Saliva and plasma levels and plasma protein binding of clofibrinic acid in uremic patients.

Clofibrinic acid in saliva and plasma and its plasma protein binding were determined in 18 patients with renal impairment after a single 2-gm dose of clofibrate. A weak but significant correlation (r2 = 0.378; p less than 0.02) between free plasma and saliva levels of clofibrinic acid was found. The free fraction of clofibrinic acid in plasma is higher (p less than 0.02) in long-term hemodialysis patients (0.0915 +/- 0.0141) than in nondialysis patients (0.0715 +/- 0.0143). During dialysis, 2 hemodialysis patients had a free fraction more than twice as high (mean, 0.2083) as that in the other hemodialysis patients who were studied on interdialysis days. These observations suggest that saliva pH determinations are essential for optimal interpretation of saliva to plasma level ratios of weakly acidic drugs and that, during hemodialysis, patients may temporarily be exposed to increased risks of drug toxicity due to rises in free concentrations of drugs.