Impact of Rifabutin or Rifampin on Bedaquiline Safety, Tolerability, and Pharmacokinetics Assessed in a Randomized Clinical Trial with Healthy Adult Volunteers.

Bedaquiline is a diarylquinoline that specifically inhibits mycobacterial ATP synthase. Bedaquiline has been used to effectively treat tuberculosis (TB) caused by drug-susceptible and drug-resistant Mycobacterium tuberculosis Rifamycins are a cornerstone of combination drug regimens for the treatment of TB. This phase 1, open-label, randomized, controlled trial evaluated the effect of steady-state dosing of rifabutin or rifampin on the safety, tolerability, and pharmacokinetics of bedaquiline given as a single dose. Thirty-three healthy subjects were enrolled to receive a 400-mg single oral dose of bedaquiline at two time points, on study days 1 and 29. Subjects were randomly assigned to once daily oral doses of rifabutin (300 mg/day, n = 17) or rifampin (600 mg/day, n = 16) during period 2 from days 20 to 41. Serial blood sampling for bedaquiline measurement occurred on days 1 and 29 through 336 h after bedaquiline administration. The day 29 bedaquiline pharmacokinetic parameter estimates were compared to the corresponding day 1 estimates for each rifamycin group. Steady-state rifampin reduced bedaquiline AUC0-336 approximately 45%, from 47.69 h·µg/ml in period 1 to 26.33 h·µg/ml in period 2. Bedaquiline apparent clearance accelerated 24% in rifampin-treated subjects from 6.59 liters/h in period 1 to 8.19 liters/h in period 2. Steady-state rifabutin resulted in little quantitative impact on bedaquiline exposure but was associated with grade 3 and 4 adverse events before and after the day 29 bedaquiline dose. Dosage adjustments may therefore be necessary to ensure that bedaquiline plasma concentrations reach therapeutic levels safely when combining bedaquiline and rifamycins in TB treatment regimens. (This single-site, randomized, open-label, prospective study in healthy adult volunteers was registered at Clinicaltrials.gov under registration no. NCT01341184.).

A Phase 1 Pharmacokinetic and Safety Study of Extended-Duration, High-dose Cefixime for Cephalosporin-resistant Neisseria gonorrhoeae in the Pharynx.

BACKGROUND: There are no fully oral recommended treatment regimens for gonorrhea. Inadequately treated pharyngeal gonococcal infections are a likely reservoir for transmission and development of antimicrobial resistance. We sought to determine an oral cefixime dosing regimen that would theoretically treat pharyngeal infections by gonococci with minimum inhibitory concentrations 0.5 µg/mL. METHODS: We conducted an open-label, nonrandomized, phase I pharmacokinetic and safety study of cefixime in 25 healthy male and female volunteers divided into 4 dosing cohorts (cohort A, 400 mg; cohort B, 800 mg; cohort C, 1200 mg; and cohort D, 800 mg every 8 hours × 3 doses [total dose 2400 mg]) with a target serum concentration of at least 2.0 µg/mL for more than 20 hours. Cefixime concentrations from serum and pharyngeal fluid were determined with use of a validated liquid chromatography-tandem mass spectrometry assay. Safety measures included laboratories, physical examinations, and symptom diaries. RESULTS: None of the single-dose regimens attained the target concentration; however, 50% of subjects in cohort D attained the target concentration. Variation in absorption and protein binding contributed to differences in concentrations. Pharyngeal fluid concentrations were negligible. The single-dose regimens were well tolerated; the multidose regimen resulted in mild to moderate gastrointestinal symptoms in 43% of subjects. CONCLUSIONS: None of the dosing regimens achieved the target concentration. However, the proposed theoretical target was extrapolated from penicillin data; there are no empirically derived pharmacokinetic/pharmacodynamic criteria for pharyngeal gonorrhea. Under alternative cephalosporin-specific therapeutic goals, the multidose regimen may be effective, although the absence of cefixime in pharyngeal fluid is concerning. A clinical trial evaluating efficacy and defining pharmacokinetic/pharmacodynamic outcomes may be warranted.

