Effects of oral prazosin on total plasma digoxin levels

Prazosin and digoxin are frequently coadministered in clinical practice. To determine the effects of oral prazosin treatment on steady-state digoxin levels, 20 patients receiving a constant maintenance dose of digoxin, who had normal renal and liver functions and were not receiving any other treatment, were given 5 mg of prazosin for 3 days. Plasma digoxin levels were measured before, on days 1 and 3 of prazosin treatment, and after prazosin had been discontinued. It was found that prazosin significantly increased plasma digoxin levels. On discontinuation of prazosin digoxin levels returned to their previous values.