaluation and potential adjustments to your treatment.
Myfembree is approved for treating uterine fibroids and endometriosis. While newer, it may have other off-label uses.
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Treatment of Uterine Fibroids
Uterine fibroids are noncancerous growths causing heavy, prolonged periods, pelvic pain, and bloating. Myfembree helps alleviate these symptoms by reducing the amount of estrogen and progesterone in the body, which can fuel fibroid growth.
Treatment of Endometriosis
Myfembree is also used to treat moderate to severe endometriosis-related pain. By gently reducing estrogen, it can slow the growth of endometrial tissue outside the uterus without causing severe low-hormone symptoms.
Common Side Effects of Myfembree
The side effects most people experience with Myfembree are generally mild and temporary, often subsiding as the body adjusts to the medication. These include:
- Hot flashes
- Increased sweating, including night sweats
- Headache
- Nausea
- Joint or back pain
- Low libido (low sex drive)
- Irregular menstruation, such as lighter, shorter, or missed periods
- Fatigue
- Hair loss (alopecia)
In clinical trials involving women with heavy menstrual bleeding associated with uterine fibroids, common adverse reactions included vasomotor symptoms, uterine bleeding, alopecia, and decreased libido. For women with moderate to severe pain associated with endometriosis, common adverse reactions included headache, vasomotor symptoms, mood disorders, abnormal uterine bleeding, nausea, toothache, back pain, decreased sexual desire and arousal, arthralgia, fatigue, and dizziness.
Hair Loss (Alopecia)
Hair loss and hair thinning can occur while taking Myfembree. In Phase 3 placebo-controlled clinical trials involving women with heavy menstrual bleeding associated with uterine fibroids, 3.5% of Myfembree-treated women experienced alopecia, hair loss, and hair thinning, compared to 0.8% of placebo-treated women. In some cases, alopecia was reported as moderate, and one woman discontinued treatment due to hair loss. The majority of affected women completed the study with reported hair loss ongoing. It is not known if this hair loss or hair thinning stops or is reversible after stopping treatment.
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Menstrual Cycle Changes
Myfembree can cause changes in menstrual bleeding, including amenorrhea (absence of menstruation) or a reduction in the amount, intensity, or duration of menstrual bleeding. This may delay the ability to recognize pregnancy. Some people stop getting periods altogether after one to two months, while others may experience light or irregular bleeding.
While changes to your cycle may happen, lack of a period is not usually a cause for concern while patients are on Myfembree. However, if your bleeding is unusually heavy or painful after starting treatment, contact your doctor. Occasional breakthrough bleeding or spotting is relatively common when patients start taking Myfembree, but this should subside after the first few months.
Impact on Weight
Myfembree is not typically associated with significant weight changes. Hormonal medications can sometimes cause mild increases or decreases in weight as the body adjusts. Some users report symptoms related to hormonal fluctuations, such as fluid retention (bloating), increased appetite, or changes in physical activity due to reduced symptoms, which can indirectly affect weight.
Serious Side Effects of Myfembree
While most side effects are mild, Myfembree can also cause serious side effects that require immediate medical attention. These include:
- Cardiovascular Conditions: Myfembree may increase the risk of heart attack, stroke, or blood clots, especially in women over 35 who smoke or have uncontrolled high blood pressure.
- Symptoms: Leg pain or swelling, sudden shortness of breath, double vision, bulging of the eyes, sudden partial or complete blindness, pain or pressure in the chest, arm, or jaw, sudden severe headache, weakness or numbness in an arm or leg, or trouble speaking.
- Bone Loss (Decreased Bone Mineral Density): Prolonged use of Myfembree can lead to bone loss, which may not be completely reversible after stopping treatment.
- Recommendation: Assessment of BMD by dual-energy X-ray absorptiometry (DXA) is recommended at baseline, periodically during treatment for women with heavy menstrual bleeding associated with uterine fibroids, and annually for women with moderate to severe pain associated with endometriosis.
- Mood Disorders: Myfembree may cause mood changes, including depression, anxiety, and suicidal ideation.
- Recommendation: Evaluate patients with a history of suicidal ideation, depression, and mood disorders prior to initiating treatment. Monitor patients for mood changes and depressive symptoms, and refer patients with new or worsening depression, anxiety, or other mood changes to a mental health professional.
- Liver Problems: Myfembree can cause liver injury, indicated by elevated liver enzymes (ALT and AST) in some patients.
- Symptoms: Jaundice (yellowing of the skin or eyes), right upper abdominal pain, dark urine, fatigue, nausea, or vomiting.
- High Blood Pressure: Myfembree may cause new or worsening hypertension.
- Recommendation: Monitor blood pressure regularly.
- Uterine Fibroid Prolapse or Expulsion: Women with known or suspected submucosal uterine fibroids should be advised about the possibility of uterine fibroid prolapse or expulsion.
- Hypersensitivity Reactions: Allergic reactions, including anaphylactoid reactions, urticaria, and angioedema, have been reported.
