Enhanced distribution of fourth-generation fluoroquinolones in prostatic tissue

Developmental stage and infection status may affect drug distribution in the prostate of rats

Prostate inflammation is often treated with drugs which are ineffective. Antibacterial agents fail to reach the prostate epithelium, and the blood-prostate barrier (BPB) may affect the drug transport process. Factors affecting drug efficacy remain unclear.Rats were categorised into groups A and B, corresponding to adulthood and puberty, respectively. Group C included the model of chronic prostate infection. Dialysates of levofloxacin and cefradine were collected from the prostate gland and jugular vein and evaluated. Pharmacokinetic analysis was conducted.The free concentrations of antimicrobials in the prostate and plasma samples of all groups peaked at 20 min, then gradually decreased. The mean AUC0-tprostate/AUC0-tplasma ratio in the levofloxacin group were 0.86, 0.53, and 0.95, and the mean values of AUC0-∞prostate/AUC0-∞plasma ratio were 0.85, 0.63, and 0.97. The corresponding values in the cefradine group were 0.67, 0.30 and 0.84, and 0.66, 0.31, and 0.85, respectively. The mean values in group B were lower than those in group A, and those in group C were higher than those in group B.The maturity of the prostate may affect the ability of the drug to cross the BPB. Infection may disrupt the BPB, affecting drug permeability.

Fluoroquinolones Hybrid Molecules as Promising Antibacterial Agents in the Fight against Antibacterial Resistance

The emergence of bacterial resistance has motivated researchers to discover new antibacterial agents. Nowadays, fluoroquinolones keep their status as one of the essential classes of antibacterial agents. The new generations of fluoroquinolones are valuable therapeutic tools with a spectrum of activity, including Gram-positive, Gram-negative, and atypical bacteria. This review article surveys the design of fluoroquinolone hybrids with other antibacterial agents or active compounds and underlines the new hybrids' antibacterial properties. Antibiotic fluoroquinolone hybrids have several advantages over combined antibiotic therapy. Thus, some challenges related to joining two different molecules are under study. Structurally, the obtained hybrids may contain a cleavable or non-cleavable linker, an essential element for their pharmacokinetic properties and mechanism of action. The design of hybrids seems to provide promising antibacterial agents helpful in the fight against more virulent and resistant strains. These hybrid structures have proven superior antibacterial activity and less susceptibility to bacterial resistance than the component molecules. In addition, fluoroquinolone hybrids have demonstrated other biological effects such as anti-HIV, antifungal, antiplasmodic/antimalarial, and antitumor activity. Many fluoroquinolone hybrids are in various phases of clinical trials, raising hopes that new antibacterial agents will be approved shortly.

MRGPRX2 and Adverse Drug Reactions

Many adverse reactions to therapeutic drugs appear to be allergic in nature, and are thought to be triggered by patient-specific Immunoglobulin E (IgE) antibodies that recognize the drug molecules and form complexes with them that activate mast cells. However, in recent years another mechanism has been proposed, in which some drugs closely associated with allergic-type events can bypass the antibody-mediated pathway and trigger mast cell degranulation directly by activating a mast cell-specific receptor called Mas-related G protein-coupled receptor X2 (MRGPRX2). This would result in symptoms similar to IgE-mediated events, but would not require immune priming. This review will cover the frequency, severity, and dose-responsiveness of allergic-type events for several drugs shown to have MRGPRX2 agonist activity. Surprisingly, the analysis shows that mild-to-moderate events are far more common than currently appreciated. A comparison with plasma drug levels suggests that MRGPRX2 mediates many of these mild-to-moderate events. For some of these drugs, then, MRGPRX2 activation may be considered a regular and predictable feature after administration of high doses.