Safety, Tolerability, Systemic Exposure, and Metabolism of CRS3123, a Methionyl-tRNA Synthetase Inhibitor Developed for Treatment of Clostridium difficile, in a Phase 1 Study.

Clostridium difficile causes antibiotic-associated diarrhea and is a major public health concern. Current therapies disrupt the protective intestinal flora, do not reliably prevent recurrent infections, and will be decreasingly effective should less susceptible strains emerge. CRS3123 is an oral agent that inhibits bacterial methionyl-tRNA synthetase and has potent activity against C. difficile and aerobic Gram-positive bacteria but little activity against Gram-negative bacteria, including anaerobes. This first-in-human, double-blind, placebo-controlled, dose escalation study evaluated the safety and systemic exposure of CRS3123 after a single oral dose in healthy adults. Five cohorts of eight subjects each received CRS3123 or placebo in a 3:1 ratio. Doses for the respective active arms were 100 mg, 200 mg, 400 mg, 800 mg, and 1,200 mg. Blood and urine were collected for pharmacokinetic analysis. CRS3123 concentrations were measured with validated LC-MS/MS techniques. There were no serious adverse events or immediate allergic reactions during administration of CRS3123. In the CRS3123-treated groups, the most frequent adverse events were decreased hemoglobin, headache, and abnormal urine analysis; all adverse events in the active-treatment groups were mild to moderate, and their frequency did not increase with dose. Although CRS3123 systemic exposure increased at higher doses, the increase was less than dose proportional. The absorbed drug was glucuronidated at reactive amino groups on the molecule, which precluded accurate pharmacokinetic analysis of the parent drug. Overall, CRS3123 was well tolerated over this wide range of doses. This safety profile supports further investigation of CRS3123 as a treatment for C. difficile infections. (This study has been registered at ClinicalTrials.gov under identifier NCT01551004.).

Determination of appropriate weight-based cutoffs for empiric cefazolin dosing using data from a phase 1 pharmacokinetics and safety study of cefazolin administered for surgical prophylaxis in pediatric patients aged 10 to 12 years.

Despite over 40 years of worldwide usage, relatively few data have been published on the pharmacokinetics of cefazolin in pediatric surgical patients. The primary objectives of this study were to examine the pharmacokinetics and safety of cefazolin in children 10 to 12 years of age (inclusive) receiving 1 or 2 g of cefazolin, based on body weight. This multiple-center, open-label study enrolled pediatric patients electively scheduled for surgical procedures who required cefazolin as part of their routine clinical management. Patients weighing ≥25 to <50 kg received a 1-g dose, and patients weighing ≥50 to ≤85 kg received a 2-g dose. Postdose pharmacokinetic and safety assessments were conducted following drug administration. Cefazolin concentration-time data were analyzed by using both noncompartmental and population pharmacokinetics methods. Monte Carlo simulations were performed to identify appropriate weight-based cutoffs for the dosing of children aged 10 to 17 years of age. Twelve patients were enrolled in this study and provided the requisite pharmacokinetic data. In general, cefazolin was well tolerated. The mean cefazolin terminal elimination half-life, clearance, and area under the concentration-time curve from time zero to infinity in this population were 1.95 h, 0.804 ml/min/kg, and 607 mg · h/liter, respectively. Patients weighing 50 to 60 kg exhibited elevated cefazolin exposures. Observed pharmacokinetic parameters and simulation results indicated that a weight-based cutoff of 60 kg is predicted to provide cefazolin exposure consistent with that observed in normal, healthy adults at recommended doses for surgical prophylaxis. (This study has been registered at ClinicalTrials.gov under registration no. NCT01904357.).

A population pharmacokinetic modeling approach shows that serum penicillin G concentrations are below inhibitory concentrations by two weeks after benzathine penicillin G injection in the majority of young adults.

