What is the term for an unintended side effect of a medication like nitroglycerin?

The term for an unintended side effect of a medication like nitroglycerin is referred to as an untoward effect. This terminology specifically denotes a negative or undesirable reaction that can occur when a medication is administered. In the context of nitroglycerin, this may include symptoms such as headache or hypotension, which are not the primary goals of treatment but can occur nonetheless as a result of the medication's action.

While the term adverse effect is often used interchangeably with untoward effect, it is somewhat broader and includes any harmful or unintended consequence of a medication. However, untoward effects highlight the unexpected nature of a medication's influence on the body, distinguishing them from expected side effects.

The placebo effect refers to a beneficial effect that arises from a patient’s expectations of a treatment rather than the treatment itself, and the therapeutic effect is the desired outcome of a medication when it is used as intended.