Can a premenopausal woman with large intramural fibroids and ongoing heavy menstrual bleeding, currently on dienogest, discontinue dienogest abruptly and start Myfembree (relugolix 40 mg + estradiol 1 mg + norethisterone acetate 0.5 mg) the same day?

Switching from Dienogest to Myfembree

Yes, you can stop dienogest abruptly and start Myfembree the same day without a washout period or taper. There is no evidence requiring a gradual transition between these medications, and immediate switching is safe for managing fibroid-related heavy menstrual bleeding.

Rationale for Immediate Switch

• Progestin-only contraceptives (including dienogest) can be stopped at any time without requiring a taper or washout period. 1
• Dienogest is a progestin-only medication that does not require gradual discontinuation to prevent withdrawal symptoms or rebound effects. 1
• Myfembree (relugolix 40 mg + estradiol 1 mg + norethisterone acetate 0.5 mg) can be initiated at any time when it is reasonably certain the patient is not pregnant. 1
• The GnRH antagonist component (relugolix) works rapidly to suppress ovarian hormone production, with the add-back hormones (estradiol and norethisterone) immediately providing bone protection and vasomotor symptom control. 2, 3

Expected Bleeding Pattern After Switch

• Stopping dienogest will trigger withdrawal bleeding within 2–7 days due to the abrupt hormone-free interval created by discontinuation. 4
• Light spotting or breakthrough bleeding is expected during the first 3–6 months of Myfembree therapy as the endometrium adjusts to the new hormonal environment. 5
• This bleeding does not indicate treatment failure or reduced efficacy; it is a benign adjustment phenomenon that typically improves with continued use. 5, 6
• Myfembree significantly reduces heavy menstrual bleeding in 71–73% of women with uterine fibroids by 24 weeks of treatment. 7

Critical Pre-Switch Assessment

• Obtain a pregnancy test before starting Myfembree, as pregnancy must be excluded before initiating GnRH antagonist therapy. 1, 5
• Screen for sexually transmitted infections if the patient has any irregular bleeding or risk factors, as STIs can cause abnormal bleeding independent of medication changes. 5, 6
• Review cervical cancer screening status and ensure it is up to date, particularly if the patient has new-onset bleeding patterns. 5

Practical Switching Protocol

• Stop dienogest on day 1 and start Myfembree on the same day (day 1). 1
• No backup contraception is needed if switching for fibroid management rather than contraception, as Myfembree is not approved as a contraceptive. 2, 3
• Counsel the patient that withdrawal bleeding from stopping dienogest may occur within 2–7 days and is expected. 4
• Advise that additional spotting during months 1–6 of Myfembree is common and benign, representing endometrial adjustment rather than pathology. 5

Management of Post-Switch Bleeding

• First-line management is reassurance and counseling that bleeding irregularities will improve with continued Myfembree use. 5, 6
• If bleeding is unacceptable to the patient, short-term NSAIDs (e.g., mefenamic acid 500 mg three times daily for 5 days or ibuprofen) may be used during active bleeding episodes. 6
• Do not attribute all bleeding to the medication switch without first excluding pregnancy, STIs, or new structural uterine pathology (e.g., polyp growth, fibroid degeneration). 5, 6

Common Pitfalls to Avoid

• Do not delay the switch by creating an artificial washout period, as this unnecessarily prolongs heavy menstrual bleeding and has no medical benefit. 1
• Do not assume all post-switch bleeding is medication-related; always exclude pregnancy and infection first. 5, 6
• Do not discontinue Myfembree prematurely due to early breakthrough bleeding, as this pattern typically resolves by 6 months and does not indicate treatment failure. 5, 7
• Do not use hormone-free intervals to manage breakthrough bleeding during the first 21 days of Myfembree therapy, as this compromises efficacy. 5

Long-Term Efficacy and Safety

• Myfembree provides sustained reduction in heavy menstrual bleeding and improvement in fibroid-related pain, distress, and anemia over 24 weeks. 7
• The add-back hormones (estradiol and norethisterone) preserve bone mineral density during treatment, avoiding the hypoestrogenic bone loss seen with GnRH agonists or relugolix monotherapy. 2, 8, 7
• Treatment can be continued for up to 2 years without clinically meaningful bone loss in the majority of women. 2
• Vasomotor symptoms (hot flashes) are the most common adverse effect but are significantly mitigated by the add-back hormone therapy. 2, 3