Serum penicillin G falls to low levels 2 weeks after injection as benzathine penicillin G (BPG) in young adults. Using Pmetrics and previously reported penicillin G pharmacokinetic data after 1.2 million units were given as BPG to 329 male military recruits, here we develop the first reported population pharmacokinetic model of penicillin G after BPG injection. We simulated time-concentration profiles over a broad range of pediatric and adult weights after alternative doses and dose frequencies to predict the probability of maintaining serum penicillin G concentrations of >0.02 mg/liter, a proposed protective threshold against group A Streptococcus pyogenes (GAS). The final population model included linear absorption into a central compartment, distribution to and from a peripheral compartment, and linear elimination from the central compartment, with allometrically scaled volumes and rate constants. With 1.2 million units of BPG given intramuscularly every 4 weeks in four total doses, only 23.2% of 5,000 simulated patients maintained serum penicillin G trough concentrations of >0.02 mg/liter 4 weeks after the last dose. When the doses were 1.8 million units and 2.4 million units, the percentages were 30.2% and 40.7%, respectively. With repeated dosing of 1.2 million units every 3 weeks and every 2 weeks for 4 doses, the percentages of simulated patients with a penicillin G trough concentration of >0.02 mg/liter were 37.8% and 65.2%, respectively. Our simulations support recommendations for more frequent rather than higher BPG doses to prevent recurrent rheumatic heart disease in areas of high GAS prevalence or during outbreaks.

Safety and effectiveness of meropenem in infants with suspected or complicated intra-abdominal infections.

BACKGROUND: Intra-abdominal infections are common in young infants and lead to significant morbidity and mortality. Meropenem is a broad-spectrum antimicrobial with excellent activity against pathogens associated with intra-abdominal infections. The purpose of this study was to determine the safety and effectiveness of meropenem in young infants with suspected or complicated intra-abdominal infections. METHODS: Preterm and term infants <91 days of age with suspected or confirmed intra-abdominal infections hospitalized in 24 neonatal intensive care units were studied in an open-label, multiple-dose study. Adverse events and serious adverse events were collected through 3 and 30 days following the last meropenem dose, respectively. Effectiveness was assessed by 3 criteria: death, bacterial cultures, and presumptive clinical cure score. RESULTS: Of 200 subjects enrolled in the study, 99 (50%) experienced an adverse event, and 34 (17%) had serious adverse events; no adverse events were probably or definitely related to meropenem. The most commonly reported adverse events were sepsis (6%), seizures (5%), elevated conjugated bilirubin (5%), and hypokalemia (5%). Only 2 of the serious adverse events were determined to be possibly related to meropenem (isolated ileal perforation and an episode of fungal sepsis). Effectiveness was evaluable in 192 (96%) subjects, and overall treatment success was 84%. CONCLUSIONS: Meropenem was well tolerated in this cohort of critically ill infants, and the majority of infants treated with meropenem met the definition of therapeutic success. CLINICAL TRIALS REGISTRATION: NCT00621192.

Effect of placebo on ambulatory blood pressure monitoring in children.

BACKGROUND: Ambulatory blood pressure monitoring (ABPM) has been proposed as a useful tool for more accurately diagnosing hypertension (HTN) and evaluating blood pressure (BP) response in pediatric anti-hypertensive trials. ABPM captures multiple BP measurements during routine daily activities and is thus an excellent method for identifying white-coat HTN. Additionally, ABPM measurements in adults do not demonstrate the placebo effect commonly seen with casual BP measurements, although this has yet to be evaluated in children. Therefore,, the aim of this study was to assess the effect of placebo on ABPM measurements in children. METHODS: A total of 141 children aged 5-16 years with elevated BP were randomized into a multi-center, single-blind, cross-over trial. Subjects received a placebo pill prior to wearing a 24-h ABPM device at one of two visits separated by 1-2 weeks. Study procedures were otherwise identical at both visits. RESULTS: Mean systolic and diastolic BP for all measured time periods were similar between visits, as was the number of children diagnosed with HTN at each visit. CONCLUSION: Having confirmed HTN at baseline did not affect the impact of placebo on mean BP. If confirmed, this lack of placebo effect on ABPM measurements may allow for the design of direct comparison pediatric anti-hypertensive trials without a placebo arm.

