Urinary bactericidal activity of extended-release ciprofloxacin (1,000 milligrams) versus levofloxacin (500 milligrams) in healthy volunteers receiving a single oral dose

Ex Vivo Urinary Bactericidal Activity and Urinary Pharmacodynamics of Fosfomycin after Two Repeated Dosing Regimens of Oral Fosfomycin Tromethamine in Healthy Adult Subjects

The ex vivo bactericidal activity and pharmacodynamics of fosfomycin in urine were evaluated in 18 healthy subjects. Subjects received 3 g every other day (QOD) for 3 doses and then every day (QD) for 7 doses or vice versa. Serial urine samples were collected before and up to 24 h after dosing on days 1 and 5. Eight bacterial strains with various genotypic and phenotypic susceptibilities to fosfomycin were used for all experiments (5 Escherichia coli, 2 Klebsiella pneumoniae, and 1 Proteus mirabilis). MICs were performed via agar dilution. Urinary bactericidal titers (UBTs) were performed via modified Schlichter test using participant's drug-free urine as the diluent. Urinary time-kill analyses were performed on pooled 24-h urine aliquots from days 1 and 5. All experiments were performed in triplicate with and without the addition of 25 mg/liter of glucose-6-phosphate (G6P). Mean 24-h urine concentrations of fosfomycin ranged from 324.7 to 434.6 mg/liter regardless of study day or dosing regimen. The urinary antibacterial activity of fosfomycin was also similar across study days and dosing regimens. UBT values did not correlate with MICs determined in the presence of G6P. Fosfomycin was reliably bactericidal in urine only against the 5 E. coli strains, regardless of genotype or MIC value. Together, these data do not support the use of oral fosfomycin tromethamine for pathogens other than E. coli or at a dosing frequency higher than QOD. Fosfomycin MICs determined in the presence of G6P may not accurately reflect the in vivo activity given the lack of G6P in human urine. (This study has been registered at ClinicalTrials.gov under identifier NCT02570074.).

Assessment of urinary pharmacokinetics and pharmacodynamics of orbifloxacin in healthy dogs with ex vivo modelling

PURPOSE

The aim of this study was to investigate the urinary pharmacokinetics (PK) of orbifloxacin (OBFX) administered at 5 mg kg-1 in six healthy dogs. A further aim was to use an ex vivo model to evaluate the urinary PK and pharmacodynamics (PD) of OBFX to determine its urinary bactericidal titre (UBT), which represents the maximal dilution of urine allowing bactericidal activity.

METHODOLOGY

Fourteen urinary tract infection (UTI) pathogenic strains of five bacterial species (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis and Staphylococcuspseudintermedius) were used. Urine samples were obtained every 4 h for the first 24 h after OBFX administration, for measurement of urine drug concentration and UBT.Results/Key findings. The urine OBFX concentration peaked at 0-4, 4-8 or 4-8 h after administration, with a maximum concentration of 383±171 µg ml-1. Overall, the fluctuation in median UBT closely correlated with that of the mean urine OBFX concentration. In addition, the median areas under the UBT-time curves (AUBTs) were significantly inversely correlated with the MICs for OBFX in the tested strains (P<0.01). Notably, median UBTs and AUBTs were extremely low (0-0.5 and 2-5, respectively) in OBFX-resistant E. coli strains with MIC ≥8 µg ml-1.

CONCLUSION

The fluctuation of UBTs closely correlated with that of urine concentration, and UBT values depended on the susceptibility of the bacterial strains to OBFX. We believe that ex vivo modelling to determine UBTs is useful to evaluate the urinary PK/PD of antimicrobials indicated for UTIs in dogs.

Pharmacodynamics of Finafloxacin, Ciprofloxacin, and Levofloxacin in Serum and Urine against TEM- and SHV-Type Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae Isolates from Patients with Urinary Tract Infections

