Experimental intravitreal application of trovafloxacin in rabbits

This study was performed to examine the retinal toxicity of trovafloxacin, a broad-spectrum fourth-generation fluoroquinolone, in rabbit eyes after intravitreal injection. The left eyes of 20 albino rabbits were divided into four groups, and each was injected intravitreally with 0.1 ml of trovafloxacin in a 50-microg, 100-microg, 250-microg or 500-microg concentration. The right eyes of these rabbits served as control and received normal saline solution. Retinal function was assessed from the electroretinogram (ERG), and retinal structure was also examined by ophthalmoscopy and histologic study (light microscopy). The intravitreal injections of 50 microg, 100 microg, and 250 microg trovafloxacin did not significantly change the ERG a-wave, b-wave or the oscillatory potential throughout the follow-up period of 4 weeks. While no ERG changes were observed at 4 weeks after injection, in the 3 eyes that received trovaloxacin 500 microg/0.1 ml, the a-wave amplitudes showed a diminution of 56-49% and those of b-waves one of 53-44% of the preinjection amplitudes at 4 weeks after injection, but oscillatory potentials remained unchanged in the other 2 rabbits intravitreally injected with 500 microg trovafloxacin. However, in none of the injected eyes and the control eyes in all groups were ophthalmoscopically visible fundus changes and histologic abnormality observed. The results suggest that intravitreally injected trovafloxacin at a dose of up to 500 microg is nontoxic to the rabbit retina. If future studies in other species confirm our findings, intravitreal trovafloxacin may be a good alternative in the treatment and prevention of clinical bacterial endophthalmitis.

Endothelial cell compatibility of trovafloxacin and levofloxacin for intravenous use

Levofloxacin and trovafloxacin have excellent activity against a variety of Gram-positive and Gram-negative organisms resistant to the established agents. One local side-effect closely related to the use of parenteral fluoroquinolones is phlebitis. To evaluate the effect of trovafloxacin and levofloxacin on endothelial cell viability, intracellular levels of adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), guanosine 5'-triphosphate (GTP) and guanosine 5'-diphosphate (GDP) levels were measured using high-performance liquid chromatography. Trovafloxacin at concentrations of 2 and 1 mg/mL reduced the intracellular ATP content from 12.5 +/- 1.7 to 1.9 +/- 0.3 nmol/10(6) cells and 9.3 +/- 0.8 nmol/10(6) cells, respectively, within 60 min. In addition, ADP, GTP and GDP levels were extensively depleted. Levofloxacin at concentrations of 5 and 2.5 mg/mL led to a significant ATP decline from 12.5 +/- 1.7 to 2.3 +/- 0.2 nmol/10(6) cells and 10.3 +/- 0.9 nmol/10(6) cells, respectively, within 60 min. These data indicate that infusions of high doses of trovafloxacin or levofloxacin are not compatible with maintenance of endothelial cell function. Commercial preparations have to be diluted and should be administered into large veins.

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

This double-blind, randomized, parallel-group comparative study investigated the phototoxic potential of gemifloxacin mesylate, a potent, novel fluoroquinolone antimicrobial. Forty healthy male and female volunteers received repeat dosing for 7 days with 160 mg or 320 mg of gemifloxacin (o.d., p.m.), 500 mg of ciprofloxacin (b.d.) or placebo (b.d.). On day 5 (large step) and day 6 (small step), graded series of wavebands were irradiated onto the back of each volunteer (phototesting). Skin reactions were assessed 0-30 min (immediate erythema) and 24 and 48 h (delayed erythema) after irradiation. Both gemifloxacin, 320 mg o.d., and ciprofloxacin, 500 mg b.d., were associated with mild phototoxicity following 7 days of administration. The range of mean phototoxic indices (the ratio of minimal erythemal dose at baseline compared with that on day 7 at the end of dosing) was 1.00-2.19 for gemifloxacin and 0.97-2.23 for ciprofloxacin. The abnormal responses occurred within the ultraviolet A region (335-365 +/-30 nm) and were maximal at 24 h. Susceptibility to phototoxicity had cleared 48 h after stopping the drug. The phototoxicity observed with gemifloxacin, 160 mg o.d., was lower than that at the higher dose and similar to that of placebo, suggesting that gemifloxacin phototoxicity is dose dependent. There were no clinically important changes in the safety profiles of gemifloxacin and ciprofloxacin compared with placebo in healthy volunteers after 7 days of repeat dosing. This study demonstrated that gemifloxacin, 320 mg o.d. given for 7 days, has a low potential to cause mild photosensitivity which is similar to that of ciprofloxacin, 500 mg b.d., given for the same period.

