Bethanechol can cause dizziness and fainting, particularly after standing, sitting or lying down. Be careful when using bethanechol and standing up or performing other activities in which dizziness can cause injury. Bethanechol can also make you drowsy. Do not drive until you know how the medication affects you. Drinking alcohol while using bethanechol can increase drowsiness. Bethanechol can have a negative interaction with the medications donepezil, quinidine and procainamide. Tell your doctor if you are using these medications before taking bethanechol.
You should also let your doctor know about medical conditions, such as asthma, overactive thyroid gland, bladder infections, Parkinson's disease, epilepsy, intestinal blockage, heart disease, abnormal blood pressure or ulcers, as these may have negative interactions with bethanechol. Pregnant and breastfeeding women should discuss the risks and benefits of using bethanechol with their doctor.