Evaluation of phototoxic potential of gemifloxacin in healthy volunteers compared with ciprofloxacin

Photochemical properties of gemifloxacin: a laser flash photolysis study

The photochemical properties of gemifloxacin (GEFX), a fluoroquinolone antibacterial drug that exhibits phototoxicity toward biological substrates, were studied in aqueous solutions by laser flash photolysis (LFP) and pulse radiolysis. GEFX triplet state ((3)GEFX(∗)) absorption spectra showed maximum absorption at 510nm. (3)GEFX(∗) was quenched by naproxen (NAP) via energy transfer with a rate constant of 1.2×10(8)dm(3)mol(-1)s(-1). The energy of (3)GEFX(∗) was 266kJmol(-1) and the transient absorption spectra showed direct evidence of electron transfer from 2'-deoxyguanosine-5'-monophosphate, N,N,N',N'-tetramethyl-p-phenylenediamine, and tryptophan to (3)GEFX(∗) with bimolecular reaction rate constants of 4.1×10(6), 2.0×10(7), and 2.2×10(7)dm(3)mol(-1)s(-1), respectively. The rate constants for reactions of GEFX with OH, eaq(-) were found to be 1.5×10(10) and 1.4×10(10)dm(3)mol(-1)s(-1), respectively. The mechanisms and products of the photosensitive damage of lysozyme were related to the GEFX concentration, irradiation time, and ambient conditions.

Differential effect of P-gp and MRP2 on cellular translocation of gemifloxacin

Fluoroquinolones are broad spectrum antibiotics widely indicated in the treatment of both human and animal diseases. The primary objective of this study was to assess short and long term affinities of gemifloxacin towards efflux transporters (P-gp, MRP2) and nuclear hormone receptor (PXR). Uptake and dose dependent inhibition studies were performed with [(14)C] erythromycin (0.25 μCi/ml) on MDCKII-MDR1 and MDCKII-MRP2 cells. Cellular accumulation of calcein-AM was further determined to confirm the affinity of gemifloxacin towards P-gp and MRP2. Transport studies were conducted to determine bi-directional permeability and to assess efflux ratio of gemifloxacin. LS-180 cells were treated with three different concentrations of gemifloxacin for 72 h and real-time PCR analysis was performed to study the quantitative gene expression levels of PXR, MDR1 and MRP2. Further, [(14)C] erythromycin uptake was also performed on LS-180 treated cells to better delineate the functional activity of efflux transporters. Results from our study suggest that gemifloxacin may be a substrate of both the efflux transporters studied. This compound inhibited both P-gp and MRP2 mediated efflux of [(14)C] erythromycin in a dose dependent manner with IC(50) values of 123 ± 2 μM and 16 ± 2 μM, respectively. The efflux ratio of [(14)C] erythromycin lowered from 3.56 to 1.63 on MDCKII-MDR1 cells and 4.93 to 1.26 on MDCKII-MRP2 cells. This significant reduction in efflux ratio further confirmed the substrate specificity of gemifloxacin towards P-gp and MRP2. Long term exposure significantly induced the expression of PXR (18 fold), MDR1 (6 fold) and MRP2 (6 fold). A decrease (20%) in [(14)C] erythromycin uptake further confirmed the elevated functional activity of P-gp and MRP2. In conclusion, our studies demonstrated that gemifloxacin is effluxed by both P-gp and MRP2. Long term exposure induced their gene expression and functional activity. This substrate specificity of gemifloxacin towards these efflux transporters may be one of the major factors accounting for low oral bioavailability (71%). Better understanding of these mechanistic interactions may aid in the development of newer strategies to achieve adequate therapeutic levels and higher bioavailability.

Acute and twenty-eight days repeated oral dose toxicity study of besifloxacin in Wistar albino rats

The purpose of this study was to investigate the potential acute and 28-day repeated oral toxicities of besifloxacin (BAF) in Wistar albino rats. In oral acute and repeated dose study, BAF was administered to both sex of rats, at dose levels of 0, 300, 600, 900 mg/kg/day and 0, 100, 200, 500 mg/kg/day, respectively. In the acute study, total white blood cell (WBC) (male, 43.74%; female, 42.60%) and total bilirubin (T-BIL) (male, 80%; female, 60%) were significantly increase, total protein (TP) (male, 23.24%; 27.80%) was significantly decreased, and significant incidence of pericholangitis (male, 83.33%; female, 75%) was shown in males and females of high-dose groups. In repeated oral dose toxicity study, similar type effects were also observed after serum hematological and serum biochemical analysis, whereas additionally sever hepatic injury and focal ulceration in gastric mucosa also observed in high dose groups of both sexes after histopathological analysis. However these toxic effects of besifloxacin were transient and reversible and no-observed adverse effect level (NOAEL) were 300 mg/kg/day for acute and 100 mg/kg/day for repeated dose toxicity study, respectively.

