Pharmacokinetics and pharmacodynamics of the nitroimidazole antimicrobials

Ten-day sequential therapy is more effective than proton pump inhibitor-based therapy in Korea: a prospective, randomized study

BACKGROUND AND AIMS

The eradication rate of proton pump inhibitor (PPI)-based triple therapy for Helicobacter pylori (H. pylori) infection has decreased, mainly due to increasing antibiotic resistance, especially against clarithromycin. It has been reported that a 10-day sequential strategy can produce good outcomes. The aim of this prospective study was to assess the efficacy of sequential therapy as the first-line treatment for the eradication of H. pylori in Korea.

METHODS

A total of 116 patients with proven H. pylori infection received 10-day sequential therapy (20 mg rabeprazole and 1 g amoxicillin, twice daily for the first 5 days, followed by 20 mg rabeprazole, 500 mg clarithromycin, and 500 mg metronidazole, twice daily for the remaining 5 days); 130 patients received 7-day triple therapy (20 mg rabeprazole, 500 mg clarithromycin, and 1 g amoxicillin, twice daily for 7 days). Eradication was evaluated by the (13) C-urea breath test, 4 weeks after the completion of treatment. Compliance and adverse events were assessed.

RESULTS

The eradication rates of 10-day sequential therapy and PPI-based triple therapy were 79.3% (92/116) and 63% (82/130) by intention-to-treat analysis, respectively (P = 0.005), and 81.9% (91/111) and 64.5% (82/127) by per protocol analysis, respectively (P = 0.003). Mild adverse events occurred in both therapy groups (27.5% vs 23.8%), but both treatments were well tolerated.

CONCLUSION

The eradication rate of the 10-day sequential therapy regimen was significantly higher than that of PPI-based triple therapy in the Korean population. Ten-day sequential therapy might be effective as a first-line treatment for H. pylori infection in Korea.

Population pharmacokinetics of metronidazole evaluated using scavenged samples from preterm infants

Pharmacokinetic (PK) studies in preterm infants are rarely conducted due to the research challenges posed by this population. To overcome these challenges, minimal-risk methods such as scavenged sampling can be used to evaluate the PK of commonly used drugs in this population. We evaluated the population PK of metronidazole using targeted sparse sampling and scavenged samples from infants that were ≤ 32 weeks of gestational age at birth and <120 postnatal days. A 5-center study was performed. A population PK model using nonlinear mixed-effect modeling (NONMEM) was developed. Covariate effects were evaluated based on estimated precision and clinical significance. Using the individual Bayesian PK estimates from the final population PK model and the dosing regimen used for each subject, the proportion of subjects achieving the therapeutic target of trough concentrations >8 mg/liter was calculated. Monte Carlo simulations were performed to evaluate the adequacy of different dosing recommendations per gestational age group. Thirty-two preterm infants were enrolled: the median (range) gestational age at birth was 27 (22 to 32) weeks, postnatal age was 41 (0 to 97) days, postmenstrual age (PMA) was 32 (24 to 43) weeks, and weight was 1,495 (678 to 3,850) g. The final PK data set contained 116 samples; 104/116 (90%) were scavenged from discarded clinical specimens. Metronidazole population PK was best described by a 1-compartment model. The population mean clearance (CL; liter/h) was determined as 0.0397 × (weight/1.5) × (PMA/32)²·⁴⁹ using a volume of distribution (V) (liter) of 1.07 × (weight/1.5). The relative standard errors around parameter estimates ranged between 11% and 30%. On average, metronidazole concentrations in scavenged samples were 30% lower than those measured in scheduled blood draws. The majority of infants (>70%) met predefined pharmacodynamic efficacy targets. A new, simplified, postmenstrual-age-based dosing regimen is recommended for this population. Minimal-risk methods such as scavenged PK sampling provided meaningful information related to development of metronidazole PK models and dosing recommendations.

