Practice Cases in primary care laboratory medicine

Pitfalls of testing and summary of guidance on safety monitoring with amiodarone and digoxin

BMJ 2007; 334 doi: https://doi.org/10.1136/bmj.39090.709537.47 (Published 08 February 2007) Cite this as: BMJ 2007;334:312
  1. W Stuart A Smellie, consultant1,
  2. Jamie J Coleman, specialist registrar2
  1. 1Clinical Laboratory, General Hospital, Bishop Auckland DL14 6AD
  2. 2Department of Clinical Pharmacology, Division of Medical Sciences, University of Birmingham, Birmingham B15 2TH
  1. Correspondence to: W S A Smellie info{at}smellie.com
  • Accepted 2 January 2007

Patients on a range of drug therapies are often not monitored appropriately, even though this can improve patient safety. Knowledge of the effects of drugs on non-target body systems is essential to guide monitoring and interpretation of monitoring tests

Considerable guidance is available on the safety monitoring required for many commonly used drugs. In some cases, where a clinical effect correlates with drug concentrations, this involves monitoring concentrations of the drug in blood (therapeutic drug monitoring). In other cases, such monitoring is of limited value, although knowing drug concentrations can help in diagnosing toxicity. Secondary effects of the drug on other body systems may also be monitored by using other tests or measurements.

Audits of compliance with drug safety monitoring recommendations in a range of prescribing situations have shown that monitoring of compliance remains an important area for improvement as a contributor to patient safety.1 2 3 4 5

This article considers two scenarios involving the cardiovascular drugs digoxin and amiodarone and the monitoring required to detect their therapeutic and adverse effects. It also reviews the evidence based and consensus guidance that is available.

Summary points

  • Drug safety monitoring in routine practice is often suboptimal

  • Consensus guidance for safely monitoring a wide range of drugs is available

  • Safe prescribing of drugs also requires a basic understanding of physiological, pathological, and pharmacological influences on the action of a drug and of its pharmacokinetics

  • Blood concentrations of drugs often do not correlate closely with activity or toxicity, which can be influenced by several other factors

  • “Therapeutic ranges” are produced as guides to a drug's activity, potential toxicity, or both: prescribers should know how to use these ranges

Case 1

A 71 year old man with longstanding congestive heart failure and atrial fibrillation was reviewed routinely by his general practitioner. The patient was being managed with …

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