This video discusses drug effects including both desired and undesired effects. Desired effects are the reason the drug is taken or the therapeutic effect. Undesired effects include side effects, adverse effects, and toxic effects. These undesired effects are also known as ADRs. Fundamental principles of pharmacology include indication which is the reason the drug is taken. Contraindication is something that prohibits the drug from being used by a certain patient. Site of action is the location in the body where the drug exerts its effect. Mechanism of action or MOA describes how or the method by which the drug exerts its effect.