In vitro evaluation of DV-7751a, a new fluoroquinolone with an enhanced spectrum of activity against gram-positive aerobic organisms and anaerobes

Therapeutic advances of new fluoroquinolones

Fluoroquinolone antimicrobials have been available for over 10 years. Recent modifications to nuclear side-chains have enhanced both the antimicrobial and pharmacokinetic profiles of this class. Rapidly increasing antimicrobial resistance among community and hospital bacterial pathogens has diminished therapeutic options. Infections caused by such pathogens, including drug-resistant Streptococcus pneumoniae and multi-resistant Enterobacteriaceae are now treatable by few classes of antibacterials, one of these being the fluoroquinolones. Ciprofloxacin was one of the first effective agents available in both iv. and oral formulations for the treatment of Gram-negative infection, resistant to other antibiotics. More recent developments, such as sparfloxacin and grepafloxacin, are more effective in vitro against Gram-positive pathogens, although their safety profile may be less promising. Fluoroquinolones not yet in widespread clinical use, including trovafloxacin, clinafloxacin and moxifloxacin, hold considerable promise as community 'respiratory antimicrobials' and the results of clinical trials are awaited with anticipation. In this review, the three generations of fluoroquinolone development are examined and the relative antimicrobial, pharmacokinetic, clinical and safety profiles of available and developmental quinolones are compared.

Ofloxacin otic solution: a review of its use in the management of ear infections

Ofloxacin is a synthetic fluoroquinolone antibacterial agent that inhibits the supercoiling activity of bacterial DNA gyrase, halting DNA replication. Ofloxacin has been formulated as a 0.3% otic solution for the treatment of ear infections. Topical administration of ofloxacin otic solution 0.3% produces very high concentrations of drug in the ear, thus broadening the spectrum of activity of ofloxacin greatly, to cover most common ear pathogens. Results of clinical trials indicate that ofloxacin otic solution 0.3% is as effective as topical neomycin/polymixin B/hydrocortisone preparations in the treatment of otitis externa (clinical cure rate >80% in adults and >95% in children for both treatments) and oral amoxicillin/clavulanic acid in the treatment of otitis media in the presence of tympanostomy tubes in children (clinical cure rates 76 and 69% for ofloxacin and amoxicillin/clavulanic acid, respectively). It is also effective in the treatment of chronic suppurative otitis media in adolescents and adults with perforated tympanic membranes (75 to 91% clinical cure rate). Because of the limited systemic absorption after topical administration, ofloxacin otic solution 0.3% is well tolerated. Adverse events were usually classed as mild to moderate, with < or =2% considered severe. The most frequent adverse events were bitter taste (5%), primarily in patients with non-intact tympanic membranes, and pruritus (2%). The incidence of adverse events with ofloxacin otic solution 0.3% was similar to that with other ototopical preparations and significantly less than that with oral amoxicillin/clavulanic acid. Unlike comparative ototopical antibacterials, ofloxacin was not ototoxic or chondrotoxic in animal studies. In addition, no ototoxicity was detected in clinical studies in humans.

CONCLUSIONS

Ofloxacin otic solution 0.3% is clinically effective in the treatment of otitis externa and otitis media in patients with tympanic membrane perforations or tympanostomy tubes. The high concentrations achieved with this ototopical solution render it active against a broad spectrum of organisms. It is well tolerated, avoiding many systemic adverse events, and is not associated with ototoxicity. As the first ototopical agent approved for use in patients with non-intact tympanic membranes, ofloxacin otic solution 0.3% provides a valuable advantage over current treatment alternatives.

The new fluoroquinolones: A critical review

OBJECTIVE

This paper reviews the literature available on the new fluoroquinolones - clinafloxacin, gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin, sparfloxacin and trovafloxacin - to compare these agents with each other and contrast them with ciprofloxacin, an older fluoroquinolone.

DATA SELECTION

Published papers used were obtained by searching MEDLINE for articles published between 1994 and 1998, inclusive. References of published papers were also obtained and reviewed. Abstracts from scientific proceedings were reviewed.

DATA EXTRACTION

Due to the limited data available on several of the agents, criteria for study inclusion in the in vitro, pharmacokinetics and in vivo sections were not restrictive.

DATA SYNTHESIS

The new fluoroquinolones offer excellent Gram-negative bacillary activity and improved Gram-positive activity (eg, against Streptococcus pneumoniae and Staphylococcus aureus) over ciprofloxacin. Clinafloxacin, gatifloxacin, moxifloxacin, sparfloxacin and trovafloxacin display improved activity against anaerobes (eg, Bacteriodes fragilis). All of the new fluoroquinolones have a longer serum half-life than ciprofloxacin (allowing for once daily dosing), and several are eliminated predominantly by nonrenal means. No clinical trials are available comparing the new fluoroquinolones with each other. Clinical trials comparing the new fluoroquinolones with standard therapy have demonstrated good efficacy in a variety of infections. Their adverse effect profile is similar to that of ciprofloxacin. Clinafloxacin and sparfloxacin cause a high incidence of phototoxicity (1.5% to 14% and 2% to 11.7%, respectively), grepafloxacin causes a high incidence of taste perversion (9% to 17%) and trovafloxacin causes a high incidence of dizziness (11%). They all interact with metal ion-containing drugs (eg, antacids), and clinafloxacin and grepafloxacin interact with theophylline. The new fluoroquinolones are expensive; however, their use may result in savings in situations where, because of their potent and broad spectrum of activity, they can be used orally in place of intravenous antibiotics.