Prospective observational study comparing three different treatment regimes in patients with Clostridium difficile infection

In a hospital-based, prospective cohort study, the effects of the three standard treatment regimens for mild Clostridium difficile infection (CDI), oral (p.o.) metronidazole at 500 mg three times/day, intravenous (i.v.) metronidazole at 500 mg three times/day, and oral (p.o.) vancomycin at 250 mg four times/day, were compared with respect to the risk of occurrence of complications, sequelae, and all-cause death within 30 days after the date of starting treatment. Differences in the incidence of these outcomes were tested by χ² or Fisher's exact tests. A Poisson regression model was performed to control for possible confounding effects of sex, age, and severity of comorbidity categorized according to the Charlson comorbidity index. The highest mortality was observed in the metronidazole i.v. group, with a mortality rate 38.1% (16/42) compared to mortality rates of 7.4% (9/121) in the metronidazole p.o. group and 9.5% (4/42) in the vancomycin p.o. group (P < 0.001). After adjustment for possible effects of sex, age (> 65 years), and severity of comorbidity, the relative risk of a 30-day fatal outcome for patients receiving metronidazole i.v. was 4.3 (95% confidence interval [CI] = 1.92 to 10; P < 0.0001) compared to patients treated with metronidazole p.o. and 4.0 (95% CI = 1.31 to 5.0; P < 0.015) compared to patients treated with vancomycin p.o. There were no significant differences in the risk of complications between the three treatment groups. This study generates the hypothesis that treatment with i.v. metronidazole is inferior to the oral alternatives metronidazole and vancomycin.

Substrate specificity of the deazaflavin-dependent nitroreductase from Mycobacterium tuberculosis responsible for the bioreductive activation of bicyclic nitroimidazoles

The bicyclic 4-nitroimidazoles PA-824 and OPC-67683 represent a promising novel class of therapeutics for tuberculosis and are currently in phase II clinical development. Both compounds are pro-drugs that are reductively activated by a deazaflavin (F(420)) dependent nitroreductase (Ddn). Herein we describe the biochemical properties of Ddn including the optimal enzymatic turnover conditions and substrate specificity. The preference of the enzyme for the (S) isomer of PA-824 over the (R) isomer is directed by the presence of a long hydrophobic tail. Nitroimidazo-oxazoles bearing only short alkyl substituents at the C-7 position of the oxazole were reduced by Ddn without any stereochemical preference. However, with bulkier substitutions on the tail of the oxazole, Ddn displayed stereospecificity. Ddn mediated metabolism of PA-824 results in the release of reactive nitrogen species. We have employed a direct chemiluminescence based nitric oxide (NO) detection assay to measure the kinetics of NO production by Ddn. Binding affinity of PA-824 to Ddn was monitored through intrinsic fluorescence quenching of the protein facilitating a turnover-independent assessment of affinity. Our results indicate that (R)-PA-824, despite not being turned over by Ddn, binds to the enzyme with the same affinity as the active (S) isomer. This result, in combination with docking studies in the active site, suggests that the (R) isomer probably has a different binding mode than the (S) with the C-3 of the imidazole ring orienting in a non-productive position with respect to the incoming hydride from F(420). The results presented provide insight into the biochemical mechanism of reduction and elucidate structural features important for understanding substrate binding.

Randomised clinical trial: a comparative study of 10-day sequential therapy with 7-day standard triple therapy for Helicobacter pylori infection in naïve patients

BACKGROUND

The eradication rates following standard triple therapy for Helicobacter pylori infection are declining worldwide. Recent studies have shown that sequential therapy for H. pylori infection yields high cure rates.

AIM

To compare the efficacy and tolerability of a sequential regimen as first-line treatment of H. pylori infection with a standard triple regimen.

METHODS

A total of 348 naïve H. pylori-infected patients from six hospitals in Korea were assigned randomly to standard triple or sequential therapy groups. Standard triple therapy consisted of 20 mg of rabeprazole, 1 g of amoxicillin and 500 mg of clarithromycin, twice daily for 7 days. Sequential therapy consisted of a 5-day dual therapy (20 mg of rabeprazole and 1 g of amoxicillin, twice daily) followed by a 5-day triple therapy (20 mg of rabeprazole, 500 mg of clarithromycin, and 500 mg of metronidazole, twice daily).

RESULTS

The intention-to-treat (ITT) and per-protocol (PP) eradication rates were 62.2% (95% CI 54.8-69.6%) and 76.0% (95% CI 68.5-83.5%) in the standard triple group, and 77.8% (95% CI 71.4-84.2%) and 87.9% (95% CI 82.3-93.5%) in the sequential group, respectively. The eradication rate was significantly higher in the sequential group compared with the standard triple group in both the ITT and PP populations (P = 0.002 and P = 0.013 respectively), whereas the incidence of adverse events was similar.

CONCLUSIONS

Ten-day sequential therapy is more effective and equally tolerated for eradication of H. pylori infection compared with standard triple therapy. Sequential therapy may have a role as first-line treatment for H. pylori infection.