Twenty-eight days repeated oral dose toxicity study of gemifloxacin in Wistar albino rats

The purpose of this study was to investigate the potential toxicity of gemifloxacin by 28-day repeated oral dose in Wistar albino rats. The test article, was administered daily by gavage to male and female rats at dose levels of 0, 50, 100, 200 mg/kg/day. At the end of treatment period, 12 rats/sex/group was sacrificed, while six extra rats/sex in the vehicle control and highest dose groups sacrificed after 14 days recovery period. During the treatment and recovery periods, clinical signs, mortality, body weights, food and water consumption, ophthalmoscopy, urinalysis, phototoxicity, hematology, serum biochemistry, synovial fluid biochemistry, electrocardiogram (ECG), gross findings, organ weights, microscopic examination of synovial fluid, and histopathology were examined. Hematological and serum biochemical investigations revealed a dose-dependent increase in the total white blood cell (WBC), total bilirubin (T-BIL), glucose (GLU), alanine aminotransferase (ALT) and significant decreases in total protein (TP) were observed in both sexes at the same dose, at the end of treatment period, but the levels returned toward normal during the recovery period. Histopathology of talar joint showed that erosion of the articular surface of that joint in both sexes at the end of treatment period at the dose level of 200 mg/kg/day. Degenerative changes in tendinocytes were observed in Achilles tendon of both sexes at the high dose level at the end of treatment period. In histopathological study shows partial effacement of liver architecture and focal ulceration in gastric mucosa at the high dose level at the end of treatment period. Based on these results, it was concluded that 28 days repeated oral dose of gemifloxacin caused increases in the liver weight, WBC count, T-BIL, glucose level, ALT, decreasing the TP, cause chronic hepatitis and acute gastritis, erosion of the articular surface of joint and histopathologic changes in Achilles tendon in rats at the dose level of 200 mg/kg/day.

Antibiotic susceptibility of conjunctival bacterial isolates from refractive surgery patients

PURPOSE

To determine the in vitro antibiotic susceptibility patterns of conjunctival bacterial flora isolated before surgery from patients undergoing refractive surgery.

DESIGN

In vitro laboratory investigation.

PARTICIPANTS

One hundred five eyes from 105 patients scheduled for refractive surgery at Balgensesang Ophthalmology Clinic between September 2005 and January 2006 were studied. Among 105 patients, 71 (67.6%) underwent LASIK using a femtosecond laser, 24 (22.9%) underwent LASIK using an automated microkeratome, 8 (7.6%) underwent LASEK, and 2 (1.9%) patients underwent phakic intraocular lens implantation.

METHODS

Preoperative conjunctival swab samples were inoculated directly in culture media at the bedside before topical anesthetic or antibiotic application. Blood agar, chocolate agar, thioglycolate broth, Sabouraud dextrose agar, and Ogawa media were used for bacterial, fungal, and mycobacterial cultures.

MAIN OUTCOME MEASURES

Minimum inhibitory concentrations (MICs) of ofloxacin (OFX), levofloxacin (LEV), gatifloxacin (GAT), moxifloxacin (MOX), gemifloxacin (GEM), and other commonly used antibiotics were determined using an E test.

RESULTS

From 105 patients, 73 (85%) coagulase-negative staphylococci (CNS), 2 (2.3%) Staphylococcus aureus, 1 (1.2%) Streptococcus pneumoniae, and 5 (4.8%) gram-negative bacilli were isolated. No fungi or mycobacteria were isolated. The MIC that would inhibit the growth of 90% of the tested bacterial isolates (MIC(90)) of OFX, LEV, GAT, MOX, and GEM for methicillin-susceptible CNS (n = 46) were 0.5 microg/ml, 0.19 microg/ml, 0.094 microg/ml, 0.047 microg/ml, and 0.023 microg/ml, respectively. The MIC(90) values for methicillin-resistant CNS (n = 27) were 32 microg/ml, 4 microg/ml, 1 microg/ml, 0.5 microg/ml, and 0.25 microg/ml, respectively (P<0.001).

CONCLUSIONS

The most effective against conjunctival bacteria isolated from refractive surgery patients were GEM, MOX, and GAT; however, resistance to earlier-generation fluoroquinolones (OFX and LEV) is increasing among methicillin-resistant CNS. It may be a therapeutic option to use newer fluoroquinolones in patients undergoing refractive eye surgery to reduce such infections as methicillin-resistant CNS.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Fluoroquinolone antibiotics having the potential to interfere with fluorescence-based diagnosis

