Hello Satish Valparin is valproic acid and a very effective drug for partail seizures and simple & complex absence seizures . There are so many side effects of this drug but as far concerned about side effect these are minor and benefits are more , so you can give this drug to your son without any complication even up to 5 years . But keep one thing in mind only hepatotoxicity is the cause of concern , so please get in ultrasound of liver from time to time ( after every 6 months ) , but this is my personal opinion and just as an precautionary measure. Other side effects are nausea, hallucination, weight gain, tremors , fatigue but as time passes the drug adjusted in body. Hope this will help you. Good luck.