Metabolism and pharmacokinetics of morinidazole in humans: identification of diastereoisomeric morpholine N+-glucuronides catalyzed by UDP glucuronosyltransferase 1A9

Morinidazole [R,S-1-(2-methyl-5-nitro-1H-imidazol-1-yl)-3-morpholinopropan-2-ol] is a new 5-nitroimidazole class antimicrobial agent. The present study aimed to determine the metabolism and pharmacokinetics of morinidazole in humans and to identify the enzymes responsible for the formation of the major metabolites. Plasma and urine samples were collected before and after an intravenous drip infusion of 500 mg of racemic morinidazole. Ultraperformance liquid chromatography/quadrupole time-of-flight mass spectrometry revealed 10 metabolites. Morinidazole glucuronidation, followed by renal excretion, was the major elimination pathway, accounting for 35% of the dose. The metabolic pathway displayed regioselectivities and stereoselectivities. Unexpectedly, the nitrogen atom of the morpholine ring, rather than the aliphatic hydroxyl group at the side chain, was glucuronidated to form S-morinidazole glucuronide (M8-1) and R-enantiomer glucuronide (M8-2). The plasma exposure of M8-2 was 6-fold higher than that of M8-1, accounting for 22.9 and 3.96% of the parent drug exposure, respectively. Investigation of morinidazole glucuronidation using human liver microsomes (HLMs) and 12 recombinant UDP glucuronosyltransferases (UGTs) indicated that this biotransformation was mainly catalyzed by UGT1A9. A kinetic study showed that N(+)-glucuronidation of racemic morinidazole in both HLMs and in UGT1A9 obeyed a typical Michaelis-Menten plot. The K(m) values for M8-1 and M8-2 formation by HLMs were similar (11.3 and 15.1 mM), but the V(max) values were significantly different (111 and 1660 pmol · min(-1) · mg protein(-1)). Overall, after an intravenous administration, morinidazole and its metabolites were eliminated in humans primarily via renal excretion. The major metabolites were two diastereoisomeric N(+)-glucuronides, and UGT1A9 played an important role in N(+)-glucuronidation.

Metronidazole-induced encephalopathy in a patient with liver cirrhosis

Encephalopathy is a disorder characterized by altered brain function, which can be attributed to various causes. Encephalopathy associated with metronidazole administration occurs rarely and depends on the cumulative metronidazole dose, and most patients with this condition recover rapidly after discontinuation of therapy. Because metronidazole is metabolized in the liver and can be transported by the cerebrospinal fluid and cross the blood-brain barrier, it may induce encephalopathy even at a low cumulative dose in patients with hepatic dysfunction. We experienced a patient who showed ataxic gait and dysarthric speech after receiving metronidazole for the treatment of hepatic encephalopathy that was not controlled by the administration of lactulose. The patient was diagnosed as metronidazole-induced encephalopathy, and stopping drug administration resulted in a complete recovery from encephalopathy. This case shows that caution should be exercised when administering metronidazole because even a low dose can induce encephalopathy in patients with liver cirrhosis.

Nitroimidazoles for the treatment of TB: past, present and future

Tuberculosis remains a leading cause of death resulting from an infectious agent, and the spread of multi- and extensively drug-resistant strains of Mycobacterium tuberculosis poses a threat to management of global health. New drugs that effectively shorten the duration of treatment and are active against drug-resistant strains of this pathogen are urgently required to develop effective chemotherapies to combat this disease. Two nitroimidazoles, PA-824 and OPC-67683, are currently in Phase II clinical trials for the treatment of TB and the outcome of these may determine the future directions of drug development for anti-tubercular nitroimidazoles. In this review we summarize the development of these nitroimidazoles and alternative analogs in these series that may offer attractive alternatives to PA-824 and OPC-67683 for further development in the drug-discovery pipeline. Lastly, the potential pitfalls in the development of nitroimidazoles as drugs for TB are discussed.

Metronidazole population pharmacokinetics in preterm neonates using dried blood-spot sampling

OBJECTIVES

To characterize the population pharmacokinetics of metronidazole in preterm neonates.

PATIENTS AND METHODS

Data were collected prospectively from 32 preterm neonates who received intravenous metronidazole for the treatment of or prophylaxis against necrotizing enterocolitis. Dried blood spots (n = 203) on filter paper were analyzed by high-performance liquid chromatography, and the data were subjected to pharmacokinetic analysis performed by using nonlinear mixed-effect modeling.

