As an adult, Drugs are technically designed to treat, cure or prevent disease. The challenge is that drugs aren't laser beams. They're more like shot guns.
Instead of exclusively targeting of the disease or condition, drugs can have residual impact that are commonly referred to as "side-effects" or "contraindications." Because each individual is unique, there's no way to know how a drug will affect someone until they actually take it. Side effects can be so severe that they actually create a bigger problem than the one you want to treat.
Children are especially at risk of side effects, not just physically, but developmentally as well. In the case of ADD/ADHD, the drugs don't cure the condition; they simply treat the symptoms.
As a parent, you need to ask yourself if giving your ADD/ADHD child drugs is the appropriate solution.