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Mefipristone, a Medical Treatment for Fibroids, is Not Looking Good

Low-dose mifepristone in treatment of uterine leiomyoma: a randomised double-blind placebo-controlled clinical trial.

Authors: Bagaria M, Suneja A, Vaid NB, Guleria K, Mishra K.

Study from: Department of Obstetrics and Gynaecology, University College of Medical Sciences, Delhi, India.

Problem: So far, no medication has worked to relieve symptoms of fibroids. In early studies, one drug that appeared to be promising was Mefipristone (RU-486).  Progesterone causes fibroid cells to grow and Mefipristone blocks this effect.

Study: The study included 40 women with bothersome symptoms from fibroids; 20 women were taking mifepristone and 20 were taking a placebo. None of the women or their doctors knew what pill they were taking.

Fibroid-related symptoms, the size of the uterus and size of the largest fibroid were measured with ultrasound at the beginning of the study and every month for three months. A biopsy of the uterine lining cells was done at the beginning and again at the end of treatment.

Results: Women who were taking Mefipristone had a 95% decrease in menstrual blood loss after three months   Complete relief of menstrual cramping occurred in 80%, but only 33% patients were free of pelvic pain.  Women taking the placebo pills had no change in any symptoms. Backache, bladder problems and pain with intercourse were not better in either group.

The size of the uterus and size of the largest fibroid were about 30% smaller by the end of the third month of therapy. Women taking Mefipristone had an increase in haemoglobin (red blood cells) from 9.5 to 11.2 . However, 63% of women taking mefipristone had benign overgrowth of the uterine lining cells (endometrial hyperplasia without atypia).

Authors’ Conclusions: A low dose of mifepristone taken for three months is effective in reducing menstrual bleeding and reducing uterine and fibroid sizes, but has the side-effect of causing uterine lining cell overgrowth.

Dr. Parker’s Comments: It would be great if there was a pill available to treat the symptoms of fibroids with few side-effects.  So far, all the tested medications have either not worked or had bothersome side-effects. Mefipristone is given orally and has few side-effects.  It is well-known that progesterone causes fibroids to grow.  Mefipristone works by blocking the action of progesterone and has been shown to shrink fibroids and decrease bleeding.  However, progesterone decreases the growth of the uterine lining cells and since mefipristone blocks this action it allows the lining cells to overgrow.  After just 3 months almost 2/3 of women had benign overgrowth. While benign overgrowth does not turn into precancer or cancer, the worry is that longer treatment with Mefipristone could stimulate actual cancer cells to form.  Further study will be needed, but this study is discouraging.

For more about medical treatment for fibroids see:


Disclaimer: The ideas, procedures and suggestions contained on this web site are not intended as a substitute for consulting with your physician. All matters regarding your health require medical supervision.

Fibroid Doctor William H. Parker

Dr. William H. Parker is a board-certified Fellow in the American College of Obstetricians and Gynecologists. Dr. Parker is an internationally recognized expert in fibroid surgery and research. Based in San Diego, California, he is considered one of the best fibroid surgeons for abdominal and laparoscopic myomectomy in the United States and abroad. He has been chosen for Best Doctors in America and Top Doctors every year beginning in the late 90's.

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