Some drugs that may help you gain muscle are:

• Creatine: a natural molecule that provides energy for your muscles and may increase muscle strength and size¹.
• Protein supplements: products that contain protein from various sources such as whey, casein, soy, egg, rice, etc. They may help you meet your protein needs for muscle growth¹.
• Insulin: a hormone that helps your cells take up glucose and amino acids from your blood. It may enhance muscle recovery and growth after exercise². However, it can also cause serious side effects such as low blood sugar, weight gain, heart problems, etc. It should only be used under medical supervision².
• Anabolic androgenic steroids (AAS): synthetic substances that mimic the effects of testosterone on your body. They may increase muscle mass and strength but also have many negative effects on your health such as liver damage, heart disease, infertility, mood disorders, etc. They are illegal to use without a prescription³.

There may be other drugs that claim to help you build muscle but they are not proven to be safe or effective. You should always consult with your doctor before using any drug for this purpose.