Is Moxifloxacin a Treatment Option for Pancreatic Infections? A Pharmacometric Analysis of Serum and Pancreatic Juice

Postoperative local infection is a major complication after pancreatic surgery. The aim of this prospective clinical trial was to assess the potential of moxifloxacin (MXF) to treat pancreatic infections from a pharmacokinetic (PK)/pharmacodynamic (PD) perspective. The PK of MXF in serum and pancreatic juice, via an inserted tube in the pancreatic duct, was determined in 19 patients up to day 7 after pancreatoduodenectomy. PK data in both specimens was analyzed with NONMEM 7.3. Intraoperative swipes were performed for microbiological examination. PK/PD target attainment was assessed in both matrices using unbound area under the plasma concentration-time curve/minimum inhibitory concentration (MIC) targets of ≥30 and ≥100, for gram-positive and gram-negative pathogens, respectively. A 2-compartment population PK model in which the measurements in pancreatic juice were assigned to a scaled peripheral compartment best described the PK in both specimens simultaneously. Median (10th-90th percentile) area under the plasma concentration-time curve values after the third dose were 28.9 mg · h/L (18.6-42.0) in serum and 55.8 mg · h/L (23.7-81.4) in pancreatic juice. Target attainment rate for the intraoperatively isolated bacterial strains was ≥0.88 after the third MXF dose. For gram-negatives, high probability of target attainment ≥0.84 was observed in serum for MIC ≤ 0.125 mg/L and in pancreatic juice for MIC ≤ 0.25 mg/L. For gram-positives, the probability of target attainment was 0.84-1 in serum for MIC ≤ 0.5 mg/L and in pancreatic juice for MIC ≤ 1 mg/L. In conclusion, penetration of MXF into pancreatic juice was substantial. The PK/PD analysis indicated that treatment of pancreatic infections by isolates with MIC ≤ 0.25 mg/L (gram-negative) and ≤1 mg/L (gram-positive) should be evaluated in further studies.

Decreased protein binding of moxifloxacin in patients with sepsis?

The mean (SD) unbound fraction of moxifloxacin in plasma from patients with severe sepsis or septic shock was determined by ultrafiltration to 85.5±3.0% (range 81.9 and 91.6%) indicating a decreased protein binding of moxifloxacin in this population compared with the value of 58-60% provided in the Summary of Product Characteristics. However, previous investigations neglected the influence of pH and temperature on the protein binding of moxifloxacin. Maintaining physiological conditions (pH 7.4, 37°C) - as in the present study - the unbound fraction of moxifloxacin in plasma from healthy volunteers was 84%. In contrast, the unbound fraction of moxifloxacin was 77% at 4°C and 66-68% in unbuffered plasma or at pH 8.5 in fair agreement with previously published data. PK/PD parameters e.g. fAUC/MIC or ratios between interstitial fluid and free plasma concentrations, which were obtained assuming a protein binding rate of moxifloxacin of 40% or more, should be revised.

Enhanced penetration of moxifloxacin into rat prostate tissue evidenced by microdialysis

Moxifloxacin is reported to have increased distribution into the prostate compared with older fluoroquinolones such as norfloxacin and ciprofloxacin, being able to reach tissue-to-plasma concentration ratios greater than unity. However, most of these studies use tissue homogenates derived from biopsy samples, which can lead to overestimation of free concentrations as fluoroquinolones tend to accumulate in the intracellular space. The aim of this study was to investigate moxifloxacin pharmacokinetics in rat prostate interstitial fluid by microdialysis. Tissue pharmacokinetics was assessed by implanting a small microdialysis catheter in the prostate gland. Blood samples were simultaneously collected for assessing plasma pharmacokinetics. Analysis of plasma (N=154) and microdialysis (N=344) concentrations after a single intravenous dose of 6 or 12mg/kg moxifloxacin was conducted in the non-linear mixed-effect modelling software NONMEM v.6 as well by a non-compartmental approach. Moxifloxacin showed a significant tissue distribution in the prostate (AUCprostate,ISF/fu·AUCplasma=1.24±0.37), 59% higher than the value obtained for levofloxacin in a previous study. A three-compartment model with non-linear kinetics could adequately describe moxifloxacin pharmacokinetics in terms of curve fitting and precision in parameter estimation. The developed pharmacokinetic model indicates that passive diffusion and active transport are the mechanisms involved in moxifloxacin distribution to the prostate. These findings suggest that moxifloxacin could be a better alternative to levofloxacin for the treatment of chronic bacterial prostatitis owing to its enhanced tissue penetration and higher AUCtissue/MIC ratios, even though it is not yet approved by the US FDA for this indication.

