Bioequivalence and the food effect of macitentan/tadalafil 10/20 fixed-dose combination tablets versus the use of single-component tablets in healthy subjects.

The primary aim was to demonstrate bioequivalence between the 10/20 mg fixed-dose combination (FDC) of macitentan/tadalafil in a single tablet and the free combination of both drugs, and to evaluate the food effect on the 10/20 mg FDC in healthy participants. In this single-center, randomized, open-label, 3-way crossover, single-dose Phase 1 study in healthy adult participants, macitentan/tadalafil was administered as a 10/20 mg FDC formulation and compared with the free combination of macitentan and tadalafil. The food effect on the FDC was also evaluated. Pharmacokinetic sampling (216 h) was conducted. The 90% confidence intervals (CIs) for the geometric mean ratios of maximum observed plasma analyte concentration (Cmax) and area under the plasma analyte concentration-time curves (AUCs) for Treatment A (FDC, fasted) versus C (free combination, fasted) were within bioequivalence limits demonstrating that the FDC formulation can be considered bioequivalent to the free combination. The 90% CIs for the geometric mean ratios of Cmax and AUC for Treatment B (FDC, fed) versus A (FDC, fasted) were contained within bioequivalence limits demonstrating that there was no food effect. The administration of the 10/20 mg FDC was generally safe and well tolerated in healthy participants. This study demonstrated bioequivalence between the FDC of macitentan/tadalafil (10/20 mg) in a single tablet and the free combination of both drugs in healthy participants, and that the FDC can be taken without regard to food, similarly to the individual components. The FDC was generally safe and well tolerated.

Bioequivalence and food effect of a fixed-dose combination of macitentan and tadalafil: Adaptive design in the COVID-19 pandemic.

The COVID-19 pandemic has forced clinical studies to accommodate imposed limitations. In this study, the bioequivalence part could not be conducted as planned. Thus, the aim was to demonstrate bioequivalence, using an adaptive study design, of tadalafil in fixed-dose combination (FDC) tablets of macitentan/tadalafil with single macitentan and tadalafil (Canadian-sourced) tablets and assess the effect of food on FDC tablets in healthy subjects. This Phase 1, single-center, open-label, single-dose, two-part, two-period, randomized, crossover study enrolled 62 subjects. Tadalafil bioequivalence as part of FDC of macitentan/tadalafil (10/40 mg) with single-component tablets of macitentan (10 mg) and tadalafil (40 mg) was determined by pharmacokinetic (PK) assessment under fasted conditions. The effect of food on FDC was evaluated under fed and fasted conditions. Fasted 90% confidence intervals (CIs) for geometric mean ratios (GMRs) were within bioequivalence limits for tadalafil and macitentan. Fed and fasted 90% CIs for area under the curve (AUC) GMR were within bioequivalence limits. However, 90% CIs for maximum plasma concentration (Cmax ) GMR for macitentan and tadalafil were outside bioequivalence limits. One FDC-treated subject experienced a serious adverse event of transient ischemic attack (bioequivalence part). To address pandemic-imposed limitations, an adaptive study design was implemented to demonstrate that the FDC tablet was bioequivalent to the free combination of macitentan and tadalafil (Canadian-sourced). No clinically significant differences in PK were determined between fed and fasted conditions; the FDC formulation could be taken irrespective of meals. The FDC formulation under fasted and fed conditions was well tolerated with no clinically relevant differences in safety profiles between the treatment groups. NCT Number: NCT04235270.

Comparison of a transdermal contraceptive patch with a newly sourced adhesive component versus EVRA patch: A double-blind, randomized, bioequivalence and adhesion study in healthy women.

