AUC Tau Research Articles

Safety, pharmacodynamics, and pharmacokinetics of BAY 59-7939—an oral, direct Factor Xa inhibitor—after multiple dosing in healthy male subjects

There is a clinical need for safe new oral anticoagulants. The safety, tolerability, pharmacodynamics, and pharmacokinetics of BAY 59-7939--a novel, oral, direct Factor Xa (FXa) inhibitor--were investigated in this single-center, placebo-controlled, single-blind, parallel-group, multiple-dose escalation study. Healthy male subjects (aged 20-45 years, body mass index 18.6-31.4 kg/m(2)) received oral BAY 59-7939 (n=8 per dose regimen) or placebo (n=4 per dose regimen) on days 0 and 3-7. Dosing regimens were 5 mg once, twice (bid), or three times daily, and 10 mg, 20 mg, or 30 mg bid. There were no clinically relevant changes in bleeding time or other safety variables across all doses and regimens. There was no dose-related increase in the frequency or severity of adverse events with BAY 59-7939. Maximum inhibition of FXa activity occurred after approximately 3 h, and inhibition was maintained for at least 12 h for all doses. Prothrombin time, activated partial thromboplastin time, and HepTest were prolonged to a similar extent to inhibition of FXa activity for all doses. Dose-proportional pharmacokinetics (AUC(tau, norm) and C(max, norm)) were observed at steady state (day 7). Maximum plasma concentrations were achieved after 3-4 h. The terminal half-life of BAY 59-7939 was 5.7-9.2 h at steady state. There was no relevant accumulation at any dose. BAY 59-7939 was safe and well tolerated across the wide dose range studied, with predictable, dose-proportional pharmacokinetics and pharmacodynamics and no relevant accumulation beyond steady state. These results support further investigation of BAY 59-7939 in phase II clinical trials.

Pharmacokinetic profile of lanreotide Autogel® in patients with acromegaly after four deep subcutaneous injections of 60, 90 or 120 mg every 28 days

To investigate the pharmacokinetic profile of a prolonged release, aqueous Autogel formulation of the somatostatin analogue lanreotide (Lan-ATG). A phase II, randomized, double-blind study, during which patients received 60, 90 or 120 mg Lan-ATG for four fixed administrations at 28-day intervals. A total of 18 patients with acromegaly were recruited; six patients were randomized to each treatment. Lanreotide minimum concentration (C(min)), maximum serum concentration (C(max)) and area under the concentration-time curve during a dosing interval (AUC(tau)) were assessed after a single dose and at steady state (ss). Serum GH and IGF-1 levels were assessed before each administration and at the end of the study. After a single administration, dose proportionality for C(min,1), C(max) and AUC(tau) was demonstrated statistically. After repeated administrations, Lan-ATG exhibited linear pharmacokinetics over the dose range and ss values of C(min), C(max) and AUC(tau) increased in a dose-dependent, linear manner. Mean C(max,ss) values were only two- to fourfold greater than C(min,ss) values, and there was good control over the entire release profile. Serum levels of GH and IGF-1 declined over the course of the study and acromegaly symptoms improved. The treatment was well tolerated. Lan-ATG showed linear pharmacokinetic profiles over the three dose levels after both single and repeated dosing, no initial burst effect and good control over the entire release profile. Despite the absence of dose adaptation, four injections of Lan-ATG were effective in lowering serum levels of GH and IGF-1.

Development of an HPLC method for determination of diphenidol in plasma and its application in an oral multi-dose bioequivalence study in a healthy female mexican population

Diphenidol was determined by an HPLC method developed in our laboratory. It was validated and proved to be linear in the 40–400 ng/ml range. Accuracy for quality-control samples for intra and inter day assays ranged from 96.1–98.9% and 98.8–101.4%, respectively. This method was applied to a multi-dose bioequivalence study. No serious side effects were observed in the multi-dose design. Pharmacokinetic parameters (mean ± standard error [S.E.]) of Cavg (ng/ml) and AUC tau (ng h/ml) for reference and test products were 139.54 ± 12.66 versus 148.60 ± 16.51 and 551.07 ± 53.53 versus 588.78 ± 69.02, respectively. Log-transformed values were compared by analysis of variance (ANOVA) followed by the classical 90% confidence interval (CI 90%) test and Schuirmann's test. Confidence limits ranged from 91.48–116.18% for C max and from 91.24–117.65% for AUC tau. These results suggest that the analytical method was linear, precise, and accurate for our purpose, and that both assayed formulations were bioequivalent.

