My son is 14 years old, he is having slight bronchial asthma, which has been well under control now, all his test reports relating to blood stool, urine, chest x-ray, lipid profile, PFT, Thyroid are reporting normal. He is loosing weight but his growth in height is good, his height is 5' 7". The doctor has advised longifene DS syrup to take before 15 minute of meal. Kindly answer if it is correct, what more to do to gain weight. His weight is 45 kgs.