OBJECTIVE: To evaluate the bioequivalence of norelgestromin and ethinyl estradiol (NGMN-EE) and adhesion of a transdermal contraceptive patch containing a newly sourced adhesive component (test) compared with the marketed (reference) patch. STUDY DESIGN: In this randomized, double-blind, 2-way crossover study, healthy women received single 7-day application of both test and reference patches. Treatment phase included two treatment periods of 11 days each separated by a 21-day washout period starting from day of patch removal (day 8) of treatment period 1. Assessments included NGMN and EE pharmacokinetics (PK), adhesion using European Medicines Agency (EMA) 5-point scale, irritation potential and application-site reactions, and safety. Patches were bioequivalent if 90% CIs of ratios of means of test/reference for AUC168h, AUCinf, and Css fell within 80-125%. Patch adhesion was comparable if ratios of mean cumulative adhesion percentage values of test/reference were ≥90.0%. RESULTS: Seventy women were randomized; 57 completed both treatments with ≥80% adhesion (score 0-1). Bioequivalence of test and reference patches was demonstrated as 90% CI of ratio of geometric means for AUC168h, AUCinf, and Css for NGMN and EE fell within 80-125%. Both patches had similar adhesion properties (geometric mean ratio was 100.3% [90% CI, 93.2-107.9]). Similar rates of mild-to-moderate itching (11% vs 10%) and erythema events (79% vs 74%) were reported for test and reference patches, respectively, on day 8. CONCLUSIONS: The test patch with the newly sourced adhesive component is bioequivalent to the currently marketed NGMN-EE transdermal patch and has similar adhesion and irritation potential. IMPLICATIONS STATEMENT: The norelgestromin and ethinyl estradiol transdermal patch containing a newly sourced adhesive component is bioequivalent to the currently marketed patch for both active moieties. Both patches had similar adhesion, irritation potential, and safety profiles.

Tramadol Hydrochloride at Steady State Lacks Clinically Relevant QTc Interval Increases in Healthy Adults.

We evaluated the effects of therapeutic and supratherapeutic doses of tramadol hydrochloride on the corrected QT (QTc) interval in healthy adults (aged 18-55 years) in a randomized, phase I, double-blind, placebo- and positive-controlled, multiple-dose, 4-way crossover study. Participants were randomized to receive 1 of 4 treatments (A-D), 1 each in 4 treatment periods (1-4), separated by a washout period (7-15 days). Treatment A comprised tramadol 400 mg (therapeutic dose) on days 1 through 3, tramadol 100 mg and moxifloxacin-matched placebo on day 4, and placebo on all 4 days. Treatment B comprised tramadol 600 mg (supratherapeutic dose) on days 1 through 3, and tramadol 150 mg and moxifloxacin-matched placebo on day 4. Treatment C comprised placebo on days 1 through 4 and moxifloxacin-matched placebo on day 4. Treatment D comprised placebo on days 1 through 4 and moxifloxacin 400 mg on day 4. Of 68 participants enrolled, 57 (83.8%) completed the study. Both therapeutic and supratherapeutic doses of tramadol were shown to be noninferior to placebo regarding their effect on QTc prolongation. Sixty-one of 68 (89.7%) participants reported at least 1 treatment-emergent adverse event (mild); nausea was the most frequently reported treatment-emergent adverse event. Summarizing, tramadol at doses up to 600 mg/day did not cause clinically relevant QTc interval prolongation in healthy adults.

Safety, Tolerability, and Pharmacokinetics of Therapeutic and Supratherapeutic Doses of Tramadol Hydrochloride in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Multiple-Ascending-Dose Study.

This randomized, double-blind, parallel-group multiple-ascending-dose study evaluated the safety, tolerability, and pharmacokinetics of tramadol hydrochloride in healthy adults to inform dosage and design for a subsequent QT/QTc study. Healthy men and women, 18 to 45 years old (inclusive), were sequentially assigned to the tramadol 200, 400, or 600 mg/day treatment cohort and within each cohort, randomized (4:1) to either tramadol or placebo every 6 hours for 9 oral doses. Of the 24 participants randomized to tramadol (n = 8/cohort), 22 (91.7%) completed the study. The AUCtau,ss of tramadol increased approximately 2.2- and 3.6-fold for the (+) enantiomer and 2.0- and 3.5-fold for the (-) enantiomer with increasing dose from 200 to 400  and 600 mg/day, whereas the Cmax,ss increased 2.1- and 3.3-fold for the (+) enantiomer and 2.0- and 3.2-fold for the (-) enantiomer. Overall, 21 participants (87.5%) participants reported ≥1 treatment-emergent adverse event; most frequent were nausea (17 of 24, 70.8%) and vomiting (7 of 24, 29.2%). Vomiting (affected participants and events) increased with increasing dose from 200 to 600 mg/day but was mild (5 of 24) or moderate (2 of 24) in severity. All tested dosage regimens of tramadol showed acceptable safety and tolerability profile for further investigation in a thorough QT/QTc study.