Fluorescence, both intrinsic and exogenously induced, is being used for diagnosis of abnormal tissue. Excitation wavelengths used by these methods range from 320 to 450 nm. The presence of absorbing or fluorescing drugs is rarely taken into account by practitioners of fluorescence diagnosis and has the potential to yield false-positive or false-negative results. Our aim is to quantify this potential by (1) comparing the quantum yield of fluoroquinolone antibiotics to those of known tissue fluorophores and (2) taking into account drug concentrations in the tissue during treatment. Quantum yields are determined relative to a working standard of Rhodamine 6G in ethanol. The working standard was calibrated against a fluorescein standard. We concentrated our initial efforts on (1) the fluoroquinolone antibiotics, ciprofloxacin, norfloxacin and ofloxacin and (2) the intrinsic tissue fluorophores, NADH, FAD and protoporphyrin IX. When ciprofloxacin, norfloxacin and ofloxacin were excited at wavelengths 310-390 nm, emission occurred from 350 to 650 nm with quantum yields ranging from 0.03 to 0.3. Quantum yields for intrinsic fluorophores excited at their peak absorption wavelengths were 0.02 (NADH, 340 nm), 0.035 (FAD, 450 nm) and 0.087 (protoporphyrin IX, 408 nm). A review of the literature shows that these fluoroquinolones have a large volume of distribution and can be found in high concentrations in almost every organ during a treatment regimen. The product of the drug tissue concentration and quantum yield, which we term the fluorescence effective concentration, is such that it is likely these fluoroquinolones will interfere during fluorescence diagnosis techniques.

Photosensitizing Potential of Ciprofloxacin at Ambient Level of UV Radiation

Ciprofloxacin is a widely used fluoroquinolone drug with broad spectrum antibacterial activities. Clinical experience has shown incidences of adverse effects related to skin, hepatic, central nervous system, gastrointestinal and phototoxicity. India is a tropical country and sunlight is abundant throughout the day. In this scenario exposure to ambient levels of ultraviolet radiation (UV-R) in sunlight may lead to harmful effects in ciprofloxacin users. Phototoxicity assessment of ciprofloxacin was studied by two mouse fibroblast cell lines L-929 and NIH-3T3. Generation of reactive oxygen species (ROS) like singlet oxygen (1O2), superoxide anion radical (O2*-) and hydroxyl radical (*OH) was studied under the exposure of ambient intensities of UV-A (1.14, 1.6 and 2.2 mW cm(-2)), UV-B (0.6, 0.9 and 1.2 mW cm(-2)) and sunlight (60 min). The drug was generating 1O2, O2*- and *OH in a concentration and dose-dependent manner. Sodium azide (NaN3) and 1,4-diazabicyclo 2-2-2-octane (DABCO) inhibited the generation of 1O2. Superoxide dismutase (SOD) inhibited 90-95% O2*- generation. The drug (5-40 microg mL(-1)) was responsible for linoleic acid peroxidation. Quenching study of linoleic acid peroxidation with SOD (25 and 50 U mL(-1)) confirms the involvement of ROS in drug-induced lipid peroxidation. The generation of *OH radical was further confirmed by using specific quenchers of *OH such as mannitol (0.5 M) and sodium benzoate (0.5 M). 2'-deoxyguanosine (2'-dGuO) assay and linoleic acid peroxidation showed that ROS were mainly responsible for ciprofloxacin-sensitized photo-degradation of guanine base. L-929 cell line showed 29%, 34% and 54% reduced cell viability at higher drug concentration (300 microg mL(-1)) under UV-A, UV-B and sunlight, respectively. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay in NIH-3T3 cell line at higher drug concentration (300 microg mL(-1)) showed a decrease in cell viability by 54%, 56% and 59% under UV-A, UV-B and sunlight, respectively. Results of neutral red uptake assay (NRU) in L-929 cell line were in accordance with MTT assay. The NIH-3T3 cell line showed a higher photosensitizing potential than L-929. The phototoxicity end point shows a time- and concentration-dependent statistically significant (P<0.001) damage. Ciprofloxacin produced ROS by Type I and Type II photodynamic reactions, interacted with nucleic acid moiety and inhibited cell viability. Further, UV-induced photo-peroxidation of linoleic acid accorded the involvement of ROS in the manifestation of drug phototoxicity. Appearance of ciprofloxacin-induced phototoxicity at the ambient level of sunlight is a real risk for the people of India and for those of other tropical countries. We suggest that sunlight exposure should be avoided (especially peak hours) during ciprofloxacin treatment.

Fluoroquinolones vs beta-lactams for empirical treatment of immunocompetent patients with skin and soft tissue infections: a meta-analysis of randomized controlled trials

OBJECTIVE

To compare the effectiveness and safety of fluoroquinolones with beta-lactams in the treatment of patients with skin and soft tissue infections (SSTIs).

METHODS

We searched the PubMed database, Cochrane Database of Controlled Trials, and references of relevant articles for study reports published between January 1980 and February 2006.