Lack of Pharmacokinetic Interaction between Esomeprazole and the Nonsteroidal Anti-Inflammatory Drugs Naproxen and Rofecoxib in Healthy Subjects

We investigated the potential interactions between esomeprazole and a non-selective nonsteroidal anti-inflammatory drug (NSAID; naproxen) or a cyclo-oxygenase (COX)-2-selective NSAID (rofecoxib) in healthy subjects. Two studies of identical randomised, open, three-way crossover design were conducted. Subjects (n = 32 for both studies) were to receive 1 week's treatment with esomeprazole 40mg once daily (studies A and B), naproxen 250mg twice daily (study A), rofecoxib 12.5mg once daily (study B), and esomeprazole in combination with naproxen (study A) or rofecoxib (study B). Study periods were separated by a 2-week washout period. On day 7 of dosing, the ratios (and 95% CIs) for the area under the plasma concentration-time curve during the dosing interval (AUC(tau)) and observed maximum plasma concentration (C(max)) of esomeprazole and NSAID combination/NSAID alone were 0.98 (0.94, 1.01) and 1.00 (0.97, 1.04), respectively, for study A, and 1.15 (1.06, 1.24) and 1.14 (1.02, 1.28), respectively, for study B. The ratios (and 95% CIs) for AUC(tau) and C(max) of esomeprazole and NSAID combination/esomeprazole alone were 0.96 (0.89, 1.03) and 0.92 (0.85, 1.00), respectively, for study A, and 1.05 (0.96, 1.15) and 1.05 (0.94, 1.18), respectively, for study B. All treatments were well tolerated during the study period. Naproxen and rofecoxib do not interact with esomeprazole, and esomeprazole does not affect the pharmacokinetics of naproxen or rofecoxib. These findings indicate that esomeprazole can be used in combination with NSAIDs without the risk of a pharmacokinetic interaction.

Evaluation of the effect of candesartan cilexetil on the steady-state pharmacokinetics of tacrolimus in renal transplant patients

Candesartan cilexetil is a possible treatment for hypertension in renal allograft recipients. Tacrolimus is widely used as an immunosuppressant following renal transplantation. The aim of this study was to evaluate the effect of multiple doses of candesartan cilexetil on the steady-state pharmacokinetics of tacrolimus. Twelve patients received oral doses of tacrolimus twice daily for 12 days from study day -2 until day 10, single oral doses of candesartan cilexetil placebo on study days -2 to -1, single oral doses of 2 mg candesartan cilexetil once daily on study days 1 to 3, oral doses of 4 mg candesartan cilexetil once daily on study days 4 to 6, and oral doses of 16 mg candesartan cilexetil once daily on study days 7 to 9. Serial blood samples were collected on days -1, 6 and 9 and were analysed for tacrolimus using microparticle enzyme immunoassay. Mean C(max,ss) and AUC(tau,ss) values for tacrolimus on day 6 (4 mg candesartan) and day 9 (16 mg candesartan cilexetil) were similar to those on day -1 (tacrolimus alone). Renal function did not change under treatment with candesartan cilexetil compared with baseline. The co-administration of multiple oral doses of cardesartan cilexetil with oral doses of tacrolimus was well tolerated. Concomitant administration of multiple doses of candesartan cilexetil does not alter the steady-state pharmacokinetics of tacrolimus.

