Human influenza virus challenge identifies cellular correlates of protection for oral vaccination.

Developing new influenza vaccines with improved performance and easier administration routes hinges on defining correlates of protection. Vaccine-elicited cellular correlates of protection for influenza in humans have not yet been demonstrated. A phase-2 double-blind randomized placebo and active (inactivated influenza vaccine) controlled study provides evidence that a human-adenovirus-5-based oral influenza vaccine tablet (VXA-A1.1) can protect from H1N1 virus challenge in humans. Mass cytometry characterization of vaccine-elicited cellular immune responses identified shared and vaccine-type-specific responses across B and T cells. For VXA-A1.1, the abundance of hemagglutinin-specific plasmablasts and plasmablasts positive for integrin α4ß7, phosphorylated STAT5, or lacking expression of CD62L at day 8 were significantly correlated with protection from developing viral shedding following virus challenge at day 90 and contributed to an effective machine learning model of protection. These findings reveal the characteristics of vaccine-elicited cellular correlates of protection for an oral influenza vaccine.

Performance of BioFire array or QuickVue influenza A + B test versus a validation qPCR assay for detection of influenza A during a volunteer A/California/2009/H1N1 challenge study.

BACKGROUND: Influenza places a significant burden on global health and economics. Individual case management and public health efforts to mitigate the spread of influenza are both strongly impacted by our ability to accurately and efficiently detect influenza viruses in clinical samples. Therefore, it is important to understand the performance characteristics of available assays to detect influenza in a variety of settings. We provide the first report of relative performance between two products marketed to streamline detection of influenza virus in the context of a highly controlled volunteer influenza challenge study. METHODS: Nasopharyngeal swab samples were collected during a controlled A/California/2009/H1N1 influenza challenge study and analyzed for detection of virus shedding using a validated qRT-PCR (qPCR) assay, a sample-to-answer qRT-PCR device (BioMerieux BioFire FilmArray RP), and an immunoassay based rapid test kit (Quidel QuickVue Influenza A + B Test). RESULTS: Relative to qPCR, the sensitivity and specificity of the BioFire assay was 72.1% [63.7-79.5%, 95% confidence interval (CI)] and 93.5% (89.3-96.4%, 95% CI) respectively. For the QuickVue rapid test the sensitivity was 8.5% (4.8-13.7%, 95% CI) and specificity was 99.2% (95.6-100%, 95% CI). CONCLUSION: Relative to qPCR, the BioFire assay had superior performance compared to rapid test in the context of a controlled influenza challenge study.

Landscape of coordinated immune responses to H1N1 challenge in humans.

Influenza is a significant cause of morbidity and mortality worldwide. Here we show changes in the abundance and activation states of more than 50 immune cell subsets in 35 individuals over 11 time points during human A/California/2009 (H1N1) virus challenge monitored using mass cytometry along with other clinical assessments. Peak change in monocyte, B cell, and T cell subset frequencies coincided with peak virus shedding, followed by marked activation of T and NK cells. Results led to the identification of CD38 as a critical regulator of plasmacytoid dendritic cell function in response to influenza virus. Machine learning using study-derived clinical parameters and single-cell data effectively classified and predicted susceptibility to infection. The coordinated immune cell dynamics defined in this study provide a framework for identifying novel correlates of protection in the evaluation of future influenza therapeutics.

QT and QTc interval with standard and supratherapeutic doses of darifenacin, a muscarinic M3 selective receptor antagonist for the treatment of overactive bladder.

Prolongation of QT interval on an electrocardiogram is a valuable predictor of a drug's ability to cause potentially fatal ventricular tachyarrhythmia (torsades de pointes). Darifenacin is a muscarinic M3 selective receptor antagonist developed for the treatment of overactive bladder, a debilitating condition that is particularly prevalent in the older population. This 7-day, randomized, parallel-group study (n=188) measured QT/QTc interval in healthy volunteers receiving once-daily darifenacin at steady-state therapeutic (15 mg) and supratherapeutic (75 mg) doses, alongside controls receiving placebo or moxifloxacin (positive control, 400 mg) once daily. There was no significant increase in QTcF interval with darifenacin treatment compared with placebo. Mean changes from baseline at pharmacokinetic Tmax versus placebo were -0.4 and -2.2 milliseconds in the darifenacin 15 mg and 75 mg groups, respectively, compared with +11.6 milliseconds in the moxifloxacin group (P<.01). This study demonstrates that darifenacin does not prolong QT/QTc interval.

