Pharmacokinetics of high-dose intravenous ciprofloxacin in young and elderly and in male and female subjects

The effect of ciprofloxacin on doxorubicin cytotoxic activity in the acquired resistance to doxorubicin in DU145 prostate carcinoma cells

The present study aimed to assess the influence of ciprofloxacin (CIP) against the doxorubicin (DOX)-resistant androgen-independent prostate cancer DU145 cells. The DOX-resistant DU145 (DU145/DOX20) cells were established by exposing DU145 cells to the increasing concentrations of DOX. The antiproliferative effect of CIP was examined through employing MTT, colony formation, and 3D culture assays. DU145/DOX20 cells exhibited a twofold higher IC₅₀ value for DOX, an increased ABCB1 transporter activity, and some morphological changes accompanied by a decrease in spheroid size, adhesive and migration potential compared to DU145 cells. CIP (5 and 25 µg mL^-1) resulted in a higher reduction in the viability of DU145/DOX20 cells than in DU145 cells. DU145/DOX20 cells were more resistant to CIP in 3D culture compared to the 2D one. No spheroid formation was observed for DU145/DOX20 cells treated with DOX and CIP combination. CIP and DOX, alone or in combination, significantly reduced the growth of DU145 spheroids. CIP in combination with 20 nM DOX prevented the colony formation of DU145 cells. The clonogenicity of DU145/DOX20 cells could not be estimated due to their low adhesive potential. CIP alone caused a significant reduction in the migration of DU145 cells and resulted in a more severe decrease in the wound closure ability of DOX-exposed ones. We identified that CIP enhanced DOX sensitivity in DU145 and DU145/DOX20 cells. This study suggested the co-delivery of low concentrations of CIP and DOX may be a promising strategy in treating the DOX-resistant and -sensitive hormone-refractory prostate cancer.

Population pharmacokinetics of ciprofloxacin in critically ill patients receiving extracorporeal membrane oxygenation (an ASAP ECMO study)

INTRODUCTION

This study aimed to describe the pharmacokinetics (PK) of ciprofloxacin in critically ill patients receiving ECMO and recommend a dosing regimen that provides adequate drug exposure.

METHODS

Serial blood samples were taken from ECMO patients receiving ciprofloxacin. Total ciprofloxacin concentrations were measured by chromatographic assay and analysed using a population PK approach with Pmetrics®. Dosing simulations were performed to ascertain the probability of target attainment (PTA) represented by the area under the curve to minimum inhibitory concentration ratio (AUC_0-24/MIC) ≥ 125.

RESULTS

Eight patients were enrolled, of which three received concurrent continuous venovenous haemodiafiltration (CVVHDF). Ciprofloxacin was best described in a two-compartment model with total body weight and creatinine clearance (CrCL) included as significant predictors of PK. Patients not requiring renal replacement therapy generated a mean clearance of 11.08 L/h while patients receiving CVVHDF had a mean clearance of 1.51 L/h. Central and peripheral volume of distribution was 77.31 L and 90.71 L, respectively. ECMO variables were not found to be significant predictors of ciprofloxacin PK. Dosing simulations reported that a 400 mg 8 -hly regimen achieved > 72% PTA in all simulated patients with CrCL of 30 mL/min, 50 mL/min and 100 mL/min and total body weights of 60 kg and 100 kg at a MIC of 0.5 mg/L.

CONCLUSION

Our study reports that established dosing recommendations for critically ill patients not on ECMO provides sufficient drug exposure for maximal ciprofloxacin activity for ECMO patients. In line with non-ECMO critically ill adult PK studies, higher doses and therapeutic drug monitoring may be required for critically ill adult patients on ECMO.

Ciprofloxacin in Patients Undergoing Extracorporeal Membrane Oxygenation (ECMO): A Population Pharmacokinetic Study

Extracorporeal membrane oxygenation (ECMO) is utilized to temporarily sustain respiratory and/or cardiac function in critically ill patients. Ciprofloxacin is used to treat nosocomial infections, but data describing the effect of ECMO on its pharmacokinetics is lacking. Therefore, a prospective, observational trial including critically ill adults (n = 17), treated with ciprofloxacin (400 mg 8–12 hourly) during ECMO, was performed. Serial blood samples were collected to determine ciprofloxacin concentrations to assess their pharmacokinetics. The pharmacometric modeling was performed (NONMEM^®) and utilized for simulations to evaluate the probability of target attainment (PTA) to achieve an AUC_0–24/MIC of 125 mg·h/L for ciprofloxacin. A two-compartment model most adequately described the concentration-time data of ciprofloxacin. Significant covariates on ciprofloxacin clearance (CL) were plasma bicarbonate and the estimated glomerular filtration rate (eGFR). For pathogens with an MIC of ≤0.25 mg/L, a PTA of ≥90% was attained. However, for pathogens with an MIC of ≥0.5 mg/L, plasma bicarbonate ≥ 22 mmol/L or eGFR ≥ 10 mL/min PTA decreased below 90%, steadily declining to 7.3% (plasma bicarbonate 39 mmol/L) and 21.4% (eGFR 150 mL/min), respectively. To reach PTAs of ≥90% for pathogens with MICs ≥ 0.5 mg/L, optimized dosing regimens may be required.

The role of antibiotic pharmacokinetic studies performed post-licensing

Post-licensing pharmacometric studies can provide a better understanding of the pharmacokinetic (PK) alterations in special patient populations and may lead to better clinical outcomes. Some patient populations exhibit markedly different pathophysiology to general ward patients or healthy individuals. This may be developmental (paediatric patients), a manifestation of an underlying disease pathology (patients with obesity or haematological malignancies) or due to medical interventions (critically ill patients receiving extracorporeal therapies). This paper outlines the factors that affect the PK of special patient populations and describes some novel methods of antimicrobial administration that may increase antimicrobial concentrations at the site of infection and improve treatment of severe infection.