Linezolid disposition after standard dosages in critically ill patients undergoing continuous venovenous hemofiltration: A report of 2 cases

Linezolid is a new oxazolidinone antibiotic active against most Gram-positive microorganisms the renal elimination of which accounts for about 30% to 35% of all the clearance. Its pharmacokinetic ability was assessed during continuous venovenous hemofiltration (CVVH) in 2 anuric patients with severe postsurgical intraabdominal infections who were receiving standard dosages (600 mg intravenously twice a day). Blood samples for quantification of linezolid in plasma and in filtrate were collected after more than 4 days of therapy before dosing and at 0, 0.5, 1, 2, 3, 5, 7, 9, and 11 hours after the morning 1-hour intravenous infusion, and concentrations were determined by means of high-performance liquid chromatography. Linezolid was partially cleared by CVVH in both the patients (hemofiltration clearance [CL CVVH ] = 0.38 and 0.35 mL/min/kg), with high sieving coefficient values (0.76 to 0.92). Efficacious plasma exposure for time-dependent antibacterial activity of linezolid, either in terms of trough levels above minimum inhibitory concentration (MIC) at which 90% of the isolates are inhibited (Cmin >MIC90 ) or of area under the plasma concentration time curve to MIC90 ratio (AUC/MIC90 ) >100 hours, was ensured during CVVH in both patients. However, despite similar CL CVVH , significant interindividual pharmacokinetic variability was found in the 2 patients (AUC during the observational period [AUC 0-tau ] 334.71 versus 109.34 mg/L x h), mainly owing to substantial differences in non-CVVH-related clearance of linezolid (total CL, 0.55 versus 1.21 mL/min/kg). Our findings indicate that linezolid, although partially removed, does not warrant dosage modification during the first 48 hours when CVVH (with polysulfide hemofilter) at standard 2,000 mL/h substitution flow rate in predilution is applied to anuric patients. Thereafter, this choice is a reasonable one with the exception of those patients who have other features of linezolid toxicity and in which non-CVVH-related clearance might be impaired, although further evaluations are warranted.

DOV 216,303, a “Triple” Reuptake Inhibitor: Safety, Tolerability, and Pharmacokinetic Profile

This report describes the first evaluation in humans of DOV 216,303, a putative antidepressive that inhibits the reuptake of norepinephrine, serotonin, and dopamine. Subjects received single oral doses of 5 to 150 mg of DOV 216,303 or placebo. At 150 mg, 4 of 7 subjects reported gastrointestinal disturbances. In the multiple-dose phase of the evaluation, subjects received total daily doses of 50, 75, or 100 mg of DOV 216,303 or placebo for 10 days. At a total daily dose of 100 mg, gastrointestinal disturbances were reported in 4 of 6 volunteers. In both the single- and multiple-dose evaluations, no significant changes were noted in vital signs, electrocardiogram, hematology, or clinical chemistry. DOV 216,303 was rapidly absorbed (plasma t(max) of 0.7-1.2 hours and t(1/2) of 3.3-4.4 hours), with dose-proportional C(max) and AUC values. Furthermore, no remarkable difference was apparent in either the C(max) or AUC(tau) of DOV 216,303 following 1 and 10 days of dosing. The present results demonstrate that DOV 216,303 is safe and well tolerated both at single doses of up to 100 mg and multiple doses of up to 100 mg/day for 10 days. Plasma concentrations of DOV 216,303 after doses > 10 mg exceed its reported IC(50) values for inhibition of biogenic amine reuptake.

Pharmacokinetics of nelfinavir and indinavir in HIV-1-infected pregnant women.

Protease inhibitor (PI)-based combination antiretroviral therapy is often indicated for treatment of maternal HIV disease, but little is known about PI pharmacokinetics during pregnancy. Increased cytochrome P450 activity may affect the disposition of PI and decrease drug exposure. Steady-state PI pharmacokinetics, measured by the area under the plasma concentration versus time curve (AUC(tau)), were evaluated in women on stable antiretroviral regimens containing nelfinavir (n = 9) or indinavir (n = 4) with or without ritonavir (n = 2) during the second and third trimesters of pregnancy and postpartum. Cytochrome P450 activity was assessed by measuring the urine 6 beta-hydroxycortisol to cortisol ratio (6 beta-OHF/F). AUC(tau) in women on indinavir alone decreased and 6 beta-OHF/F ratios increased during pregnancy compared with postpartum control values (n = 2). Nelfinavir results demonstrated no clear change and were highly variable. The results for indinavir suggest that metabolic induction occurs during pregnancy, which apparently resolves spontaneously postpartum. This may warrant dosage adjustment during pregnancy. This induction is offset by concomitant use of ritonavir. Nelfinavir results were variable and, therefore, the impact of pregnancy on nelfinavir disposition was not fully determined.

