Pharmacokinetics of vandetanib in subjects with renal or hepatic impairment.

BACKGROUND AND OBJECTIVE: Vandetanib, an oncology drug being evaluated in phase III clinical trials, undergoes significant renal and hepatic excretion. The objective of these two studies was to investigate the single-dose pharmacokinetics of vandetanib in subjects with renal or hepatic impairment in comparison with healthy subjects. SUBJECTS AND METHODS: Two open-label, parallel-group studies were conducted at a single centre in Germany. Subjects aged 18-75 years with a body mass index of 18-32 kg/m2 were eligible. The renal impairment study recruited subjects with normal renal function and mild, moderate and severe renal impairment according to creatinine clearance calculated from a 24-hour urine collection pre-dose. The hepatic impairment study recruited subjects with normal hepatic function and mild, moderate and severe hepatic impairment according to the Child-Pugh classification. All subjects received a single 800 mg oral vandetanib dose. Blood samples for measurement of vandetanib, N-desmethylvandetanib and vandetanib N-oxide were collected before and at various timepoints after vandetanib administration for up to 63 days. Pharmacokinetic parameters were determined using noncompartmental methods. RESULTS: Thirty-two subjects were recruited for the renal impairment study (ten with normal renal function and six, ten and six with mild, moderate and severe impairment, respectively). Thirty subjects were recruited for the hepatic impairment study (eight with normal hepatic function and eight, eight and six with mild, moderate and severe impairment, respectively). The area under the plasma concentration-time curve from time zero to infinity (AUC(infinity)) values of free vandetanib increased by approximately 46%, 62% and 79% in subjects with mild, moderate and severe renal impairment, respectively. These increases were statistically significant, with the increase in the severe renal impairment group having the possibility of being double the value observed in subjects with normal renal function (geometric least squares [GLS] mean ratio [renal impairment : normal renal function] of 1.79; 90% CI 1.39, 2.31). Peak plasma concentrations of free vandetanib increased slightly by approximately 7%, 9% and 11% in subjects with mild, moderate and severe renal impairment, respectively. Total plasma clearance of free vandetanib decreased with all degrees of renal dysfunction. Hepatic impairment did not have a statistically significant effect on the AUC(infinity) of total vandetanib. Peak plasma concentrations of total vandetanib were reduced in subjects with all classifications of hepatic impairment compared with normal hepatic function, with a statistically significant effect in the severe hepatic impairment group (GLS mean ratio 0.71; 90% CI 0.53, 0.96). Increased exposure to both metabolites was seen in subjects with renal impairment. Exposure to N-desmethylvandetanib was reduced in subjects with hepatic impairment, while exposure to vandetanib N-oxide was increased in subjects with severe hepatic impairment. Vandetanib was well tolerated and had a similar tolerability profile in subjects with renal or hepatic impairment compared with healthy subjects. CONCLUSION: Exposure to vandetanib was increased by about 46%, 62% and 79% in subjects with mild, moderate and severe renal impairment, respectively. A doubling in exposure could be ruled out in subjects with mild or moderate renal impairment but not for those with severe renal impairment. The possibility of dose reductions in patients with severe renal impairment will need to be assessed when the safety and tolerability profile is fully defined. Exposure to vandetanib was not altered in subjects with hepatic impairment, and no dose adjustment would be expected in patients with hepatic impairment.

The pharmacokinetics of escitalopram in patients with hepatic impairment.

The effect of hepatic impairment on the pharmacokinetics of escitalopram was determined by means of nonlinear mixed effect modeling, considering both the Child-Pugh classification (and its components) and cytochrome P450 2C19 (CYP2C19) activity. Twenty-four subjects were grouped according to their Child-Pugh score as healthy, with mild hepatic impairment or with moderate hepatic impairment. The subjects were administered a single oral dose of escitalopram 20 mg, and blood was sampled up to 168 hours after dosage. The serum concentration of escitalopram was determined and the pharmacokinetics assessed by nonlinear mixed effect modeling. The CYP2C19 activity was measured from the urinary excretion ratio of S/R-mephenytoin. All subjects tolerated the treatment well, and no serious adverse events were reported. Predicted mean area under the curve from zero to infinity (AUC(inf)) values were 51% and 69% higher for patients with mild and moderate hepatic impairment (Child-Pugh classification), respectively, compared with healthy subjects. The best-fitting model showed an influence of CYP2C19 activity on clearance and body weight on the volume of distribution for escitalopram. CYP2C19 activity is a better predictor of escitalopram clearance than is Child-Pugh classification.

Pharmacokinetics and sedative effects in healthy subjects and subjects with impaired liver function after continuous infusion of clomethiazole.

OBJECTIVE: Clomethiazole is virtually completely eliminated by hepatic metabolism. This study was designed to assess the impact of liver impairment on its elimination and sedative effects. METHODS: Eight patients with mild liver impairment (Child-Pugh grade A), eight patients with moderate/severe liver impairment (Child-Pugh grade B/C) and eight healthy subjects of similar age were given 68 mg/kg clomethiazole edisilate according to a 24-h infusion scheme aimed at producing minimum sedation as it was intended for clinical use in patients with stroke. Concentrations of clomethiazole and its active alpha-carbon hydroxylated metabolite NLA-715 were followed in plasma and urine for 96 h and 24 h, respectively. Sedation was monitored using a scale from 1 to 6. RESULTS: The fraction excreted unchanged in urine was less than 0.2% for clomethiazole and less than 0.4% for NLA-715. Urine concentrations of clomethiazole were strongly correlated (r(2)=0.60) to plasma concentrations and approximately equal to unbound plasma concentrations. Plasma levels of NLA-715 increased steadily during the infusion, eventually reaching mean levels exceeding those of clomethiazole in all groups. Plasma clearance of clomethiazole in subjects with mildly impaired liver function was not statistically different from that of healthy controls (40 l/h vs 44 l/h). In subjects with moderate/severe liver impairment, there was a 50% reduction in clearance. Sedation was not observed except in two subjects in the Child-Pugh A group showing mild sedation. CONCLUSION: The reduced clomethiazole clearance in patients with moderate/severe liver impairment seems to call for a reduction of clomethiazole dosage. However, sedation was not observed in this group at the investigated dose level.