Adverse Drug Events
Adverse Reaction vs. Side Effects
While sometimes used interchangeably with side effects, the terms have slightly different meanings:
An adverse drug reaction is always negative, and not a commonly known side effect.
A side effect is simply a secondary effect of a medication, which may be harmful, neutral, or even beneficial. A side effect is well known and documented and not always negative, it is to be expected.
For example, some medications that cause fatigue as a side effect may be a problem for some people but could be used as a sleep aid for others. An example of this is Benadryl, it is an antihistamine primarily used to treat allergy symptoms, but is well known to cause drowsiness, thus is included in some OTC meds such as Tylenol PM for sleep..
