What is defined as an unwanted or unintended effect of a medication?

The term that describes an unwanted or unintended effect of a medication is known as a side effect. Side effects can occur in addition to the desired therapeutic effects of a medication and may range from mild to severe. They are often predictable based on the medication's pharmacological properties and can occur due to the way the drug interacts with the body.

Understanding side effects is crucial for pharmacy assistants as they help in educating patients about potential reactions they might experience while on medication. This knowledge allows pharmacy assistants to provide better patient care and guidance concerning medication use.

While the other options relate to effects that medications can have, they do not specifically capture the idea of an unwanted reaction. The primary effect refers to the main intended action of the drug. An adverse reaction is a more serious term often used in clinical contexts to describe harmful effects that require medical attention. The therapeutic effect is the intended beneficial outcome of the drug. None of these terms encapsulates the broader notion of unintended effects quite like side effects do.