Pharmacokinetics of single-dose reboxetine in volunteers with renal insufficiency.

Reboxetine is a new selective norepinephrine reuptake inhibitor (selective NRI) for the short- and long-term treatment of depression that is effective and well tolerated at a dose of 8 to 10 mg/day. This study assessed the pharmacokinetics of reboxetine in volunteers with renal impairment. A single 4 mg dose of reboxetine was administered to a total of 18 volunteers with mild (n = 6), moderate (n = 6), or severe (n = 6) renal impairment (creatinine clearance: 56-64, 26-51, and 9-19 ml/min, respectively), and reboxetine concentrations were measured in plasma by HPLC. Mean AUC infinity increased by 43% (mild vs. severe; p < 0.01) as renal function declined, while renal clearance and total urinary excretion of unchanged reboxetine decreased by 67% and 62%, respectively (mild vs. severe; p < 0.01 for both parameters). tmax and t1/2 were not significantly different between groups. In comparison with historical data from young healthy volunteers, AUC infinity and t1/2 are at least doubled in volunteers with renal impairment, while CLr is halved. This pharmacokinetic study has shown that increasing renal dysfunction leads to increasing systemic exposure to reboxetine, particularly in severe renal insufficiency, although reboxetine was well tolerated by all volunteers. Thus, a reduction of the starting dose of reboxetine to 2 mg twice daily would be prudent in patients with renal dysfunction.

Comparative bioavailability study of codeine and ibuprofen after administration of the two products alone or in association to 24 healthy volunteers.

The study objective was to compare the bioavailability of codeine and ibuprofen after oral administration of the two drugs alone or in association. The study was performed in three different periods, each separated by a wash-out of 6 days. Plasma concentrations were measured in 24 healthy volunteers after administration of a single oral dose of codeine phosphate (25 mg) and/or ibuprofen (200 mg). Codeine and ibuprofen assays were performed using two different HPLC methods. The relative bioavailabilities of codeine and ibuprofen (alone or in association) were 106 +/- 24% (mean +/- sd) and 101 +/- 19%, respectively. The results obtained demonstrated that bioavailabilities of codeine and ibuprofen were not modified when the two drugs were administrated alone or in association.

Pharmacokinetics of reboxetine in healthy, elderly volunteers.

The pharmacokinetic characteristics of reboxetine, a unique selective noradrenaline reuptake inhibitor (selective NRI) for the treatment of depression, were studied in 12 healthy, elderly volunteers (mean age 81 years +/- 9 years). All subjects received a single 4-mg dose of reboxetine, and plasma reboxetine concentrations were measured by HPLC. Reboxetine was well tolerated by all subjects. Exposure to reboxetine was higher in this group of very elderly subjects, compared with data obtained in a similar study of young, healthy volunteers. Cmax in the elderly was 271 +/- 86 ng/ml, compared with 111 +/- 28 ng/ml in the young subjects after a single 4-mg dose, although in both groups Cmax was observed after 2 h. The AUC infinity was nearly four times that in the younger subjects (8345 +/- 3107 ng.h/ml vs. 2106 +/- 881 ng.h/ml) and the t1/2 was twice as long (24 +/- 6 h vs. 12 +/- 3 h). Renal clearance was also reduced. Reboxetine 8-10 mg/day has been effective and well tolerated in clinical trials in non-elderly depressed patients. The increased exposure to reboxetine observed in our very elderly subjects supports a reduction of the starting dose to 4 mg/day (in two divided doses) in the elderly.

Stability of cephalosporin prodrug esters in human intestinal juice: implications for oral bioavailability.

The levels of degradation of cefetamet pivoxil (CAT), cefuroxime axetil (CAE), and cefpodoxime proxetil (CPD) in 0.6 M phosphate buffer (pH 7.4) and human intestinal juice (pH 7.4) at 37 degreesC over 24 h were compared. Significant differences in the time courses of degradation and in the patterns of degradation products were observed. (i) The relative proportions of the Delta2- and Delta3-cephalosporins were roughly reversed in the two incubation media. In phosphate buffer, the major degradation product was the Delta2-cephalosporin (CAT = 61%; CAE = 74%; CPD = 85%), while in intestinal juice it was the Delta3-cephalosporin (CAT = 86%; CAE = 75%; CPD = 87%). (ii) Generally, the degradation of the prodrug esters progressed faster in intestinal juice than in phosphate buffer (e.g., for CAT the half-lives [t1/2s] were 0.78 and 4.3 h, respectively). (iii) The two diastereoisomers of CAE and CPD were degraded at different rates in intestinal juice (for the CAE diasteroisomers, t1/2s = 0.37 and 0.93 h; for the CPD diastereoisomers, t1/2s = 0.18 and 0.98 h) but were degraded at similar rates in phosphate buffer (for the CAE diastereoisomers, t1/2 = 1.6 h; for the CPD t1/2 diastereoisomers, = 2.2 h). It is concluded that (i) the Delta2 isomerization does not significantly affect the bioavailability of prodrug esters since enzymatic hydrolysis in the intestinal fluid proceeds mainly to the active Delta3-cephalosporin and (ii) the high degree of stereoselectivity of the enzymatic ester hydrolysis should make it possible to increase the bioavailabilities of certain prodrug esters (CAE, CPD) by using the more stable diasterioisomer.

Pharmacokinetics, metabolism and bioavailability of the new anti-allergic drug BM 113. Part III: Pharmacokinetics, metabolism, dose dependency and gender effect after single or repeated administration to human healthy volunteers.

A new anti-allergic drug, BM 113 (1-(benzhydryloxyethyl)piperidino-4- ethylacetate, CAS 115313-90-1; BM 113 maleate: CAS 115313-91-2), with a piperidinic structure, showing anti-histaminic properties was studied after administration to healthy human volunteers. The focus was on the pharmacokinetics, the metabolism, the dose dependency and gender differences of the pharmacokinetic parameters of BM 113 and its main desacetylated metabolite, BM 212. Unchanged BM 113 was not recovered in plasma or in urine. The elimination of the radioactivity was essentially urinary with about 81% recovered within 24 h. The elimination was completed with 97% of the administered dose recovered after 120 h. HPLC dosage of BM 212, using a specific method, showed that BM 212 represented 62% of the urine radioactivity. The plasma profile of radioactivity was characterized by two decreasing phases with respective half-lives of 3.71 +/- 0.66 h and 24.67 +/- 25.01 h. A dose dependency study realised with 20, 40, 60 and 80 mg oral doses administered to 8 healthy volunteers has proven the linearity of the pharmacokinetics of BM 212 in the studied range. BM 212 disposition after single and repeated BM 113 oral doses in a 14-day study did not vary and permitted to conclude that no auto-induction or auto-inhibition phenomenon was involved. No significant difference between men and women was observed. The concentration profile was mono or biexponential, depending on the subject but whatever the gender. An inter-individual variability appeared for both sexes and caused some variations in the pharmacokinetic parameters.