Hi, Zen Retard contains carbamazepine which belongs to the group of medications known as anti epileptics is used to treat epilepsy. It helps prevent certain types of seizures. It is also prescribed for a painful conditions of the face, head and neck known as trigeminal neuralgia and diabetes related nerve pain. Some people who take carbamazepine salt like Zen Retard may become more sensitive to sunlight than they are normally. Exposure to sunlight, even for brief periods of time, may cause itching, skin rash, redness or other discolouration of the skin or a severe sunburn. Even this drug may develop symptoms of allergic reactions like rash, itching, swelling of tongue, lips or throat, trouble breathing, dizziness etc. It can also increase liver enzymes level like GGT, alkaline phosphatase etc. If you suffer from such type of side side effects of Zen Retard, immediately consult your doctor for medical help. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Zubayer Alam, General And Family Physician