Thanks for posting your query at HealthCareMagic. Let me ascertain that there is no medicine that helps in gaining weight. Cyproheptidine is a drug that is supposed to increase appetite but its effectivity is doubtful and there is no proof in its favour. But at the same time when parents demand some medicine for the weight gain of the child, doctors have nothing else other than this medicine or vitamins. Vitamin supplements too are ineffective as they are required in very small amounts and we can get adequate amounts anyway through normal diet provided that we do not have a specific deficiency. So the only way that your child can gain weight is to take more proteins and carbohydrates through diet. Protein is responsible for the body mass and is available in meat, fish, eggs, carrots, spinach, soyabeans, pulses etc. whereas carbohydrate is available from cereals. No medicine will help.

I hope that this will clarify your doubts. Feel free to revert back in case of further queries.