Dosing Colistimethate Every 8 h Results in Higher Plasma Concentrations of Active Colistin Than Every 12-Hourly Dosing without Increase in Nephrotoxicity: A Phase 1 Pharmacokinetics Trial in Healthy Adult Volunteers.

Despite its use for decades, pharmacokinetic (PK) and safety studies on colistin are limited. We conducted a phase l, open-label trial to evaluate the safety and PK of multiple doses of intravenous (IV) and aerosolized colistimethate sodium (CMS) administered separately and in combination. In total, 31 healthy adults were enrolled into three cohorts of 9, 10, and 12 participants, respectively. Each cohort received increasing doses of CMS over three dosing periods as follows: Period 1 (IV only), 2.5 mg/kg every 12 h (q12h) to 3.3 mg/kg every 8 h (q8h); Period 2 (aerosolized only), 75 mg 2-4 doses, and Period 3 (combined IV aerosolized), in which was Periods 1 and 2 combined. Safety assessments, serum and lung concentrations of colistin analytes (colistin A, colistin B, CMS A, and CMS B), and kidney biomarkers were measured at specified time points. Increasing the CMS dose from 2.5 mg/kg q12h to q8h resulted in a 33% increase in serum colistin A concentrations from 3.9 µg/mL to 5.3 µg/mL-well above the accepted target of 2 µg/mL for 6 h after dosing, without evidence of nephrotoxicity. However, there was an increase in neurotoxicity, primarily perioral and lingual paresthesias, and self-limited ataxia. IV administration did not increase the lung concentrations of colistin.

Comparison of pharmacokinetics and safety of voriconazole intravenous-to-oral switch in immunocompromised adolescents and healthy adults.

The current voriconazole dosing recommendation in adolescents is based on limited efficacy and pharmacokinetic data. To confirm the appropriateness of dosing adolescents like adults, a pharmacokinetic study was conducted in 26 immunocompromised adolescents aged 12 to <17 years following intravenous (IV) voriconazole to oral switch regimens: 6 mg/kg IV every 12 h (q12h) on day 1 followed by 4 mg/kg IV q12h, then switched to 300 mg orally q12h. Area under the curve over a 12-hour dosing interval (AUC(0-12)) was calculated using a noncompartmental method and compared to the value for adults receiving the same dosing regimens. On average, the AUC(0-12) in adolescents after the first loading dose on day 1 and at steady state during IV treatment were 9.14 and 22.4 µg·h/ml, respectively (approximately 34% and 36% lower, respectively, than values for adults). At steady state during oral treatment, adolescents also had lower average exposure than adults (16.7 versus 34.0 µg·h/ml). Larger intersubject variability was observed in adolescents than in adults. There was a slight trend for some young adolescents with low body weight to have lower voriconazole exposure. It is likely that these young adolescents may metabolize voriconazole more similarly to children than to adults. Overall, with the same dosing regimens, voriconazole exposures in the majority of adolescents were comparable to those in adults. The young adolescents with low body weight during the transitioning period from childhood to adolescence (e.g., 12 to 14 years old) may need to receive higher doses to match the adult exposures. Safety of voriconazole in adolescents was consistent with the known safety profile of voriconazole.

Comparison of pharmacokinetics and safety of voriconazole intravenous-to-oral switch in immunocompromised children and healthy adults.