Single-dose pharmacokinetics and tolerability of pegylated interferon-alpha2b in young and elderly healthy subjects.

AIMS: To assess the single-dose pharmacokinetics and tolerability of pegylated interferon-alpha2b (PEG-Intron) in young and elderly healthy subjects. METHODS: In this parallel-design study, a single 1 microg x kg(-1) PEG-Intron dose was given subcutaneously to 24 subjects in the age groups 20-45, 65-69, 70-74 and 75-80 years (n = 6/group). Blood sampling and tolerability assessments were performed up to 168 h postdose. RESULTS: The pharmacokinetic parameters were similar in all age groups. The elderly to young subject ratios for Cmax were 91.1, 79.5, and 107% for the 65-69 years, 70-74 years and 75-80 years groups, respectively. The corresponding values for AUC(0- infinity ) and CL/F were 111, 102 and 108%, and 82.5, 95.8 and 86.4%, respectively. Mean differences from the 20 to 45 years group and the 65-69 years, 70-74 years and 75-80 years groups for PEG-Intron Vd/F were 108, 128 and 104%, respectively. None of these differences was statistically significant based on ANOVA. Results from a Dunnett's test (as post hoc assessment) confirmed that the pharmacokinetic parameters of Group II, Group III or Group IV were not different from those of Group I. Almost all (23/24; 96%) subjects reported typical interferon-alpha side-effects (flu-like symptoms, headache). One elderly patient had a myocardial infarction 12 h postdose, but recovered fully. CONCLUSIONS: There are no pharmacokinetic reasons for initial dose adjustment of PEG-Intron based on age.

Ribavirin dosing in chronic hepatitis C: application of population pharmacokinetic-pharmacodynamic models.

BACKGROUND: Combination therapy of ribavirin with interferon alfa-2b and pegylated interferon alfa-2b is currently approved for the treatment of chronic hepatitis C. Approved ribavirin dosages vary from a fixed dosage of 800 mg/d to as much as 1200 mg/d on the basis of body weight. OBJECTIVE: Our objective was to evaluate ribavirin dosing strategies by comparison of their relative efficacy and toxicity profiles. METHODS: Three models were developed on the basis of data collected from a large phase III trial. A population pharmacokinetic model was used to describe the ribavirin dose-concentration relationship and the influence of covariates. Logistic regression models were developed for both sustained virologic response and hematologic toxicity. Ribavirin concentration was an important explanatory variable for both response and toxicity. Simulations of these models were developed for different ribavirin doses to obtain efficacy and toxicity profiles across the various dosing strategies. These strategies included a fixed 800-mg/d dose, empiric weight-adjusted doses (ie, 1000 mg/d for patients who weighed < or =75 kg and 1200 mg/d for patients who weighed >75 kg [1000/1200 mg/d on the basis of body weights < or =75/>75 kg] and 800 mg/d for patients who weighed <65 kg, 1000 mg/d for patients who weighed from 65 to 85 kg, and 1200 mg/d for patients who weighed >85 kg [800/1000/1200 mg/d on the basis of body weights <65/65-85/>85 kg]), a dose of 13 mg/kg per day, and other per-body weight doses between 9 and 16 mg/kg per day. RESULTS: Simulation results showed that both efficacy and toxicity increased as the milligrams-per-kilogram dose of ribavirin increased. The body weight-based 800/1000/1200-mg/d dose had overall response and toxicity rates that were 6.3% and 2.5% higher than those of the fixed 800-mg/d dose. In particular, patients with genotype-1 disease had a 7.4% increase in response rate. There were no differences in response and toxicity rates between the 800/1000/1200-mg/d and 13-mg/kg per day dose groups. CONCLUSIONS: This simulation suggests that ribavirin dosage (in combination with pegylated interferon alfa-2b) for patients with chronic hepatitis C should be based on body weight.

Single-dose pharmacokinetics and safety of pegylated interferon-alpha2b in patients with chronic renal dysfunction.