RESULTS

A 1-compartment model best described the data. Significant covariates were weight (WT) and postmenstrual age (PMA). The final population models for metronidazole clearance (CL) and volume of distribution (V) were: CL = 0.0247 × (WT/1.00)(0.75) × (1 + 0.107 × [PMA - 30]) and V = 0.726 × WT, where CL is in liters per hour, WT is in kilograms, PMA is in weeks, and V is in liters. This model predicts that the half-life of metronidazole decreases rapidly from ∼40 hours at 25 weeks' PMA to 19 hours at 32 weeks' PMA, after which it starts to plateau. This decrease in half-life is the result of a 5-fold increase in CL compared with only a 2.5-fold increase in V during the same period.

CONCLUSIONS

Currently, there are no specific dose recommendations for metronidazole in preterm neonates. However, a dosing scheme for preterm neonates that takes into consideration both the weight and PMA has been suggested and should avoid administration of doses that are excessive or more frequent than necessary.

Simultaneous determination of metronidazole and spiramycin in bulk powder and in tablets using different spectrophotometric techniques

Metronidazole (MZ) is an anti-infective drug used in the treatment of anaerobic bacterial and protozoa infections in humans. It is also used as a veterinary antiparasitic drug. Spiramycin (SP) is a medium-spectrum antibiotic with high effectiveness against Gram-positive bacteria. Three simple, sensitive, selective and precise spectrophotometric methods were developed and validated for the simultaneous determination of MZ and SP in their pure form and in pharmaceutical formulations. In methods A and B, MZ was determined by the application of direct spectrophotometry and by measuring its zero-order (D(0)) absorption spectra at its λ(max) = 311 nm. In method A, SP was determined by the application of first derivative spectrophotometry (D(1)) and by measuring the amplitude at 218.3 nm. In method B, the first derivative of the ratio spectra (DD(1)) was applied, and SP was determined by measuring the peak amplitude at 245.6 nm. Method C entailed mean centering of the ratio spectra (MCR), which allows the determination of both MZ and SP. The methods developed were used for the determination of MZ and SP over a concentration range of 5-25 µg ml(-1). The proposed methods were used to determine both drugs in their pure, powdered forms with mean percentage recoveries of 100.16 ± 0.73 for MZ in methods A and B, 101.10 ± 0.90 in method C, 100.09 ± 0.70, 100.02 ± 0.88 and 100.49 ± 1.26 for SP in methods A, B and C, respectively. The proposed methods were proved using laboratory-prepared mixtures of the two drugs and were successfully applied to the analysis of MZ and SP in tablet formulation without any interference from each other or from the excipients. The results obtained by applying the proposed methods were compared statistically with a reported HPLC method and no significant difference was observed between these methods regarding both accuracy and precision.

Optimization, characterisation and pharmacokinetic studies of mucoadhesive oral multiple unit systems of ornidazole

The objective of the present study was to investigate the applicability of matrix type mucoadhesive oral multiple unit systems (MUS) for sustaining the release of ornidazole in the gastrointestinal tract (GIT). The MUS were prepared by ionotropic gelation method using chitosan and hydroxypropyl methyl cellulose K4M (HPMC K4M) according to 3² factorial designs and were evaluated in vitro and in vivo. The particle size length ranged from 0.78 to 1.30 mm and breadth from 0.76 to 1.30 mm, respectively. The entrapment efficiency was in range of 80 to 96%. The rapid wash-off test was observed faster at intestinal pH 6.8 as compared to acidic pH 1.2. The fluoroscopic study revealed the retention of MUS in GIT for more than 5 hours. The pharmacokinetic parameters C_max, T_max, mean residence time (MRT) and area under curve (AUC) of developed MUS were found to be improved significantly (p<0.05) when compared with marketed immediate release tablets each containing 500 mg of drug. This study demonstrates that the MUS could be a good alternative to immediate release tablets to deliver ornidazole and expected to be less irritant to gastric and intestinal mucosa.

Activity of Extracts and Procesterol from Calotropis gigantea against Entamoeba histolytica

Extracts from the root bark of Calotropis gigantea were subjected to bioactivity-guided fractionation using growth inhibitory effects against Entamoeba histolytica. The n-hexane soluble portion of the chloroform extract showed in vitro antiamoebic activity against the HK-9 strain of Entamoeba histolytica. Chromatographic separation of the chloroform extract afforded the known compound, procesterol, which showed activity against E. histolytica.