Pathogenic copy number variants and SCN1A mutations in patients with intellectual disability and childhood-onset epilepsy.

BACKGROUND: Copy number variants (CNVs) have been linked to neurodevelopmental disorders such as intellectual disability (ID), autism, epilepsy and psychiatric disease. There are few studies of CNVs in patients with both ID and epilepsy. METHODS: We evaluated the range of rare CNVs found in 80 Welsh patients with ID or developmental delay (DD), and childhood-onset epilepsy. We performed molecular cytogenetic testing by single nucleotide polymorphism array or microarray-based comparative genome hybridisation. RESULTS: 8.8 % (7/80) of the patients had at least one rare CNVs that was considered to be pathogenic or likely pathogenic. The CNVs involved known disease genes (EHMT1, MBD5 and SCN1A) and imbalances in genomic regions associated with neurodevelopmental disorders (16p11.2, 16p13.11 and 2q13). Prompted by the observation of two deletions disrupting SCN1A we undertook further testing of this gene in selected patients. This led to the identification of four pathogenic SCN1A mutations in our cohort. CONCLUSIONS: We identified five rare de novo deletions and confirmed the clinical utility of array analysis in patients with ID/DD and childhood-onset epilepsy. This report adds to our clinical understanding of these rare genomic disorders and highlights SCN1A mutations as a cause of ID and epilepsy, which can easily be overlooked in adults.

Absence of QTc Prolongation with Domperidone: A Randomized, Double-Blind, Placebo- and Positive-Controlled Thorough QT/QTc Study in Healthy Volunteers.

Domperidone effects on QTc duration were assessed in a single-center, double-blind, four-way crossover study of 44 healthy participants randomized to one of four treatment sequences consisting of four treatment periods separated by 4-9 days washout. On Day 1 of each 4-day period, participants began oral domperidone 10 or 20 mg q.i.d., matching placebo q.i.d., or single-dose moxifloxacin 400 mg (positive control)/placebo q.i.d. In each period, triplicate 12-lead electrocardiograms were recorded at baseline (30, 20, and 10 minutes predose), 8 timepoints after dosing on Days 1 and 4, and predose on Day 4. In mixed effects models, the largest difference for domperidone in least squares means for change from baseline QTcP versus placebo was 3.4 milliseconds (20 mg q.i.d., Day 4), 90% CI: 1.0-5.9, and <10 milliseconds at all timepoints for both domperidone dosages. Moxifloxacin response confirmed assay sensitivity. Participants achieved expected domperidone plasma exposures. No significant exposure-response relationship was found for QTc increase per ng/mL domperidone (90% CI of the slope estimate included zero at mean Cmax on Day 1 or Day 4). In summary, domperidone at doses up to 80 mg/day did not cause clinically relevant QTc interval prolongation.

Switching from rivaroxaban to warfarin: an open label pharmacodynamic study in healthy subjects.

AIMS: The primary objective was to explore the pharmacodynamic changes during transition from rivaroxaban to warfarin in healthy subjects. Safety, tolerability and pharmacokinetics were assessed as secondary objectives. METHODS: An open label, non-randomized, sequential two period study. In treatment period 1 (TP1), subjects received rivaroxaban 20 mg once daily (5 days), followed by co-administration with a warfarin loading dose regimen of 5 or 10 mg (for the 10 mg regimen, the dose could be uptitrated to attain target international normalized ratio [INR] ≥2.0) once daily (2-4 days). When trough INR values ≥2.0 were attained, rivaroxaban was discontinued and warfarin treatment continued as monotherapy (INR 2.0-3.0). During treatment period 2, subjects received the same warfarin regimen as in TP1, but without rivaroxaban. RESULTS: During co-administration, maximum INR and prothrombin time (PT) values were higher than with rivaroxaban or warfarin monotherapy. The mean maximum effect (Emax ) for INR after co-administration was 2.79-4.15 (mean PT Emax 41.0-62.7 s), compared with 1.41-1.74 (mean PT Emax 20.1-25.2 s) for warfarin alone. However, rivaroxaban had the smallest effect on INR at trough rivaroxaban concentrations. Neither rivaroxaban nor warfarin significantly affected maximum plasma concentrations of the other drug. CONCLUSIONS: The combined pharmacodynamic effects during co-administration of rivaroxaban and warfarin were greater than additive, but the pharmacokinetics of both drugs were unaffected. Co-administration was well tolerated. When transitioning from rivaroxaban to warfarin, INR monitoring during co-administration should be performed at the trough rivaroxaban concentration to minimize the effect of rivaroxaban on INR.

