Pharmacokinetics of Febuxostat in Healthy Chinese Volunteers

A pharmacokinetic-pharmacodynamic study of a single dose of febuxostat in healthy subjects

AIMS

To examine the pharmacokinetic-phamacodynamic (PK-PD) relationships of plasma febuxostat and serum urate and the effect of a single dose of the drug on renal excretion and fractional clearance of urate (FCU).

METHODS

Blood and urine samples were collected at baseline and up to 145 hours following administration of febuxostat (80 mg) to healthy subjects (n = 9). Plasma febuxostat and serum and urinary urate and creatinine concentrations were determined. Febuxostat pharmacokinetics were estimated using a two-compartment model with first-order absorption. An Emax PK-PD model was fitted to mean febuxostat and urate concentrations. Urinary urate excretion and FCU were calculated pre- and post-dose.

RESULTS

Maximum mean plasma concentration of febuxostat (2.7 mg L^-1 ) was observed 1.2 hours after dosage. Febuxostat initial and terminal half-lives were 2.0 ± 1.0 and 14.0 ± 4.7 hours (mean ± SD), respectively. The majority (81%) of the drug was eliminated in the 9 hours after dosing. Serum urate declined slowly achieving mean nadir (0.20 mmol L^-1 ) at 24 hours. The IC₅₀ (plasma febuxostat concentration that inhibits urate production by 50%) was 0.11 ± 0.09 mg L^-1 (mean ± SD). Urinary urate excretion changed in parallel with serum urate. There was no systematic or significant change in FCU from baseline.

CONCLUSION

The PK-PD model could potentially be used to individualise febuxostat treatment and improve clinical outcomes. A single dose of febuxostat does not affect the efficiency of the kidney to excrete urate. Further investigations are required to confirm the present results following multiple dosing with febuxostat.

Formulation and Characterization of Nanosized Ethosomal Formulations of Antigout Model Drug (Febuxostat) Prepared by Cold Method: In Vitro/Ex Vivo and In Vivo Assessment

Febuxostat (FXT) is a xanthine oxidase (XO) drug which indicated for the treatment of gout. FXT loaded nanosized ethosomes were prepared using cold method with varied concentrations of ethyl alcohol and soya lecithin (SL). The prepared ethosomes were characterized by size, entrapment efficiency (DEE), FT-IR, in vitro release, kinetic studies of in vitro release profile, in vitro skin permeation and deposition, and stability study. The selected ethosomal formulation was incorporated in HPMC gel and characterized for drug content, ex vivo diffusion study through rat skin, and in vivo study and determination of pharmacokinetic parameters using HPLC technique. The results of size analysis showed that minimum size was 124.2 ± 16.77 nm with PDI values between 0.2 and 0.6. The zeta potential was from - 43.5 ± 3.0 to - 20.6 ± 1.42 mV. DEE ranged from 48 to 86%. The results of in vitro skin permeation showed that the amount FXT permeated ranged from 43.33 ± 5.3 to 82.14 ± 5.8%, flux ranged from 14.85 to 28.02. The results of ex vivo study showed that the amount of FXT permeated from unprocessed FXT gel was 49.42 ± 3.29% which was lesser than from FXT ethosomal gel. The results of in vivo study showed that C_max and t_max were significantly different and higher for transdermal administration of FXT than oral administration. The developed FXT nanosized selected ethosome-based transdermal drug delivery gel system would provide a promising method for better management of gout.

Clinical Pharmacokinetics and Pharmacodynamics of Febuxostat

Febuxostat is a xanthine oxidoreductase inhibitor that has been developed to treat chronic gout. In healthy subjects, the pharmacokinetic parameters of febuxostat after multiple oral dose administration include an oral availability of about 85 %, an apparent oral clearance (CL/F) of 10.5 ± 3.4 L/h and an apparent volume of distribution at steady state (V _ss/F) of 48 ± 23 L. The time course of plasma concentrations follows a two-compartment model. The initial half-life (t _½) is approximately 2 h and the terminal t _½ determined at daily doses of 40 mg or more is 9.4 ± 4.9 h. Febuxostat is administered once daily. The maximum (peak) plasma concentrations are approximately 100-fold greater than the trough concentrations. Consequently, there is no significant accumulation of the drug during multiple dose administration. There are few data on the pharmacokinetics of febuxostat in patients with gout. While the pharmacokinetic parameters are not affected by mild to moderate hepatic impairment, there is no consensus on whether renal impairment has any effect on the pharmacokinetics of febuxostat. Febuxostat is extensively metabolised by oxidation (approximately 35 %) and acyl glucuronidation (up to 40 %); febuxostat acyl glucuronides are cleared by the kidney. In healthy subjects treated with multiple doses of febuxostat 10-240 mg, the concentrations of serum urate are reduced by a maximum of about 80 %. The percentage reduction in the concentrations of serum urate is slightly less in gouty patients than in healthy subjects.

Pharmacokinetics and Bioequivalence of Two Formulations of Febuxostat 40-Mg and 80-Mg Tablets: A Randomized, Open-Label, 4-Way Crossover Study in Healthy Chinese Male Volunteers

The present study aimed to investigate the pharmacokinetic properties of febuxostat in healthy Chinese male volunteers and evaluate whether the two formulations of febuxostat 40-mg and 80-mg tablets are bioequivalent. A randomized, open-label, 4-way crossover study was conducted in healthy Chinese male volunteers under fasting conditions. 24 eligible subjects were randomized in a 1:1:1:1 ratio to receive a single dose of test or reference formulation of febuxostat 40-mg or 80-mg tablet. The washout period between each administration was 1 week. Plasma febuxostat was quantified by a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Tolerability was evaluated by monitoring adverse events, physical examinations, 12-lead ECG and laboratory tests. After single-dosing of 1 tablet of 40-mg febuxostat, the pharmacokinetic parameters of test and reference formulations were: Tmax 1.22±0.87 and 1.85±1.03 h, Cmax 1689.16±461.31 and 1613.80±608.43 ng·mL-1, AUC0-t 5139.87±1349.28 and 5517.91±2024.26 ng·mL-1·h, AUC0-∞ 5263.06±1339.16 and 5640.48±2040.22 ng·mL-1·h, t1/2 4.82±2.61 and 4.85±1.78 h, respectively. After single-dosing of 1 tablet of 80-mg febuxostat, the pharmacokinetic parameters of test and reference formulations were: Tmax 1.71±1.21 and 2.23±1.55 h, Cmax 2744.47±1157.44 and 2998.17±1200.13 ng·mL-1, AUC0-t 9634.03±2768.25 and 10467.95±3501.65 ng·mL-1·h, AUC0-∞ 9834.32±2730.51 and 10626.63±3504.08 ng·mL-1·h, t1/2 6.25±2.44 and 5.46±1.65 h, respectively. For single-dosing of 1 tablet of 40-mg febuxostat, 90% CIs for the test/reference ratio of AUC0-t, AUC0-∞ and Cmax were 89.79 to 102.55, 90.14 to 102.56 and 93.99 to 129.63, respectively. For single-dosing of 1 tablet of 80-mg febuxostat, 90% CIs for the test/reference ratio of AUC0-t, AUC0-∞ and Cmax were 86.67 to 100.00, 87.50 to 100.51 and 79.48 to 105.99, respectively. This single dose study revealed similar pharmacokinetic properties in healthy Chinese male volunteers as those found in Caucasic population. The test and reference febuxostat tablets formulations met the regulatory criteria for bioequivalence at 40-mg and 80-mg strengths in fasting healthy Chinese male volunteers.

TRIAL REGISTRATION

Chictr.org ChiCTR-TTRCC-14004288.