Myfembree is a prescription medication used to treat heavy menstrual bleeding caused by uterine fibroids and pain caused by endometriosis. It’s a once-daily tablet that combines three active ingredients into a single pill, designed to lower estrogen levels enough to reduce symptoms while adding back just enough hormones to protect bone health.
The Two Conditions Myfembree Treats
Myfembree has two FDA-approved uses, both related to conditions driven by estrogen and other reproductive hormones. The first is heavy menstrual bleeding associated with uterine fibroids, which are noncancerous growths in the uterus that can cause periods so heavy they interfere with daily life. The second is moderate to severe pain associated with endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, causing chronic pelvic pain and painful periods.
Both conditions are extremely common. Fibroids affect up to 80% of women by age 50, though not all cause symptoms. Endometriosis affects roughly 1 in 10 women of reproductive age. For both, Myfembree offers a non-surgical option that targets the hormonal root of symptoms.
How It Works
Myfembree contains three components that work together. The primary ingredient is a type of drug called a GnRH antagonist, which blocks signals from the brain that tell the ovaries to produce estrogen and progesterone. With those hormone levels lowered, fibroid-related bleeding slows and endometriosis-related pain decreases.
The problem with simply suppressing estrogen is that your body needs some estrogen to maintain bone density, regulate body temperature, and prevent other menopausal symptoms. So Myfembree includes a small amount of estrogen and a progestin (a synthetic form of progesterone) as “add-back therapy.” The estrogen helps protect bones. The progestin protects the uterine lining from the effects of taking estrogen alone, which over time can cause abnormal cell growth.
This combination approach is what distinguishes Myfembree from older treatments that simply shut down estrogen production entirely and left women dealing with hot flashes, bone loss, and other side effects of very low estrogen.
How Well It Works for Endometriosis Pain
Clinical trials showed Myfembree significantly reduces both period pain and the everyday pelvic pain that comes with endometriosis. In two large studies (called SPIRIT 1 and SPIRIT 2), 75% of women taking Myfembree met the threshold for meaningful relief from menstrual pain, compared to about 27-30% of women taking a placebo. That’s a striking difference.
Non-menstrual pelvic pain, the kind that can show up at any point in your cycle, also improved. Between 58% and 66% of women on Myfembree reported meaningful relief, compared to 40-43% on placebo. The improvement in everyday pelvic pain was real but more modest than the effect on period pain, which makes sense given that Myfembree primarily works by lowering the hormones that drive cyclical symptoms.
How Well It Works for Fibroid Bleeding
For uterine fibroids, the key measure is reduction in menstrual blood loss. In clinical trials, a significant majority of women on Myfembree achieved blood loss levels below the clinical threshold for heavy bleeding. Many women who had been soaking through pads or tampons every hour during their worst days saw their bleeding decrease to manageable levels or stop altogether during treatment.
What Taking It Looks Like
Myfembree is a single tablet taken once a day, at roughly the same time each day. You can take it with or without food. If you miss a dose, the guidance is to take it as soon as you remember that same day, then go back to your normal schedule the next day.
One practical note: certain medications that affect how drugs are absorbed in the gut can interact with Myfembree. If you’re taking one of these, you may need to space the doses at least six hours apart. Your prescriber will flag this if it applies to you.
Bone Density and Duration of Use
Even with the estrogen add-back, Myfembree does cause some bone density loss over time. In clinical trials, women who took it for up to a year lost an average of 0.80% of bone mineral density in the lower spine. That’s a small but measurable decline. For context, postmenopausal women typically lose about 1-2% per year without treatment.
Because of this effect, there are limits on how long you can take Myfembree. Your prescriber will weigh the benefit of symptom relief against the gradual impact on your bones, especially if you have other risk factors for osteoporosis. The bone density changes are generally considered reversible after stopping the medication, but long-term continuous use isn’t the intended approach.
Who Should Not Take Myfembree
Because Myfembree contains estrogen and a progestin, it carries the same restrictions as other estrogen-containing medications. Women with a history of blood clots, stroke, or heart attack should not take it. The same applies to those with certain types of liver disease, undiagnosed abnormal uterine bleeding (before fibroid or endometriosis diagnosis is confirmed), or known or suspected pregnancy. Myfembree is not a contraceptive, so a non-hormonal method of birth control is needed during treatment.
Smoking while taking estrogen-containing medications raises the risk of serious cardiovascular events, particularly in women over 35. This is a well-established risk that applies to Myfembree just as it does to combination birth control pills.
How Myfembree Fits Into Treatment
For both fibroids and endometriosis, Myfembree typically enters the picture after first-line options like hormonal birth control or anti-inflammatory pain relievers haven’t provided enough relief. It sits between those simpler approaches and more invasive options like surgery. Some women use it to manage symptoms while deciding whether to pursue a procedure, while others use it as their primary long-term strategy within the recommended treatment duration.
The medication doesn’t shrink fibroids or eliminate endometriosis tissue. It manages symptoms by changing the hormonal environment that drives them. When you stop taking Myfembree, symptoms typically return as hormone levels normalize, which is an important factor when thinking about your overall treatment plan.