Aims The objective of this study was to compare the pharmacokinetics, safety and tolerability of the antiepileptic drug felbamate in young and elderly healthy vounteers. Methods The single and multiple dose pharmacokinetics of felbamate were examined in an open-label two-dose level parallel group study in 24 elderly (66 to 78-yearold) and 11 young (18 to 45-year-old) healthy volunteer subjects. Pharmacokinetics were determined from blood samples obtained over 120 h after administration of single 600 mg or 1200 mg doses, and after multiple doses of 600 mg or 1200 mg administered every 12 h. Safety and tolerability were assessed through laboratory tests, ECGs, vital signs and reported adverse events. Results Single dose felbamate pharmacokinetic parameters differed between young and elderly subjects; compared with young subjects, elderly subjects had lower mean clearance (31.2 vs 25.1 ml min −1 ; 90% CI −11.4 to −0.9; P=0.02) and a trend towards a greater half-life (18.6 vs 21.0 h; 90% CI −0.6 to 5.4; P=0.11). Mean AUC and C max values were also higher in elderly subjects. No gender differences were noted for weight-adjusted pharmacokinetic variables. Felbamate was less well tolerated in elderly subjects compared with young subjects, as shown by higher rates of adverse event reporting and dropouts at the higher dose level. This may be due to age-related pharmacokinetic differences, to the rapid dose titration schedule used in this study, and/or to altered sensitivity to felbamate's pharmacodynamic effects. Conclusions These findings imply that elderly subjects require lower initial dosing and slower dose titration of felbamate than non-elderly subjects.
Pramipexole is the first‐line medication recommended by the British National Institute for Health and Care Excellence. Pramipexole is predominantly eliminated by renal excretion. The aim was to develop a physiologically based pharmacokinetic (PBPK) model of pramipexole, providing a basis for its individualized administration. The role of glomerular filtration and organic cation transporter 2 (OCT2) in renal tubular secretion was considered. Plasma concentration‐time profiles of pramipexole were predicted and validated, first in healthy populations and then in PD patients with varied renal function. Finally, the pharmacokinetics of PD patients with different degrees of renal impairment were predicted. The simulated pharmacokinetic parameters, including maximum plasma concentration (Cmax), area under the plasma concentration‐time curve (AUC), time to maximum plasma concentration (tmax), and steady‐state trough plasma concentration values, obtained using the PBPK model were validated using fold error values, which were all smaller than 2. The successfully validated model supported that OCT2‐mediated tubular secretion was affected proportionally to changes in glomerular filtration for various degrees of renal impairment. The predicted AUC0‐inf values were increased 1.16‐, 1.76‐, 3.26‐, and 9.48‐fold in mild, moderate, and severe renal impairment and end‐stage renal disease (ESRD) subjects, resepctively, compared with PD patients with normal renal function. It appears that PD patients with mild renal impairment are unlikely to require dose adjustment (0.125 mg 3 times a day). The pramipexole dose should be reduced to approximately 0.125 mg twice daily, 0.125 mg once daily, and 0.0375 mg once daily in PD patients with moderate renal impairment, severe renal impairment, and ESRD, respectively.
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