The pharmacodynamics of finafloxacin, ciprofloxacin, and levofloxacin against extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae isolates were compared. Since quinolones lose activity in acidic media, and particularly in urine, their activities were tested in parallel under conventional conditions and in acidic artificial urine. For this purpose, TEM- and SHV-type ESBL-producing Escherichia coli and Klebsiella pneumoniae strains and their wild-type counterparts were exposed in a modified Grasso model to simulated concentrations of drugs in serum and urine following oral doses of either finafloxacin at 800 mg once a day (q.d.), immediate-release ciprofloxacin at 500 mg twice a day (b.i.d.), extended-release ciprofloxacin at 1,000 mg q.d., or levofloxacin at 500 or 750 mg q.d. The concentrations of the drugs in urine were fitted by compartmental modeling. Bacteria were cultivated in Mueller-Hinton broth (MHB) at pH 7.2 or 5.8 or in artificial urine at pH 5.8. Bacteria were counted every 2 h until 10 h and at 24 h; the areas under the bacterial-count-versus-time curves were calculated. It was found that finafloxacin eliminated all strains within 2 h under all the conditions studied. At all doses studied, ciprofloxacin and levofloxacin were highly active against wild-type strains in MHB at pH 7.2 but lost activity in MHB, and particularly in urine, at pH 5.8. Viable counts of ESBL producers were reduced for 6 to 8 h by 3 log10 titers, but the bacteria regrew thereafter. Ciprofloxacin and levofloxacin were almost inactive against the SHV producer grown in artificial urine. We conclude that pharmacodynamic models using artificial urine may mirror the physiology of urinary tract infections more closely than those using conventional media. In contrast to ciprofloxacin and levofloxacin, finafloxacin gained activity in this model at an acidic pH, maintained activity in artificial urine, and was active against TEM and SHV producers.

Effect of urinary excretion on the bladder tissue distribution of fluoroquinolones in rats

The purpose of this study was to evaluate which of blood or urine has the greater effect on bladder tissue concentrations of fluoroquinolones important for the treatment of urinary tract infections by measuring concentrations of fluoroquinolones in the vesical tissue (chemically and immunohistochemically) and intravesical space (chemically). Thirty-minute incubation of isolated rat bladders with fluoroquinolones showed only a 1.9-fold difference in transferability among norfloxacin, levofloxacin, ciprofloxacin and sparfloxacin. Intravesical instillation of norfloxacin and sparfloxacin in rats yielded similar vesical tissue distributions. Thus, there were no large differences in vesical tissue transfer among the four fluoroquinolones. The bladder tissue/plasma concentration ratios of norfloxacin (high urinary excretion-type) and sparfloxacin (low urinary excretion-type) at 1 h after a single oral dose (10 mg/kg) to rats were 15.4 and 1.3, respectively. The bladder tissue/plasma concentration ratios of norfloxacin after an intravenous injection (10 mg/kg) to ureter-catheterized and sham-operated rats were 1.36 and 57.8. Thus the bladder tissue distribution was significantly higher in the urine-exposed bladder. Immunohistochemical examination of the vesical tissue localization of norfloxacin in rats given a single intravenous dose revealed the presence of the drug-positive image in the cytoplasm of surface layer cells (both in umbrella and cover cells) of the bladder transitional epithelium. In conclusion, the results suggest that norfloxacin and other fluoroquinolones are excreted into urine and then transferred to the surface layer of the bladder transitional epithelium. Therefore, the urine levels have a greater effect on the vesicle tissue distribution of fluoroquinolones than the plasma levels in rats.

Urinary concentrations and antibacterial activities of nitroxoline at 250 milligrams versus trimethoprim at 200 milligrams against uropathogens in healthy volunteers

Because of the increasing bacterial resistance of uropathogens against standard antibiotics, such as trimethoprim (TMP), older antimicrobial drugs, such as nitroxoline (NTX), should be reevaluated. This randomized crossover study investigated the urinary concentrations of parent drugs and their metabolites and their antibacterial activities (urinary inhibitory titers [UITs] and urinary bactericidal titers [UBTs]) against uropathogens at three different urinary pH values within 24 h in six healthy volunteers after a single oral dose of NTX at 250 mg versus TMP at 200 mg. In three additional volunteers, urinary bactericidal kinetics (UBK) were studied after oral administration of NTX at 250 mg three times a day. The mean urinary concentrations of NTX and NTX sulfate in 24 h were 0.012 to 0.507 mg/liter and 0.28 to 27.83 mg/liter, respectively. The mean urinary concentrations of TMP were 18.79 to 41.59 mg/liter. The antibacterial activity of NTX was higher in acidic urine than in alkaline urine, and that of TMP was higher in alkaline urine than in acidic urine. The UITs and UBTs of NTX were generally lower than those of TMP except for a TMP-resistant Escherichia coli strain, for which NTX showed higher UITs/UBTs than did TMP. UBK showed mainly bacteriostatic activity of NTX in urine. NTX exhibits mainly bacteriostatic activity and TMP also shows bactericidal activity in urine against susceptible strains. NTX is a more active antibacterial in acidic urine, and TMP is more active in alkaline urine. The cumulative effects of multiple doses or inhibition of bacterial adherence could not be evaluated. (This study has been registered at EudraCT under registration no. 2009-015631-32.).