RESULTS

Twenty randomized controlled trials that enrolled 4817 patients were included in the analysis. Fluoroquinolones as empirical treatment of patients with SSTIs were more effective than beta-lactams for the clinically evaluable patients (90.4% vs 88.2%; odds ratio [OR], 1.29; 95% confidence interval [CI], 1.00-1.66). This was also true in subset analyses of randomized controlled trials that studied ciprofloxacin (OR, 2.49; 95% CI, 1.45-4.26) and for patients with mild to moderate infections (OR, 1.83; 95% CI, 1.13-2.96). In contrast, no difference was found between the compared regimens for patients with moderate to severe infections (OR, 1.12; 95% CI, 0.80-1.55), for patients who did not receive third-generation cephalosporins as the comparator antibiotic (OR, 0.99; 95% CI, 0.73-1.34), or for the microbiologically evaluable patients (OR, 1.19; 95% CI, 0.89-1.59). Fluoroquinolones were also associated with more adverse effects (19.2% vs 15.2%; OR, 1.33; 95% CI, 1.13-1.57).

CONCLUSION

The high proportion of successfully treated patients in the compared groups of antibiotics and the development of more adverse effects associated with fluoroquinolone use suggest that these antibiotics do not have substantial advantages compared with beta-lactams for empirical treatment of patients with SSTIs.

Gemifloxacin for the treatment of respiratory tract infections: in vitro susceptibility, pharmacokinetics and pharmacodynamics, clinical efficacy, and safety

Gemifloxacin is a synthetic fluoroquinolone antimicrobial agent exhibiting potent activity against most gram-negative and gram-positive organisms, such as the important community-acquired respiratory pathogens Streptococcus pneumoniae (including multidrug-resistant S. pneumoniae), Haemophilus influenzae , and Moraxella catarrhalis . The agent's mechanism of action involves dual targeting of two essential bacterial enzymes: DNA gyrase and topoisomerase IV. Gemifloxacin was approved by the Food and Drug Administration in April 2003 for treatment of community-acquired pneumonia and acute bacterial exacerbation of chronic bronchitis. The drug has an oral bioavailability of approximately 71%. Approximately 20-35% of gemifloxacin is excreted unchanged in the urine after 24 hours. The elimination half-life of gemifloxacin is 6-8 hours in patients with normal renal function, supporting once-daily dosing. The 24-hour free-drug area under the plasma concentration-time curve:minimum inhibitory concentration ratio (fAUC(0-24):MIC) associated with efficacy, based on results from in vitro and animal models of infection, is approximately 30. With a mean fAUC(0-24) of approximately 3 microg*hour/ml (35% of total AUC(0-24) of 8.4) and a median S. pneumoniae MIC for 90% of tested strains of 0.03, a fAUC(0-24):MIC ratio of 100 would be expected after standard dosing (320 mg once/day). In clinical studies involving both hospitalized and outpatient populations, gemifloxacin has been highly effective in the treatment of community-acquired pneumonia and acute exacerbation of chronic bronchitis. Clinical success rates ranged from 93.9-95.9% in patients with community-acquired pneumonia and 96.1-97.5% in those with acute exacerbation of chronic bronchitis. Gemifloxacin is well tolerated; the frequency of adverse events with this agent is low. Most adverse events are mild-to-moderate in severity, with diarrhea (< 4%), nausea and rash (< 3%), and headache (< 2%) most commonly reported. Drug interactions with gemifloxacin are not common, although absorption is greatly reduced when given with divalent and trivalent cation-containing compounds, such as antacids. Due to its potent activity against many common gram-positive and gram-negative respiratory pathogens, its proven clinical efficacy, and its favorable safety profile, gemifloxacin is a highly effective empiric treatment for community-acquired lower respiratory tract infections.

Evaluation of phototoxic and photoallergic potentials of 13 compounds by different in vitro and in vivo methods

Phototoxic side effects of pharmaceutical and cosmetic products are of increasing concern for patients, dermatologists and the chemical industry. Moreover, the need of new chemicals and drugs puts pressure on pre-clinical test methods for side effects, especially interactive adverse-effects with UV-light. So, the predictive potential of different established test methods, which are used regularly in our departments in order to detect the phototoxic potential of chemicals, were analyzed. Namely the fibroblast 3T3 test, the photo hen's egg test, a guinea pig test for measuring acute photoreactions, and a modified Local Lymph Node Assay, the Integrated Model for the Differentiation of Skin Reactions. Various agents with different photoreactive potential were tested: quinolones like Bay y 3118, ciprofloxacin, enoxacin, lomefloxacin, moxifloxacin, ofloxacin, sparfloxacin, as well as promethazine, chlorpromazine, 8-methoxypsoralen and olaquindox serving as control. Special emphasis was taken to evaluate the capability of the employed test procedures to predict phototoxic side effects in patients. Following our results, both in vitro assays were useful tools to detect photoirritancy while the photoallergic potentials of tested compounds were exclusively detected by an in vivo assay. As long as no in vitro model for photoallergy is available, the UV-IMDS should be considered to evaluate photoallergic properties of a supposed photoreactive agent.

