Quantitative and qualitative binding characteristics of disopyramide in serum from patients with decreased renal and hepatic function.

Protein binding of disopyramide, binding capacities, affinity constants and serum concentrations of alpha 1‐acid glycoprotein (AAG) were studied in five groups of patients. A: young healthy volunteers (n = 8); B: elderly patients with minor symptoms of ischaemic heart disease (n = 9); C: patients with cirrhosis of the liver and normal values of coagulation factors (II, VII and X), albumin and immunoglobulin G (n = 8); D: patients with cirrhosis and at least two abnormal of the previously mentioned values (n = 9) and E: eleven patients with severely impaired renal function. Subfractions of AAG (Fr1, Fr2 and Fr3) were determined by affinoimmunoelectrophoresis. AAG concentration was significantly (P less than 0.005) elevated in group E patients and decreased (P less than 0.025) in group D patients. Fr2 is probably associated with the high affinity, first binding site of disopyramide to AAG. Earlier observations of a reduced qualitative binding of disopyramide in patients with cirrhosis can be explained by a significant decrease in Fr2 (P less than 0.001) in group D patients. The protein binding of disopyramide in patients with uraemia was significantly increased due to a significant (P less than 0.005) increase in AAG concentration in spite of a smaller (P less than 0.025) affinity constant. Suggestions for therapeutic drug monitoring based on total serum concentrations are given.

DOI: 10.1111/j.1365-2125.1987.tb03007.x

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