Nonlinear models for in vitro kill kinetics of antibiotics

In this study, we developed nonlinear regression models to analyze the data generated from an in vitro continuous culture system to assess the kinetics of metronidazole and trovafloxacin in inhibiting the growth of Bacteroides fragilis. The model includes parameters describing the initial shock effect of an antibiotic pulse, the overall antibiotic wash-out rate from the system, and the long-term toxicity of the antibiotic in the environment after one pulse and before the next pulse.

Metabolism-dependent neutrophil cytotoxicity of amodiaquine: A comparison with pyronaridine and related antimalarial drugs

Life-threatening agranulocytosis and hepatotoxicity during prophylactic administration of amodiaquine have led to its withdrawal. Agranulocytosis is thought to involve bioactivation to a protein-reactive quinoneimine metabolite. The toxicity of amodiaquine and the lack of cheap drugs have prompted a search for alternative antimalarial agents. The aim of this study was to determine the metabolism and neutrophil toxicity of amodiaquine, pyronaridine, and other related antimalarial agents. Horseradish peroxidase and hydrogen peroxide were used to activate drugs to their respective quinoneimine metabolites. Metabolites were trapped as stable glutathione conjugates, prior to analysis by LC/MS. Amodiaquine was metabolized to a polar metabolite (m/z 661), identified as a glutathione adduct. Tebuquine was converted to two polar metabolites. The principal metabolite (m/z 686) was derived from glutathione conjugation and side chain elimination, while the minor metabolite gave a protonated molecule (m/z 496). Only parent ions were identified when chloroquine, cycloquine, or pyronaridine was incubated with the activating system and glutathione. Calculation of the heat of formation of the drugs, however, demonstrated that amodiaquine, tebuquine, cycloquine, and pyronaridine readily undergo oxidation to their quinoneimine. None of the antimalarial compounds depleted the level of intracellular glutathione (1-300 microM) when incubated with neutrophils alone. Additionally, with the exception of tebuquine, no cytotoxicity below 100 microM was observed. In the presence of the full activating system, however, all compounds except chloroquine resulted in depletion of the level of glutathione and were cytotoxic. Pretreating the cells with glutathione and other antioxidants inhibited metabolism-dependent cytotoxicity. In summary, our data show that amodiaquine and related antimalarials containing a p-aminophenol moiety undergo bioactivation in vitro to chemically reactive and cytotoxic intermediates. In particular, pyronaridine, which is currently being investigated in humans, was metabolized to a compound which was toxic to neutrophils. Thus, the possibility that it will cause agranulocytosis in clinical practice cannot be excluded, and will require careful monitoring.

Antitumor agents. 178. Synthesis and biological evaluation of substituted 2-aryl-1,8-naphthyridin-4(1H)-ones as antitumor agents that inhibit tubulin polymerization

As part of our continuing search for potential anticancer drug candidates in the 2-aryl-1,8-naphthyridin-4(1H)-one series, we have synthesized two series of 3'-substituted 2-phenyl-1,8-naphthyridin-4(1H)-ones and 2-naphthyl-1,8-naphthyridin-4(1H)-ones. All compounds showed significant cytotoxic effects (log GI50 < -4.0; log molar drug concentration required to cause 50% growth inhibition) against a variety of human tumor cell lines of the National Cancer Institute's in vitro screen, including cells derived from solid tumors such as non-small cell lung, colon, central nervous system, melanoma, ovarian, prostate, and breast cancers. All 3'-substituted compounds demonstrated strong cytotoxic effects in almost all tumor cell lines. Introduction of an aromatic ring at the 2'- and 3'-positions also generated compounds with potent antitumor activity. Incorporation of an aromatic ring at the 3'- and 4'-positions produced compounds with reduced activity. Interestingly, introduction of a halogen at the 3'-position yielded compounds with different selectivity for the tumor cell lines tested. All 3'-halogenated compounds (29-36) and compounds 38 and 42-44 were potent inhibitors of tubulin polymerization with activities nearly comparable to those of the potent antimitotic natural products colchicine, podophyllotoxin, and combretastatin A-4. Active agents also inhibited the binding of [3H]colchicine to tubulin.

