MEDICINAL COMPOSITIONS FOR PERIODIC ADMINISTRATION

When it is intended to administer an estrogen antagonist for the treatment or prevention of endometriosis and/or abnormal menstruation, it is unnecessary to administer the drug constantly and continuously throughout the period of time requiring drug administration for therapeutic or preventive purposes (i.e., chronic administration), but therapeutic effects almost comparable to those of chronic administration can be achieved by adminstering the drug for only 5 to 13 consecutive days during a period of time extending from the menstrual period to immediately before ovulation in the menstrual cycle (i.e., periodic administration). Moreover, the periodic administration is substantially free from such side effects as are observed in the chronic administration of estrogen antagonists.; Thus, the periodic administration is a useful method for administering an estrogen antagonist for the treatment or prevention of endometriosis and/or abnormal menstruation..