Gemifloxacin: a new fluoroquinolone

Gemifloxacin is a dual targeted fluoroquinolone with potent in vitro activity against Gram-positive, -negative and atypical human pathogens--pathogens considered to be important causes of community-acquired respiratory tract infections. Gemifloxacin demonstrates impressive minimal inhibitory concentrations (MIC 90 ) values against clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Chlamydia pneumoniae and Legionella spp., with MIC 90 values reported to be 0.016-0.06, < 0.0008-0.06, 0.008-0.3, 0.25, 0.125 and 0.016-0.07 microg/ml, respectively. Gemifloxacin is also active in vitro against a broad range of Gram-negative bacilli with MIC 90 values against the Enterobacteriaceae in the range of 0.016 to > 16 microg/ml ( Escherichia coli and Providencia stuartii, respectively), with the majority of the genus having MIC 90 drug concentrations < 0.5 microg/ml. The in vitro activity of gemifloxacin against anaerobic organisms is variable. The MIC values for gemifloxacin are not affected by beta-lactamase production nor by penicillin or macrolide resistance in S. pneumoniae. Gemifloxacin is approved by the FDA to be clinically efficacious against multi-drug resistant S. pneumoniae. The pharmacokinetics of gemifloxacin are such that the drug can be administered orally once-daily to yield or achieve sustainable drug concentrations exceeding the MIC values of clinically important organisms. Gemifloxacin has been shown to target both DNA gyrase (preferred target) and topoisomerase IV (secondary target) - enzymes critical for DNA replication and organism survival - against clinical isolates of S. pneumoniae. This dual targeting activity is thought to be important for reducing the likelihood for selecting for quinolone resistance. Gemifloxacin has been investigated and approved for therapy in patients with community-acquired pneumonia (CAP) and acute exacerbations of chronic bronchitis. In one study, more patients receiving gemifloxacin compared to clarithromycin remained free of exacerbations for longer periods of time (p < 0.016) and gemifloxacin had a shorter time to eradication of H. influenzae than did clarithromycin (p < 0.02). From efficacy studies, gemifloxacin was found to have an adverse profile that was comparable with other compounds. The most frequent side effects were diarrhoea, abdominal pain and headache. Gemifloxacin is a welcomed addition to currently available agents for the treatment of community-acquired lower respiratory tract infections. Other potential indications appear to be within the spectrum of this compound.

New Findings on the Structure-Phototoxicity Relationship and Photostability of Fluoroquinolones

The present study examined the phototoxicities of a series of 7-(3-aminopyrrolidinyl) quinolones containing various substituents at position 1 by use of a mouse model. For the 7-(3-aminopyrrolidinyl) quinolones with a halogen atom at position 8, well-known substituent groups such as a cyclopropyl, an ethyl, or a difluorophenyl at position 1 were found to be responsible for severe phototoxicity. However, when an aminodifluorophenyl or an isoxazolyl group was placed at position 1, even 8-halogeno quinolones were found to be mildly phototoxic. This is the first report of 8-halogeno quinolones that are not severely phototoxic. Two structurally similar 8-chloro quinolones (the 1-aminodifluorophenyl 8-chloro quinolone and the 1-difluorophenyl 8-chloro quinolone) were investigated further. The former was mildly phototoxic; the latter was severely phototoxic. We demonstrate that these two 8-chloro quinolones have practically the same areas under the concentration-time curves from 0 to 4 h in auricular tissue, suggesting that the mild phototoxicity is not due to pharmacokinetic instability. The rates of UV photodegradation of these compounds were also measured. We found that these two quinolones photodegrade at similar rates, suggesting that the mild phototoxicity is not attained through increased photostability. In conclusion, the phototoxic potentials of fluoroquinolones are influenced not only by the substituent at position 8 but also by that at position 1. We also discovered a mildly phototoxic 8-chloro quinolone which did not have increased photostability.

A new respiratory fluoroquinolone, oral gemifloxacin: a safety profile in context