Pharmacokinetics and Pharmacodynamics of Intravenous Levofloxacin in Patients with Early-Onset Ventilator-Associated Pneumonia

To investigate the pharmacokinetics of levofloxacin and the pharmacokinetic-pharmacodynamic appropriateness of its total body exposure in patients in the intensive care unit (ICU) treated for early-onset ventilator-associated pneumonia (VAP) with intravenous levofloxacin 500mg twice daily. Prospective non-blinded pharmacokinetic-pharmacodynamic study. Ten critically ill adult patients with normal renal function. Blood and urine samples were collected at appropriate times during a 12-hour administration interval at steady state. Levofloxacin concentrations were determined by high-performance liquid chromatography. Clinical and microbiological outcomes were assessed. Levofloxacin pharmacokinetics were only partially comparable with those obtained from literature data for healthy volunteers. Area under the concentration-time curve (AUC(tau)) over the 12-hour dosage interval was about 30-40% lower than in healthy volunteers (33.90 vs 49.60 mg. h/L). The reduced exposure may be due to a greater clearance of levofloxacin (0.204 vs 0.145 L/h/kg [3.40 vs 2.42 mL/min/kg]), leading to a shorter elimination half-life (5.2 vs 7.6 hours). Cumulative urinary excretion during the 12-hour dosage interval confirmed the greater excretion of unchanged drug in these patients compared with healthy subjects (76% vs 68%). Coadministered drugs used to treat underlying diseases (dopamine, furosemide, mannitol) may at least partially account for this enhanced elimination in critically ill patients. Intravenous levofloxacin 500mg twice daily ensured a median C(max)/MIC (maximum plasma concentration/minimum inhibitory concentration) ratio of 102 and a median 24-hour AUC/MIC ratio of 930 SIT(-1). h (inverse serum inhibitory titre integrated over time) against methicillin-sensitive Staphylococcus aureus and Haemophilus influenzae. The overall success rate of the assessable cases was 75% (6/8). Bacterial eradication was obtained in all of the assessable cases (8/8), but a superinfection (Acinetobacter anitratus,Pseudomonas aeruginosa) occurred in three cases. The findings support the suitability of intravenous levofloxacin 500mg twice daily in the treatment of early-onset VAP in ICU patients with normal renal function. Levofloxacin may represent a valid alternative to non-pseudomonal beta-lactams or aminoglycosides in the empirical treatment of early-onset VAP. However, further larger studies are warranted to investigate its efficacy.

Candesartan Cilexetil in Haemodialysis Patients

Intermittent activation of the renin-angiotensin system during dialysis may be related to the high risk of cardiovascular disease in dialysis patients. The aim of the present study was to investigate the pharmacokinetics and short-term tolerability of the angiotensin II type 1 receptor antagonist candesartan cilexetil in patients receiving chronic haemodialysis. The study was a double-blind, randomised, placebo-controlled, dose-escalation study. Candesartan cilexetil was administered once daily, starting at 4mg with up-titration biweekly to 8mg and 16mg, respectively. Trough plasma concentrations of candesartan were determined before dialysis. After 2 weeks on the highest dose, plasma concentrations were obtained at frequent intervals after dose administration. Twenty patients receiving chronic haemodialysis and with adequately controlled blood pressure were included in the study. Fourteen patients were randomised to candesartan cilexetil and six to placebo. Nine of the patients randomised to candesartan cilexitil reached the maximum dose of 16mg and completed the study according to protocol. Their blood pressure remained stable. Four patients discontinued active treatment due to hypotension at the lowest dose. Trough plasma concentrations of candesartan determined at the end of each study period increased linearly with dose. Following administration of candesartan cilexetil 16mg the maximum plasma concentration of candesartan was 244 +/- 54 mug/L and the area under the concentration-time curve over 24 hours, i.e. one dosing interval (AUC(tau)), was 2767 +/- 1162 mug/L . h. Steady-state plasma concentrations of candesartan were approximately twice as high in haemodialysis patients as in subjects with normal renal function. Provided blood pressure is carefully monitored, candesartan cilexetil can be titrated from 4mg up to 16mg once daily in haemodialysis patients.

