Digoxin renal clearance

The answer is b. (Hardman, pp 816-818.) Digoxin levels rise with concomitant administration of diltiazem by an unknown mechanism that reduces renal clearance... 

Digoxin (Lanoxin) (should not exceed 125 mg/d except when treating atrial arrhythmias) Decreased renal clearance may lead to increased risk of toxic effects. Low... 

Digoxin is not extensively metabolized in humans almost two thirds is excreted unchanged by the kidneys. Its renal clearance is proportional to creatinine clearance and the half-life is 36-40 hours in patients with normal renal function. Equations and nomograms are available for adjusting digoxin dosage in patients with renal impairment. 

A single dose of fluvastatin increased the steady-state Cmax of digoxin 0.125-0.5 mg/day by 11% and renal clearance by 15%, without changing AUC or fmax (8). 

Figure 7 Change in the biliary and renal clearance of digoxin caused by quinidine or quinine treatment. After a steady state concentration of quinine or quinidine was achieved by multiple oral administrations, the plasma concentration and biliary and urinary excretion of digoxin after oral administration were measured in healthy volunteers. The steady state concentrations of quinine and quinidine were 7.0 2.5 and 4.5 0.5 pM, respectively. Source From Ref. 291.

The ratio of renal clearance of digoxin to creatinine clearance decreased with the coadministration of clarithromycin (0.64 and 0.73), and was restored (1.30) after administration of clarithromycin had stopped (326). The role of P-gp efflux in this interaction was confirmed using an in vitro kidney epithelial cell line (326). The administration of itraconazole, a P-gp inhibitor, with digoxin resulted in an increased trough concentration and a decrease in the amount of renal clearance, possibly by an inhibition of the renal tubular secretion of digoxin via P-gp (329). The P-gp modulator verapamil has also been shown to decrease the renal clearance of digoxin (330). 

CARVEDILOL DIGOXIN Carvedilol may t digoxin plasma concentrations, particularly in children i P-gp-mediated renal clearance of digoxin 1 the dose of digoxin by 25% watch for signs of digoxin toxicity and monitor digoxin levels... 

DIGITOXIN AMIODARONE Reports of digitoxin toxicity in two patients on digitoxin after starting amiodarone Uncertain thought to be due to inhibition of P-gp-mediated renal clearance of digoxin Watch for digitoxin toxicity... 

DIGOXIN TRIMETHOPRIM, CO-TRIMOXAZOLE Trimethoprim may t plasma concentrations of digoxin, particularly in elderly people Uncertain postulated that trimethoprim 1 renal clearance of digoxin Monitor digoxin levels watch for digoxin toxicity... 

As in the liver, drugs that undergo renal P-gp transport are susceptible to interactions resulting from modulation of P-gp- Inhibition of renal P-gp may lead to the development of unexpected toxicities or improved clinical efficacy secondary to increased drug exposure. Clarithromycin was found to increase the bioavailability of and reduce the renal clearance of digoxin in a group of healthy volunteers, resulting... 

Rengelshausen J, Goggelmann C, Burhenn J et al. Contribution of increased oral bioavailability and reduced renal clearance of digoxin to the digoxin-clarithromycin interaction. Br J Clin Pharmacol 2003 56 32-8. 

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