Gemifloxacin is a broad-spectrum quinolone antibacterial with enhanced potency against Gram-positive bacteria, including multi-drug resistant Streptococcus pneumoniae, and retained potency against Gram-negative bacilli and bacterial strains resistant to other antibiotics. It has proven particularly effective in respiratory and urinary tract infection. This review presents safety data from 6775 patients included in clinical trials, receiving either the recommended 320 mg once daily oral dose of gemifloxacin, or standard dose of other quinolones, macrolides or beta-lactams (n = 5248). Studies in healthy volunteer and special populations are also reported. Adverse experiences (AEs) were observed in 44.7% of gemifloxacin-treated patients and 47.5% of those who received comparator drugs. Mild gastro-intestinal adverse drug reactions (ADRs) (diarrhoea 5.1%, nausea 3.9%) predominated. Rash, usually maculo-papular and in no case proceeding to more severe eruptions, was observed in 3.6% of those receiving gemifloxacin. A higher incidence of rash (>20%) was observed in young women and was the subject of further study. Adverse drug reactions suspected or probably related to treatment occurred in 17.4% of patients receiving gemifloxacin and in 20% of those receiving comparator antibiotics. Diarrhoea and nausea were experienced by 3.6 and 2.7%, respectively, of gemifloxacin-treated patients (4.6 and 3.2% of comparators), rash by 2.8% (0.6% of comparators) and headache by 1.2% (1.5% of comparators). Gemifloxacin-related vomiting (0.9%), dizziness (0.8%) and taste perversion (0.3%) were uncommon. Treatment discontinuation followed one or more adverse drug reactions in 2.2% of gemifloxacin-treated patients (0.9% due to rash) and 2.1% of comparator-treated patients. A total of 63 deaths (33 receiving gemifloxacin) occurred in the trial population: none were considered related to treatment. A slight prolongation in QT interval (2.56 ms (S.D. +/-24.5)) was observed in gemifloxacin-treated patients: no cardiac arrhythmias were reported. There was a low incidence of liver function tests (LFTs) classified as of potential clinical concern: gemifloxacin (0.4-1.2%), comparators (0.2-1.3%). Serious adverse events (SAEs), occurring during but not necessarily related to therapy, occurred in 3.6% of gemifloxacin-treated patients (4.3% of comparators). SAEs related to treatment agents were rare (0.4% in each group) and included rash (0.1%) and elevated liver enzymes (<0.1%). Gemifloxacin was well tolerated by the elderly, those with renal or hepatic impairment and when co-administered with omeprazole, digoxin, theophylline, warfarin (with which there were no significant interactions) and Maalox. In conclusion, gemifloxacin 320 mg once daily demonstrated a favourable safety and tolerability profile similar to that of comparator antibiotics, including other quinolones.

Gemifloxacin: a new fluoroquinolone approved for treatment of respiratory infections

OBJECTIVE

To evaluate the microbiology, pharmacokinetic parameters, drug interactions, and results of the available clinical trials of gemifloxacin for the treatment of community-acquired pneumonia (CAP) and acute exacerbation of chronic bronchitis (AECB).

DATA SOURCES

MEDLINE (1966-September 2003) was searched for primary and review articles. Data from the manufacturer were also included. Key words included adverse effects, clinical trials, drug interactions, gemifloxacin, and pharmacokinetic parameters.

STUDY SELECTION AND DATA EXTRACTION

All articles and product labeling concerning gemifloxacin, a fluoroquinolone antibiotic recently approved by the Food and Drug Administration for treatment of CAP and AECB, were included for review.

DATA SYNTHESIS

Compared with currently available fluoroquinolones, gemifloxacin demonstrated improved in vitro activity against Streptococcus pneumoniae (minimum inhibitory concentration for 90% eradication 0.03 microg/mL) and similar activity against gram-negative respiratory pathogens (Haemophilus influenzae, Moraxella catarrhalis) and atypical pathogens such as Chlamydia pneumoniae, Legionella pneumophila, and Mycoplasma pneumoniae. Gemifloxacin, consistent with other available fluoroquinolones, has insufficient activity against methicillin-resistant Staphylococcus aureus to allow clinical use for such infections. Gemifloxacin has adequate bioavailability and a favorable drug interaction profile. Gemifloxacin was comparable to commonly employed nonfluoroquinolone regimens for treatment of CAP and AECB, although the studies were designed to demonstrate equivalence. Gemifloxacin once daily for 5-7 days was well tolerated in controlled and uncontrolled clinical studies. Available clinical data, however, are insufficient to draw clinical or toxicologic distinctions between gemifloxacin and other fluoroquinolones.

CONCLUSIONS

Gemifloxacin may be a suitable choice for empiric treatment of CAP or AECB. However, due to the significant history of fluoroquinolone-induced hepatic failure and dermatologic complications, the use of this drug should be closely monitored.

New findings on the structure-phototoxicity relationship and photostability of fluoroquinolones with various substituents at position 1

The present study examined the phototoxicities of a series of 7-(3-aminopyrrolidinyl) quinolones containing various substituents at position 1 (in which the substituent at R8 is a hydrogen or a halogen) by use of a mouse model. For the 7-(3-aminopyrrolidinyl) quinolones with a halogen atom at position 8, well-known substituent groups such as a cyclopropyl, an ethyl, or a difluorophenyl at position 1 were found to be responsible for severe phototoxicity. However, when an aminodifluorophenyl or an isoxazolyl group was placed at position 1, even 8-halogeno quinolones were found to be mildly phototoxic. This is the first report of 8-halogeno quinolones that are not severely phototoxic. Two structurally similar 8-chloro quinolones (the 1-aminodifluorophenyl 8-chloro quinolone and the 1-difluorophenyl 8-chloro quinolone) were investigated further. The former was mildly phototoxic; the latter was severely phototoxic. We demonstrate that these two 8-chloro quinolones have practically the same areas under the concentration-time curves from 0 to 4 h in auricular tissue, suggesting that the mild phototoxicity is not due to pharmacokinetic instability. The rates of UV photodegradation of these compounds were also measured. We found that these two quinolones photodegrade at similar rates, suggesting that the mild phototoxicity is not attained through increased photostability. In conclusion, the phototoxic potentials of fluoroquinolones are influenced not only by the substituent at position 8 but also by that at position 1 (a new finding from this study). We also discovered a mildly phototoxic 8-chloro quinolone which did not have increased photostability.