Voriconazole pharmacokinetics are not well characterized in children despite prior studies. To assess the appropriate pediatric dosing, a study was conducted in 40 immunocompromised children aged 2 to <12 years to evaluate the pharmacokinetics and safety of voriconazole following intravenous (IV)-to-oral (PO) switch regimens based on a previous population pharmacokinetic modeling: 7 mg/kg IV every 12 h (q12h) and 200 mg PO q12h. Area under the curve over the 12-h dosing interval (AUC(0-12)) was calculated using the noncompartmental method and compared to that for adults receiving approved dosing regimens (6 → 4 mg/kg IV q12h, 200 mg PO q12h). On average, the AUC(0-12) in children receiving 7 mg/kg IV q12h on day 1 and at IV steady state were 7.85 and 21.4 µg · h/ml, respectively, and approximately 44% and 40% lower, respectively, than those for adults at 6 → 4 mg/kg IV q12h. Large intersubject variability was observed. At steady state during oral treatment (200 mg q12h), children had higher average exposure than adults, with much larger intersubject variability. The exposure achieved with oral dosing in children tended to decrease as weight and age increased. The most common treatment-related adverse events were transient elevated liver function tests. No clear threshold of voriconazole exposure was identified that would predict the occurrence of treatment-related hepatic events. Overall, voriconazole IV doses higher than 7 mg/kg are needed in children to closely match adult exposures, and a weight-based oral dose may be more appropriate for children than a fixed dose. Safety of voriconazole in children was consistent with the known safety profile of voriconazole.

Single-dose pharmacokinetics of famciclovir in infants and population pharmacokinetic analysis in infants and children.

A multicenter, open-label study evaluated the single-dose pharmacokinetics and safety of a pediatric oral famciclovir (prodrug of penciclovir) formulation in infants aged 1 to 12 months with suspicion or evidence of herpes simplex virus infection. Individualized single doses of famciclovir based on the infant's body weight ranged from 25 to 175 mg. Eighteen infants were enrolled (1 to <3 months old [n = 8], 3 to <6 months old [n = 5], and 6 to 12 months old [n = 5]). Seventeen infants were included in the pharmacokinetic analysis; one infant experienced immediate emesis and was excluded. Mean C(max) and AUC(0-6) values of penciclovir in infants <6 months of age were approximately 3- to 4-fold lower than those in the 6- to 12-month age group. Specifically, mean AUC(0-6) was 2.2 microg h/ml in infants aged 1 to <3 months, 3.2 microg h/ml in infants aged 3 to <6 months, and 8.8 microg h/ml in infants aged 6 to 12 months. These data suggested that the dose administered to infants <6 months was less than optimal. Eight (44.4%) infants experienced at least one adverse event with gastrointestinal events reported most commonly. An updated pharmacokinetic analysis was conducted, which incorporated the data in infants from the present study and previously published data on children 1 to 12 years of age. An eight-step dosing regimen was derived that targeted exposure in infants and children 6 months to 12 years of age to match the penciclovir AUC seen in adults after a 500-mg dose of famciclovir.

Assessing time to pulmonary function benefit following antibiotic treatment of acute cystic fibrosis exacerbations.

BACKGROUND: Cystic Fibrosis (CF) is a life-shortening genetic disease in which ~80% of deaths result from loss of lung function linked to inflammation due to chronic bacterial infection (principally Pseudomonas aeruginosa). Pulmonary exacerbations (intermittent episodes during which symptoms of lung infection increase and lung function decreases) can cause substantial resource utilization, morbidity, and irreversible loss of lung function. Intravenous antibiotic treatment to reduce exacerbation symptoms is standard management practice. However, no prospective studies have identified an optimal antibiotic treatment duration and this lack of objective data has been identified as an area of concern and interest. METHODS: We have retrospectively analyzed pulmonary function response data (as forced expiratory volume in one second; FEV1) from a previous blinded controlled CF exacerbation management study of intravenous ceftazidime/tobramycin and meropenem/tobramycin in which spirometry was conducted daily to assess the time course of pulmonary function response. RESULTS: Ninety-five patients in the study received antibiotics for at least 4 days and were included in our analyses. Patients received antibiotics for an average of 12.6 days (median = 13, SD = 3.2 days), with a range of 4 to 27 days. No significant differences were observed in mean or median treatment durations as functions of either treatment group or baseline lung disease stage. Average time from initiation of antibiotic treatment to highest observed FEV1 was 8.7 days (median = 10, SD = 4.0 days), with a range of zero to 19 days. Patients were treated an average of 3.9 days beyond the day of peak FEV1 (median = 3, SD = 3.8 days), with 89 patients (93.7%) experiencing their peak FEV1 improvement within 13 days. There were no differences in mean or median times to peak FEV1 as a function of treatment group, although the magnitude of FEV1 improvement differed between groups. CONCLUSIONS: Our results suggest that antibiotic response to exacerbation as assessed by pulmonary function is essentially complete within 2 weeks of treatment initiation and relatively independent of the magnitude of pulmonary function response observed.

