Binding of alfentanil to human alpha 1-acid glycoprotein, albumin and serum.

The variability of the serum binding of the short-acting narcotic analgesic alfentanil was studied. Binding of alfentanil was measured in human alpha 1-acid glycoprotein (AAG) and human albumin solutions, and in serum from 6 groups of individuals: control subjects, patients with renal failure, cirrhosis, rheumatoid arthritis and myocardial infarction, and intensive care patients. Alfentanil is mainly bound to AAG and the influence of a change of the AAG concentration on its binding is much more marked than that of a change of the albumin concentration. In patients with renal failure, myocardial infarction and rheumatoid arthritis and in intensive care patients, AAG concentrations are increased, but alfentanil binding is significantly increased only in patients with myocardial infarction. In patients with cirrhosis, AAG, albumin concentrations, and alfentanil binding are decreased. In vitro addition of lidocaine, disopyramide, bupivacaine and quinidine, in concentrations that are observed clinically, lead only with disopyramide to an important increase in free fraction of alfentanil (from 7 to 19%). This latter finding was confirmed in 2 volunteers, treated chronically with disopyramide.