Febrile infection in post-prostate biopsy: results of a ten-year single-institution study in South Taiwan

BACKGROUND

Post-biopsy infection is one of the major concerns of urologists and patients for prostate biopsy. Many efforts have been made to reduce the infection rate. We conducted a study at a single institution with the goal of describing the bacteriology and incidence trends of febrile infections following trans-rectal ultrasound (TRUS)-guided biopsy of the prostate.

MATERIALS AND METHODS

From January 1998 to December 2002 (Period 1 of the study), January 2003 to August 2005 (Period 2), September 2005 to October 2007 (Period 3), and November 2007 to December 2009 (Period 4), 1,406 patients underwent prostate biopsy at our hospital. All biopsies were conducted under TRUS guidance without preparation by enemas. Several steps were taken to reduce infectious complications following biopsy, including a shift to levofloxacin prophylaxis starting from Period 3 of our study and thorough instructions in post-biopsy self-care starting from the beginning of Period 4. The incidence and bacteriology of urinary tract infection (UTI) following the prostate biopsies were reviewed from chart records.

RESULTS

Twenty-eight of 514 (5.4%), 13 of 276 (4.7%) nine of 274 (3.2%), and three of 342 (0.9%) patients had post-biopsy febrile infections during the four periods of the study, respectively. Fifteen of 28 (53.5%), four of 13 (30.8%), five of nine (55.6%), and zero of three patients, respectively, had positive cultures of blood, urine, or both during the four study periods. Escherichia coli was the pathogen isolated most commonly and ampicillin- and fluoroquinolone-resistant strains of this organism were identified at a high frequency. The times to onset of fever after biopsy in the four study periods were 1.5±1.3 d, 3.7±2.7 d, 2.2±1.6 d, and 2.5±0.9 d, respectively.

CONCLUSIONS

Ampicillin- and fluoroquinolone-resistant strains of E. coli were the uropathogenic bacteria identified most commonly after prostate biopsy at our hospital. The incidence of UTI following prostate biopsy can be reduced by explaining instructions for medication and self-care thoroughly to patients undergoing such biopsy.

Population pharmacokinetic modeling of the unbound levofloxacin concentrations in rat plasma and prostate tissue measured by microdialysis

Levofloxacin is a broad-spectrum fluoroquinolone used in the treatment of both acute and chronic bacterial prostatitis. Currently, the treatment of bacterial prostatitis is still difficult, especially due to the poor distribution of many antimicrobials into the prostate, thus preventing the drug to reach effective interstitial concentrations at the infection site. Newer fluoroquinolones show a greater penetration into the prostate. In the present study, we compared the unbound levofloxacin prostate concentrations measured by microdialysis to those in plasma after a 7-mg/kg intravenous bolus dose to Wistar rats. Plasma and dialysate samples were analyzed using a validated high-pressure liquid chromatography-fluorescence method. Both noncompartmental analysis (NCA) and population-based compartmental modeling (NONMEM 6) were performed. Unbound prostate tissue concentrations represented 78% of unbound plasma levels over a period of 12 h by comparing the extent of exposure (unbound AUC0-∞) of 6.4 and 4.8 h·μg/ml in plasma and tissue, respectively. A three-compartment model with simultaneous passive diffusion and saturable distribution kinetics from the prostate to the central compartment gave the best results in terms of curve fitting, precision of parameter estimates, and model stability. The following parameter values were estimated by the population model: V1 (0.38 liter; where V1 represents the volume of the central compartment), CL (0.22 liter/h), k12 (2.27 h(-1)), k21 (1.44 h(-1)), k13 (0.69 h(-1)), Vmax (7.19 μg/h), kM (0.35 μg/ml), V3/fuprostate (0.05 liter; where fuprostate represents the fraction unbound in the prostate), and k31 (3.67 h(-1)). The interindividual variability values for V1, CL, Vmax, and kM were 21, 37, 42, and 76%, respectively. Our results suggest that levofloxacin is likely to be substrate for efflux transporters in the prostate.

