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Effect of quinidine on plasma concentration and renal clearance of digoxin. A clinically important drug interaction.
Author(s) -
Dahlqvist R,
Ejvinsson G,
SchenckGustafsson K
Publication year - 1980
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/j.1365-2125.1980.tb01070.x
Subject(s) - digoxin , quinidine , medicine , digitalis , renal function , drug interaction , pharmacokinetics , pharmacology , endocrinology , heart failure
1 Thirty patients on maintenance digoxin therapy and admitted for cardioversion of atrial fibrillation were closely monitored with regard to plasma levels of digoxin and quinidine. 2 Seventeen of these patients were kept on maintenance digoxin therapy. After an initial lag period of 6 to 18 h after the addition of quinidine their digoxin levels started to increase and had increased by between 20 and 330% after 3 days on quinidine. Side‐effects attributed to the raised digoxin concentration occurred in 6 of these patients. 3 As studied in 5 of these 17 patients the renal clearance of digoxin decreased markedly when quinidine was added to the therapy. There was also a slight but significant reduction in creatinine clearance (n = 4). 4 In 13 patients digoxin was discontinued 36 h prior to the first quinidine dose. Also in these patients digoxin plasma levels increased significantly. 5 It is concluded that quinidine causes an unpredictably large increase in plasma digoxin and that this effect is probably at least initially to a large part due to a redistribution of digoxin in the body. The relative contributions of re‐distribution and impaired renal clearance of digoxin to the increase in digoxin steady‐state levels are presently unknown. 6 It is recommended that close monitoring of digoxin concentration and appropriate reduction of the maintenance dose is undertaken when quinidine is to be given to patients on digitalis therapy.