Drug companies expediently and glibly list drug actions, meaning beneficial effects for which they are prescribed, separately from another section called side effects, meaning undesirable effects for which they are not prescribed. The action of a statin drug would be the lowering of bad cholesterol to reduce heart attacks and strokes. The side effects would be muscle pain and weakness, liver inflammation, malaise and memory difficulties. It is implied that side effects are unexpected and infrequent, and somehow accidental.
However, the changes resulting from taking a drug are all EFFECTS. Some are good effects and some are bad effects, but they are still EFFECTS. They are predictable from the interference the drug imposes on normal body functions. They are usually dose-related, and do not occur in all people because different bodies have different sensitivities and different rates of metabolism. However, they are not accidental. They are a part of the basic nature of the drug, as an explosion is part of the basic nature of a bomb, and one would have to expect that once in a while an innocent bystander will be blown up.