Possible Interaction: Digoxin and Quinidine

“ Quinidine , verapamil and spironolactone could inhibit the transcellular transport of digoxin by 50%.”

“We next examined the inhibitory effect of quinidine , verapamil and spironolactone on the transcellular transport of digoxin by using human P-glycoprotein overexpressing LLC-GA5-COL150 cells.”

“In contrast, coadministration of quinidine into one jejunal segment caused a considerable increase in the amount of digoxin absorbed from this segment compared with the absorption from the other quinidine-free segment (22.3 ± 8.9% vs 55.8 ± 21.2% of the dose; p < 0.05).”

“Of the 11 receiving quinidine and digoxin (10 randomized and one crossover), three (28%) had a recurrence of atrial flutter, two of whom also had intolerable side effects, and two more (18%) had side effects alone requiring withdrawal of therapy (total 46% failed).”

“Fourteen percent of the population took either quinidine or verapamil concurrently with digoxin (mean quinidine dose = 857 +/- 397 mg/day, verapamil = 261 +/- 110 mg/day).”

“Asymptomatic phases of atrial flutter with > or = 2:1 atrio-ventricular conduction ratio were observed during Holter monitoring, before conversion to sinus rhythm, in four patients treated with propafenone, in one patient taking digoxin plus quinidine and in four patients with placebo.(ABSTRACT TRUNCATED AT 250 WORDS)”

“Mean conversion times within 48 h were 267 +/- 238 min for propafenone, 648 +/- 631 min for digoxin plus quinidine (P < 0.01 vs. propafenone) and 893 +/- 622 min for placebo (P < 0.001 vs. propafenone).”

“ Quinidine has been reported to increase digoxin plasma concentrations, which increases the risk of digoxin overdose.”

“Although quinidine and digoxin are frequently given together, it has only recently become apparent that serum digoxin concentration may rise during quinidine treatment.”

“ Quinidine has been observed to inhibit the metabolism of digoxin , tricyclic antidepressants and codeine.”

“BACKGROUND Although quinidine is known to elevate plasma digoxin concentrations, the mechanism underlying this interaction is not fully understood.”

“In addition, 5 micromol/L quinidine inhibited P-glycoprotein-mediated digoxin transport by 57%.”

“Moreover, quinidine increased digoxin brain concentrations by 73.2% (P=0.05) in wild-type animals; by contrast, quinidine did not increase digoxin brain concentrations in mdr1a(-/-) mice but rather decreased them (-30.7%, P<0.01).”

“ Quinidine increased plasma digoxin concentrations by 73.0% (P=0.05) in wild-type animals, compared with 19.5% (P=NS) in mdr1a(-/-) mice.”

“Several drugs, including quinidine , amiodarone, verapamil, and propafenone can interact with digoxin , leading to toxic accumulation of the glycoside.”