Effect of canagliflozin, a sodium glucose co-transporter 2 inhibitor, on C-peptide kinetics.

Canagliflozin, a sodium glucose co-transporter 2 inhibitor, improves indices of ß-cell function estimated based on circulating C-peptide and glucose concentrations (e.g., Homeostasis Model Assessment [HOMA2-%B], meal tolerance test-based indices). However, use of these ß-cell function indices assumes C-peptide kinetics are not altered by canagliflozin. This 2-period crossover study assessed the effect of a single canagliflozin 300-mg dose on C-peptide kinetics in 10 healthy participants. Two hours after receiving canagliflozin or placebo, participants received intravenous somatostatin infusion to suppress endogenous C-peptide secretion and 1 hour later received a bolus injection of synthetic human C-peptide 150 µg. Serum C-peptide was measured over 3 hours and urinary glucose and C-peptide excretion were measured. C-peptide kinetic parameters, including total clearance (CLtotal ) and renal clearance (CLrenal ), were calculated. Serum C-peptide profiles were similar following canagliflozin or placebo treatment. C-peptide CLtotal was slightly lower with canagliflozin versus placebo (mean (SD) of 190 (37) vs. 197 (30) mL/min; canagliflozin/placebo ratio [90% CI] = 96.1% [93.0%; 99.3%]). Other kinetic parameters, including CLrenal , were generally similar between treatments. Results indicate canagliflozin 300 mg does not meaningfully alter C-peptide clearance or other kinetic parameters; therefore, C-peptide-based measurements of insulin secretion are appropriate for assessing ß-cell function in canagliflozin-treated participants.

An open-label study to estimate the effect of steady-state erythromycin on the pharmacokinetics, pharmacodynamics, and safety of a single dose of rivaroxaban in subjects with renal impairment and normal renal function.

Two previously conducted rivaroxaban studies showed that, separately, renal impairment (RI) and concomitant administration of erythromycin (P-glycoprotein and moderate cytochrome P450 3A4 [CYP3A4] inhibitor) can result in increases in rivaroxaban exposure. However, these studies did not assess the potential for combined drug-drug-disease interactions, which-in theory-could lead to additive or synergistic increases in exposure. This study investigated rivaroxaban pharmacokinetics and pharmacodynamics when co-administered with steady-state (SS) erythromycin in subjects with either mild or moderate RI. Similar to previous studies, rivaroxaban administered alone in RI subjects, or when co-administered with SS erythromycin in normal renal function (NRF) subjects, increased rivaroxaban exposure. When combined, the co-administration of rivaroxaban 10 mg with SS erythromycin in subjects with mild or moderate RI produced mean increases in rivaroxaban AUC∞ and Cmax of approximately 76% and 56%, and 99% and 64%, respectively, relative to NRF subjects, with PD changes displaying a similar trend. No serious adverse events occurred and no persistent adverse events were reported at the end of study. Although these increases were slightly more than additive, rivaroxaban should not be used in patients with RI receiving concomitant combined P-glycoprotein and moderate CYP3A4 inhibitors, unless the potential benefit justifies the potential risk.

Randomized 5-treatment crossover study to assess the effects of external heat on serum fentanyl concentrations during treatment with transdermal fentanyl systems.

This randomized, open-label, 5-treatment, 5-sequence crossover study was designed to evaluate the effects of a heating pad on serum fentanyl concentrations with reservoir and matrix transdermal fentanyl systems. Subjects were randomized to 1 of 5 treatment sequences, receiving 5 fentanyl treatments (1 per period) for 36 hours: 25 µg/h reservoir without heat, 25 µg/h reservoir with heat, 25 µg/h matrix without heat, 25 µg/h matrix with heat, and a 50 µg/h reservoir without heat. The 25 µg/h systems with heat had a heating pad applied from 0 to 10 and 26 to 36 hours post application. Washout periods between treatments were 5 to 14 days. Naltrexone was given to block the opioid effects of fentanyl. Study results indicate that external heat had a similar effect on both matrix and reservoir systems, with heat applied during the first 10 hours of treatment increasing fentanyl exposure by approximately 61% to 81% at 10 hours (observed serum concentration at 10 hours) and overall exposure (area under the curve from 0 to 10 hours) by approximately 120% to 184%, but had minimal effect from 26 to 36 hours. The increased exposure observed with heat in both 25 µg/h systems, between 0 and 10 hours, was higher than that obtained with the 50 µg/h reservoir system applied without heat.