Diagnosis and management of complicated intra-abdominal infection in adults and children: guidelines by the Surgical Infection Society and the Infectious Diseases Society of America

Evidence-based guidelines for managing patients with intra-abdominal infection were prepared by an Expert Panel of the Surgical Infection Society and the Infectious Diseases Society of America. These updated guidelines replace those previously published in 2002 and 2003. The guidelines are intended for treating patients who either have these infections or may be at risk for them. New information, based on publications from the period 2003-2008, is incorporated into this guideline document. The panel has also added recommendations for managing intra-abdominal infection in children, particularly where such management differs from that of adults; for appendicitis in patients of all ages; and for necrotizing enterocolitis in neonates.

Compliance with dosing recommendations from common references in prescribing antibiotics for preterm neonates

PURPOSE

Incorrect dosage was the most common type of medication errors in neonate patients. Different dosing recommendations from common reference sources may have contributed to the errors. This study assesses the compliance rate with the common reference sources in antibiotic dosage prescribed for preterm infants in a neonatal intensive care unit (NICU).

METHODS

A retrospective study using chart review was conducted at a tertiary care medical center with university affiliation in Taiwan. Study subjects were preterm neonates admitted to the NICU of the medical center between 2000 and 2002 and prescribed at least one antibiotic during the stay. Recommendations from three commonly used reference sources (Pediatric Dosage Handbook, Neonatal Drug Formulary, and Neofax) were employed to evaluate the dosage compliance of the antibiotic prescriptions.

RESULTS

A total of 433 preterm infants and 3459 prescriptions were included. Depending on the reference source used, the percentages of antibiotic prescriptions where both the dose and the interval were compliant with recommendations ranged from 36.88 to 87.54%.

CONCLUSIONS

A significant proportion of antibiotics prescribed for preterm neonates in this medical center did not comply with the recommended dosage from common reference sources. Future studies should investigate the clinical impacts of the dosing deviation.

Diagnosis and Management of Complicated Intra-abdominal Infection in Adults and Children: Guidelines by the Surgical Infection Society and the Infectious Diseases Society of America

Evidence-based guidelines for managing patients with intra-abdominal infection were prepared by an Expert Panel of the Surgical Infection Society and the Infectious Diseases Society of America. These updated guidelines replace those previously published in 2002 and 2003. The guidelines are intended for treating patients who either have these infections or may be at risk for them. New information, based on publications from the period 2003–2008, is incorporated into this guideline document. The panel has also added recommendations for managing intra-abdominal infection in children, particularly where such management differs from that of adults; for appendicitis in patients of all ages; and for necrotizing enterocolitis in neonates.

Synthesis and evaluation of N-nicotinoyl-2-{2-(2-methyl-5-nitroimidazol-1-yl)ethyloxy}-D,L-glycine as a colon-specific prodrug of metronidazole

Metronidazole (MTZ) is a drug of choice for protozoal infections such as luminal amoebiasis. We designed and synthesized N-nicotinoyl-2-{2-(2-methyl-5-nitroimidazol-1-yl)ethyloxy}-D,L-glycine (NMG) as a colon-specific prodrug of MTZ. The synthetic yield of NMG was about 34%. The apparent partition coefficient of MTZ was greatly reduced by the chemical modification. While (bio)chemically stable in the contents of the upper intestine, NMG was rapidly cleaved to liberate MTZ on incubation with the cecal contents of rats. MTZ metabolized quickly in the cecal contents at least partly by a microbial nitroreductase, suggesting that the metabolism of MTZ is relevant to its bioactivation leading to amoebicidal action. The systemic absorption, analyzed by the blood concentration and urinary recovery of NMG, was very low after oral administration of NMG. In parallel with this, whereas MTZ disappeared mostly during the transit of the proximal small intestine, a substantial amount of NMG remained in the small intestine moving down to the large intestine where it metabolized rapidly. Moreover, comparing systemic absorption of MTZ after oral administration of NMG or MTZ, NMG markedly reduced the systemic absorption. These results suggest that NMG is a potential colon-specific prodrug of MTZ which improves therapeutic and toxicological properties.