Novel Formulations of Cetrorelix Acetate in Healthy Men: Pharmacodynamic Effects and Noncompartmental Pharmacokinetics

The objective of this study was to investigate the effects on the pharmacodynamics and noncompartmental pharmacokinetics after weekly subcutaneous administration of novel formulations of cetrorelix acetate in healthy men. In a randomized parallel-group study, single subcutaneous doses of cetrorelix acetate (concentration: 2.5 mg peptide base/ml) dissolved in aqueous gluconic acid (CET/glu, dose: 5 or 10 mg peptide base) or in water (CET/wat, dose: 10 mg peptide base) were given to 36 subjects once weekly in the morning for 4 weeks. Cetrorelix plasma, serum testosterone, luteinizing hormone, andfollicle-stimulating hormone concentrations were monitored after each administration for 1 week, with extensive profiling after the first and fourth administration. Cetrorelix plasma concentrations were analyzed by radioimmunoassay and serum hormone concentrations by enzyme immunoassays. At least half-maximum testosterone suppression started with all treatments within less than 1 day. Deepest and longest testosterone suppression was achieved by 10 mg CET/glu. Duration of atleasthalf-maximum suppression was after the first dose median of 82 hours and after the fourth dose median of 122 hours, respectively. Substantial suppression was also evidentfor luteinizing hormone (LH) and, to a lesser extent, forfollicle-stimulating hormone (FSH). On average, Cmax was nearly doubled after single and multiple doses, and AUC(tau) was increased by about 50% after single doses and about 30% after multiple doses of 10 mg CET/glu as compared to 10 mg CET/wat. For tmax and t1/2, no significant differences were found between formulations. It was concluded that testosterone suppression increased with weekly subcutaneous administrations of 10 mg CET/glu. Compared to CET/wat, bioavailability and duration of suppression were increased with CET/glu.

Cirrhosis Does Not Affect the Pharmacokinetics and Pharmacodynamics of Clopidogrel

Clopidogrel, a new platelet ADP receptor antagonist used for the prevention of vascular ischemic events, is converted to an active metabolite via the cytochrome P450 system. Patients with cirrhosis may not metabolize drugs normally and may, in addition, have a number of defects in the coagulation system. To assess the effect of cirrhosis on the pharmacokinetics and pharmacodynamics of clopidogrel, the authors performed an open-label, parallel-group study of 12 patients with Child-Pugh Class A or B cirrhosis and 12 matched controls. All 24 subjects received clopidogrel 75 mg PO QD for 10 days. Pharmacokinetics of clopidogrel and the major metabolite SR 26334 were analyzed on Days 1 and 10; pharmacodynamics were assessed by the inhibition of ADP-induced platelet aggregation and by bleeding time prolongation factor. Pharmacokinetic analysis of clopidogrel was limited due to low plasma concentrations arising from rapid hydrolysis to SR 26334. The Cmax at SS for clopidogrel was higher in cirrhotics than in normals. However, exposures to the metabolite SR 26334, as measured by AUC(tau), were comparable. At Day 10, there was not a statistically significant difference in mean inhibition of platelet aggregation (49.2% +/- 38.6% in cirrhotics vs. 66.7% +/- 7.5% in normals) or in bleeding time prolongation factor (1.64 +/- 0.49 in cirrhotics vs. 1.54 +/- 0.87 in normals) between groups. No significant adverse events, including bleeding events, were reported. In conclusion, there were no significant differences in the pharmacokinetics and pharmacodynamics of clopidogrel in this group of subjects with cirrhosis and matched normals. Therefore, no dosage adjustment of clopidogrel is required in patients with Child-Pugh Class A or B cirrhosis.