Oral Ciprofloxacin Pharmacokinetics in Healthy Mexican Volunteers and Other Populations: Is There Interethnic Variability?

BACKGROUND

There is evidence that the pharmacokinetics of certain drugs in Mexicans may differ with respect to other ethnic groups. On the other hand, there is controversy about the existence of interethnic variability in the pharmacokinetics of ciprofloxacin.

AIM OF THE STUDY

To study oral ciprofloxacin pharmacokinetics in Mexicans at various dose levels and make comparisons with other populations in order to gain insight on interethnic variability.

METHODS

Healthy Mexican volunteers received oral ciprofloxacin as 250 mg and 500 mg immediate-release tablets or a 1,000 mg extended-release formulation. Plasma concentration against time curves were constructed, and pharmacokinetic parameters were compared with those reported for other populations.

RESULTS

Ciprofloxacin pharmacokinetics in Mexicans was linear and no significant differences between males and females were detected. When several populations were compared, it appeared that bioavailability in Mexicans was similar to that of Caucasians, being lower than that of Asians. These variations were attenuated when data were normalized by body weight.

CONCLUSIONS

Ciprofloxacin pharmacokinetics exhibit interethnic variability, Asians exhibiting an increased bioavailability with regard to Mexicans and Caucasians. Data suggest that these differences are due to body weight.

A Physiologically-Based Pharmacokinetic Model to Describe Ciprofloxacin Pharmacokinetics Over the Entire Span of Life

Background

Physiologically-based pharmacokinetic (PBPK) modeling has received growing interest as a useful tool for the assessment of drug pharmacokinetics by continuous knowledge integration.

Objective

The objective of this study was to build a ciprofloxacin PBPK model for intravenous and oral dosing based on a comprehensive literature review, and evaluate the predictive performance towards pediatric and geriatric patients.

Methods

The aim of this report was to establish confidence in simulations of the ciprofloxacin PBPK model along the development process to facilitate reliable predictions outside of the tested adult age range towards the extremes of ages. Therefore, mean data of 69 published clinical trials were identified and integrated into the model building, simulation and verification process. The predictive performance on both ends of the age scale was assessed using individual data of 258 subjects observed in own clinical trials.

Results

Ciprofloxacin model verification demonstrated no concentration-related bias and accurate simulations for the adult age range, with only 4.8% of the mean observed data points for intravenous administration and 12.1% for oral administration being outside the simulated twofold range. Predictions towards the extremes of ages for the area under the plasma concentration–time curve (AUC) and the maximum plasma concentration (C_max) over the entire span of life revealed a reliable estimation, with only two pediatric AUC observations outside the 90% prediction interval.

Conclusion

Overall, this ciprofloxacin PBPK modeling approach demonstrated the predictive power of a thoroughly informed middle-out approach towards age groups of interest to potentially support the decision-making process.

Electronic supplementary material

The online version of this article (10.1007/s40262-018-0661-6) contains supplementary material, which is available to authorized users.

Application of a Physiologically Based Pharmacokinetic Model to Study Theophylline Metabolism and Its Interactions With Ciprofloxacin and Caffeine

Theophylline is a commonly used bronchodilator. However, due to its narrow therapeutic range, moderate elevation of serum concentration can result in adverse drug reactions (ADRs). ADRs occur because of interhuman pharmacokinetic variability and interactions with coprescribed medicines. We developed a physiologically based pharmacokinetic (PBPK) model of theophylline, caffeine, and ciprofloxacin metabolisms to: examine theophylline pharmacokinetic variability, and predict population‐level outcomes of drug–drug interactions (DDIs). A simulation‐based equation for personalized dosing of theophylline was derived. Simulations of DDI show that calculated personalized doses are safe even after cotreatment with large doses of strong inhibitors. Simulations of adult populations indicate that the elderly are most susceptible to ADRs stemming from theophylline–ciprofloxacin and theophylline–caffeine interactions. Females, especially Asians, due to their smaller average size, are more susceptible to DDI‐induced ADRs following typical dosing practices. Our simulations also show that the higher adipose and lower muscle fractions in females significantly alter the pharmacokinetics of theophylline or ciprofloxacin.

Population pharmacokinetic analysis of ciprofloxacin in the elderly patients with lower respiratory tract infections

The aims of the study were to develop a population pharmacokinetic model of ciprofloxacin (CPX) in the elderly patients and to examine the impact of patient-dependent variables on pharmacokinetic parameter values of this drug. The study was conducted in a group of 44 patients at the age of 44-96years, hospitalized due to pneumonia lobaris or bronchopneumonia. Patients received CPX at a dose of 200mg every 12h as a constant rate infusion over 0.5h. Concentrations of CPX in serum were measured by HPLC with UV detection. Population pharmacokinetic analysis revealed that CPX concentration versus time data were best described by a one-compartment model. The mean values of volume of distribution and clearance of CPX in the patients above 65years of age were 78.41±13.17L and 18.39±4.15L/h, respectively. The creatinine clearance influenced CPX clearance according to the equation: CLCPX (L/h)=8.0+0.21·CLCr, while the volume of distribution of CPX was dependent on the body weight of the patient as follows: VdCPX (L)=22.72+0.86·WT. In summary, the developed population model can be used to assess the pharmacokinetic parameters of CPX in the elderly patients and to select on the basis of these parameters and MIC values an optimal dosage regimen of this drug.