Oral levofloxacin 500 mg once daily in the treatment of chronic bacterial prostatitis

The aim of this study was to confirm further the efficacy and safety of levofloxacin in patients with chronic bacterial prostatitis (CBP) in Europe. Men with a history of CBP were enrolled in a prospective, multinational (eight countries), open-label study to receive levofloxacin 500 mg once daily per os (p.o.) for 28 days. Patients were followed for 6 months. A total of 117 patients were treated. Gram-negative bacteria were identified in 57/106 patients (mainly Escherichia coli (n=37)) and Gram-positive bacteria in 60/106 patients (mainly Enterococcus faecalis (n=18) and Staphylococcus epidermidis (n=14)). Among the intention-to-treat population (n=116), the clinical success rate (cured and improved patients) was 92% (95% confidence interval (CI) 84.8-96.5%), 77.4% (95% CI 68.2-84.9%), 66.0% (95% CI 56.2-75.0%) and 61.9% (95% CI 51.9-71.2%) at 5-12 days, 1 month, 3 months and 6 months post treatment. The microbiological eradication rate according to evaluation scheme II was 82/98 (83.7%, 95% CI 74.8-90.4%) at 1 month and the continued eradication rate was 52/57 (91.2%, 95% CI 80.7-97.1%) at 6 months post treatment. Comparison of four classification schemes showed similar results. Thus, the present investigation is suitably comparable in methods and results to previous studies. Levofloxacin was well tolerated. Four patients (3.4%) discontinued therapy due to adverse events and 15 patients (12.8%) experienced at least one adverse event. Levofloxacin 500 mg p.o. once daily for 28 days is clinically and microbiologically effective in the treatment of CBP caused by susceptible pathogens and is well tolerated.

Organic anion transporter 3 (oat3/slc22a8) interacts with carboxyfluoroquinolones, and deletion increases systemic exposure to ciprofloxacin

Carboxyfluoroquinolones, such as ciprofloxacin, are used for the treatment of numerous infectious diseases. Renal secretion is a major determinant of their systemic and urinary concentration, but the specific transporters involved are virtually unknown. In vivo studies implicate the organic anion transporter (OAT) family as a pivotal component of carboxyfluoroquinolone renal secretion. Therefore, this study identified the specific renal basolateral OAT(s) involved, thereby highlighting potential sources of carboxyfluoroquinolone-drug interactions and variable efficacy. Two heterologous expression systems, Xenopus laevis oocytes and cell monolayers, were used to determine the roles of murine and human renal basolateral mOat1/hOAT1 and mOat3/hOAT3. Ciprofloxacin was transported by mOat3 in both systems (K(m) value, 70 +/- 6 microM) and demonstrated no interaction with mOat1 or hOAT1. Furthermore, ciprofloxacin, norfloxacin, ofloxacin, and gatifloxacin exhibited concentration-dependent inhibition of transport on mOat3 in cells with inhibition constants of 198 +/- 39, 558 +/- 75, 745 +/- 165, and 941 +/- 232 microM, respectively. Ciprofloxacin and gatifloxacin also inhibited hOAT3. Thereafter, in vivo elimination of ciprofloxacin was assessed in wild-type and Oat3 null mice [Oat3-/-]. Oat3-/- mice exhibited significantly elevated plasma levels of ciprofloxacin at clinically relevant concentrations (P < 0.05, male mice; P < 0.01, female mice). Oat3-/- mice also demonstrated a reduced volume of distribution (27%, P < 0.01, male mice; 14%, P < 0.01, female mice) and increased area under the concentration-time curve (25%, P < 0.05, male mice; 33%, P < 0.01, female mice). Female Oat3-/- mice had a 35% (P < 0.01) reduction in total clearance of ciprofloxacin relative to wild type. In addition, putative ciprofloxacin metabolites were significantly elevated in Oat3-/- mice. The present findings indicate that polymorphisms of and drug interactions on hOAT3 may influence carboxyfluoroquinolone efficacy, especially in urinary tract infections.

