Why are "drugs" (medicine) and drugs (like cocaine) spelled and spoken in the same way?

Drugs are drugs, a drug is a substance that enters the body with the intention of altering it's make up, permanently or temporary. A drug can be produced from natural plants and/or from man mixing chemicals together to make a pill or similar. Different drugs have different effects on the human body. Therefore your Doctor will prescribe different drugs for different illnesses and leisure drugs such as cocaine, alcohol, nicotine are taken at different times according to the situation and effect the person wants to achieve. There is no difference and that is why drugs are called drugs and the word covers all sorts of items. You can try to classify them by adding a prefix or suffix to the word drug.