Pharmacokinetics of valsartan in pediatric and adolescent subjects with hypertension.

An open-label, single-dose study is conducted in 26 children with hypertension to characterize the pharmacokinetics of valsartan. Valsartan is administered as an oral suspension (dose of 2 mg/kg), with the maximum single dose being 80 mg. Subjects are stratified into 4 age categories: group 1, 1 to less than 4 years; group 2, 4 to less than 6 years; group 3, 6 to less than 12 years; group 4, 12 to 16 years. Blood samples are collected before and for 24 hours after dosing to quantitate valsartan. Because the body weight of most children in groups 3 and 4 exceeds 40 kg and they received a dose of less than 2 mg/kg, major pharmacokinetic parameters are dose normalized for comparison across the age groups. Dose-normalized maximum plasma concentration and area under the plasma-concentration curve and body weight-normalized apparent oral clearance are comparable for the 4 groups (P > or = .1011). Body weight-normalized apparent oral clearance ranges from 0.061 to 0.089 L/h/kg.

Safety and tolerability of ertapenem versus ceftriaxone in a double-blind study performed in children with complicated urinary tract infection, community-acquired pneumonia or skin and soft-tissue infection.

The carbapenem antibiotic ertapenem has been shown to be safe, well tolerated and effective in treating adults with complicated urinary tract infection, skin and soft-tissue infection and community-acquired pneumonia. In this study, we evaluated ertapenem for treating these infections in children in a randomised, double-blind, active-controlled clinical trial. The primary outcome was the incidence of clinical and laboratory drug-related serious adverse events (AEs). Children were randomised in a 3:1 ratio (ertapenem:ceftriaxone) stratified by index infection and age to receive ertapenem or ceftriaxone; 303 children received ertapenem and 100 children received ceftriaxone. The median duration of parenteral therapy was 4 days for both treatments. The most commonly reported drug-related clinical AEs during parenteral therapy were diarrhoea (5.9% ertapenem, 10% ceftriaxone), infusion site erythema (3% ertapenem, 2% ceftriaxone) and infusion site pain (5% ertapenem, 1% ceftriaxone). One child in each group reported a serious drug-related clinical AE. No serious drug-related laboratory AEs were reported. In children aged 3 months to 17 years, ertapenem was well tolerated and had a comparable safety profile to that of ceftriaxone.

Meropenem use and colonization by antibiotic-resistant Gram-negative bacilli in a pediatric intensive care unit.

OBJECTIVE: The carbapenems are broad-spectrum beta-lactam antibiotics with activity against most organisms encountered in the pediatric intensive care unit (PICU). In anticipation of their increased use in critically ill children, we measured the effect of sustained meropenem use on the pattern of Gram-negative bacillus colonization in patients admitted to a tertiary care PICU. DESIGN: : Prospective preintervention/postintervention comparison. SETTING: Medical/surgical PICU. PATIENTS: Consecutive PICU admissions over 2.5 yrs. INTERVENTIONS: After a 6-mo baseline period, all children with serious infections admitted to the PICU during the subsequent 2 yrs were administered meropenem. The incidence of colonization by Gram-negative bacilli resistant to one of a battery of broad-spectrum parenteral agents, and by organisms resistant specifically to meropenem, during the baseline period was compared with the period of preferred meropenem use. RESULTS: During the period of preferred meropenem use, the amount of meropenem used increased >seven-fold, whereas the use of other advanced generation beta-lactams was reduced by nearly 80%. The mean prevalence of colonization by antibiotic-resistant bacilli in general was not statistically altered during the period of meropenem preference (7.3 organisms/100 patient-days, vs. 9.4 organisms/100 patient-days at baseline, p < 0.09). The prevalence of colonization by Gram-negative organisms resistant specifically to meropenem was 0.61 organisms/100 patient-days during the baseline period vs. 1.04 organisms/100 patient-days during the period of meropenem preference (p < 0.30). The incidence of nosocomial infections did not change, and the prevalence of nosocomial infections caused by meropenem-resistant organisms was always <1% of all admissions during the period of meropenem preference. CONCLUSION: There was no statistically detectable effect on the prevalence of colonization by Gram-negative organisms resistant to one or more classes of broad-spectrum parenteral antibiotics, or to colonization by organisms resistant specifically to meropenem, when meropenem was the preferred antibiotic in a PICU.

