Hello and thanks for the query. zen retard is carbamazipine,a relatively safe drug for chronic treatment of epilepsy..mild side effects include nausea vomitting dizziness,dry mouth abd pain..on long term it can cause lymphopenia(decreased lymphocytes) and decreased renal fuction..as such no need for special precaution you can have a regular blood test done for blood cell counts and kidney function tests.  Be cautious when drinking alcoholic beverages or taking over-the-counter sleeping pills or antihistamines; these substances add to the drowsiness caused by carbamazepine.  Thanks