Importance of relating efficacy measures to unbound drug concentrations for anti-infective agents

For the optimization of dosing regimens of anti-infective agents, it is imperative to have a good understanding of pharmacokinetics (PK) and pharmacodynamics (PD). Whenever possible, drug efficacy needs to be related to unbound concentrations at the site of action. For anti-infective drugs, the infection site is typically located outside plasma, and a drug must diffuse through capillary membranes to reach its target. Disease- and drug-related factors can contribute to differential tissue distribution. As a result, the assumption that the plasma concentration of drugs represents a suitable surrogate of tissue concentrations may lead to erroneous conclusions. Quantifying drug exposure in tissues represents an opportunity to relate the pharmacologically active concentrations to an observed pharmacodynamic parameter, such as the MIC. Selection of an appropriate specimen to sample and the advantages and limitations of the available sampling techniques require careful consideration. Ultimately, the goal will be to assess the appropriateness of a drug and dosing regimen for a specific pathogen and infection.

Antimicrobial therapy for chronic bacterial prostatitis

BACKGROUND

Chronic bacterial prostatitis (CBP) is frequently diagnosed in men of fertile age, and is characterized by a disabling array of symptoms, including pain in the pelvic area (for example, perineum, testicles), voiding symptoms (increased frequency and urgency, also at night; pain or discomfort at micturition), and sexual dysfunction. Cure of CBP can be attempted by long-term therapy with antibacterial agents, but relapses are frequent. Few antibacterial agents are able to distribute to the prostatic tissue and achieve sufficient concentrations at the site of infection. These agents include fluoroquinolones, macrolides, tetracyclines and trimethoprim. After the introduction of fluoroquinolones into clinical practice, a number of studies have been performed to optimize the antimicrobial treatment of CBP, and to improve eradication rates and symptom relief.

OBJECTIVES

To assess and compare the efficacy and harm of antimicrobial treatments for chronic bacterial prostatitis.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (PubMed), EMBASE, other national or international databases and abstracts from conference proceedings on 8 August 2012.

SELECTION CRITERIA

We included all randomized controlled comparisons of one antimicrobial agent versus placebo or one or more comparator antimicrobial agents, combined or not with non-antimicrobial drugs. We also included trials comparing different doses, treatment durations, dosing frequencies, or routes of administration of antimicrobial agents. We excluded studies in which patients were not diagnosed according to internationally recommended criteria, or were not subjected to lower urinary tract segmented tests.

DATA COLLECTION AND ANALYSIS

Study data were extracted independently by two review authors. Study outcomes were microbiological efficacy (pathogen eradication), clinical efficacy (symptom cure or improvement, or symptom scores) at test-of-cure visits or at follow-up, or both, and adverse effects of therapy. Secondary outcomes included microbiological recurrence rates.Statistical analysis was performed using a fixed-effect model for microbiological outcomes and a random-effects model for clinical outcomes and adverse effects. The results were expressed as risk ratios for dichotomous outcomes (with 95% confidence intervals) or as standardized mean differences for continuous or non-dichotomous variables.

MAIN RESULTS

We identified 18 studies, enrolling a total of 2196 randomized patients. The oral fluoroquinolones ciprofloxacin, levofloxacin, lomefloxacin, ofloxacin and prulifloxacin were compared. There were no significant differences in clinical or microbiological efficacy or in the rate of adverse effects between these fluoroquinolones. In chlamydial prostatitis, (i) azithromycin showed improved eradication rates and clinical cure rates compared to ciprofloxacin, with no significant differences regarding adverse effects; (ii) azithromycin was equivalent to clarithromycin, both microbiologically and clinically; (iii) prulifloxacin appeared to improve clinical symptoms, but not eradication rates, compared to doxycycline. In ureaplasmal prostatitis, the comparisons ofloxacin versus minocycline and azithromycin versus doxycycline showed similar microbiological, clinical and toxicity profiles.

AUTHORS' CONCLUSIONS

The microbiological and clinical efficacy, as well as the adverse effect profile, of different oral fluoroquinolones are comparable. No conclusions can be drawn regarding the optimal treatment duration of fluoroquinolones in the treatment of CBP caused by traditional pathogens.Alternative antimicrobial agents tested for the treatment of CBP caused by traditional pathogens are co-trimoxazole, beta-lactams and tetracyclines, but no conclusive evidence can be drawn regarding the role of non-fluoroquinolone antibiotics in the treatment of CBP caused by traditional pathogens.In patients with CBP caused by obligate intracellular pathogens, macrolides showed higher microbiological and clinical cure rates compared to fluoroquinolones.

