Abstract: A medical device for insertion into a vaginal cavity comprising an elastomeric ring containing a compound selected from the group consisting of a compound of the formula ##STR1## wherein R.sub.1 is hydrogen or alkyl of 1 to 6 carbon atoms, R.sub.2 and R.sub.5 are individually alkyl of 1 to 6 carbon atoms, n is an integer from 2 to 6, R.sub.3 and R.sub.4 are individually aryl of 6 to 12 carbon atoms optionally substituted with 1 or 2 members of the group consisting of halogen and alkyl and alkoxy of 1 to 6 carbon atoms and their non-toxic, pharmaceutically acceptable acid addition salts for the treatment and prevention of cancer.