Development and validation of an LC-MS/MS method for the simultaneous determination of bedaquiline and rifabutin in human plasma.

This article describes the simultaneous determination of bedaquiline fumarate (TMC-207) and rifabutin in human plasma by stable isotope dilution tandem mass spectrometry. The methodology was developed for an investigation of potential drug-drug interactions of the two anti-tuberculosis drugs when given together to healthy human volunteers. Use of the two drugs in combination to treat disease caused by Mycobacterium tuberculosis is contemplated as the bacterium becomes resistant to many currently available drugs.

Effects of Rifamycin Coadministration on Bedaquiline Desmethylation in Healthy Adult Volunteers.

There is an urgent need to identify safe and effective combination treatments for multidrug-resistant (MDR) Mycobacterium tuberculosis infection (TB). Bedaquiline, a new diarylquinoline, is approved for the treatment of MDR pulmonary TB in combination with other drugs, which could include rifabutin, which is also used to treat drug-resistant TB. Both rifabutin and bedaquiline are metabolized via cytochrome P450 3A4, and rifabutin is an inducer of this enzyme. Bedaquiline is metabolized into its primary N-monodesmethyl metabolite, M2, and further desmethylated into an N-didesmethyl metabolite, M3. Both metabolites are cytotoxic and induce phospholipidosis. The effect of rifabutin on the generation and disposition of the 2 metabolites was investigated in healthy adult volunteers coadministered bedaquiline and either rifabutin or rifampin. Subjects received single oral doses (400 mg) of bedaquiline on days 1 and 29. Oral rifabutin (300 mg) or rifampin (600 mg) were given daily on days 20-41. In the rifabutin group maximum M2 concentrations (Cmax ) increased significantly (P < .001) from 47.59 to 79.53 ng/mL, and clearance slowed slightly (P = .01). This resulted in significantly (P < .001) increased overall exposure (area under the concentration-time curve [AUC0-τ ]). Peak concentrations of M3 increased approximately 3-fold with little decline thereafter. In rifampin recipients M2 Cmax doubled (48.44 to 101.52 ng/mL), but M2 clearance and time to Cmax significantly (P < .001) increased, and AUC0-∞ and mean residence time significantly decreased (P < .001). Peak M3 concentrations increased 4-fold and rapidly declined. Although both rifamycins accelerate desmethylation of bedaquiline and M2, differences in clearance resulted in sustained elevations of both metabolites during rifabutin, but not rifampin, treatment.

A randomized comparative study of levofloxacin versus amoxicillin/clavulanate for treatment of infants and young children with recurrent or persistent acute otitis media.

BACKGROUND: The need for alternative antimicrobial therapy for recurrent and persistent acute otitis media (AOM) in children has raised interest in assessing the efficacy and safety of fluoroquinolones for treatment of these infections. METHODS: In an evaluator-blinded, active-comparator, noninferiority, multicenter study, children (6 months to <5 years) were randomized 1:1 to receive levofloxacin (10 mg/kg twice daily) or amoxicillin/clavulanate (14:1; amoxicillin 45 mg/kg twice daily) for 10 days, with evaluations 4-6 days of therapy (visit 2), 2-5 days after completing therapy (visit 3), and 10-17 days after last dose (visit 4). Primary outcome was clinical cure at visit 3 based on resolution of clinical signs and symptoms of AOM. RESULTS: A total of 1650 children were randomized and 1305 were clinically evaluable at visit 3 (630 levofloxacin, 675 comparator). Clinical cure rates were 72.4% (456 of 630) in levofloxacin-treated and 69.9% (472 of 675) in amoxicillin/clavulanate-treated children. Cure rates were also similar for levofloxacin and comparator for each age group (< or =24 months: 68.9% versus 66.2%; >24 months: 76.9% versus 75.1%; respectively). Cure rates at visit 4 were 74.9% and 73.8% in levofloxacin and amoxicillin/clavulanate groups, respectively. The upper limits of the confidence intervals were less than the noninferiority margin of 10% indicating that levofloxacin treatment is noninferior to comparator treatment overall and in both infants (6 months to 2 years) and children 2-5 years. No differences between treatment groups regarding the frequency or type of adverse events were apparent. CONCLUSIONS: Levofloxacin was not inferior to amoxicillin/clavulanate for the treatment of recurrent and/or persistent AOM in infants and children.