Bioequivalence and safety of a novel fentanyl transdermal matrix system compared with a transdermal reservoir system.

OBJECTIVES: Fentanyl is a potent synthetic opioid used for the management of chronic pain. A newer transdermal matrix system was developed and compared with a reservoir system used in the United States. SETTING: An open-label, single-center, randomized, two-period crossover study was conducted to evaluate the bioequivalence of the transdermal matrix system to the transdermal reservoir system. Seventy-four subjects completed treatment with both the reservoir system (100 microg/h) and the matrix system (100 microg/h), each applied for 72 hours. After application of the first system, subjects completed a 9-day washout and then crossed over to receive the other system for another 72 hours. MAIN OUTCOME MEASURE: Blood samples for the determination of serum fentanyl concentrations were taken in each treatment period for up to 120 hours following application. RESULTS: The ratios of geometric means for maximum fentanyl concentration (Cmax) and area under the concentration-time curve (AUClast, and AUCinfinity) were 106 percent, 110 percent, and 110 percent, respectively. The 90% confidence intervals for the ratios of the geometric means were contained within the bioequivalence criteria of 80-125 percent. The matrix system adhered well to skin. Systemic and topical safety profiles were comparable between treatments. CONCLUSIONS: The transdermal fentanyl matrix system adhered well, was well tolerated, and produced systemic exposures of fentanyl that were bioequivalent to the reservoir system.

Evaluation of the effect of paliperidone extended release and quetiapine on corrected QT intervals: a randomized, double-blind, placebo-controlled study.

The effect of two atypical antipsychotics on QTc intervals (heart rate-corrected QT interval) was evaluated. Patients (N=109) with schizophrenia (79%) or schizoaffective disorder (21%) were randomly assigned in 2 : 2 : 1 ratio to paliperidone extended release (ER), quetiapine, or placebo. Doses of 12 and 18 mg/day of paliperidone ER were compared with quetiapine 800 mg/day. Least-squares mean change from baseline in population-specific linear-derived correction method from baseline to days 6-7 at individual tmax was 5.1 ms less [90% confidence interval: -9.2 to -0.9] with paliperidone ER 12 mg/day than with quetiapine 800 mg/day. On the basis of a prespecified 10-ms noninferiority margin, paliperidone ER was thus declared noninferior to quetiapine (primary analysis). Mean change in population-specific linear-derived correction method from baseline to days 11-12 at individual tmax was 2.3 ms less (90% confidence interval: -6.8 to 2.3) with paliperidone ER 18 mg/day than with quetiapine 800 mg/day. Treatment-emergent adverse events occurred in 36 (82%) patients treated with paliperidone ER, 41 (95%) patients treated with quetiapine, and 14 (64%) patients treated with placebo. No adverse events of a proarrhythmic nature were noted. The effect on the QTc interval in patients with schizophrenia or schizoaffective disorder was comparable between paliperidone ER 12 mg/day (maximum recommended dose), paliperidone ER 18 mg/day (supratherapeutic dose), and quetiapine 800 mg/day.

A comparison of several methods for analyzing data from thorough QT studies.

Currently, the intersection-union test (IUT) is the standard method of analysis of the data from a thorough QT (TQT) study. In this current work, we compared the methods proposed in three recent publications (Boos et al., 2007; Cheng et al., 2008; Eaton et al., 2006) to IUT using a simulation study. The methods proposed by Cheng and Eaton did not produce a considerable improvement over IUT in the power and size of the test. The power of the Boos et al. method was a substantial improvement over IUT, but the size of the test was found to be greater than 5%.

Pharmacokinetics, safety, and tolerability of doripenem after 0.5-, 1-, and 4-hour infusions in healthy volunteers.

