Thanks for your question on Healthcare Magic.
I can understand your concern.
There is no specific drug available for weight gain as none of them are US FDA approved and have many side effects.
So better not to take any of such commercially available drugs.
You should do following things for weight gain.
1. Avoid
stress and tension, be relax and calm.
2. Take sound sleep of 6-8 hours.
3. Take milk with protein powder twice daily.
4. Also take high protein diet like pulses, milk products, fruits, vegetables etc.
5. Do regular
aerobic exercise like running, cycling, swimming etc.
Don't worry, you will definitely gain weight with all these.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.