Single-dose pharmacokinetics of oral and intravenous pantoprazole in children and adolescents.

The primary objective was to determine the pharmacokinetics of single oral and intravenous doses of pantoprazole in children 2 to 16 years of age. The secondary objective was to assess the safety and tolerability of these doses. Male and female hospitalized and nonhospitalized patients from ages 5 to 16 years received single oral doses (20 mg or 40 mg), and those from ages 2 to 16 years received single intravenous doses (0.8 mg/kg or 1.6 mg/kg) of pantoprazole. The plasma concentration-time data for each patient were analyzed using noncompartmental methods. Routine safety and tolerability assessments were also obtained. The mean values for peak plasma concentration and total area under the plasma concentration-time curve increased with increasing dose. Pharmacokinetic values were similar in patients from ages 2 to 16 years and to those previously obtained in adults. Statistically significant differences were observed for dose-normalized pantoprazole area under the plasma concentration-time curve when compared between CYP2C19 extensive metabolizers with 1 versus 2 functional alleles. All adverse events were mild in severity and considered to be unrelated to study drug. The pharmacokinetic profile of oral and intravenous pantoprazole was similar in children ages 2 to 16 years. The doses used here were safe and well tolerated in this population.

Mycobactericidal activity of bedaquiline plus rifabutin or rifampin in ex vivo whole blood cultures of healthy volunteers: A randomized controlled trial.

BACKGROUND: Bedaquiline, an antimycobacterial agent approved for drug-resistant tuberculosis, is metabolized by CYP3A4, an hepatic enzyme strongly induced by rifampin, an essential part of drug-sensitive tuberculosis treatment. We examined the pharmacokinetic interactions of bedaquiline plus either rifampin or rifabutin in 33 healthy volunteers. This sub-study of that trial examined the mycobactericidal activity of these drugs against intracellular Mycobacterium tuberculosis using ex vivo whole blood culture. METHODS: Subjects were randomly assigned to receive two single 400 mg doses of bedaquiline, alone, and, after a 4 week washout period, in combination with steady-state daily dosing of either rifabutin 300 mg or rifampin 600 mg. Blood samples were collected prior to dosing and at multiple time points subsequently, to measure plasma drug concentrations and bactericidal activity in ex vivo M tuberculosis-infected whole blood cultures (WBA). RESULTS: Single oral doses of bedaquiline produced readily detectable WBA ex vivo, reaching a maximal effect of -0.28 log/day, with negative values indicating bacterial killing. Plasma concentrations of 355 ng/ml were sufficient for intracellular mycobacteriostasis. Combined dosing with rifampin or rifabutin produced maximal effects of -0.91 and -0.79 log/d, respectively. However, the activity of the rifabutin combination was sustained throughout the dosing interval, thereby producing a greater cumulative or total effect. At low drug concentrations, rifabutin plus bedaquiline yielded greater mycobactericidal activity than the sum of their separate effects. Neither drug metabolites nor cellular drug accumulation could account for this observation. CONCLUSIONS: The combination of rifabutin plus bedaquiline produces sustained intracellular mycobactericidal activity that is greater than the sum of their individual effects. Further studies of the treatment-shortening potential of this combination are warranted.