Guidelines for the treatment of bacterial vaginosis: focus on tinidazole

Bacterial vaginosis (BV) is a complex vaginal infection most commonly associated with women of child-bearing age. Risk factors for BV are numerous. There are currently multiple clinical and laboratory tests for diagnosis of BV, including the most commonly used diagnostic methods: Amsel’s criteria or Nugent’s Gram stain scale. The mainstay of BV therapy is metronidazole, but tinidazole as well as a few other agents have also been used successfully. Tinidazole is the second nitroimidazole antiprotozoal agent and a structural derivative of metronidazole. With a favorable pharmacokinetic profile and reduced side effects, tinidazole is an alternative agent for BV treatment. There are minimal head-to-head comparative data to establish tinidazole’s superiority to metronidazole or other therapeutic agents. Available data suggest tinidazole has a role in special populations particularly for refractory or relapsing BV.

In vitro activity of secnidazole against Atopobium vaginae, an anaerobic pathogen involved in bacterial vaginosis

Bacterial vaginosis is a polymicrobial syndrome. The most important marker for bacterial vaginosis is the presence of Gardnerella vaginalis and Atopobium vaginae. In this study, the in vitro susceptibilities to metronidazole and secnidazole of 16 strains of A. vaginae were tested with the agar dilution method. We observed an MIC range for metronidazole of 4-64 mg/L (MIC(50), 8 mg/L; MIC(90), 32 mg/L) and an MIC range for secnidazole of 4-128 mg/L (MIC(50), 16 mg/L; MIC(90), 64 mg/L). According to these findings, we can conclude that the activity of secnidazole is similar to that of metronidazole.

Metronidazole-loaded bioabsorbable films as local antibacterial treatment of infected periodontal pockets

BACKGROUND

Periodontal disease is infectious in nature and leads to an inflammatory response. It arises from the accumulation of subgingival bacterial plaque and leads to the loss of attachment, increased probing depth, and bone loss. It is one of the world's most prevalent chronic diseases. In this study we developed and studied metronidazole-loaded 50/50 poly(DL-lactide-co-glycolide) (PDLGA), 75/25 PDLGA, and poly(DL-lactic acid) (PDLLA) films. These films are designed to be inserted into the periodontal pocket and treat infections with controlled-release metronidazole for >or=1 month.

METHODS

The structured films were prepared using the solution-casting technique. Concentrated solutions and high solvent-evaporation rates were used to get most of the drug located in the bulk, i.e., in whole film's volume. The effects of copolymer composition and drug content on the release profile, cell growth, and bacterial inhibition were investigated.

RESULTS

The PDLLA and 75/25 PDLGA films generally exhibited a low- or medium-burst release followed by a moderate release at an approximately constant rate, whereas the 50/50 PDLGA films exhibited a biphasic release profile. The drug released from films loaded with 10% weight/weight metronidazole resulted in a significant decrease in bacterial viability within several days. When exposed to human gingival fibroblasts in cell culture conditions, these films maintained their normal fibroblastic features.

CONCLUSIONS

This study enabled the understanding of metronidazole-release kinetics from bioabsorbable polymeric films. The developed systems demonstrated good biocompatibility and the ability to inhibit Bacteroides fragilis growth; therefore, they may be useful in the treatment of periodontal diseases.

The Frequency of Sister Chromatid Exchanges in Cultured Human Peripheral Blood Lymphocyte Treated with Metronidazolein Vitro

5-Nitroimidazoles are a group of antiprotozoal and antibacterial agents. Thanks to their antimicrobial activity, these chemotherapeutic agents inhibit the growth of both anaerobic bacteria and certain anaerobic protozoa. One of the useful drugs used in the treatment of infections caused by Trichomonas vaginalis, Entamoeba histolytica, and Giardia lamblia is metronidazole (MTZ). The mutagenicity of metronidazole [1-(hydroxyethyl)-2-methyl-5-nitroimidazole] has been previously shown in different prokaryotic systems but not in eukaryotic systems. The objective of this study is to determine the mutagenic and cytotoxic effects of MTZ at plasma concentration and higher in vitro. In this study, we evaluated the mutagenicity and cytotoxicity of MTZ in cultured human peripheral blood lymphocytes. Doses were selected according to plasma concentration of drug. End points analyzed included mitotic index (MI), replication index (RI), and sister chromatid exchange (SCE). An analysis of variance test (ANOVA) was performed to evaluate the results. A significant decrease (p < 0.001) in MI and RI as well as an increase in SCE frequency (p < 0.001) was observed compared with control cultures. Our results indicate the genotoxic and cytotoxic effect of MTZ in cultured human peripheral blood lymphocytes at plasma concentrations slightly higher than encountered therapeutically.