Short-term therapy for urinary tract infection: success and failure

The pharmacokinetic characteristics of some antimicrobials lead to very high urinary concentrations. This, together with the superficial nature of bladder infection and effective voiding, supports the use of short-course antimicrobial therapy for treatment of acute uncomplicated cystitis. Even a single dose is effective for >90% of episodes for some antimicrobials. Short-course therapy for 3 days is, however, the current accepted standard of therapy for acute uncomplicated urinary tract infection (UTI). Complicated UTI is a more diverse clinical entity. For individuals with some underlying abnormalities, including incomplete drainage of urine or renal failure, short-course therapy is never appropriate. However, some individuals with complicated UTI have adequate urinary emptying, infection limited to the bladder and normal renal function. For these persons, the same principles that promote effective short-course therapy for treatment of acute uncomplicated UTI should also apply. However, clinical studies reported to date do not support the use of short-course therapy for treatment of complicated cystitis. Further studies enrolling well-characterised patient populations with consistent clinical presentations are required to define the role, if any, of short-course therapy in complicated UTI.

Optimal management of urosepsis from the urological perspective

Urosepsis in adults comprises approximately 25% of all sepsis cases and in most cases is due to complicated urinary tract infections (UTIs). In this paper we review the optimal management of urosepsis from the urological point of view. Urosepsis is often due to obstructed uropathy of the upper or lower urinary tract. The treatment of urosepsis comprises four major aspects: 1. Early goal-directed therapy; 2. Optimal pharmacodynamic exposure to antimicrobials both in blood and in the urinary tract; 3. Control of complicating factors in the urinary tract; 4. Specific sepsis therapy. Early tissue oxygenation, appropriate initial antibiotic therapy and rapid identification and control of the septic focus in the urinary tract are critical steps in the successful management of a patient with severe urosepsis. To achieve this goal an optimal interdisciplinary approach encompassing the emergency unit, urological specialties and intensive-care medicine is necessary.

Pharmacokinetic Characteristics of Antimicrobials and Optimal Treatment of Urosepsis

Urosepsis accounts for approximately 25% of all sepsis cases and may develop from a community-acquired or nosocomial urinary tract infection (UTI). Nevertheless, the underlying UTI is almost exclusively a complicated one with involvement of the parenchymatous urogenital organs (e.g. kidneys, prostate) and mostly associated with any kind of obstructive uropathy. If urosepsis originates from a nosocomial infection, a broad spectrum of Gram-negative and Gram-positive pathogens have to be expected, which are often multiresistant. In urosepsis, as in other types of sepsis, the severity of sepsis depends mostly upon the host response. The treatment of urosepsis follows the generally accepted rules of the 'Surviving Sepsis' campaign guidelines. Early normalisation of blood pressure and early adequate empirical antibacterial therapy with optimised dosing are equally important to meet the requirements of early goal-directed therapy. In most cases of urosepsis, early control of the infectious focus is possible and as important. Optimal supportive measures need to follow the early phase of resuscitation. To lower mortality from urosepsis, an optimal interdisciplinary approach between intensive care, anti-infective therapy and urology is essential, assisted by easy access to the necessary laboratory and imaging diagnostic procedures. Although most antibacterials achieve high urinary concentrations, there are several unique features of complicated UTI, and thus urosepsis, that influence the activity of antibacterial substances: (i) renal pharmacokinetics differ in unilateral and bilateral renal impairment and in unilateral and bilateral renal obstruction; (ii) variations in pH may influence the activity of certain antibacterials; and (iii) biofilm infection is frequently found under these conditions, which may increase the minimal inhibitory concentrations (MIC) of the antibacterials at the site of infection by several hundred folds. Assessment of antibacterial pharmacodynamic properties in such situations should take into account not only the MIC as determined in vitro and the plasma concentrations of the free (unbound) drug, which are the guiding principles for many infections, but also the actual renal excretion and urinary bactericidal activity of the antibacterial substance. In the treatment of urosepsis, it is important to achieve optimal exposure to antibacterials both in plasma and in the urinary tract. The role of drugs with low renal excretion rates is therefore limited. Since urosepsis quite often originates from catheter-associated UTI and urological interventions, optimal catheter care and optimal strategies to prevent nosocomial UTI may be able to reduce the frequency of urosepsis.