To answer this question, we need to first understand how medications work in general.
All cells have ‘receptors’ that control the way they function. These receptors can be switched ‘on’ and ‘off’ when a molecule binds to them.
Medications can also bind to these receptors and affect how these cells work such as destroying a cancer cell or a bacterial cell. However, medications don’t only target ‘sick’ cells, they can also bind to the receptors of healthy cells causing a disruption in the normal functioning of the cell which gives us unwanted side effects.