Entamoeba histolytica: response of the parasite to metronidazole challenge on the levels of mRNA and protein expression

Entamoeba histolytica remains a cause of significant morbidity and mortality in many countries. Although metronidazole has been used for the treatment of amoebiasis for several decades, little is known on how the amoebae react to this challenge on the levels of mRNA and protein expression. In this study, we examined their response using a focused microarray, quantitative RT-PCR, and two-dimensional gel electrophoresis (2DE). The amoebae modestly increased the levels of mRNA coding for superoxide dismutase, peroxiredoxin, ferredoxin, thioredoxin reductase, and the galactose/N-acetylgalactosamine specific lectin light and heavy chains. The mRNAs encoding actin and the 70kDa and 101kDa heat shock proteins were decreased. All the changes occured within 1h of exposition, with very little further changes. In addition, the proteome revealed only very few changes. Taken together, E. histolytica appears to make only modest mRNA and protein expression changes when confronted with an unknown chemical stress.

Structured Drug-eluting Bioresorbable Films: Microstructure and Release Profile

Bioresorbable drug-eluting films can be used in many biomedical applications. Examples for such applications include biodegradable medical support devices which combine mechanical support with drug release and antibiotic-eluting film coatings for prevention of bacterial infections associated with orthopedic implants or during gingival healing. In the current study, bioresorbable drug-loaded polymer films are prepared by solution processing. Two film structures are studied: A polymer film with large drug crystals located on its surface (A-type) and a polymer film with small drug particles and crystals distributed within the bulk (B-type). The basic mode of drug dispersion/location in the film (A or B-type) is found to be determined mainly by the process of film formation and depends mainly on the solvent evaporation rate, whereas the drug's hydrophilicity has a minor effect on this structuring process. Most release profiles from A-type films exhibit a burst effect of ~30% and a second release stage that occurs at an approximately constant rate and is determined mainly by the polymer weight loss rate. An extremely high burst release is exhibited only by a very hydrophilic drug. The matrix (monolithic) nature of the B-type film enables release profiles that are determined mainly by the host polymer's degradation profile, with a very low burst effect in most of the studied systems. In addition to the drug location/ dispersion in the film, the host polymer and drug type also strongly affect the drug's release profile from the film. It has been demonstrated that appropriate selection of the process parameters and film components (polymer and drug) can yield film structures with desirable drug release behaviors. This can lead to the engineering of new bioresorbable drug-eluting film-based implants for various applications.

New concepts of resistance in the treatment of Helicobacter pylori infections

The prevalence of antimicrobial drug resistance is now so high that all patients infected with Helicobacter pylori should be considered as having resistant infections. Ideally, therapy should be based on pretreatment antibiotic-susceptibility testing but this strategy is not currently practical. At present, clarithromycin-containing triple therapies do not reliably produce a > or =80% cure rate on an intention-to-treat basis and are, therefore, no longer acceptable as empiric therapy. In this Review, we discuss concepts of resistance that have become part of mainstream thinking for other infectious diseases but have not yet become so with regard to H. pylori. We also put data on the pharmacokinetics and pharmacodynamics of the drugs used in H. pylori therapy and the effect of host cytochrome P450 genotypes in context with treatment outcomes. Our primary focus is to address the problem of H. pylori resistance from a novel perspective, which also attempts to anticipate the direction that research will need to take to provide clinicians with reliable approaches to this serious infection. We also discuss current therapies that provide acceptable cure rates when used empirically (i.e. sequential therapy; four-drug, three-antibiotic, non-bismuth-containing 'concomitant' therapy; and bismuth-containing quadruple therapy) and how they might be further improved.

A comparison of metronidazole and single-dose ornidazole for the treatment of dientamoebiasis

Recent reports of the pathogenic potential of Dientamoeba fragilis have underlined the need for an effective treatment against this colon-dwelling protozoan. Metronidazole is a well-known and commonly used anti-protozoal agent, but another 5-nitroimidazole derivative, ornidazole, may be preferable, where available, because of its longer half-life and fewer side-effects. This study compared the efficacies of metronidazole and ornidazole in a group of 112 patients with dientamoebiasis. Patients were randomised into two treatment groups: group 1 (n = 56) received metronidazole for 5 days, 20 mg/kg/day for children and 1.5 g/day for adults, in three oral doses, while group 2 (n = 56) received a single oral dose of ornidazole, 30 mg/kg for children and 2 g for adults. Stool samples were examined on the seventh and 14th days after treatment, and clinical symptoms were recorded to evaluate the efficacy of treatment. A statistically significant difference was recorded between the efficacies of ornidazole and metronidazole, both parasitologically (92.9% vs. 69.6%, p 0.001) and clinically (96.4% vs. 76.8%, p 0.001). Patients in the metronidazole group reported more side-effects than patients in the ornidazole group, none of whom required termination of treatment. These results suggest that single-dose ornidazole may be an important alternative agent for the treatment of dientamoebiasis.