Multiple-dose pharmacokinetics of selegiline and desmethylselegiline suggest saturable tissue binding.

The goal of this study was to examine the multiple-dose pharmacokinetics of selegiline and its metabolites desmethylselegiline, 1-methamphetamine, and 1-amphetamine after oral administration of selegiline HCl. Twelve healthy volunteers received 10 mg of selegiline HCl once daily for 8 days. The pharmacokinetic profiles of selegiline and the metabolites were examined from serum samples for 24 hours (i.e., the dosing interval, tau) on days 1, 4, and 8. The results indicated significant apparent accumulation of selegiline and desmethylselegiline during the 8-day period of selegiline administration. The AUC tau S of selegiline and desmethylselegiline were increased 2.7 fold (p < 0.001) and 1.5 fold (p < 0.001), respectively, from day 1 to day 8. However, the half-lives of selegiline (range, 1.5-3.5 h) and desmethylselegiline (range, 3.4-5.3 h) were found to be relatively short. Accordingly, the short half-lives of these compounds failed to predict the apparent accumulation. With both of the 1-amphetamine metabolites of selegiline, steady state was reached by day 4. We suggest that the most likely explanation for the apparent accumulation of selegiline and desmethylselegiline was the saturation of the MAO-B binding sites in tissues, although decreased first-pass metabolism of selegiline cannot be ruled out. The observed increase in selegiline and desmethylselegiline concentrations on multiple dosing is not likely to significantly increase the pharmacodynamic effect or adverse effects of selegiline compared with what has been found after a single 10-mg dose.

Effect of Nifedipine on the Steady-State Pharmacokinetics and Pharmacodynamics of Irbesartan in Healthy Subjects.

BACKGROUND: In clinical practice, nifedipine has the potential to alter the pharmacokinetics, and therefore possibly the pharmacodynamics and efficacy or safety, of irbesartan. The objectives of the current study were to determine the effects of concomitant administration of nifedipine on the steady-state pharmacokinetics and pharmacodynamics of irbesartan in 12 healthy subjects. METHODS AND RESULTS: This was an open-label, randomized, crossover study. Each subject received irbesartan 300 mg once daily for 4 days in one period and irbesartan 300 mg once daily plus long-acting nifedipine (Procardia XL, Pratt Pharmaceuticals, New York, NY) 30 mg once daily for 4 days in the other period. The order of treatment periods was randomized, and a minimum 7-day washout phase separated the two periods. Steady state was achieved by day 3. On day 4, no significant differences were observed between the two treatments with respect to maximum concentration of irbesartan at the end of the dosing interval (C(max)) or the area under the plasma concentration versus time curve during a dosing interval (AUC(tau)) of irbesartan. Steady-state C(max) and AUC(tau) met the criteria for bioequivalence when irbesartan was administered alone or with nifedipine. On day 4, mean plasma renin activity was somewhat higher at every point but one when irbesartan was administered with nifedipine; however, no significant difference was observed between the two treatments in mean 24-hour AUC values. On day 4, there was a modest overall decrease from baseline in mean blood pressure for both treatments. No significant differences were observed between the two treatments in mean 24-hour AUC values for seated diastolic or systolic blood pressure. No serious adverse events were reported. CONCLUSIONS: Concomitant administration of nifedipine 30 mg with irbesartan 300 mg for 4 days in healthy subjects (1) does not alter the steady-state pharmacokinetic parameters of irbesartan, (2) results in C(max) and AUC(tau) values for irbesartan that meet the criteria for bioequivalence, and (3) is well tolerated.

Effects of age, gender, and diurnal variation on the steady-state pharmacokinetics of BMS-181101, an antidepressant, in healthy subjects.