A randomized controlled trial (volunteer study) of sitafloxacin, enoxacin, levofloxacin and sparfloxacin phototoxicity

BACKGROUND

Fluoroquinolone antibiotics (FQs) are associated with phototoxic skin reactions following exposure to sunlight.

OBJECTIVES

We aimed to compare the phototoxic potential of sitafloxacin, a novel FQ with three others: sparfloxacin, enoxacin, levofloxacin and placebo in Caucasian volunteers. In a second study, two dosage regimens of sitafloxacin were compared with placebo in Oriental subjects.

METHODS

Randomized, placebo-controlled, assessor-blinded clinical trial. In 40 healthy Caucasians, sitafloxacin 100 mg twice a day (n = 8), sparfloxacin 200 mg day-1 (n = 8), enoxacin 200 mg three times a day (n = 8), levofloxacin 100 mg three times a day (n = 8) and placebo (n = 8) were given in oral doses for 6 days. In the second study, sitafloxacin 50 mg and 100 mg, both twice daily, were compared with placebo in 17 healthy Oriental subjects. Using an established monochromator technique, baseline threshold erythema levels were established pre-drug and on-drug. The phototoxic index (PI) baseline, minimal erythema dose (MED) divided by on-drug MED for each medication at each wavelength was determined and related to sitafloxacin peak plasma levels. The duration of susceptibility to phototoxicity was assessed by repeat phototesting daily after stopping medication.

RESULTS

In the Caucasian study, sitafloxacin 100 mg twice a day produced mild ultraviolet (UV) A-dependent phototoxicity (median PI = 1.45) at 365 +/- 30 nm (half-maximum bandwidth), maximal at 24 h with normalization by 24 h postdrug cessation. The sparfloxacin group experienced severe phototoxicity maximal at 24 h and, unusually for an FQ, extended in the visible region (430 +/- 30 nm), maximal at 400 +/- 30 nm (median PI = 12.35) with abnormal pigmentation at on-drug phototest sites lasting, although fading, for up to 1 year. Enoxacin showed UVA-dependent phototoxicity (335-365 +/- 30 nm) median PI 3.94 (at 365 +/- 30 nm) returning to normal 48 h after stopping the drug. Fading pigmentation at phototoxic sites also lasted up to 1 year. Phototoxicity was not detected in the levofloxacin or placebo groups. In the Oriental study, no clinically relevant phototoxicity was seen with either sitafloxacin or placebo groups.

CONCLUSIONS

We conclude that 100 mg twice a day sitafloxacin in Caucasians is associated with a mild degree of cutaneous phototoxicity. Enoxacin 200 mg three times a day and sparfloxacin 200 mg day-1 are much more photoactive. Sparfloxacin phototoxicity is induced by UVA and visible wavelengths. Levofloxacin and placebo failed to show a phototoxic effect. In the Oriental study, sitafloxacin 50 mg twice a day and 100 mg twice a day failed to demonstrate a clinically significant phototoxic effect.

Gemifloxacin Mesylate

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Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. If you would like information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The September 2003 monograph topics are tositumomab, omalizumab, emtricitabine, testosterone buccal system mucoadhesive, and alfuzosin. The DUE is on omalizumab.

Novel antibacterial agents for the treatment of serious Gram-positive infections

With the continuing development of clinical drug resistance among bacteria and the advent of resistance to the recently released agents quinupristin-dalfopristin and linezolid, the need for new, effective agents to treat multi-drug-resistant Gram-positive infections remains important. This review focuses on agents presently in clinical development for the treatment of serious multidrug-resistant staphylococcal, enterococcal and pneumococcal infections, including methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and penicillin-resistant Streptococcus pneumoniae. Agents to be discussed that affect the prokaryotic cell wall include the antimethicillin-resistant S. aureus cephalosporins BAL9141 and RWJ-54428, the glycopeptides oritavancin and dalbavancin and the lipopeptide daptomycin. Topoisomerase inhibitors include the fluoroquinolones gemifloxacin, sitafloxacin and garenoxacin. Protein synthesis inhibitors are represented by the ketolides telithromycin and cethromycin, the oxazolidinones and the glycylcycline tigecycline. Although each of these compounds has demonstrated antibacterial activity against antibiotic-resistant pathogens, their final regulatory approval will depend on an acceptable clinical safety profile.