Synthesis of N-benzyl-4-oxo-1,2,3,4-tetrahydrocinnolines

The method of preparation of N1 and N2-substituted 4-hydroxycinnolines by alkylation with benzyl bromide of the corresponding 4-hydroxycinnolines is described. The obtained derivatives were reduced to the corresponding N-benzyl-4-oxo-1,2,3,4-tetrahydrocinnolines. The effect of some synthesized derivatives on central nervous system was studied.

Antitumor agents. 174. 2',3',4',5,6,7-Substituted 2-phenyl-1,8-naphthyridin-4-ones: their synthesis, cytotoxicity, and inhibition of tubulin polymerization

Two series of 2',3',4',5,6,7-substituted 2-phenyl-1,8-naphthyridin-4-ones and 2-phenylpyrido[1,2-alpha]pyrimidin-4-ones have been synthesized and evaluated as cytotoxic compounds and as inhibitors of tubulin polymerization. Most 2-phenyl-1,8-naphthyridin-4-ones showed potent cytotoxic and antitubulin activities, whereas 2-phenylpyrido[1,2-alpha]pyrimidin-4-ones showed no activity in either assay. In general, a good correlation was found between cytotoxicity and inhibition of tubulin polymerization in the 2-phenyl-1,8-naphthyridin-4-one series. The 2-phenyl-1,8-naphthyridin-4-ones (44-49) with a methoxy group at the 3'-position showed potent cytotoxicity against most tumor cell lines with GI50 values in the low micromolar to nanomolar concentration range in the National Cancer Institute's 60 human tumor cell line in vitro screen. Introduction of substituents (e.g. F, Cl, CH3, and OCH3) at the 4'-position led to compounds with reduced or little activity and substitution at the 2'-position resulted in inactive compounds. The effects of various A-ring substitutions on activity depend on the substitution in ring C. Compounds 44-50 were potent inhibitors of tubulin polymerization, with activity nearly comparable to that of the potent antimitotic natural products colchicine, podophyllotoxin, and combretastatin A-4. Compounds 44-49 also inhibited the binding of radiolabeled colchicine to tubulin, but the inhibition was less potent than that obtained with the natural products. Further investigation is underway to determine if substitution at the 3'-position and multisubstitutions in ring C will result in compounds with increased activity.

A study of the phototoxic potential of trovafloxacin in BALB/c mice

Trovafloxacin, a broad-spectrum naphthyridone antimicrobial agent, was evaluated for potential phototoxicity in a standardized in-vivo test system that has been used previously to assess quinolone antibiotics. Fasted BALB/c mice were given a single oral dose of either trovafloxacin mesylate (10, 30, 90 or 250 mg/kg) or the positive control lomefloxacin hydrochloride (71 mg/kg) and immediately exposed to long-wave ultraviolet (UVA) light. Animals were irradiated for 4 h, equal to a total UV light irradiation of approximately 18 J/cm2. Before dosing, at the end of the irradiation period and at approximately 24, 48, 72 and 96 h after dosing, both ears of each mouse were evaluated for changes indicative of a positive response: erythema, oedema or a measurable increase in ear thickness. Under the conditions of this study, trovafloxacin produced a mild response (erythema and a slight increase in ear thickness) in mice given a dose of 90 or 250 mg/kg; no significant response was observed in mice given either lower doses (10 or 30 mg/kg) or the vehicle. In contrast, 71 mg/kg of lomefloxacin produced a strong and persistent phototoxic response. The results of this study demonstrate that the phototoxic potential of trovafloxacin is considerably less than that of lomefloxacin and, when compared with similar studies with related compounds, suggest that trovafloxacin is among the least phototoxic of the fluoroquinolone class.