To investigate the effects of age, gender, and diurnal variation on the safety, tolerability, and steady-state pharmacokinetics of BMS-181101, an antidepressant, in humans. This was a multiple-dose parallel-design study in 51 healthy subjects (12 young and 12 elderly men and 12 young and 15 elderly women). Each subject received a 15 mg oral dose of BMS-181101 every 12 hours on days 1 through 6 and one dose on day 7. After the evening dose on day 6 and morning dose on day 7, serial blood samples were collected at specified times after administration. Plasma was analyzed for BMS-181101 with use of an HPLC method. Male subjects tolerated BMS-181101 better than female subjects. The mean values for area under the plasma concentration-time curve over the dosing interval tau (AUC tau; 58.8 to 102.4 ng.hr/ml) and elimination half-life t1/2; 5.7 to 10.4 hours) for the elderly subjects were significantly greater than those for the young subjects (39.0 to 64.3 ng.hr/ml and 3.2 to 4.5 hours). The mean values for peak plasma concentration (Cmax; 14.7 to 25.2 ng/ml) and AUC tau (52.4 to 102.4 ng.hr/ml) for the women were significantly greater than those for the men (9.08 to 15.3 ng/ml and 39.0 to 73.6 ng.hr/ml). The mean values for Cmax (14.7 to 25.2 ng/ml) and AUC tau (54.8 to 102.4 ng.hr/ml) on the morning of day 7 were significantly greater than those after the evening dose on day 6 (9.08 to 17.3 ng/ml; 39.0 to 83.4 ng.hr/ml). An initial lower dose or appropriate titration of daily doses of BMS-181101 may be necessary for the treatment of elderly and female subjects, and the pharmacokinetics of BMS-181101 exhibited significant diurnal effects.

Pharmacokinetics of ticlopidine during chronic oral administration to healthy volunteers and its effects on antipyrine pharmacokinetics.

1. The pharmacokinetics of ticlopidine, a novel antithrombotic agent, have been investigated in 10 healthy volunteers dosed orally with the drug (250 mg 12 hourly for 21 days), to determine the basic pharmacokinetic parameters in humans, to investigate its accumulation during repeated administration, and to assess its effects on hepatic drug-metabolizing enzymes. 2. After the first dose, peak plasma concentrations (median 0.31, range 0.08-0.80 mg/l) were generally found at 2 h. The levels decreased rapidly to a median concentration of 0.087 mg/l by 4 h then declined to 0.022 (range less than 0.005-0.128) mg/l at 12 h after administration, with apparent half-lives of approx. 4 h. The median AUC value for this first dosage interval (AUC tau) was 0.97 (range 0.41-3.49) mg h l-1. 3. Pre-dose plasma concentrations indicated that steady state was reached after 5-10 days, and then remained essentially unchanged through to the end of the study. From 30 h after the final dose, drug levels declined exponentially with a median half-life of 28.8 (range less than or equal to 20-50) h. 4. Following the final dose, the median peak concentration and AUC tau were 0.99 (range 0.22-2.12) mg/l and 4.06 (range 0.90-15.2) mg h l-1 respectively. Based on AUC values, the mean accumulation factor +/- SD was 3.73 +/- 1.14. 5. The metabolic status of subjects was assessed by administration of single doses of antipyrine (700 mg orally) 7 days before the first dose of ticlopidine and 2 days after the final dose. Treatment with ticlopidine decreased antipyrine clearance, demonstrating that it inhibited drug-metabolizing enzymes. Significant correlations (r2 = 0.84, p less than 0.01) were found between the AUC values for ticlopidine and antipyrine, indicating that the interindividual variation in the pharmacokinetics of ticlopidine are explained by differences in metabolic clearance.

Dose Proportionality of Moricizine After Escalating Multiple Doses in Healthy Volunteers

This study was designed to determine the dose linearity and proportionality of moricizine after multiple-dose administrations of 450 to 900 mg/day. The study design was an open-label, four-treatment, four-period sequentials escalating dose. Twelve subjects each received multiple doses of 150, 200, 250, and 300 mg of moricizine every 8 hours during 7 days of treatment. Blood samples for pharmacokinetic determinations were obtained on day 7 of each treatment period during an 8-hour time interval. Cmin determinations were also made on specific days of each treatment period. The AUC tau (area under the curve from time 0 to 8 hours), Cmax, and Cmin parameters were all normalized to the 250-mg (750 mg/day) dose. No statistically significant differences were seen in these parameters at the four treatment levels. It was concluded that moricizine follows first-order or linear pharmacokinetics after multiple dosing and exhibits dose proportional pharmacokinetics in the dosage-range studies. This range corresponds to the clinically useful dosage range.

