Interactions: Introduction

Last updated: Thursday, November 23, 2017

NB: See learning outcomes for this tutorial mapped to competencies, a PDF of the whole text, and a one-page summary.

☞ Why this subject matters...

Courtesy of Siba Majid
Pharmacists are the NHS experts on drug interactions. Preventing, detecting and managing them is part of their clinical role. In practice, pharmacists are asked about them a lot: interactions are flagged up by e-prescribing systems, and appear in patient information leaflets and in the BNF. Clinicians want to know if these interactions will affect their patient and what to do about them. And that's where pharmacists come in.

Drug interactions can pose a significant risk to patients, although in practice they are a much less common cause of harm than adverse reactions. However, interactions are perhaps recognised less often and the pharmacist's active safeguarding role helps to protect patients.

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.

Not all drug interactions have an adverse outcome, 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.