Pharmacokinetics of ciprofloxacin and its penetration into bronchial secretions of mechanically ventilated patients with chronic obstructive pulmonary disease

We evaluated the pharmacokinetic profile of ciprofloxacin and its penetration into bronchial secretions of critically ill patients with chronic obstructive pulmonary disease (COPD). Twenty-five mechanically ventilated patients with severe COPD who were suffering from an acute, infectious exacerbation were included in this prospective, open-label study. All subjects received a 1-hour intravenous infusion of 400 mg ciprofloxacin every 8 h. Serial blood and bronchial secretion samples were obtained at steady state, and concentrations were determined using high-performance liquid chromatography. The pharmacodynamic parameters that are associated with the efficacy of fluoroquinolones against Gram-negative pathogens were also calculated. The mean peak (maximum) concentration (C(max)) and trough (minimum) concentration in plasma were 5.37 ± 1.57 and 1 ± 0.53 mg/liter, respectively. Mean values for volume of distribution, clearance, half-life, and area under the curve from 0 to 24 h (AUC(0-24)) were 169.87 ± 84.11 liters, 26.96 ± 8.86 liters/h, 5.35 ± 2.21 h, and 47.41 ± 17.02 mg · h/liter, respectively. In bronchial secretions, a mean C(max) of 3.08 ± 1.21 mg/liter was achieved in 3.12 ± 1.01 h, and the penetration ratio was 1.16 ± 0.59. The target of AUC(0-24)/MIC of ≥125 was attained in all patients, in the majority of them (76%), and in none at MICs of 0.125, 0.25, and 1 μg/ml, respectively. Slightly better results were obtained for the ratio C(max)/MIC of ≥10. In conclusion, ciprofloxacin demonstrates excellent penetration into bronchial secretions. There is wide interindividual variability in its pharmacokinetic parameters in critically ill COPD patients and inadequate pharmacodynamic exposure against bacteria with MICs of ≥0.5 μg/ml.

Optimizing ciprofloxacin dosing in intensive care unit patients through the use of population pharmacokinetic-pharmacodynamic analysis and Monte Carlo simulations

OBJECTIVES

To explore different ciprofloxacin dosage regimens for the treatment of intensive care unit (ICU) patients with respect to clinical outcome and the development of bacterial resistance for the major Gram-negative pathogens.

METHODS

A population pharmacokinetic model was first developed on ciprofloxacin serum concentrations obtained in 102 ICU patients. Then, based on this model, pharmacokinetic-pharmacodynamic Monte Carlo simulations (MCSs) were carried out to explore the appropriateness of different ciprofloxacin dosage regimens in ICU patients. The defined targets were free AUC(24)/MIC ≥90 h (as a predictor of clinical outcome) and T(MSW) ≤20% (as a predictor of selecting resistance), where T(MSW) is the time spent within the mutant selection window over 24 h. Two simulation trials were conducted: Trial 1 took into account the whole MIC distribution for each causative pathogen in line with empirical antibiotherapy; Trial 2 used MIC breakpoints given by the Antibiogram Committee of the French Microbiology Society in order to treat the 'worst-case' scenario.

RESULTS

Trial 1 showed that for Pseudomonas aeruginosa and Acinetobacter baumannii, the common dosage regimens of 400 mg twice or three times a day did not achieve the desired target attainment rates (TARs) with respect to T(MSW), while suboptimal TARs were found for AUC(24)/MIC. Trial 2 showed that ≤ 18% of patients reached the target of T(MSW) ≤ 20% for MIC breakpoints of 0.5 and 1 mg/L, regardless of the administered dose.

CONCLUSIONS

Based on the mutant selection window concept, our simulations truly question the use of ciprofloxacin for the treatment of P. aeruginosa and A. baumannii infections in ICU patients due to the potential for developing resistance.

Appropriateness of Ciprofloxacin Dosing Based on a Population Pharmacokinetic Model

Purpose

Over the past two decades, the minimum inhibitory concentrations (MICs) of ciprofloxacin have been steadily increasing for gram-negative bacteria. One major reason cited for this “MIC creep” is underdosing of ciprofloxacin due to a lack of understanding of its pharmacodynamic properties. The primary objective of this study was to evaluate the frequency of underdosing of ciprofloxacin in a tertiary acute care medical center based on a population pharmacokinetic model. Secondary objectives included evaluation of appropriateness of dosing based on renal function and approved product labeling.

Methods

Seventy-six patients were included in this single-center, retrospective study. Data collection included demographic, laboratory, and microbiology data along with details on antibiotic administration. Patient-specific predicted 24-hour area under the curve/MIC (AUC24/MIC) values were estimated using a population pharmacokinetic model with a goal predicted AUC24/MIC of at least 100 and a preferred target value of 250.

Results

Only 8% of the subjects obtained a predicted AUC24/MIC higher than 250, while 34% of the subjects achieved a predicted AUC24/MIC of 100 or less. The majority of patients (79%) received a total daily intravenous-equivalent dose of 800 mg, whereas only 8% of subjects received an initial total daily intravenous-equivalent dose of 1,200 mg, which is the recommended dose for most severe infections. Overall 26% of subjects were prescribed an appropriate initial dose for their estimated renal function based on infection type and severity.

Conclusion

Ciprofloxacin for acute infection treatment was frequently underdosed based on US Food and Drug Administration–approved labeling and estimated predicted AUC24/MIC at a tertiary acute care medical center.