This study evaluates the pharmacokinetics and safety of pegylated interferon-alpha2b (PEG-Intron) following a single-dose subcutaneous injection into subjects with normal renal function, subjects with chronic renal impairment, and patients on hemodialysis. In this open-label, single-dose, parallel group study, subjects were divided into five groups according to their degree of renal function: four groups as defined by measured creatinine clearance and a fifth hemodialysis dependent group. They received 1 microg/kg PEG-Intron subcutaneously after a 10-hour fast. Pharmacokinetic and safety assessments were performed up to 168 hours postdose. Hemodialysis patients had a second PEG-Intron dose 12 hours prior to a hemodialysis session. PEG-Intron pharmacokinetic parameters (AUCtf, Cmax, and t1/2) increased progressively as CL(CR) declined. All subjects reported at least one adverse event, which were typical of those reported after alpha-interferon administration (e.g., flu-like symptoms, headache). Single-dose PEG-Intron administration to volunteers with normal renal function and chronic renal impairment was safe and well tolerated. In patients with CL(CR) < 30 ml/min, AUCand Cmax values were increased 90% compared with controls, while half-life was increased by up to 40% over controls. Based on the relationship between PEG-Intron apparent clearance and CL(CR), renal clearance accountsfor less than half of its total clearance. Hemodialysis did not affect PEG-Intron apparent clearance.

Pharmacodynamic interaction between the new selective cholesterol absorption inhibitor ezetimibe and simvastatin.

AIMS: The primary aims of these two single-centre, randomized, evaluator-blind, placebo/positive-controlled, parallel-group studies were to evaluate the potential for pharmacodynamic and pharmacokinetic interaction between ezetimibe 0.25, 1, or 10 mg and simvastatin 10 mg (Study 1), and a pharmacodynamic interaction between ezetimibe 10 mg and simvastatin 20 mg (Study 2). Evaluation of the tolerance of the coadministration of ezetimibe and simvastatin was a secondary objective. METHODS: Eighty-two healthy men with low-density lipoprotein cholesterol (LDL-C) >or=130 mg dl-1 received study drug once daily in the morning for 14 days. In Study 1 (n=58), five groups of 11-12 subjects received simvastatin 10 mg alone, or with ezetimibe 0.25, 1, or 10 mg or placebo. In Study 2 (n=24), three groups of eight subjects received simvastatin 20 mg alone, ezetimibe 10 mg alone, or the combination. Blood samples were collected to measure serum lipids in both studies. Steady-state pharmacokinetics of simvastatin and its beta-hydroxy metabolite were evaluated in Study 1 only. RESULTS: In both studies, reported side-effects were generally mild, nonspecific, and similar among treatment groups. In Study 1, there were no indications of pharmacokinetic interactions between simvastatin and ezetimibe. All active treatments caused statistically significant (P<0.01) decreases in LDL-C concentration vs placebo from baseline to day 14. The coadministration of ezetimibe and simvastatin caused a dose-dependent reduction in LDL-C and total cholesterol, with no apparent effect on high-density lipoprotein cholesterol (HDL-C) or triglycerides. The coadministration of ezetimibe 10 mg and simvastatin 10 mg or 20 mg caused a statistically (P<0.01) greater percentage reduction (mean -17%, 95% CI -27.7, -6.2, and -18%, -28.4, -7.4, respectively) in LDL-C than simvastatin alone. CONCLUSIONS: The coadministration of ezetimibe at doses up to 10 mg with simvastatin 10 or 20 mg daily was well tolerated and caused a significant additive reduction in LDL-C compared with simvastatin alone. Additional clinical studies to assess the efficacy and safety of coadministration of ezetimibe and simvastatin are warranted.

Desloratadine demonstrates dose proportionality in healthy adults after single doses.