The pharmacokinetics, safety, and tolerability of doripenem in healthy subjects were evaluated in 2 studies. Study 1 was a double-blind, randomized, placebo-controlled dose-escalation study in which doripenem was administered for 7 days by infusion over 30 minutes (500 mg) or 1 hour (1000 mg). Study 2 was an open-label, randomized, 3-way crossover study in which each subject received a single dose of each of the following doripenem treatments on separate occasions: 500 mg infused over 1 hour, 500 mg infused over 4 hours, and 1000 mg infused over 4 hours. Doripenem exhibited linear pharmacokinetics with concordance between the studies for pharmacokinetic parameters. Doripenem did not accumulate with repeated dosing over 7 days. The area under the plasma concentration-time curve (AUC) for doripenem 500 mg infused over 1 hour versus 4 hours was bioequivalent, and the AUC and Cmax increased proportionally with dose for the 500- and 1000-mg doses administered over 4 hours. These results, along with the stability profile of doripenem, support its use as a prolonged infusion. All regimens of doripenem were safe and well tolerated.

Effect of baseline measurement on the change from baseline in QTc intervals.

Phase I thorough QT (TQT) studies are routinely conducted by pharmaceutical companies for all new compounds to satisfy the requirements of International Conference on Harmonisation (ICH) E14 guidance on the evaluation of QTc prolongation. The primary endpoint is the change from baseline in QT interval corrected for heart rate (QTc), and the hypothesis of interest is the noninferiority of drug to placebo. Sometimes, due to the properties of the compound, it becomes necessary to use parallel group designs for TQT studies. In such situations, the effect of the baseline on the change from baseline in QTc becomes an important issue because differing baseline between the drug and placebo groups may not allow for proper estimation of the drug's effect. In this work, we evaluate the effect of baseline on the change from baseline using the placebo data from several TQT studies. Resampling techniques are used to evaluate the impact of differing baselines across groups.

Levofloxacin pharmacokinetics in children.

Levofloxacin is a broad-spectrum fluoroquinolone antibiotic with activity against many pathogens that cause bacterial infections in children, including penicillin-resistant pneumococci. To provide dosing guidance for children, 3 single-dose, multicenter pharmacokinetic studies were conducted in 85 children in 5 age groups: 6 months to <2 years, 2 to <5 years, 5 to <10 years, 10 to <12 years, and 12 to 16 years. Each child received a single 7-mg/kg dose of levofloxacin (not to exceed 500 mg) intravenously or orally. Plasma and urine samples were collected through 24 hours after dose. Pharmacokinetic parameters were estimated and compared among the 5 age groups and to previously collected adult data. Levofloxacin absorption (as indicated by C(max) and t(max)) and distribution in children are not age dependent and are comparable to those in adults. Levofloxacin elimination (reflected by t1/2 and clearance), however, is age dependent. Children younger than 5 years of age clear levofloxacin nearly twice as fast (intravenous dose, 0.32+/-0.08 L/h/kg; oral dose, 0.28+/-0.05 L/h/kg) as adults and, as a result, have the total systemic exposure (area under the plasma drug concentration-time curve) approximately one half that of adults. The levofloxacin area under the plasma drug concentration-time curve (dose normalized) in children receiving a single dose of the oral liquid formulation is comparable to that in children receiving the intravenous formulation. To provide compatible levofloxacin exposures associated with clinical effectiveness and safety in adults, children > or =5 years need a daily dose of 10 mg/kg, whereas children 6 months to <5 years should receive 10 mg/kg every 12 hours.

Population pharmacokinetics of erythropoietin in critically ill subjects.

The effects of various covariate factors on the pharmacokinetics of erythropoietin (EPO) in subjects who are critically ill and admitted to an intensive care unit were evaluated. Nonlinear mixed-effects modeling was used to analyze the data from 48 patients receiving subcutaneous doses of 40,000 IU/wk epoetin alfa enrolled in a randomized, double-blind, placebo-controlled, multicenter study. The pharmacokinetics of EPO follows a 1-compartment disposition model with first-order absorption and an endogenous input rate. For a patient weighing 70 kg, the typical apparent clearance (CL/F) and apparent volume of distribution (V/F) were estimated to be 1.86 L/h and 27.8 L. The interindividual variability in CL/F and V/F was estimated to be 57.2% and 83.8%. CL/F and V/F of EPO increased with body weight, as described by the following relation: CL/F = (CL/F)std*(W/W(std))0.75, and V/F = (V/F)std*(W/W(std))1.37, where W is individual weight, and W(std) is the median weight of the study population. There was a 46% drop in exposure of EPO from the first to the subsequent dosing events. The endogenous EPO production rate was found to decrease progressively with the course of the study. In addition, the modeled endogenous EPO production rate increased with body weight. The net effect of this increase on the endogenous plasma EPO levels may not be significant because EPO clearance was found to increase with body weight. All other factors investigated (eg, Sequential Organ Failure Assessment [SOFA] scores and APACHE II scores) had no significant effect on EPO pharmacokinetics. The typical population estimate of CL/F of EPO was close to previously reported values in healthy volunteers.