CONCLUSIONS

The new fluoroquinolones offer advantages over ciprofloxacin in terms of improved in vitro activity and pharmacokinetics. Whether these advantages translate into improved clinical outcomes is presently unknown. The new fluoroquinolones have the potential to emerge as important therapeutic agents in the treatment of respiratory tract and genitourinary tract infections.

Levofloxacin. Its use in infections of the respiratory tract, skin, soft tissues and urinary tract

Levofloxacin, the optically pure levorotatory isomer of ofloxacin, is a fluoroquinolone antibacterial agent. Like other fluoroquinolones, it acts on bacterial topoisomerase and has activity against a broad range of Gram-positive and Gram-negative organisms. Levofloxacin also appears to have improved activity against Streptococcus pneumoniae compared with ciprofloxacin or ofloxacin. Levofloxacin distributes well and achieves high levels in excess of plasma concentrations in many tissues (e.g., lung, skin, prostate). High oral bioavailability allows switching from intravenous to oral therapy without dosage adjustment. In patients with mild to severe community-acquired pneumonia receiving treatment for 7 to 14 days, oral levofloxacin was similar in efficacy to amoxicillin/clavulanic acid, and intravenous and/or oral levofloxacin was superior to intravenous ceftriaxone and/or oral cefuroxime axetil. With levofloxacin use, clinical success (clinical cure or improvement) rates were 87 to 96% and bacteriological eradication rates were 87 to 100%. In the 5- to 10-day treatment of acute exacerbations of chronic bronchitis, oral levofloxacin was similar in efficacy to oral cefuroxime axetil or cefaclor. Levofloxacin resulted in clinical success in 78 to 94.6% of patients and bacteriological eradication in 77 to 97%. Oral levofloxacin was also similar in efficacy to amoxicillin/clavulanic acid or oral clarithromycin in patients with acute maxillary sinusitis treated for 7 to 14 days. Equivalence between 7- to 10-day therapy with oral levofloxacin and ciprofloxacin was seen in patients with uncomplicated skin and soft tissue infections. Clinical success was seen in 97.8 and 96.1% of levofloxacin recipients and bacteriological eradication in 97.5 and 93.2%. Complicated urinary tract infections, including pyelonephritis, responded similarly well to oral levofloxacin or ciprofloxacin for 10 days or lomefloxacin for 14 days. Clinical success and bacteriological eradication rates with levofloxacin occurred in 92 to 93.3% and 93.6 to 94.7% of patients.

CONCLUSIONS

Levofloxacin can be administered in a once-daily regimen as an alternative to other fluoroquinolones in the treatment of infections of the urinary tract, skin and soft tissues. Its more interesting use is as an alternative to established treatments of respiratory tract infections. S. pneumoniae appears to be more susceptible to levofloxacin than to ciprofloxacin or ofloxacin. Other newer fluoroquinolone agents that also have enhanced in vitro antipneumococcal activity may not share the well established tolerability profile of levofloxacin, which also appears to improve on that of some older fluoroquinolones.

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.

Activity of two novel fluoroquinolones (DU-6859a and DV-7751a) tested against glycopeptide-resistant enterococcal isolates

Two novel fluoroquinolones, DU-6859a and DV-7751a, were compared with three peer compounds (ciprofloxacin, levofloxacin, and ofloxacin) by testing 150 strains of enterococci that were resistant to vancomycin. Standardized methods recommended by the National Committee for Clinical Laboratory Standards were used for all minimum inhibitory concentration tests, and DU-6859a was additionally tested by the standardized disk diffusion procedure (5-mu g disks). The rank order of the fluoroquinolone spectrums against these Enterococcus spp. isolates was DU-6859a (71.3% of strains inhibited at < or = 2 mu g/ml) > DV-7751a (38.7%) > levofloxacin (33.3%) > ofloxacin (32.0%) > ciprofloxacin (3.3%). Using previously proposed break point zone diameters of > or = 16 mm (susceptible) and < or = 12 mm (resistant), the DU-6859a disk diffusion tests for these glycopeptide-resistant organisms were without false-susceptible or false-resistant error (81.3% absolute agreement). These results indicate that among the investigational and currently marketed fluoroquinolones, DU-6859a appears to have the greatest potential value in the therapy of Enterococcus spp. strains that are resistant to the glycopeptides and many other therapeutic agents.