What factors affect drug binding to plasma proteins?

Drug concentration, affinity to binding sites and number of binding sites. Also some disease affect it (hypoalbuminemia (2ary to liver disease), Acute phase response conditions (MI, Crohns, cancer...) elevate a1 acidic glycoprotein enhancing the binding Competition may occur between drugs (unconjugated bilirubin replaced by sulfonamide on albumin binding sites causing bilirubin encephalopathy for newborns