Absorption of the anxiolytic pazinaclone in animals as a criterion for species selection for toxicity studies

In rats, mice, hamsters, and guinea pigs given a 5 mg/kg oral dose of pazinaclone (CAS 103255-66-9), unchanged drug concentration in plasma was highest in mice (AUC; 90 ng.h/ml), followed in decreasing order by guinea pigs (AUC; 41 ng.h/ml), hamsters (AUC; 18 ng.h/ml), and rats (AUC; 17 ng.h/ml). In terms of plasma drug concentrations and toxicological background data, there was no better alternative rodents than mice and rats for the toxicity studies. Among rabbits, dogs, and monkeys, the dogs had the highest plasma drug concentrations: AUCs of pazinaclone in dogs and monkeys were 1035 and 458 ng. h/ml, respectively (drug concentration in rabbit plasma was very low). Of the two polymorphs, forms 1 and 2 with particle size of < or = 5 microns, the oral absorption of form 2 in rats was more efficient than that of form 1 at 1000 mg/kg: AUCs of pazinaclone after dosing of form 1 and 2 were 489 and 965 ng.h/ml, respectively. However, form 1 was selected for the toxicity studies because of the poor physico-chemical properties of forms 2. Form 3 was not included in this study, because this form was relatively unstable and contained relatively large amount of impurities. The absorption of pazinaclone in dogs was improved by decreasing its particle size: AUCs of pazinaclone after dosing of the drug having particle size of 5.5, 20.8, and 79.3 microns were 1361, 822, and 297 ng.h/ml, respectively. Since large-scale preparation of bulk pazinaclone with a particle size of 5 microns or smaller was not feasible, the drug having a particle size of about 20 microns was used in the toxicity studies. The absorption of pazinaclone was more extensive when the drug was given to fed animals as suspension. Thus, the toxicity studies were performed using form I of pazinaclone with a particle size of about 20 microns primarily in rats, mice, and dogs.

Enantiomeric toxicokinetics of the new isoindoline anxiolytic pazinaclone in rats and dogs

Enantiomeric toxicokinetics of the new isoindoline pazinaclone (CAS 103255-66-9, DN-2327) were studied in rats and dogs of both sexes after oral administration by gavage. Non-toxic doses in 4-week toxicity studies in rats are > or = 3000 mg/kg/d and 500 mg/kg/d for S- and R-pazinaclone, respectively; the corresponding doses in dogs are 10 and 4 mg/kg/d, respectively. R-Pazinaclone is more toxic in female rats than in male rats. In both rats and dogs, circulating enantiomer concentrations of pazinaclone and the active M-II metabolite increased with dose. Higher S- and R-pazinaclone concentrations were found in female rats than in male rats; the concentrations in dogs were sex independent. In rats, the AUCs for the parent compound after a 3000 mg/kg oral dose of S-pazinaclone were about 9-fold (males) and 4-fold (females) greater than those after dosing of R-pazinaclone at 500 mg/kg. In dogs, the AUC for the parent compound after a 10 mg/kg oral dose of S-pazinaclone was 33-fold greater than that after oral dosing of the R-enantiomer at 4 mg/kg. The toxic activity is thus likely to reside predominantly in the R-enantiomers of pazinaclone and M-II. The exposure of the R-enantiomers in humans, after administration of the anticipated clinical dose of the racemic drug, seemed to be no more than that in rats and dogs at nontoxic doses.