OBJECTIVE: To evaluate the dose proportionality and linearity and pharmacokinetic profile of desloratadine after single oral doses over the range of 5 to 20mg. DESIGN: Single centre, randomised, open-label, 4-way crossover study in which healthy adults received single doses of desloratadine (5, 7.5, 10 and 20mg) in 4 different treatment periods. Desloratadine was administered each morning after a 10-hour fast. A washout period of at least 14 days separated each dose. Plasma concentrations were measured prior to each treatment and over the 168 hours after drug administration to determine the area under the plasma concentration-time curve (AUC) and maximum observed plasma concentration (C(max)). PARTICIPANTS: 20 healthy male volunteers (3 White, 17 Black) ranging in age from 19 to 45 (mean 37) years and weighing 54 to 91 (mean 75) kg were enrolled and completed this study. MAIN OUTCOME MEASURES: The primary parameter to assess dose proportionality and linearity was AUC from time zero to final concentration time point (AUC(S)). RESULTS: The C(max) for all doses was observed approximately 4 hours after administration, revealing no dose-related differences in absorption rate. The half-life (t((1/2))) ranged from 21.2 to 24.1 hours. C(max) and AUC(S) increased in a dose-proportional manner over a dose range of 5 to 20mg. Although the recommended clinical dose is 5mg, doses up to 20mg were well tolerated. CONCLUSION: In this study, single doses of desloratadine as high as 4 times the recommended clinical dose of 5mg were well tolerated. The C(max) and AUC(S) for doses of 5 to 20mg increased in a dose-proportional manner.

Oral bioavailability of desloratadine is unaffected by food.

OBJECTIVE: To determine the effect of coadministration of food on the bioavailability of oral desloratadine. DESIGN: A randomised, open-label, single dose crossover study in which healthy adults received a single, oral dose of desloratadine 7.5mg, 50% greater than the recommended dose of 5mg, under fed or fasted conditions and were then crossed over to receive the other treatment regimen. PARTICIPANTS: 18 healthy volunteers (11 men, 7 women) aged from 18 to 43 (mean 29) years and weighing 54 to 104 (mean 76.4) kg were enrolled and completed this study. MAIN OUTCOME MEASURES: C(max), AUC(S) and AUC(infinity ). RESULTS: Maximum mean plasma concentration (C(max)) was 3.53 microg/L in fed compared with 3.30 microg/L in fasted participants. Area under the plasma concentration-time curve from time 0 to time of final quantifiable sample (AUC(S)) mean values were 61.0 microg/L x h in fed and 61.9 microg/L x h in fasted participants. Fed individuals had mean AUC extrapolated to infinity (AUC(infinity )) of 62.5 microg/L x h compared with 63.5 microg/L x h in fasted participants. None of these differences between the fed and fasted state was statistically significant. The most frequently reported adverse event was headache. There were no statistically significant changes in ECG parameters. CONCLUSION: The results of this study indicate that food has no effect on the oral bioavailability of a single oral dose of desloratadine 7.5mg.

A pharmacokinetic profile of desloratadine in healthy adults, including elderly.

OBJECTIVE: To characterise the pharmacokinetic profile of desloratadine and its main metabolite, 3-hydroxy (3-OH) desloratadine, in a patient population representative of the population studied in the desloratadine clinical efficacy and safety studies, including the elderly. DESIGN: A multicentre, multidose, open-label pharmacokinetic trial. PARTICIPANTS: 113 healthy adult volunteers (57 men, 56 women; 95 White, 18 Black) were enrolled, and 112 completed the study. INTERVENTIONS: A 5mg oral dose of desloratadine once daily for 10 days. MAIN OUTCOME MEASURES: C(max), t(max), t((1/2)) and AUC(24h). RESULTS: Steady-state plasma concentrations were attained by day 7. Peak plasma concentrations (C(max)) of desloratadine (mean 3.98 micro g/L) and 3-OH desloratadine (mean 1.99 micro g/L) were reached at a mean of 3.17 and 4.76 hours (t(max)), respectively, after administration. The area under the plasma concentration-time curve from 0 to 24 hours (AUC(24h)) was 56.9 micro g/L x h for desloratadine and 32.3 micro g/L x h for 3-OH desloratadine. The mean half-lives (t((1/2))) of desloratadine and 3-OH desloratadine were 26.8 and 36 hours, respectively. There were no clinically relevant differences in the calculated pharmacokinetic parameters of desloratadine when participants were stratified into 3 age groups (19 to 45, 46 to 64 and 65 to 70 years). Treatment-emergent adverse events occurred in 31 of the 113 participants (3 of the 17 aged >or=65 years reported adverse events). All adverse events were mild to moderate in severity, and none resulted in discontinuation of treatment. There were no consistent clinically relevant changes in blood pressure, pulse, oral body temperature or electrocardiogram evaluations and no reports of syncope or sedation. CONCLUSION: Daily administration of desloratadine 5mg is well tolerated. The 27-hour half-life of desloratadine permits once daily administration. No dosage adjustment of desloratadine is required in the elderly.