Influence of Sex on the Pharmacokinetics of Ciprofloxacin and Ofloxacin

The pharmacokinetics of orally administered ciprofloxacin and ofloxacin were studied in healthy volunteers to assess the influence of sex on drug bioavailability. The first group of subjects (9 males and 9 females) received a single oral dose of 200 mg ofloxacin, and the second group of volunteers included 24 subjects (12 males and 12 females) treated with a single oral dose of 100 mg ciprofloxacin. Blood samples (3 ml) were collected and investigated in this parallel design study in both groups, and ciprofloxacin and ofloxacin concentrations were determined. These experimental data, which had not been changed by any mathematical operation, were collected and used to determine the effect of sex on the pharmacokinetic profile using parametric and non-parametric tests as well as multivariate classification tools like cluster analysis (CA) and principal component analysis (PCA). The following variables demonstrated significant differences (p < 0.05) in c(0.5), c(1.5), c(2.0), c(4.0), c(10), c(12.0), c(24) and c(6.0), c(8.0), c(10.0) for ofloxacin and ciprofloxacin, respectively, using Student's t test and ANOVA. Therefore the alternative hypothesis about sex differences between males and females was accepted. The CA and PCA plot separated females from males and allowed to select subjects accounting for differences between males and females. Data on the whole pharmacokinetic profile enabled to determine subtle sex differences between males and females.

Pharmacokinetics of Intravenously Administered Levofloxacin in Men and Women

STUDY OBJECTIVE

To characterize and compare the pharmacokinetics of levofloxacin in men and women after systemic administration.

DESIGN

Prospective, open-label, parallel group pharmacokinetic study.

SETTING

University research center.

SUBJECTS

Eleven healthy men and nine healthy women stratified by body mass index.

INTERVENTION

Subjects received levofloxacin as a single 500-mg intravenous dose. Serum and urine were collected over 36 hours.

MEASUREMENTS AND MAIN RESULTS

Levofloxacin concentrations were determined by high-performance liquid chromatography with ultraviolet detection. Pharmacokinetic analysis was performed with ADAPT II software (University of Southern California, Los Angeles, CA). Median (range) body mass index was 23.2 kg/m2 (19.9-28.3 kg/m2) for men and 23.6 kg/m2 (16.0-32.4 kg/m2) for women (p = 0.67). A two-compartment model best fit the pharmacokinetic data: median (range) R2 was 0.996 (0.990-0.999). Women had a 24% greater exposure to levofloxacin, with a significantly smaller steady-state volume of distribution (p < 0.01) and a slower clearance (p < 0.01).

CONCLUSIONS

Differences exist in the disposition of levofloxacin between healthy men and women after systemic administration. Fixed intravenous doses of levofloxacin will lead to greater drug exposure in women. Thus, women may have more of an increased risk of fluoroquinolone toxicity than men, and men may need higher doses to achieve similar drug efficacy than women. Levofloxacin dosage adjustments based on sex should be considered on an individual basis.

Evolution of ciprofloxacin-resistant Staphylococcus aureus in in vitro pharmacokinetic environments

The development of novel antibacterial agents is decreasing despite increasing resistance to presently available agents among common pathogens. Insights into relationships between pharmacodynamics and resistance may provide ways to optimize the use of existing agents. The evolution of resistance was examined in two ciprofloxacin-susceptible Staphylococcus aureus strains exposed to in vitro-simulated clinical and experimental ciprofloxacin pharmacokinetic profiles for 96 h. As the average steady-state concentration (C(avg ss)) increased, the rate of killing approached a maximum, and the rate of regrowth decreased. The enrichment of subpopulations with mutations in grlA and low-level ciprofloxacin resistance also varied depending on the pharmacokinetic environment. A regimen producing values for C(avg ss) slightly above the MIC selected resistant variants with grlA mutations that did not evolve to higher levels of resistance. Clinical regimens which provided values for C(avg ss) intermediate to the MIC and mutant prevention concentration (MPC) resulted in the emergence of subpopulations with gyrA mutations and higher levels of resistance. A regimen producing values for C(avg ss) close to the MPC selected grlA mutants, but the appearance of subpopulations with higher levels of resistance was diminished. A regimen designed to maintain ciprofloxacin concentrations entirely above the MPC appeared to eradicate low-level resistant variants in the inoculum and prevent the emergence of higher levels of resistance. There was no relationship between the time that ciprofloxacin concentrations remained between the MIC and the MPC and the degree of resistance or the presence or type of ciprofloxacin-resistance mutations that appeared in grlA or gyrA. Regimens designed to eradicate low-level resistant variants in S. aureus populations may prevent the emergence of higher levels of fluoroquinolone resistance.

Sex-related differences in the pharmacokinetics of oral ciprofloxacin

The oral pharmacokinetics of ciprofloxacin were studied in healthy volunteers to assess the influence of sex on its disposition. Subjects (8 males, 7 females) received a single oral dose of ciprofloxacin 750 mg, blood and urine samples were collected, and ciprofloxacin concentrations were determined. A two-compartment open-model with two or three absorption phases, each one having a fitted independent lag time, best fit the data using a weighted least squares estimator. Univariate and multivariate regression analyses were performed to determine the influence of renal function, weight, and subject sex on the oral clearance (CL(S)/F) and apparent steady-state volume of distribution (V(ss)/F) of ciprofloxacin. Females had a median C(max) of ciprofloxacin that was 30% greater than males and a significantly smaller median (range) V(ss)/F: 81.1 (44.8-111.6) versus 170.9 (140.9-213.4), respectively (p < 0.01). In addition, females had increased exposure to ciprofloxacin, with a slower median (range) CL(S)/F of 28.3 L/h (24.5-33.4) compared to 44.4 L/h (41.4-53.7) for males (p < 0.01). Regression analyses revealed that subject sex was the only significant predictor of CL(S)/F (p < 0.001), but both body weight (p = 0.04) and subject sex (p < 0.005) were significant predictors of V(ss)/F. Fixed oral doses of ciprofloxacin will lead to higher maximum concentration and total drug exposure in females compared to males and do not appear to be solely related to weight-based differences.