Prenatal exposure to cocaine: effects on aggression in Sprague-Dawley rats

Social/aggressive behavior in adult rat offspring (beginning at postnatal Day 180) prenatally exposed to saline, cocaine, or amfonelic acid (AFA) was examined. Pregnant rats received injections of 15 mg/kg of cocaine, or 0.9% saline twice daily, s.c., or on 2 consecutive days at 4-day intervals, or 1.5 mg/kg amfonelic acid daily throughout gestational Days 1-20. Frequency, duration, and latency of 11 social/aggressive behaviors were recorded for two 15-min sessions during which a smaller male intruder replaced an ovariectomized female in the resident's home cage. Subjects received a s.c. saline injection before Session 1 and 2.0 mg/kg of gepirone, a 5HT1a partial agonist, prior to Session 2. Prenatal cocaine treatment resulted in alterations of aggressive behavior. Aggressive behavior was reduced by gepirone in all groups but to a lesser extent in the AFA group.

Substituted 1,8-naphthyridin-2(1H)-ones as selective phosphodiesterase IV inhibitors

New substituted 1,8-naphthyridin-2(1H)-ones have been found to exhibit highly selective phosphodiesterase (PDE) IV inhibition. These compounds inhibited polymorphonuclear leukocyte activation induced by N-formylmethionyl-leucyl-phenylalanine and caused relaxation of isolated guinea pig trachea precontracted by histamine or leukotriene D4. In anesthetized guinea pigs, presensitized with the antigen, these compounds also alleviated airway constriction induced by the antigen. Since these compounds differ in their chemical structure compared with theophylline and other PDE IV inhibitors so far reported and some of them have been shown to be well tolerated in acute toxicity studies, they will provide a new tool for investigating the possible relationship between PDE IV inhibition and anti-asthmatic activity.

1,8-naphthyridines II. 2,4-disubstituted N,N-dialkyl-1,8-naphthyridine-3-carboxamides with anti-inflammatory and/or antiaggressive activities

The preparation of the novel N,N-dialkyl-2,4-dichloro-1,8-naphthyridine-3-carboxamides 1c, e and N,N-dialkyl-2-(alkylamino or cycloalkylamino)-4-chloro-1,8-naphthyridine-3- carboxamides 2b, d-g, j-p is described. These compounds and the previously obtained analogs 1a, b, d, f and 2a, c, h, i have been tested for their anti-inflammatory and antiaggressive activities, as well as for their gross behavioral effects and acute toxicity. Nine of the twenty-two tested compounds exhibited a statistically significant anti-inflammatory activity in the carrageenin-induced edema assay in the rat (1e, f and 2h, o were the most active compounds). On the other hand, an interesting antiaggressive activity was displayed by ten compounds in the isolation-induced aggressiveness test in mice (compounds 2d, i, k showed the highest activity). Structure-activity relationships are briefly discussed.

Changes in dopamine, serotonin and their metabolites in discrete brain areas of rat offspring after in utero exposure to cocaine or related drugs

The concentrations of dopamine (DA), serotonin (5HT) and their metabolites were quantified in 5 brain areas of rats exposed to saline, cocaine (15 mg/kg b.i.d.), amitriptyline (10 mg/kg), or amfonelic acid (AFA, 1.5 mg/kg) throughout gestation. Male pups from 3 similarly treated dams were fostered to 2 surrogate dams. The process of breeding and rearing was repeated 4 times with new dams to build the groups to 4-12, since only one pup per litter was used for any one measurement. AFA was used to mimic the dopamine (DA) uptake blockade and stimulant properties of cocaine and amitriptyline was used to mimic the other pharmacological effects of cocaine. At postnatal days (PND) 30, 60, and 180, one pup per litter was removed for HPLC analysis of monoamines. A second pup received 0.3 mg/kg haloperidol, catalepsy assessed after 1 hr, and the brain used for analysis. The cataleptic response to haloperidol was unaffected by any prenatal treatment. The striatum from PND 30 cocaine rats had decreased levels of DA without a decrease in DA metabolites. At PND 60 in cocaine exposed rats, DA and DOPAC concentrations were increased, and 5HT levels were decreased in the striatum. The amitriptyline-exposed group exhibited decreased 5HT and 5-HIAA levels in the striatum. The hypothalamus of the cocaine group had lower levels of 5-HIAA, and other brain areas had a trend for lower levels of 5HT and 5-HIAA. At PND 180, DOPAC was increased in the striatum and prefrontal cortex of the cocaine group. Haloperidol-induced altered monoamine metabolism was unaffected by any prenatal treatment at any age. These data suggest that age-related changes in the DA and 5HT neurotransmission systems occur in rats exposed prenatally to cocaine. However, the ability of the dopaminergic system to respond to a challenge by a DA receptor blocker is unaltered by these in utero treatments.