Lack of clinically relevant interaction between desloratadine and erythromycin.

OBJECTIVE: To evaluate the bioavailability, cardiac safety and tolerability of desloratadine when given in combination with the CYP3A4 inhibitor erythromycin. DESIGN: A randomised, 2-way crossover, placebo-controlled, third party-blind, multiple dose study. PARTICIPANTS: 24 healthy volunteers (12 men, 12 women) aged 19 to 46 years. INTERVENTIONS: Oral desloratadine 7.5mg daily in combination with either placebo (n = 24) or erythromycin 500mg every 8 hours (n = 24) for 10 days. After a minimum 7-day washout period, participants crossed over to the alternative regimen. MAIN OUTCOME MEASURES: ECG parameters. RESULTS: Desloratadine/erythromycin did not induce clinically or statistically significant changes in any ECG parameter. The maximum corrected QT (QT(c)) interval was 445 msec for both treatments. The peak plasma concentration and area under the plasma concentration-time curve from 0 to 24 hours of desloratadine were slightly increased by 1.2- and 1.1-fold by concomitant administration of erythromycin compared with desloratadine/placebo. Gastrointestinal adverse events were more frequent after desloratadine/erythromycin than desloratadine/placebo (46 vs 4%), reflecting the poor gastrointestinal tolerability of erythromycin. There were no reports of syncope. CONCLUSION: Combined desloratadine/erythromycin therapy was well tolerated and had no clinically relevant electrocardiographic effects at a dose that was 50% higher than the recommended dose of 5mg. Although coadministration of erythromycin slightly increased plasma concentrations of desloratadine, this change did not correlate with any prolongation of the QT(c) interval, and no toxicity was observed clinically.

Effect of race and sex on single and multiple dose pharmacokinetics of desloratadine.

OBJECTIVE: This study was designed to characterise the single and multiple dose pharmacokinetic profile of desloratadine, a new antihistamine, and its main metabolite, 3-hydroxy (3-OH) desloratadine, in healthy volunteers differing in sex and race. DESIGN: An open-label, parallel-group, single- and multiple-dose pharmacokinetic trial. INTERVENTION: A single 7.5mg oral tablet of desloratadine on day 1, followed by 7.5mg daily doses on days 4 to 17. PARTICIPANTS: 48 healthy, nonsmoking volunteers (12 White men, 12 Black men, 12 White women, 12 Black women). MAIN OUTCOME MEASURES: AUC(24h) and C(max) determined from serial blood samples of desloratadine and 3-OH desloratadine. RESULTS: There were no clinically relevant differences between men and women or Black participants and White participants for desloratadine and 3-OH desloratadine maximum plasma concentrations (C(max)) and area under the plasma concentration-time curve (AUC). Following multiple doses, the geometric mean C(max) was 5.17 microg/L in men, 5.68 microg/L in women, 5.87 microg/L in Black participants and 5.00 microg/L in White participants; the corresponding AUC from 0 to 24 hours (AUC(24h)) values were 77.9, 80.0, 90.6 and 68.8 micro g/L x h. Corresponding 3-OH desloratadine geometric mean C(max) values were 1.93, 2.79, 2.20 and 2.45 microg/L, and the AUC(24h) values were 32.1, 47.5, 37.1 and 41.1 microg/L. h. CONCLUSIONS: Oral administration of multiple doses of desloratadine 7.5mg, a dose 50% higher than the recommended 5mg clinical dose, was well tolerated by healthy adults differing in sex and race. Comparison of the C(max) and AUC values following 14 days of treatment with desloratadine indicates that no dosage adjustment is needed on the basis of sex or race.

Desloratadine has no clinically relevant electrocardiographic or pharmacodynamic interactions with ketoconazole.