Human variability in the renal elimination of foreign compounds and renal excretion-related uncertainty factors for risk assessment

Renal excretion is an important route of elimination for xenobiotics and three processes determine the renal clearance of a compound [glomerular filtration (about 120 ml/min), active renal tubular secretion (>120 ml/min) and passive reabsorption (<120 ml/min)]. Human variability in kinetics has been quantified using a database of 15 compounds excreted extensively by the kidney (>60% of a dose) to develop renal-excretion related uncertainty factors for the risk assessment of environmental contaminants handled via this route. Data were analysed from published pharmacokinetic studies (after oral and intravenous dosing) in healthy adults and other subgroups using parameters relating primarily to chronic exposure [renal and total clearances, area under the plasma concentration time-curve (AUC)] and acute exposure (Cmax). Interindividual variability in kinetics was low for both routes of exposure, with coefficients of variation of 21% (oral) and 24% (intravenous) that were largely independent of the renal processes involved. Renal-excretion related uncertainty factors were below the default kinetic uncertainty factor of 3.16 for most subgroups analysed with the exception of the elderly (oral data) and neonates (intravenous data) for whom renal excretion-related factors of 4.2 and 3.2 would be required to cover up to 99% of these subgroups respectively.

Comparative in vitro activity and pharmacodynamics of five fluoroquinolones against clinical isolates of Streptococcus pneumoniae

STUDY OBJECTIVE

To compare in vitro activity and pharmacodynamics of five fluoroquinolones against clinical isolates of Streptococcus pneumoniae.

DESIGN

In vitro analysis.

SETTING

University research laboratory.

INTERVENTION

Minimum inhibitory concentrations (MICs) were determined for penicillin and five fluoroquinolones by E test for 201 S. pneumoniae isolates. Serum concentration-time profiles were simulated for the following regimens: ciprofloxacin 750 mg orally every 12 hours and 400 mg intravenously every 8 hours; levofloxacin 500 mg orally and intravenously every 24 hours; trovafloxacin 200 mg orally and intravenously every 24 hours; gatifloxacin 400 mg orally and intravenously every 24 hours; and clinafloxacin 200 mg orally and intravenously every 12 hours.

MEASUREMENTS AND MAIN RESULTS

Free 24-hour areas under the serum concentration-time curves (AUC0-24) were calculated using the trapezoidal rule, and the average AUC0-24:MIC ratio was calculated for each regimen. Differences in ratios among agents were determined by analysis of variance (Scheffe post hoc test, p < 0.05). For intravenous dosing, the average AUC0-24:MIC for gatifloxacin, clinafloxacin, trovafloxacin, ciprofloxacin, and levofloxacin was 146, 142, 122, 71, and 61, respectively. For both oral and intravenous regimens, gatifloxacin and clinafloxacin ratios were significantly greater than those for trovafloxacin, levofloxacin, and ciprofloxacin (p < or = 0.007). Ratios for trovafloxacin were significantly greater than those for levofloxacin and ciprofloxacin (p < 0.0001), and levofloxacin and ciprofloxacin ratios were not significantly different from each other.

CONCLUSION

Gatifloxacin and clinafloxacin achieve significantly higher AUC0-24:MIC ratios for S. pneumoniae than trovafloxacin, levofloxacin, and ciprofloxacin. Large comparative studies are necessary to determine the clinical significance of these findings.

Ciprofloxacin disposition in elderly patients with LRTI being treated with sequential therapy (200 mg intravenously twice daily followed by 500 mg per os twice daily): comparative pharmacokinetics and the role of therapeutic drug monitoring

Ciprofloxacin is a fluoroquinolone antibiotic effective in the treatment of lower respiratory tract infections (LRTI). The aim of this study was to assess the pharmacokinetic appropriateness of a standard switch i.v./os regimen of ciprofloxacin (200 mg i.v. bid for 3 to 5 days followed by 500 mg os bid for 7 to 10 days) frequently used in routine clinical practice in the treatment of elderly patients with mild to moderate LRTI. The pharmacokinetic study was performed on a cohort of 17 elderly inpatients. Blood samples were collected in steady state conditions at appropriate intervals. Ciprofloxacin serum concentrations were analyzed using an HPLC method and pharmacokinetic parameters were estimated using the WinNonlin software package. The pharmacokinetic data were at least partially different from those obtained by other authors in elderly patients (lower Cmax after i.v. administration and higher CL both after i.v. and oral administration). Cmax after a 1-hour 200-mg infusion were similar to those observed during the 500 mg bid peroral regimen (2.1 +/- 0.9 mg/L vs 2.6 +/- 1.0 mg/L; p = 0.054). The absolute oral bioavailability (84.1%) allowed a total body exposure 2.1-fold greater after 500 mg bid oral administration than after 200 mg bid i.v. administration (AUC(0-tau) 11.4 +/- 4.3 mg/L x h vs 5.5 +/- 1.8 mg/L x h). The results show that in malabsorption-free elderly patients a regimen of 500 mg os bid may be considered a valid therapeutic approach from the beginning of therapy for mild to moderate LRTI caused by sensitive microorganisms (MIC < 0.1 mg/L). In fact, because the peak serum level to MIC ratio (Cmax/MIC) and the area under the inhibitory serum concentration-time curve (AUIC24 = AUC24h/MIC) are actually considered major pharmacodynamic determinants for the outcome of treatment with fluoroquinolones, this regimen could guarantee both a better pharmacokinetic exposure than the 200 mg i.v. bid regimen and a cost-effective treatment of LRTI. However, because of the great pharmacokinetic interindividual variability observed a normalized dosage per kg (3 mg/kg/12h i.v. and 8 mg/kg/12h os) should be considered, especially for body weight >90 kg and, whenever possible, TDM of AUC(0-tau) or at least of Cmax should be performed to individualize therapy in this subpopulation.

