Interactions: Introduction

Last updated: Sunday, July 05, 2015

You can download a PDF of the text of this tutorial (it doesn't include the Learning Exercises).

Definition of a drug interaction

A drug interaction occurs when the effects of a medicine given to a patient are altered by the presence of another medicine, a chemical, or food. Don't forget that one of the interacting entities involved could be a herbal medicine or a street drug. Drugs may also interact with laboratory tests to render them inaccurate. Not all drug interactions produce an adverse effect, but for the purpose of this tutorial we will deal only with interactions between medicines that could have negative consequences for patients. These form the majority of drug interactions that pharmacists get involved with in practice.

Courtesy of Siba Majid