Interaction of cimetidine with human serum albumin

Ultrafiltration studies have detected the existence of a weak interaction between cimetidine and human serum albumin, a finding supported by corresponding studies with this xenobiotic and bovine serum albumin. Furthermore, the binding characteristics of the interaction with human serum albumin (4 sites, K = 630 M-1) more than suffice to account for the proportion of protein-bound drug in the serum of patients subjected to cimetidine therapy. Thus, although alpha 1-acid glycoprotein is usually regarded as the specific transporter of basic drugs, the present evidence implicates albumin as the likely binding protein for cimetidine in serum.