Hot Flash Due to Medication

The goal of this randomized intrapatient cross-over study is to assess the efficacy of oxybutynin versus venlafaxine in reducing hot flashes in women using endocrine therapy after breast cancer. The objectives it aims to answer are: * To assess the efficacy of oxybutynin versus venlafaxine in reducing hot flashes in women using endocrine therapy after breast cancer * To assess side effects of oxybutynin versus venlafaxine. * To assess the personal preference of women for oxybutynin versus venlafaxine in reducing hot flashes. * To assess quality of life of women when reducing hot flashes in women using endocrine therapy after breast cancer. Participants will fill-out a patient diary during 15 weeks total on a daily basis and receive an (online) questionnaire three times total. Researchers will compare two groups (venlafaxine group versus oxubutynine group) to assess its efficacy concerning hot flashes.