Risk of digoxin intoxication in heart failure patients exposed to digoxin-diuretic interactions: a population-based study.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT * Increased frequency of electrolyte abnormalities and cardiac arrhythmias among patients exposed to digoxin-diuretic interactions has been well-documented in numerous descriptive studies. * Nonetheless, a clear causal relationship has not been established in these studies. WHAT THIS STUDY ADDS * The risks of digoxin intoxication associated with use of digoxin in combination with any diuretic use, types of diuretics, combinations of diuretics, and individual diuretics were quantified using a population-based nested case-control study design. * The combined therapy of digoxin with any diuretic is associated with a 3.08-fold increase in the risk of digoxin intoxication. * Regarding diuretic class, the risk carried by loop diuretics is greater than that of thiazides or potassium-sparing diuretics, and the risk varies with different combinations of diuretic classes and individual diuretics. AIMS To quantify the digoxin intoxication risk associated with exposure to digoxin-diuretic interactions, and evaluate whether the risk varies by diuretic type, individually or in combination. METHODS This was a population-based nested case-control study in which data from the National Health Insurance Research Database (NHIRD) in Taiwan were analysed. RESULTS The study cohort comprised 154 058 heart failure (HF) patients taking digoxin between 2001 and 2004, in whom digoxin intoxication requiring a hospitalization (ICD-9 code 972.1) occurred in 595 cases. A total of 28 243 matched controls were also selected for analysis. Cases were 3.08 times (adjusted OR 3.08, 95% CI 2.50, 3.79) more likely to have been prescribed diuretic medication in the previous month than controls. Regarding the class of diuretics, loop diuretics carried the greatest risk (adjusted OR 2.97, 95% CI 2.35, 3.75), followed by thiazides (OR 2.36, 95% CI 1.70, 3.29) and potassium-sparing diuretics (OR 1.72, 95% CI 0.83, 3.56). The risk was also observed to vary with different combinations of diuretics, and the loops/thiazides/potassium-sparing diuretics combination carried the greatest risk (adjusted OR 6.85, 95% CI 4.93, 9.53). Among the individual diuretics examined, hydrochlorothiazide carried the greatest risk (adjusted OR 4.63, 95% CI 2.50, 8.57). CONCLUSIONS This study provided empirical evidence that digoxin-diuretic interactions increased the risk of hospitalization for digoxin intoxication in HF patients. The risk was particularly high for concomitant use of digoxin with a combination of loop diuretics, thiazide and potassium-sparing diuretics. The combined use of digoxin and diuretics should be avoided if possible.