- Female patients of childbearing potential may participate only in case of availability of a negative urine pregnancy test and a confirmed menstrual period prior to study entry and using a highly effective method of birth control. Highly effective methods of birth control are defined as those which result in a low failure rate (i.e. less than 1 % per year) when used consistently and correctly such as implants, injectables, combined oral contraceptives, appropriate intrauterine devices, sexual abstinence or vasectomised partner. Barrier methods of contraception (e.g. condom, diaphragma or occlusive cap) are accepted if used in combination with spermicides (e.g. foam, gel). Female patients will be considered being of childbearing potential unless surgically sterilised by bilateral tubal ligation/salpingectomy or hysterectomy or post-menopausal for at least one year.