OBJECTIVE: This study was performed to assess the electrocardiographic safety and pharmacokinetics of desloratadine in combination with the CYP3A4 inhibitor ketoconazole. DESIGN: A randomised, placebo-controlled, third-party-blind, 2-way crossover study. PARTICIPANTS: 24 healthy volunteers (12 men, 12 women; age 19 to 50 years). INTERVENTIONS: 7.5mg of desloratadine orally per day in combination with placebo or with 200mg of ketoconazole every 12 hours for 10 days. After a minimum 7-day washout period, participants received the alternative treatment. MAIN OUTCOME MEASURES: ECG parameters. RESULTS: Comparable maximum corrected QT (QT(c)) intervals were observed after coadministration of desloratadine and placebo or ketoconazole (431 and 435 msec, respectively). The desloratadine/ketoconazole combination did not induce any statistically significant or clinically relevant changes in QT(c), QT, PR or QRS intervals compared with desloratadine alone; ventricular rate was slightly slower when desloratadine was given with ketoconazole. At steady state, coadministration of ketoconazole resulted in no significant change in area under the desloratadine concentration-time curve (AUC) from 0 to 24 hours compared with desloratadine/placebo. Coadministration of desloratadine and ketoconazole resulted in a 1.3-fold increase in desloratadine maximum concentration (C(max)) that was not clinically relevant. The most common adverse event was headache, reported in 42 and 38% of individuals, respectively, after coadministration of desloratadine/placebo and desloratadine/ketoconazole. There were no reports of dizziness or syncope. CONCLUSION: Coadministration of desloratadine and ketoconazole was well tolerated and was associated with minimal increase in AUC and C(max). The combination did not induce any clinically relevant electrocardiographic changes.

Grapefruit juice reduces the oral bioavailability of fexofenadine but not desloratadine.

BACKGROUND: Certain foods, such as grapefruit juice, are known to substantially alter the bioavailability of some drugs. These effects may be mediated by interactions with enzyme systems, such as cytochrome P450, or with active transporter systems, such as P-glycoprotein and organic anion transporting polypeptides. OBJECTIVE: To assess the effect of consumption of grapefruit juice on the oral bioavailability of two nonsedating antihistamines, fexofenadine and desloratadine. DESIGN: Non-blinded, randomised, single-dose, four-way crossover study. PARTICIPANTS: Twenty-four healthy adult volunteers. INTERVENTIONS: Single oral doses of desloratadine 5mg and fexofenadine 60mg taken without and with grapefruit juice (pretreatment with 240ml of double-strength juice three times daily for 2 days prior to administration of study drug, plus the same amount simultaneously with, and 2 hours after, the drug dose). Each treatment was separated by at least 10 days. MAIN OUTCOME MEASURES: Log-transformed pharmacokinetic parameters [peak plasma concentration (C(max)) and area under the curve (AUC)], time to maximum concentration, elimination half-life and electrocardiographic (ECG) parameters. RESULTS: Comparing the ratio of the pharmacokinetic parameter means (C(max) and AUC) with and without grapefruit juice (expressed as a percentage), the rate (C(max)) and extent (AUC) of absorption of fexofenadine were reduced by 30% by consumption of grapefruit juice. In contrast, the bioavailability of desloratadine was unaffected by grapefruit juice. No clinically significant changes in ECG parameters were observed following coadministration of grapefruit juice with desloratadine or fexofenadine compared with either antihistamine given alone. CONCLUSION: The bioavailability of drugs that do not undergo significant intestinal or hepatic metabolism, such as fexofenadine, may be altered when administered with agents that influence drug transport mechanisms.

Disposition of the selective cholesterol absorption inhibitor ezetimibe in healthy male subjects.

Ezetimibe [SCH 58235; 1-(4-fluorophenyl)-3(R)-[3-(4-fluorophenyl)-3(S)-hydroxypropyl]-4(S)-(4-hydroxyphenyl)-2-azetidinone], a selective cholesterol absorption inhibitor, is being developed for the treatment of primary hypercholesterolemia. The absorption, metabolism, and excretion of ezetimibe were characterized in eight healthy male volunteers in this single-center, single-dose, open-label study. Subjects received a single oral 20-mg dose of [14C]ezetimibe (approximately 100 microCi) with 200 ml of noncarbonated water after a 10-h fast. Concentrations of radioactivity and/or ezetimibe (conjugated and unconjugated) were determined in plasma, urine, and fecal samples. Ezetimibe was rapidly absorbed and extensively conjugated following oral administration. The main circulating metabolite in plasma was SCH 60663 [1-O-[4-[trans-(2S,3R)-1-(4-fluorophenyl)-4-oxo-3-[3(S)-hydroxy-3-(4-fluorophenyl)propyl]-2-azetidinyl]phenyl]-beta-D-glucuronic acid], the glucuronide conjugate of ezetimibe. Plasma concentration-time profiles of unconjugated and conjugated drug exhibited multiple peaks, indicating enterohepatic recycling. Approximately 78 and 11% of the administered [14C]ezetimibe dose were excreted in feces and urine, respectively, by 240 h after drug administration. Total recovery of radioactivity averaged 89% of the administered dose. The main excreted metabolite was the glucuronide conjugate of ezetimibe. The primary metabolite in urine (0- to72-h composite) was also the glucuronide conjugate (about 9% of the administered dose). Significant amounts (69% of the dose) of ezetimibe were present in the feces, presumably as a result of SCH 60663 hydrolysis and/or unabsorbed drug. No adverse events were reported in this study. A single 20-mg capsule of [(14)C]ezetimibe was safe and well tolerated after oral administration. The pharmacokinetics of ezetimibe are consistent with extensive glucuronidation and enterohepatic recirculation. The primary metabolic pathway for ezetimibe is by glucuronidation of the 4-hydroxyphenyl group.

