Analysis of hospital admissions associated with digitalis glycosides

BACKGROUND: Although the value of digitalis glycosides in the treatment of heart failure is limited, approximately 255 million DDDs of digitalis glycosides (DGs) were prescribed in Germany in 2004. METHOD: The authors analyzed data from adverse drug reactions (ADRs) resulting in hospitalization in the four German Pharmacovigilance Centers (PVCs) associated with DGs between 2000 and 2004. All patients with an at least "probable" ADR were included. RESULTS: Out of 3,092 ADR patients, in 314 patients (10.2%, 244 women) admission was caused by a DG-related ADR. Patients with DG-related ADR had a significantly lower body weight and were significantly older than patients with other ADRs. Per 1,000 patients exposed to DGs the incidence [95% CI] was calculated to 1.9 [1.0; 3.3] ADRs per 3 months exposition. Oral digitoxin was involved in 296 patients (228 women). 70.6% of women but only 29.3% of men were overdosed (> 1 mug/kg body weight per day). Women received significantly higher body weight-related digitoxin doses and had significantly higher digitoxin plasma levels than men. ADRs in patients with nonelevated digitoxin serum level were mainly caused by pharmacodynamic drug-drug interactions (e.g., beta-blockers). Overall, 42.4% of the ADRs were supposed to be preventable. CONCLUSION: Body weight-adapted dosing of digitoxin is essential for preventing DG-ADRs, particularly in elderly women with low body weight. Beyond giving attention to pharmacodynamic and pharmakokinetic drug-drug interactions, regular measurements of digitoxin plasma concentrations are crucial accounting for the increased half-life of digitoxin in the very old.