How can i gain my weight?

What are the medications needed to gain weight?
There is no drug that increases weight directly but these drugs can be used:
    Cyprohiptadine pills to increase appetite
    Yeast pills to increase appetite
Omega 3 tablets once-twice daily
    Vitamins and supplements
What are the ways to gain weight?
Weight gain can be achieved through:
    High caloric diet
    Increase the number of meals to 6
    Dairy products
    Avocado
    Meat, Chicken, Fish
    Add cheese or butter to the meals
  Avoid excessive effort
What causes low weight?
    Genetic
    Neurodegenerative disease
    Stress
    Hyperthyroidism
    Worms and intestinal parasites
    Malabsorption diseases
    Malnutrition

You are welcome 
Kind regards