Pharmacokinetic and Pharmacodynamic Aspects of Antibiotic Use in High-Risk Populations

The study of pharmacokinetics includes the absorption, distribution, metabolism, and elimination of drugs. The pharmacologic effect that a medication has on the body is known as pharmacodynamics. With antimicrobials, pharmacokinetic and pharmacodynamic parameters become especially important because of the association between host drug concentrations, microorganism eradication, and resistance. This article focuses on the pharmacokinetic changes that can occur with antimicrobials when they are used in patients at high risk of infections and how they influence pharmacodynamic effects. The populations described here include patients with obesity and diabetes mellitus, renal or hepatic failure, chronic lung disease, severe burns, and long-term prosthetic devices and the elderly.

W/O/W multiple emulsions containing nitroimidazole derivates for vaginal delivery

The aim of our study was to formulate a stable multiple emulsions containing two nitroimidazole derivates, metronidazole (MT) and ornidazole (OR), for vaginal therapy. MT and OR were located internal and external phases of multiple emulsion, respectively, and the in vitro release studies were realized in phosphate (pH 7) and lactate buffer (pH 4.5) solutions to investigate better the effect of pH and location of active substance on the release. The imaging studies were realized in rabbits following labeling MT and OR with Technethium-99m ((99m)Tc) to evaluate the in vivo absorption characteristics. The percentage of MT and OR released from the multiple emulsions in alkaline media were 3.2- and 2.8-fold greater than that observed in acidic media, respectively, when they were introduced in the internal phase of the multiple emulsions. The absorption rate of MT from vaginal epithelium was faster than OR. We observed that especially in alkaline medium a high release was found that was convenient for the vaginal infections seen in the alkaline pH. We concluded that W/O/W multiple emulsions were locally effective in vagina and they could be introduced as a new drug carrier system for vaginal delivery.

Tinidazole for the treatment of vaginal infections

Tinidazole has been used for vaginal infection worldwide but not in the US for > 40 years. Recently, tinidazole has been re-introduced and approved by the FDA for trichomoniasis and restudied as an alternative to metronidazole for bacterial vaginosis. In vitro antimicrobial activity and pharmacokinetics studies indicate that tinidazole has minor but possibly relevant antimicrobial as well as pharmacokinetic advantages when compared directly with metronidazole. Clinical comparison has been infrequent although the limited head-to-head studies indicate minimal therapeutic advantage with tinidazole. Perhaps the more relevant differences relate to the enhanced tolerance and reduced toxicity of tinidazole. Ongoing, as yet incomplete, studies directly comparing the clinical efficacy of metronidazole and tinidazole for bacterial vaginosis should clarify the status of tinidazole; however, cure rates are unlikely to be significantly different. Although uncommon, high-level trichomonal metronidazole resistance can be reliably cured by using tinidazole, which is an invaluable advantage.

Metronidazole plus rifampin sterilizes long-term dormant Mycobacterium tuberculosis

Long-term nonreplicating (dormant) Mycobacterium tuberculosis populations (26-day-old cells) were sterilized by metronidazole plus rifampin, but not by metronidazole or rifampin alone, after 7 and 11 days of exposure to the drugs. Lower or no drug activity was observed against 19- or 12-day-old dormant or 5-day-old actively replicating populations.

Drugs, their targets and the nature and number of drug targets

What is a drug target? And how many such targets are there? Here, we consider the nature of drug targets, and by classifying known drug substances on the basis of the discussed principles we provide an estimation of the total number of current drug targets.

Susceptibility of vaginal bacteria to metronidazole and tinidazole

In vitro antimicrobial susceptibility testing was performed on 470 vaginal isolates from women with bacterial vaginosis and three species of Lactobacillus, to metronidazole and tinidazole using the agar dilution method. There was no significant difference observed in the inhibitory activity of either drug to any of the isolates tested.