Loratadine: multiple-dose pharmacokinetics.

The steady-state pharmacokinetics of loratadine (L), a new long-acting antihistamine devoid of CNS activity, was investigated in 12 healthy male volunteers. Each volunteer received 40-mg L capsules q24h for ten days. Blood samples were collected at various times on day 1, 5, 7, and 10 and assayed for L by radioimmunoassay (RIA) and for descarboethoxyloratadine (DCL), a known active metabolite, by high-performance liquid chromatography (HPLC). The plasma L and DCL concentration-time data in the disposition phases were fitted to a biexponential equation for pharmacokinetic analysis. Steady-state plasma L Cmax concentrations were reached at 1.5 hour (Tmax) after each dose. DCL steady-state Cmax values ranged 26 to 29 ng/mL at a Tmax ranging from 1.8 to 3 hours. The AUC at steady state, AUC tau, was 80 to 96 and 349 to 421 h X ng/mL for L and DCL, respectively. The accumulation indexes (Ra) based on AUC tau ratios, did not change for either compound after day 5. Ra values for L and DCL after the fifth dose were 1.4 and 1.9, respectively, indicating that there is little accumulation of either L or DCL after a multiple (once-a-day) dosage regimen. The t1/2 beta at steady state were 14.4 and 18.7 hours for L and DCL, respectively, which were similar to those reported following a single-dose L administration. Observed plasma drug concentrations were in good agreement with predicted values derived for pharmacokinetic parameters.

Interaction of bisoprolol with cimetidine and rifampicin.

In 6 healthy volunteers the pharmacokinetics of bisoprolol under steady-state conditions was investigated over three consecutive phases: over 7 days of 10 mg of bisoprolol once daily per os, 7 days of 10 mg of bisoprolol once daily plus 400 mg of cimetidine t.i.d. and 14 days of 10 mg of bisoprolol and 600 mg of rifampicin once daily with adequate intervals free of medication. After therapy with bisoprolol alone peak plasma levels (Cssmax) of the beta-blocker were 55.5 +/- 6.4 ng/ml (means +/- SEM), area under the plasma level-time curve (AUC tau) was 597 +/- 70 ng/ml.h, total body clearance (CL) 15.8 +/- 1.8 l/h and elimination half-lives (t1/2 beta) 10.1 +/- 1.2 h. Cimetidine did not cause any significant changes in the pharmacokinetics of bisoprolol. Co-administration of rifampicin resulted in a decrease in Cssmax (43.0 +/- 6.9 ng/ml), AUC tau (397 +/- 54 ng/ml X h) and t1/2 beta (6.2 +/- 0.4 h). Accordingly, total body clearance increased to 23.8 +/- 2.5 l/h (p less than 0.05). In conclusion bisoprolol showed a statistically significant but probably clinically not important interaction with the enzyme-inducing drug rifampicin, but not with the enzyme inhibitor cimetidine.

Michaelis-Menten elimination kinetics: areas under curves, steady-state concentrations, and clearances for compartment models with different types of input.

For single bolus administration, intermittent bolus administrations to steady-state, a single dose as a zero order input, intermittent zero order inputs to steady-state, and continuous zero order input to steady-state, and for both simple Michaelis-Menten elimination and parallel Michaelis-Menten and first order elimination, the appropriate equations are given for the areas, AUC 0-oo or AUC 0-tau, steady-state concentrations, and clearances. Some 20 new equations have been derived. For the case of first order input and Michaelis-Menten elimination, no solution is given but the effect of input rate on systemic availability is reported following some numerical integrations. The effect of slow input in reducing systemic bioavailability when Michaelis-Menten elimination kinetics are operative is stressed and the implications of this in the field of sustained-release medication mentioned.