QUINIDINE ENHANCES DIGITALIS TOXICITY AT THERAPEUTIC SERUM DIGOXIN LEVELS

Citation
A. Mordel et al., QUINIDINE ENHANCES DIGITALIS TOXICITY AT THERAPEUTIC SERUM DIGOXIN LEVELS, Clinical pharmacology and therapeutics, 53(4), 1993, pp. 457-462
Citations number
22
Categorie Soggetti
Pharmacology & Pharmacy
ISSN journal
00099236
Volume
53
Issue
4
Year of publication
1993
Pages
457 - 462
Database
ISI
SICI code
0009-9236(1993)53:4<457:QEDTAT>2.0.ZU;2-5
Abstract
Objective: To determine the effect of the digoxin-quinidine interactio n on rate of in-hospital digitalis toxicity. Methods: This was a prosp ective observational study over 9 months, set in two general medical w ards. We studied consecutive patients (n = 141) who were receiving dig oxin. Measurements included digitalis toxicity, defined by ECG criteri a and resolution after stopping digoxin; all additional medications (i ncluding antiarrhythmics) continued. The observer was ''blinded'' to s erum digoxin level and to concomitant drugs. Results: Digitalis toxici ty rates were as follows: digoxin alone, 4.90/o (5 of 101 patients); w ith amiodarone or verapamil, 5.0% (I of 20 patients); with quinidine, 50% (10 of 20 patients) (p < 0.01). No toxicity was seen at digoxin le vels < 1.0 ng/ml. Toxicity at 1.0 to 2.0 ng/ml was as follows: digoxin alone, 1 of 41 patients; with quinidine, 4 of 15 patients (p = 0.014) . Toxicity was similar at levels >2.0 ng/ml: 4 of 8 patients and 7 of 11 patients, respectively. Independent relative risks and 95% confiden ce intervals (CI) of digitalis toxicity were as follows: serum digoxin , 9.1 (95% CI. 2.9 to 13.0); concurrent quinidine, 24.3 (95% CI, 3.4 t o 124). There was a significant (p < 0.01) interaction between concurr ent quinidine, serum digoxin of 1.0 to 2.0 ng/ml, and digitalis toxici ty. Conclusion: The digoxin-quinidine interaction significantly increa ses digitalis toxicity, even in the therapeutic range of serum digoxin levels.