The plasma protein binding of metoclopramide in health and renal disease.

The plasma protein binding of metoclopramide was measured after addition of the drug (60 ng ml-1) to plasma from 18 patients with renal disease and 18 age and sex matched healthy individuals. The mean free fraction in renal disease (0.59 range 0.41-0.71) was not significantly different from controls (mean 0.6 range 0.56-0.69). In both groups the binding ratio of metoclopramide was significantly related to plasma alpha 1-acid glycoprotein (AAG) concentration but not to albumin or plasma non-esterified fatty acids concentration. Metoclopramide bound to human serum albumin (HSA) to a limited extent and to human AAG to a greater extent indicating that AAG is the major binding protein for the drug in plasma.