Interchangeability of 400-mg intravenous and oral gatifloxacin in healthy adults

STUDY OBJECTIVE

To evaluate the interchangeability of 400-mg intravenous and oral doses of gatifloxacin.

DESIGN

Randomized, open-label, crossover study.

SETTING

GFI Pharmaceutical Services, Inc., Evansville, Indiana, USA.

SUBJECTS

Twenty-four healthy men and women (12 of each gender), aged 18-42 years.

INTERVENTIONS

Subjects received single doses of gatifloxacin 400 mg either by intravenous infusion over 1 hour or a 400-mg tablet orally with 240 ml of water, each dose separated by a 1-week washout. Plasma concentrations of gatifloxacin were determined by a validated high-performance liquid chromatography; pharmacokinetic parameters were calculated using noncompartmental methods. Distributions of pharmacokinetic parameter values were summarized by route of administration and gender. Effects of treatment on pharmacokinetic parameter values of gatifloxacin were assessed by an analysis of variance model suitable for a two-way, two-treatment, crossover design. Clinical evaluations were performed to assess drug safety and tolerability.

MEASUREMENTS AND MAIN RESULTS

Intravenous and oral gatifloxacin were considered interchangeable because both routes were bioequivalent with respect to area under the curve (AUC; 90% confidence interval for the ratio of geometric means contained within 0.8-1.25). The plasma concentration-time profile after intravenous administration was similar and comparable in extent of exposure (AUC0-infinity) with that for the oral route when equal doses were administered to men and women. The absolute bioavailability of gatifloxacin after oral administration was 96%, consistent with bioequivalence of the 400-mg intravenous and oral doses. The drug was well tolerated; the frequency of adverse events was comparable after intravenous and oral administration.

CONCLUSION

Intravenous and tablet formulations of gatifloxacin are bioequivalent and therefore interchangeable. This permits greater flexibility in choosing oral or parenteral therapy, with the possibility of avoiding hospitalization based on knowledge that oral administration will deliver therapeutic exposure to the drug, or abbreviating hospital stay due to ease of switching from intravenous to oral therapy.

A dose-escalation study of the safety, tolerability, and pharmacokinetics of intravenous gatifloxacin in healthy adult men

STUDY OBJECTIVES

To examine single- and multiple-dose safety, tolerability, and pharmacokinetics of gatifloxacin administered as daily 1-hour intravenous infusions for 14 days, and to determine the effect of gatifloxacin on glucose tolerance, pancreatic beta-cell function, and electrocardiogram (ECG).

DESIGN

Randomized, double-blind, placebo-controlled, ascending-dose study.

SETTING

Bristol-Myers Squibb, Clinical Pharmacology Unit, Princeton, New Jersey, USA.

PATIENTS

Forty healthy male subjects, eight in each of five groups, were enrolled to receive sequential doses of gatifloxacin: 200 mg (10 mg/ml), 200 mg (1 mg/ml), and 400, 600, and 800 mg (2 mg/ml); six subjects per group received active drug and two received placebo.

INTERVENTIONS

A single dose of the drug was administered as an intravenous infusion over 1 hour. After a 72-hour washout period, the drug was administered once/day for 14 days by 1-hour intravenous infusion. Physical examinations, ECGs, spirometry, and clinical laboratory tests, including glucose tolerance test (GTT) and assessment of glucose homeostasis, were performed before treatment and on selected dosing days. A safety evaluation was performed before escalating doses. No intrasubject dose escalation was permitted.

MEASUREMENTS AND MAIN RESULTS

The pharmacokinetics of gatifloxacin were dose linear and time independent after intravenous administration over the range of 200-800 mg. After daily repeated administration, a predictable, modest accumulation was observed; steady state was reached by the third dose. Approximately 80% of the dose was recovered as unchanged drug in urine. Mean changes (before the first dose to the last dose) after oral GTT and in fasting serum glucose, insulin, and C-peptide concentrations were comparable among the gatifloxacin and placebo treatment groups. A mild, transient decrease in serum glucose was associated with the end of the 1-hour infusion of gatifloxacin. No clinically important changes in QTc interval or spirometry occurred. The most frequent treatment-related adverse effects were local intravenous site reactions, which were associated with dose and/or concentration of intravenous solution.

CONCLUSION

Gatifloxacin was safe and well tolerated at intravenous doses of up to 800 mg/day for 14 days. Gatifloxacin pharmacokinetics were linear and time independent.

Age and gender effects on the pharmacokinetics of gatifloxacin

STUDY OBJECTIVE

To compare the pharmacokinetics and safety of gatifloxacin in elderly (> or = 65 yrs) and young (18-45 yrs) men and women.

DESIGN

Open-label, parallel-group, single-dose study.

SETTING

GFI Pharmaceutical Services Inc., Evansville, Indiana, USA.

SUBJECTS

Forty-eight healthy subjects in four groups of 12 each.

INTERVENTIONS

Subjects received single oral doses of gatifloxacin 400 mg. Serial blood and urine samples were collected for 96 hours after dosing to determine drug concentrations.

MEASUREMENTS AND MAIN RESULTS

Age and gender had moderate effects on the pharmacokinetics of gatifloxacin. Elderly women had a 21% higher geometric mean peak plasma concentration (Cmax) and a 32% higher area under the plasma concentration-time curve (AUC0-infinity) than young women. Adjustment for creatinine clearance had only a slight effect on Cmax but reduced the estimated effect of age on AUC0-infinity in women from a 32% increase to a 15% increase. Gender effects on pharmacokinetic values were noted among elderly subjects only. Geometric means for Cmax and AUC0-infinity were 21% and 33% higher, respectively, for elderly women and elderly men. Adjustment for body weight reduced these differences to 11% and 20%, respectively.

