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.