Rapid estimation of creatinine clearances in patients with liver dysfunction.

Different methods are available for rapid assessment of renal function using the patient's serum creatinine concentration and body weight without obtaining urine collection over 24 hr. However, the reliability of these methods in patients with liver diseases has not been established. The purpose of this study was to determine the accuracy and precision of the estimated creatinine clearances obtained by the methods of Cockcroft-Gault, Jelliffe, Mawer, and Siersbaek-Nielsen in patients with liver diseases who have different degrees of renal function. Creatinine clearances obtained from 24-hr urine collection were used as the standard. The different methods for rapid renal function estimation had limited accuracy and reliability in patients with severe liver dysfunction (Child-Pugh class C) and also in those with creatinine clearances of less than 60 ml/min. Creatinine clearances were overestimated by about 40-100%. Using lean body weights, instead of total body weights, reduced the prediction errors. In patients with mild liver dysfunction (Child-Pugh class A), all four estimation methods provided reasonable estimation of the creatinine clearances.

Pharmacokinetics and safety of tiagabine in subjects with various degrees of hepatic function.

PURPOSE: To evaluate the pharmacokinetics and safety of multiple oral doses of tiagabine HCl in subjects with different degrees of hepatic impairment. METHODS: Four subjects with mild hepatic impairment, three subjects with moderate hepatic impairment, and six matched normal subjects received twice daily oral tiagabine HCl for 5.5 days. Serial blood specimens were obtained for 48 h after the final dose. Total and unbound tiagabine plasma concentrations were determined by high-performance liquid chromatography (HPLC) and ultrafiltration, respectively. Pharmacokinetic parameters were compared between the groups by analysis of covariance. RESULTS: For total tiagabine concentrations in normal subjects and subjects with mild and moderate hepatic impairment, C(max) values (mean +/- SD) were 117 +/- 54, 172 +/- 40, and 172 +/- 28 ng/ml; C(min) values were 13 +/- 4, 27 +/- 4, and 28 +/- 6 ng/ml; areas under the plasma concentration-time curve were 396 +/- 59, 633 +/- 16, and 675 +/- 32 ng x h/ml, and elimination half-lives (harmonic means) were 7, 12, and 16 h, respectively. Unbound tiagabine concentrations, area under the unbound plasma concentration-time curve, and the free fractions were increased in the hepatically impaired subjects. Reduced serum albumin and alpha1-acid glycoprotein concentrations may have contributed to increases in the unbound fraction. Adverse events observed included dizziness, tremor, nausea, somnolence, incoordination, and unsteady gait. The frequency of these events was increased in the subjects with liver impairment. CONCLUSIONS: Because of the decreased drug elimination caused by liver function impairment, reduced doses or increased dosing interval or both may be needed to attain therapeutic plasma drug concentrations. Time to reach steady state also may be prolonged. The patients should be monitored closely for potential neurologic adverse events.