CONCLUSION

The effects of age on gatifloxacin pharmacokinetic values were largely attributed to declining renal function, whereas those of gender were largely attributed to differences in body weight. These modest age- and gender-related differences do not warrant dosage adjustment.

Comparison of the fluoroquinolones based on pharmacokinetic and pharmacodynamic parameters

Assessment of pharmacodynamic activity from standard in vitro minimum inhibitory concentrations (MICs) alone is insufficient to predict in vivo potency. Achievable serum and tissue concentrations as well as pharmacokinetic characteristics must be considered. When pharmacokinetic and pharmacodynamic values are combined, the area under the inhibitory curve (AUIC) and peak concentration:MIC ratio predict clinical cure for fluoroquinolones. Clinical data and animal models indicate that a peak:MIC of 10:1 and above and an AUIC of 125 and above are predictive of a clinical cure for this class of antimicrobials against gram-negative organisms. The values may be used to compare and contrast fluoroquinolones to determine which would be best for treating a specific microorganism. Pharmacodynamic data also can be used to design regimens that minimize the risk of suboptimal drug levels. Ensuring the optimal fluoroquinolone dosage based on pharmacodynamic principles would diminish the emergence of resistant organisms and prevent treatment failures.

Effect of gender on the pharmacokinetics of ofloxacin

STUDY OBJECTIVES

To assess the influence of gender on the pharmacokinetics of ofloxacin.

DESIGN

Open-label study.

SETTING

Academic medical center.

PATIENTS

Five healthy men and seven healthy women volunteers.

INTERVENTIONS

Subjects received a single oral dose of ofloxacin 400 mg, and serial blood samples were collected for 24 hours. Plasma concentrations of ofloxacin were determined by high-performance liquid chromatography and pharmacokinetic parameters were determined. Statistical comparisons between genders were made with the Wilcoxon rank sum test.

MEASUREMENTS AND MAIN RESULTS

Median volume of distribution at steady state/systemic bioavailability (V(ss)/F) was significantly smaller in women than in men, although when normalized for total body weight there were no differences. Except for terminal elimination half-life, which was 10% shorter in women, no other pharmacokinetic values were significantly different between genders. Median peak concentrations, although not statistically different, were 28% higher in women.

CONCLUSION

Ofloxacin V(ss)/F values were smaller in women than in men, explained by gender-related differences in weight.

Pharmacokinetic profiles of high-dose intravenous ciprofloxacin in severe sepsis. The Baragwanath Ciprofloxacin Study Group

The pharmacokinetics of 400 mg of ciprofloxacin given intravenously (i.v.) every 8 h (q8h) in severely septic adults was documented in a multidisciplinary, tertiary referral intensive care unit (ICU). Sixteen evaluable patients (three pharmacokinetic profiles) without renal dysfunction and with severe sepsis were studied. Ciprofloxacin at a dosage of 400 mg given i.v. q8h was administered over 1 h. Plasma samples for assay (high-pressure liquid chromatography) were taken at timed intervals (preinfusion, at the end of infusion, and at 1, 2, 3, 5, and 7 h postinfusion) for first-dose kinetics (day 0 [D0]), D2, and between D6 and D8. All pharmacokinetic variables were calculated by noncompartmental methods. Standard intensive care was provided. Peak ciprofloxacin concentrations were as follows: D0, 6. 01 +/- 1.93 mg/liter; D2, 6.68 +/- 2.01 mg/liter; and D6 to D8 6.45 +/- 1.54 mg/liter. Trough levels were as follows: D0, 0.6 +/- 0.5 mg/liter; D2, 0.7 +/- 0.4 mg/liter; and D6 to D8 0.6 +/- 0.4 mg/liter. The areas under the concentration curves (8 h) were as follows: D0, 13.3 +/- 3.8 mg . h/liter; D2, 16.8 +/- 5.4 mg . h/liter; and D6 to D8, 15.5 +/- 4.7 mg . h/liter. No drug-related serious adverse events occurred. For 17 of 18 patients enrolled in the study, the causative organisms were susceptible to ciprofloxacin. One patient developed renal failure (non-drug related) after the administration of three doses of ciprofloxacin. One patient was infected with ciprofloxacin-resistant organisms on enrollment. Nine of 16 evaluable patients had clinical cures, and 8 had bacteriological cures. One patient developed a ciprofloxacin-resistant superinfection. In two patients the clinical course was indeterminate. Two bacteriological failures occurred. We conclude that in critically ill adults ciprofloxacin at a dosage of 400 mg given i.v. q8h is safe. Its pharmacokinetic profile provides bactericidal activity against most organisms encountered in an ICU. Except for some initial accumulation on D2, no further accumulation occurred in patients without renal failure. Ciprofloxacin should be administered i.v. at a dosage of 400 mg q8h for severe sepsis.

Analysis of fluoroquinolones in biological fluids by high-performance liquid chromatography

High-performance liquid chromatographic methods for the analysis of fluoroquinolones in biological fluids are reviewed. In particular, sample preparation and handling procedures, chromatographic conditions, and detection methods are discussed. A summary of published high-performance liquid chromatographic assays for individual fluoroquinolones is included.

