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Assessing the safety of drugs through observational research
  1. Ross J Simpson Jr
  1. Professor R J Simpson Jr, 6th Floor Burnett-Womack, CB7075, 99 Manning Drive, University of North Carolina Chapel Hill, 27514 USA; rsimpson{at}

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Digitalis is probably the oldest drug still used by clinicians. It is inexpensive, easy to dose, well tolerated, aids control of the ventricular rate during atrial fibrillation and improves symptoms of heart failure. Its toxicity, mechanism of action and pharmacology are well understood.1 2 However, despite this long history and these established advantages; digitalis is still suspected of harming patients.

Concern comes from several lines of research. A randomised trial of digitalis in patients with congestive heart failure did not show improved survival.3 Other drugs that are similar to digitalis and increase the force of cardiac contraction are harmful.1 Although well understood, the pharmacology of digitalis is complex. The relationship of blood levels to toxicity is not always clear and toxicity may occur with therapeutic levels.1 Moreover, in patients with severe heart failure, blood levels in the higher therapeutic range are associated with excess deaths.4 Major drug interactions with commonly used medications like verapamil, warfarin (Coumadin), and amiodarone and non-potassium sparing diuretic agents have been well described.2 Of most concern, patients who seem most likely to need digitalis may be most vulnerable to its toxicity. Women, …

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  • Competing interests: None.

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