- Symptoms: Swelling of the face, lips, mouth, or tongue, trouble breathing, skin rashes, redness, or swelling.
- Abnormal Liver Tests: Elevations in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) have been reported in clinical trials.
- High Blood Pressure: New or worsening hypertension has been observed in some patients.
- Uterine Fibroid Prolapse or Expulsion: Fibroids can come out completely or partially through the vagina.
- Severe Allergic Reactions: Myfembree may cause swelling of your face, lips, mouth or tongue, trouble breathing, skin rashes, and redness.
Boxed Warning: Risk of Blood Clots and Blood Vessel Disorders
Myfembree carries a boxed warning, the most serious warning issued by the FDA, regarding the increased risk of blood clots and blood vessel disorders. Estrogen and progestin combinations, including the estradiol/norethindrone acetate component of Myfembree, increase the risk of thrombotic or thromboembolic disorders, including pulmonary embolism, deep vein thrombosis, stroke, and myocardial infarction, especially in women at high risk for these events.
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Discontinue Myfembree immediately if an arterial or venous thrombotic, cardiovascular, or cerebrovascular event occurs or is suspected.
Mood Changes and Suicidal Ideation
Myfembree may cause mood changes, such as depression or anxiety. In clinical trials, a greater proportion of women treated with Myfembree reported depression, irritability, and anxiety compared to those treated with placebo. Cases of suicidal ideation have also been reported with Myfembree use.
Patients with a history of suicidal ideation, depression, and mood disorders should be evaluated prior to initiating treatment and monitored for mood changes and depressive symptoms. Patients with new or worsening depression, anxiety, or other mood changes should be referred to a mental health professional.
Liver and Gallbladder Issues
Myfembree is contraindicated in patients with known hepatic impairment or disease. In placebo-controlled clinical trials, elevations in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) occurred in some Myfembree-treated women.
Instruct women to promptly seek medical attention for symptoms or signs that may reflect liver injury, such as jaundice or right upper abdominal pain. Discontinue Myfembree if signs or symptoms of gallbladder disease or jaundice occur.
Precautions and Contraindications
Before taking Myfembree, consider the following precautions and contraindications:
- Cardiovascular Conditions: Myfembree is contraindicated in women with current or a history of thrombotic or thromboembolic disorders, stroke, or myocardial infarction.
- Hormone-Sensitive Malignancies: Myfembree is contraindicated in women with current or a history of hormone-sensitive malignancies (e.g., breast cancer) and in women at increased risk for hormone-sensitive malignancies.
- Osteoporosis: Myfembree is contraindicated in women with known osteoporosis.
- Hepatic Impairment: Myfembree is contraindicated in patients with known hepatic impairment or disease.
- Uncontrolled Hypertension: Myfembree is contraindicated in women with uncontrolled hypertension.
- Pregnancy: Myfembree is contraindicated for use in pregnancy.
- Hypersensitivity: Myfembree is contraindicated in women with a history of hypersensitivity reactions to relugolix or any component of Myfembree.
- Smoking: Women who smoke and are over 35 years old should not take Myfembree.
Managing Side Effects
While taking Myfembree, it's essential to manage potential side effects effectively:
- Monitor Mood Changes: Pay attention to any changes in mood, behaviors, thoughts, or feelings. Contact your healthcare provider immediately if you experience symptoms of depression, anxiety, or suicidal thoughts.
- Regular Blood Pressure Checks: See your healthcare provider to check your blood pressure regularly.
- Bone Density Monitoring: If you have uterine fibroids, periodic DXA scans are recommended. If you have pain associated with endometriosis, annual DXA scans are recommended.
- Non-Hormonal Contraception: Use effective non-hormonal contraception during treatment with Myfembree and for one week after the final dose.
- Prompt Medical Attention: Seek prompt medical attention for symptoms or signs that may reflect liver injury, gallbladder disease, or cardiovascular events.
- Communicate with Your Healthcare Provider: Inform your healthcare provider about all prescription and over-the-counter medicines, vitamins, and herbal supplements you are taking.
Myfembree and Weight Loss
Myfembree is not expected to cause weight changes. Neither weight loss nor weight gain was reported in clinical trials of the drug. If you're concerned about changes in your weight while taking Myfembree, talk with your doctor or pharmacist.
Important Considerations
- Pregnancy: Do not take Myfembree if you are trying to become pregnant or are pregnant. If you think you are pregnant, stop treatment right away and call your healthcare provider.
- Breastfeeding: Myfembree may pass into your breast milk. Talk to your healthcare provider if you are breastfeeding or planning to breastfeed.
- Surgery: Myfembree may increase your risk of blood clots after surgery. Your healthcare provider may advise you to stop taking Myfembree before you have surgery.
- Other Medications: Tell your doctor about all your other medicines, including prescription and over-the-counter medicines, vitamins, and herbal products.
- Lifestyle: Maintain a healthy lifestyle, including a balanced diet and regular exercise. If you smoke, talk to your doctor about ways to quit.