A critical review of the fluoroquinolones: focus on respiratory infections

The new fluoroquinolones (clinafloxacin, gatifloxacin, gemifloxacin, grepafloxacin, levofloxacin, moxifloxacin, sitafloxacin, sparfloxacin and trovafloxacin) offer excellent activity against Gram-negative bacilli and improved Gram-positive activity (e.g. against Streptococcus pneumoniae and Staphylococcus aureus) over ciprofloxacin. Ciprofloxacin still maintains the best in vitro activity against Pseudomonas aeruginosa. Clinafloxacin, gatifloxacin, moxifloxacin, sitafloxacin, sparfloxacin and trovafloxacin display improved activity against anaerobes (e.g. Bacteroides fragilis) versus ciprofloxacin. All of the new fluoroquinolones display excellent bioavailability and have longer serum half-lives than ciprofloxacin allowing for once daily dose administration. Clinical trials comparing the new fluoroquinolones to each other or to standard therapy have demonstrated good efficacy in a variety of community-acquired respiratory infections (e.g. pneumonia, acute exacerbations of chronic bronchitis and acute sinusitis). Limited data suggest that the new fluoroquinolones as a class may lead to better outcomes in community-acquired pneumonia and acute exacerbations of chronic bronchitis versus comparators. Several of these agents have either been withdrawn from the market, had their use severely restricted because of adverse effects (clinafloxacin because of phototoxicity and hypoglycaemia; grepafloxacin because of prolongation of the QTc and resultant torsades de pointes; sparfloxacin because of phototoxicity; and trovafloxacin because of hepatotoxicity), or were discontinued during developmental phases. The remaining fluoroquinolones such as gatifloxacin, gemifloxacin, levofloxacin and moxifloxacin have adverse effect profiles similar to ciprofloxacin. Extensive post-marketing safety surveillance data (as are available with ciprofloxacin and levofloxacin) are required for all new fluoroquinolones before safety can be definitively established. Drug interactions are limited; however, all fluoroquinolones interact with metal ion containing drugs (eg. antacids). The new fluoroquinolones (gatifloxacin, gemifloxacin, levofloxacin and moxifloxacin) offer several advantages over ciprofloxacin and are emerging as important therapeutic agents in the treatment of community-acquired respiratory infections. Their broad spectrum of activity which includes respiratory pathogens such as penicillin and macrolide resistant S. pneumoniae, favourable pharmacokinetic parameters, good bacteriological and clinical efficacy will lead to growing use of these agents in the treatment of community-acquired pneumonia, acute exacerbations of chronic bronchitis and acute sinusitis. These agents may result in cost savings especially in situations where, because of their potent broad-spectrum activity and excellent bioavailability, they may be used orally in place of intravenous antibacterials. Prudent use of the new fluoroquinolones will be required to minimise the development of resistance to these agents.

Advances in DNA gyrase inhibitors

The therapeutic use of DNA gyrase inhibitors, mainly quinolone antibacterials, has proven to be a tremendous success story in the treatment of bacterial infections. The rapid changes in quinolone research and development in recent years have produced several new quinolones: moxifloxacin, gatifloxacin, gemifloxacin and des-6-fluoroquinolone antibacterials. These newly developed compounds are equal or superior to existing ones in their potency, spectrum of activity, pharmacodynamics/pharmacokinetics and safety profiles. The recent discovery of non-fluoroquinolones and 2-pyridone antibacterials represents yet additional progress in the search for novel DNA gyrase inhibitors. Although these two classes of compounds are either in the discovery or early development phase, they extend the possibilities of establishing new structure-activity relationships and new chemotypes for DNA gyrase inhibition.

Gemifloxacin

Gemifloxacin is a fluoroquinolone antibacterial agent which has an enhanced affinity for topoisomerase i.v.. It has potent activity against most Gram-positive bacteria, particularly Streptococcus pneumoniae. Gemifloxacin is over 30-fold more active than ciprofloxacin and 4- to 8-fold more active than moxifloxacin against this pathogen. Gemifloxacin has excellent activity against Haemophilus influenzae and Moraxella catarrhalis, and is unaffected by beta-lactamase production. It is generally 2-fold less active than ciprofloxacin against most Enterobacteriaceae. Atypical respiratory pathogens (Legionella, Mycoplasma and Chlamydia spp.) are highly susceptible to gemifloxacin. Preliminary results from phase II trials show that oral gemifloxacin 320 mg/day produced bacteriological responses of 94.7% in patients with acute exacerbations of chronic bronchitis and 95% of patients with uncomplicated urinary tract infections. Adverse events included nausea, abdominal pain, headache and mild rash in patients and healthy volunteers treated with gemifloxacin 320 mg/day. Gemifloxacin has a low potential for mild phototoxicity (comparable to that of ciprofloxacin).