Paracetamol test : modification by renal function, urine flow and pH

• Published in: European journal of clinical pharmacology 1990-01, Vol.39 (3), p.245-251
• Main Authors: KIETZMANN, D, BOCK, K. W, KRÄHMER, B, KETTLER, D, BIRCHER, J
• Format: Article
• Language: English
• Subjects: Acetaminophen - blood; Acetaminophen - pharmacokinetics; Acetaminophen - urine; Administration, Oral; Adult; Aged; Analgesics; Biological and medical sciences; Chromatography, High Pressure Liquid; Creatinine - metabolism; Female; Humans; Hydrogen-Ion Concentration; Kidney - drug effects; Kidney - metabolism; Male; Medical sciences; Metabolic Clearance Rate; Middle Aged; Neuropharmacology; Pharmacology. Drug treatments
• ISSN: 0031-6970; 1432-1041
• DOI: 10.1007/BF00315104

Factors which might affect paracetamol disposition have been studied in a heterogenous group of patients in need of mild analgesia in an intensive care unit. Following oral administration of 1 g of paracetamol, plasma and urinary concentrations of the parent compound and metabolites were assessed by HPLC. The renal clearance of paracetamol was significantly correlated with urine flow (r = 0.84) and creatinine clearance (r = 0.77), but not with urine pH. Metabolite output was diminished in patients with reduced renal function. Despite the heterogeneity of patients and the diversity of drug treatment, the urine to plasma paracetamol concentration ratio appeared remarkably constant in patients with normal renal function (9.8 +/- 2.7). It is concluded that the metabolite to paracetamol ratio may only be regarded as a measure of the drug metabolizing capacity in subjects with normal renal function, if factors influencing urine volume and paracetamol absorption are standardized.