High capacity in vitro micronucleus assay for assessment of chromosome damage: results with quinolone/naphthyridone antibacterials

A high capacity in vitro micronucleus assay was developed to evaluate the ability of selected 6-fluorinated quinolone and naphthyridone antibacterial compounds to induce micronuclei (MN) in vitro in V79 Chinese hamster lung cells. Log-phase cells in six-well cluster dishes were exposed for 3 h in the absence of S9 to 34 compounds. After treatment, cells were refed with media containing cytochalasin B, incubated for 16 h, and harvested for cell-cycle kinetics (CCK) and MN analyses. The quinolones tested were grouped according to the substituent at the 8-position. All 4 compounds having a halogen substitution at position 8, five of the six 8-trifluoromethyl quinolones, and all eight 8-methoxy-substituted compounds induced a significant increase in MN. Only 5 of the 10 naphthyridone compounds tested, having a variety of substituents at the 7-position, were inducers of MN and the overall magnitude of the response was less than with the quinolones. The minimum clastogenic concentration for the quinolones ranged from 4 to 400 micrograms/ml and for the naphthyridones this range was from 22.5 to 100 micrograms/ml. In the groups examined, napthyridone compounds were less likely than quinolones to induce in vitro MN, particularly when the substituent at the 7-position in the naphthyridone contains some bulk (methyl groups) around the amine side-chain. Most of the quinolones tested induced MN, irrespective of the substituents at positions 7 or 8.

Studies on a new antimalarial compound: pyronaridine

Pyronaridine, a hydroxyanilino-benzonaphthyridine derivative synthesized in 1970, is a new antimalarial compound which has been in use in China for more than 10 years. The drug is highly effective against Plasmodium falciparum and P. vivax. Furthermore, it is efficacious in combatting chloroquine-resistant strains of falciparum malaria both in vitro and in vivo, in human patients. Extensive field studies involving several thousand cases have shown that pyronaridine has promising therapeutic value in the treatment of malarial infection, including chloroquine-resistant infections. Pyronaridine given orally, intramuscularly or by intravenous drip is not only effective against malaria but also has low toxicity.

Experimental studies on combinations of pyronaridine/primaquine versus chloroquine/primaquine

The toxicity of combined use of blood schizontocide pyronaridine (PND) and primaquine (PQ) in mice and rats was significantly lower than that of chloroquine (CQ) plus primaquine (PQ). PND 1/2 LD50 (ca 600 mg/kg) in combination with PQ reduced the toxic action of PQ in mice, while CQ 1/2 LD50 (ca 300 mg/kg) plus PQ produced synergistic toxic effect. In animal models such as Plasmodium yoelii sporozoite infection in mice and P. cynomolgi sporozoite infection in rhesus monkeys, the tissue schizontocidal action of PQ was not affected by PND. Therefore, clinical evaluation of PND/PQ in comparison with CQ/PQ in treating vivax malaria is suggested.

Antimalarial and toxic effect of triple combination of pyronaridine, sulfadoxine and pyrimethamine

The triple combination of pyronaridine, sulfadoxine and pyrimethamine which has been proven to be efficient in delaying emergence of drug resistance of rodent malarial parasites was further studied for potential application to malaria control. The antimalarial effect of the triple combination on Plasmodium berghei ANKA-infected mice and the toxic effects in mice and rats were additive. A single dose of pyronaridine 500 mg in combination with sulfadoxine, 1000 or 1500 mg, and pyrimethamine, 50 or 75 mg, given to 72 acute falciparum malaria patients resulted in a 100% cure rate with nil or mild side effects, and no recrudescence of asexual parasite over 4-week follow-up. Preliminary experiments on the drug effect on sporogony showed that the drug combination at the dose used could not completely interrupt the sporozoite formation although many retarded oocysts were found.