Preliminary findings now suggest that it may be possible in the near future to reversibly suppress menstruation using new progestin antagonists, a class of drugs that includes the controversial abortion pill RU-486. Robert Brenner and his colleagues in the Division of Reproductive Sciences at the Oregon Regional Primate Research Center tested two such antiprogestins in rhesus macaque monkeys and report in the journal Human Reproduction that they discovered no ill effects. "Our goal in these studies was to obtain pre-clinical data prior to clinical development," Brenner says, "and these results are very encouraging."

One drug the scientists evaluated, dubbed ZK 137 316, blocked menstruation while, at a certain dose, allowing ovulation to continue. The other compound, ZK 230 211, blocked both processes. All of the treated animals remained healthy throughout the trials, and all returned to normal menstrual cycles within 15 to 41 days after receiving either drug. Because both antiprogestins stop estrogen from promoting the buildup of tissue in the uterus, they might prove useful in preventing the dangerous accumulation of endometrial cells that occurs in endometriosis. The excess cells can escape the womb and attach to other organs, where they bleed each month and cause pain.

"I would emphasis that we are not talking here only about lifestyle choices but also about the potential to bring relief to the many women who suffer years of misery from distressing complaints such as endometriosis and painful and excessive monthly bleeding," Brenner notes. "In fact, excessive bleeding is one of the major reasons that women undergo hysterectomy, and this treatment may also reduce the need for this surgical procedure, with all its attendant risks and costs."

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