Measuring the effects of supratherapeutic doses of levofloxacin on healthy volunteers using four methods of QT correction and periodic and continuous ECG recordings.

A clinical trial was conducted in healthy volunteers using both periodic and continuous ECG recordings to assess the effect of increasing doses of levofloxacin on the QT and QTc interval. Periodic and continuous ECGs were recorded before and after subjects were dosed with placebo and increasing doses of levofloxacin (500 mg, 1000 mg, 1500 mg) that included doses twice the maximum recommended dose of 750 mg in a double-blind, randomized, four-period, four-sequence crossover trial. Mean heart rate (HR) and the QT and QTc interval after dosing with levofloxacin and placebo were compared, and HR-QT interval relationships defined by linear regression analysis were calculated. After single doses of 1000 and 1500 mg of levofloxacin, HR increased significantly, as measured by periodic and continuous ECG recordings. This transient increase occurred at times of peak plasma concentration and was without symptoms. Mean QT intervals after placebo and mean intervals after levofloxacin were indistinguishable. Using periodic ECG recordings, single doses of 1500 mg were associated with small increases in QTc that were statistically significant. In contrast, an effect on QTc was shown only using the Bazett formula with data obtained from continuous ECG recordings. Together with the finding that levofloxacin does not influence HR-QT relationships, these findings suggest that levofloxacin has little effect on prolonging ventricular repolarization and that small increases in HR associated with high doses of levofloxacin contribute to the drug's apparent effect on QTc. Single doses of 1000 or 1500 mg of levofloxacin transiently increase HR without affecting the uncorrected QT interval. Differences in mean QTc after levofloxacin compared to placebo vary depending on the correction formula used and whether the data analyzed are from periodic or continuous ECG recordings. This work suggests that using continuous ECG recordings in assessing QT/QTc effects of drugs may be of value, particularly with drugs that might influence HR.

Effects of three fluoroquinolones on QT interval in healthy adults after single doses.

OBJECTIVE: A clinical trial was conducted in healthy adult volunteers to assess the effect of levofloxacin, moxifloxacin, and ciprofloxacin on the QT and QTc interval. METHODS: Electrocardiograms were recorded 24 hours before and after subjects took placebo, 1000 mg levofloxacin, 800 mg moxifloxacin, and 1500 mg ciprofloxacin in a double-blind, randomized, 4-period, 4-treatment, 4-sequence crossover trial. Changes in QT and QTc interval from baseline were assessed by several different methods. RESULTS: Increases in QT and QTc interval compared with placebo were consistently greater after moxifloxacin compared with either levofloxacin or ciprofloxacin. The mean postdose change from baseline QTc (Bazett) intervals for the 24-hour period after treatment with moxifloxacin ranged from 16.34 to 17.83 ms (P < .001, compared with placebo). For levofloxacin, this change ranged from 3.53 to 4.88 ms (P < .05, compared with placebo), and for ciprofloxacin, this change ranged from 2.27 to 4.93 ms (P < .05, compared with placebo, with the use of 3 of 5 baseline methods). CONCLUSIONS: A change in QTc (Bazett) interval from baseline can be demonstrated safely in healthy volunteers after single high doses of fluoroquinolones that achieve approximately 1.5 times the maximum plasma drug concentration that occurs after recommended doses. There is substantial daily variation in both QT and QTc interval, and the magnitude and frequency of changes in QTc interval can depend on the methods used. These factors need to be considered because clinical trials measuring the effects of drugs on QT intervals are used to estimate the risk of using these drugs. Greater changes in QT and QTc intervals after treatment with moxifloxacin compared with levofloxacin or ciprofloxacin are consistent with in vitro observations related to the effect of these drugs on rapid potassium (IK(r)) channels. The clinical relevance of these differences is not known.