Longterm affects of anti-epileptic drugs?

Male 22 years of age,History of Tuberculosis at the age of 12 years which resulted in a calcified lesion in the frontal lobe of the brain.This resulted in epileptic attacks.Patient was given anti-epileptic drugs which solved the problem.There was no episode of attack until the age of 21 when he travelled to the united states .Few days after his arrival he had an attack.All investigations were done the MRI did not show any new lesions.He was put on tegretol 600mg twice a day.He suffered from an attack again two years later,even this episode was followed by travel, the investigations done showed that the attack could be due to reduced dosage levels.Patient was not taking his medication regularly.Now he is on Tegretol and epitoin.Doctor has said that a surgery is not required since it is a controllable condition.Doctor advised the patient to take the prescribed medication and monthly blood tests should be done to check the tegretol levels.I would like to know if this condition could be a serious problem in the future and since these drugs are to be used for life what adverse effects can this medication have in the long run?Can they be prevented?