Pharmacokinetics of Loratadine in Pediatric Subjects.

The pharmacokinetics of loratadine, a new nonsedating antihistamine, was studied in 14 pediatric volunteers between the ages of 8 to 12 years. In an open-label design, one volunteer (with body weight less than 30 kg) received 5 mg of loratadine syrup and 13 volunteers (with body weights greater than 30 kg) received 10 mg of loratadine syrup. Blood samples were collected up to 72 h after dosing. Plasma concentrations of loratadine and its metabolite, descarboethoxyloratadine, were determined by a specific and sensitive gas-liquid chromatographic method. Following a 10-mg dose as a syrup, plasma concentrations of loratadine and descarboethoxyloratadine could be determined up to 8 and 48 h, respectively. The maximum concentration (C(max)) of loratadine and descarboethoxyloratadine were approximately 4 ng ml(minus sign1) each. However, the AUC of the metabolite was about six times that of loratadine. The elimination phase half-life of descarboethoxyloratadine averaged about 13.8 hr. The pharmacokinetics of loratadine in pediatric subjects was similar to that in healthy adult volunteers.

Multiple-Dose Pharmacokinetics of Ceftibuten in Healthy Adults and Geriatric Volunteers.

The steady-state pharmacokinetics of ceftibuten, an orally active cephalosporin were investigated in 12 healthy male volunteers (19--38 years) and in 12 geriatric volunteers (65--76 years). Each received one 200-mg ceftibuten capsule every 12 h on days 1--3 and one capsule in the morning on day 4. Plasma and urine samples were collected at various times on days 1--4 and assayed by high-pressure liquid chromatographic method for ceftibuten and ceftibuten-trans, a conversion product. The T(max) for ceftibuten and ceftibuten-trans occurred at about 2 and 3 h, respectively, in both populations. The C(max) and AUC((0--12 h)) ranged from 10.8 to 12.4 &mgr;g ml(minus sign1) and from 47.5 to 55.1 &mgr;g h ml(minus sign1), respectively, for normal volunteers compared to 12.9--17.5 &mgr;g ml(minus sign1) and 62.3--87.1 &mgr;g h ml(minus sign1), respectively, for geriatric volunteers. The respective values for ceftibuten-trans in normal and geriatric volunteers were 1.3 and 1.3 &mgr;g ml(minus sign1), respectively, and 6.9--8.2 and 5.9--9.8 &mgr;g h ml(minus sign1). At steady state, the C(max) and AUC((0--12 h)) of ceftibuten-trans were about 10--11% and 13--16% those of ceftibuten in normal volunteers and about 8--9% and 9--11% those of ceftibuten, respectively, in geriatric volunteers. The accumulation factor of ceftibuten in normal volunteers was 1.1 as compared to 1.3 in geriatric volunteers. The terminal phase half-life was 2.5 h in healthy volunteers and 3.2 h in geriatric volunteers. Urinary excretion appeared to be the major route of elimination in both populations accounting for more than 90% of the dose recovered in the urine during the dosing interval. The results of this study demonstrate that ceftibuten, 200 mg given twice a day, is safe and well tolerated, is well absorbed, and that steady-state is achieved on days 3 and 4. There is some accumulation in the elderly, but dosage regimen based on age is not warranted.