Bacterial prostatitis

OBJECTIVES

The prostatitis syndrome is classified into bacterial prostatitis (acute and chronic), chronic pelvic pain syndrome and asymptomatic prostatitis. The aim of this report is to review current management standards for bacterial prostatitis.

METHODS

A research was performed on literature dealing with acute and chronic bacterial prostatitis.

RESULTS

There is a consensus on diagnostic management of bacterial prostatitis comprising microbiological sampling of midstream urine in acute bacterial prostatitis and performance of a bacterial localisation test in chronic bacterial prostatitis. Approximately 10 % of acute bacterial prostatitis cases eventually develop into chronic bacterial prostatitis and further 10 % into chronic pelvic pain syndrome. Bacterial isolates causing acute bacterial prostatitis are highly virulent strains comprising an array of different virulence factors. Presumably, the additional ability of isolates to form biofilms might be one factor amongst others to facilitate development of chronic bacterial prostatitis. Therapy for infectious prostatitis is standardised with antibiotics as the primary agents, empirically administered in acute prostatitis and after susceptibility testing in chronic bacterial prostatitis. Fluoroquinolones exhibit more favourable pharmacological properties; therefore, fluoroquinolones have been recommended as first-line agents in the treatment for chronic bacterial prostatitis. Antibiotic resistance to fluoroquinolones, however, is increasing and is posing significant clinical problems. Further studies on alternative antibiotics active within the prostate are therefore needed both for prophylaxis in transrectal prostate biopsy, for example, and for therapy of chronic bacterial prostatitis.

CONCLUSIONS

Bacterial prostatitis has developed into well-managed entities with increasing antimicrobial resistance being the most severe drawback of yielding therapeutic success.

Fluoroquinolone-macrolide combination therapy for chronic bacterial prostatitis: retrospective analysis of pathogen eradication rates, inflammatory findings and sexual dysfunction

We previously demonstrated the safety and efficacy of fluoroquinolone-macrolide combination therapy in category II chronic bacterial prostatitis (CBP). The aim of this study is to retrospectively compare the microbiological and clinical findings of two treatment schemes for CBP based on the combination of azithromycin (500 mg, thrice-weekly) with a once-daily 500- or 750-mg dose of ciprofloxacin (Cipro-500 or Cipro-750 cohort, respectively). Combined administration of azithromycin (1500 mg week(-1)) with ciprofloxacin at the rate of 750 mg day(-1) for 4 weeks rather than at 500 mg day(-1) for 6 weeks increased the eradication rates from 62.35% to 77.32% and the total bacteriological success from 71.76% to 85.57%. A significant decrease in pain and voiding signs/symptoms and a significant reduction in inflammatory leukocyte counts and serum prostate-specific antigen (PSA) were sustained throughout an 18-month follow-up period in both groups. Ejaculatory pain, haemospermia and premature ejaculation were significantly attenuated on microbiological eradication in both groups, but the latter subsided more promptly in the Cipro-750 cohort. In total, 59 Cipro-750 patients showed mild-to-severe erectile dysfunction (ED) at baseline, while 22 patients had no ED on microbiological eradication and throughout the follow-up period. In conclusion fluoroquinolone-macrolide therapy resulted in pathogen eradication and CBP symptom attenuation, including pain, voiding disturbances and sexual dysfunction. A once-daily 750-mg dose of ciprofloxacin for 4 weeks showed enhanced eradication rates and lower inflammatory white blood cell counts compared to the 500-mg dose for 6 weeks. Our results are open to further prospective validation.

Influence of type and neutralisation capacity of antacids on dissolution rate of ciprofloxacin and moxifloxacin from tablets

Dissolution rate of two fluoroquinolone antibiotics (ciprofloxacin and moxifloxacin) was analysed in presence/absence of three antacid formulations. Disintegration time and neutralisation capacity of antacid tablets were also checked. Variation in disintegration time indicated the importance of this parameter, and allowed evaluation of the influence of postponed antacid-fluoroquinolone contact. The results obtained in this study showed decreased dissolution rate of fluoroquinolone antibiotics from tablets in simultaneous presence of antacids, regardless of their type and neutralisation capacity.