MEDICINAL COMPOSITIONS FOR PERIODIC ADMINISTRATION

In the case of administering an estrogen antagonist for treating or preventing endometriosis and/or menstrual abnormality, it is needless to administer the drug constantly and continuously during the period with a need of the treatment or prevention (i.e., chronic administration) but almost comparable therapeutic effects to those of the chronic administration can be achieved by continuously administering for 5 to 13 days from the menstrual period to immediately before ovulation (i.e., periodic administration). Moreover, the periodic administration is almost completely free from such side effects as observed in the case of the chronic administration of the estrogen antagonist. Thus, the periodic administration is a useful method for administering the estrogen antagonist for treating or preventing endometriosis and/or menstrual abnormality.