- Participants of child-bearing or child-fathering potential must be willing to use a medically effective form of birth control, which includes abstinence, while taking vandetanib and for 4 months after the last dose. [Female patients must be 1 year postmenopausal, surgically sterile, or using an acceptable method of contraception (an acceptable method of contraception is defined as a barrier method in conjunction with a spermicide) for the duration of the study (from the time they sign the informed consent form [ICF]) and for 3 months after the last dose of vandetanib to prevent pregnancy. In addition, oral contraceptives, approved contraceptive implant, long-term injectable contraception, intrauterine device, or tubal ligation are allowed. Oral contraception alone is not acceptable; additional barrier methods in conjunction with spermicide must be used.