Binding of beta-adrenoceptor blocking drugs to human serum albumin, to alpha 1-acid glycoprotein and to human serum.

The binding of 8 beta-adrenergic blocking drugs to human serum albumin, to alpha 1-acid glycoprotein and to serum from normal volunteers and from patients with rheumatoid arthritis was studied. Protein binding was determined in vitro using equilibrium dialysis of labelled drug at 25 degrees C. Oxprenolol and propranolol were highly bound to serum, alprenolol, pindolol and timolol to a lesser degree, and atenolol, metoprolol and sotalol were negligibly bound. For the five compounds which were appreciably bound, the mean binding was significantly higher in serum from patients with rheumatoid arthritis than in serum from normal volunteers. For those drugs, binding to alpha 1-acid glycoprotein was higher than to human serum albumin, and binding to a mixture of both proteins approached that to serum from healthy volunteers. For each of these drugs there was a strong correlation between the serum alpha 1-glycoprotein concentration and the percentage binding.