Absence of age and gender effects on the pharmacokinetics of a single 500-milligram oral dose of levofloxacin in healthy subjects

The influence of age and gender on the pharmacokinetics of levofloxacin in healthy subjects receiving a single oral 500-mg dose of levofloxacin was investigated in this parallel design study. Six young males (aged 18 to 40 years), six elderly males (aged > or = 65 years), six young females (aged 18 to 40 years), and six elderly females (aged > or = 65 years) were enrolled and completed the study. The study reveals that the bioavailability (rate and extent) of levofloxacin was not affected by either age or gender. In both age (young and elderly) and gender (male and female) groups of subjects, peak concentrations in plasma were reached at approximately 1.5 h after dosing; renal clearance of levofloxacin accounted for approximately 77% of total body clearance, and approximately 76% of the administered dose was recovered unchanged in urine over the 36 h of collection. The apparent differences in the calculated pharmacokinetic parameters for levofloxacin between the age groups (young versus elderly) and between the gender groups (males versus females) could be explained by differences in renal function among the subjects. A single dose of 500 mg of levofloxacin administered orally to both young and old, male and female healthy subjects was found to be safe and well tolerated. As the differences in levofloxacin kinetics between the young and the elderly or the males and the females are limited and are mainly related to the renal function of the subjects, dose adjustment based on age or gender alone is not necessary.

Comparative study of pharmacokinetics of two new fluoroquinolones, balofloxacin and grepafloxacin, in elderly subjects

Comparative pharmacokinetics and tolerability were studied in healthy elderly volunteers for two new fluoroquinolones, balofloxacin (Q-35) and grepafloxacin (OPC-17116), the main excretion routes being the renal and hepatic routes, respectively. Both agents were well tolerated in elderly subjects. In comparison with previously reported data from healthy younger adults, the absorption of balofloxacin was slightly delayed and urinary excretion was delayed and diminished. As a significant linear correlation was observed between renal clearance of balofloxacin and creatinine clearance, the delayed and diminished urinary recovery was attributed to the reduced renal function of the elderly subjects enrolled in the study. The absorption of grepafloxacin was also delayed, and the maximum plasma drug concentration and area under the plasma drug concentration-time curve were increased in the elderly by 31 and 48%, respectively, over those in younger adults on the basis of dose normalized to body weight. The plasma terminal elimination half-life and urinary recovery remained unchanged. Decreases in distribution volume and total body clearance in the elderly were considered to be the primary factors contributing to these differences.

Lack of gender effect on ciprofloxacin pharmacokinetics in humans

The influence of gender on the single-dose pharmacokinetics of oral ciprofloxacin was investigated in a parallel designed study in 24 healthy, fasted volunteers. Ciprofloxacin (750 mg) was administered as a single tablet to 10 women and 14 men. All subjects were Caucasian except for one African American man. The mean age was 36 years for men and 33 years for women. Women received the drug during the nonmenstruating phase of their menstrual cycle and were not taking oral contraceptives at the time of the study. Plasma samples were collected over a 24 h period and assayed by h.p.l.c. The 90% confidence limits for the ratio of geometric means of maximum plasma concentration, apparent terminal half-life, and apparent oral plasma clearance (corrected for body weight) were between 80% and 125%, and those for the area under the plasma concentration-time curve were 71% and 101%. Results suggest that there were no gender-related differences in ciprofloxacin pharmacokinetics in men and nonmenstruating women of middle age.

Ciprofloxacin. An updated review of its pharmacology, therapeutic efficacy and tolerability

Ciprofloxacin is a broad spectrum fluoroquinolone antibacterial agent. Since its introduction in the 1980s, most Gram-negative bacteria have remained highly susceptible to this agent in vitro; Gram-positive bacteria are generally susceptible or moderately susceptible. Ciprofloxacin attains therapeutic concentrations in most tissues and body fluids. The results of clinical trials with ciprofloxacin have confirmed its clinical efficacy and low potential for adverse effects. Ciprofloxacin is effective in the treatment of a wide variety of infections, particularly those caused by Gram-negative pathogens. These include complicated urinary tract infections, sexually transmitted diseases (gonorrhoea and chancroid), skin and bone infections, gastrointestinal infections caused by multiresistant organisms, lower respiratory tract infections (including those in patients with cystic fibrosis), febrile neutropenia (combined with an agent which possesses good activity against Gram-positive bacteria), intra-abdominal infections (combined with an antianaerobic agent) and malignant external otitis. Ciprofloxacin should not be considered a first-line empirical therapy for respiratory tract infections if penicillin-susceptible Streptococcus pneumoniae is the primary pathogen; however, it is an appropriate treatment option in patients with mixed infections (where S. pneumoniae may or may not be present) or in patients with predisposing factors for Gram-negative infections. Clinically important drug interactions involving ciprofloxacin are well documented and avoidable with conscientious prescribing. Recommended dosage adjustments in patients with impaired renal function vary between countries; major adjustments are not required until the estimated creatinine clearance is < 30 ml/min/1.73m2 (or when the serum creatinine level is > or = 2 mg/dl). Ciprofloxacin is one of the few broad spectrum antibacterials available in both intravenous and oral formulations. In this respect, it offers the potential for cost savings with sequential intravenous and oral therapy in appropriately selected patients and may allow early discharge from hospital in some instances. In conclusion, ciprofloxacin has retained its excellent activity against most Gram-negative bacteria, and fulfilled its potential as an important antibacterial drug in the treatment of a wide range of infections. Rational prescribing will help to ensure the continued clinical usefulness of this valuable antimicrobial drug.

Pharmacokinetics of oral fleroxacin in male and premenopausal female volunteers

The pharmacokinetics of oral fleroxacin were compared in men and premenopausal women. The total volume of distribution of the drug was significantly smaller in women in the single-dose trial. No difference in other pharmacokinetic parameters was noted. Since adverse events appear to occur in women more commonly than in men, dose-response studies of fleroxacin in women may be appropriate.