Modeling the biotransformation of trimethoprim in biological nutrient removal system

A pilot scale biological nutrient removal (BNR) process, batch experiments and modeling exercises were employed to investigate the removal and biotransformation of trimethoprim (TMP) in a BNR activated sludge process. The concentrations of the active microbial groups - ammonia oxidizing bacteria (AOB), ordinary heterotrophic organisms (OHOs) and polyphosphate accumulating organisms (PAOs) - in the BNR bioreactor were quantified through modeling of the pilot bioreactor. The overall TMP removal efficiency for the pilot BNR process was 64 ± 14% while the TMP biotransformation efficiencies in the anaerobic, anoxic and aerobic zones were 22 ± 20%, 27 ± 8% and 36 ± 5% respectively. Batch tests with and without nitrification inhibition showed that AOB played a role in the biotransformation of TMP in BNR activated sludge. A pseudo first order model which incorporated the contributions of PAOs, OHOs and AOB to the overall biodegradation of TMP was found to describe the biodegradation of TMP in batch tests with and without nitrification inhibition. This model showed that PAOs, OHOs and AOB contributed towards the biotransformation of TMP in aerobic BNR activated sludge with the biotransformation rate constants following the trend of k_AOB > k_OHOs > k_PAOs.

New insights into the transformation of trimethoprim during biological wastewater treatment

The antibiotic trimethoprim (TMP), a micropollutant found at μg/L levels in raw wastewater, was investigated with regard to its (bio)transformation during biological wastewater treatment. A pilot-scale, nitrifying/denitrifying Sequencing Batch Reactor (SBR) fed with municipal wastewater was monitored for TMP removal during a 16-month monitoring study. Laboratory-scaled bioreactors spiked with TMP were applied to identify the transformation products (TPs). In total, six TPs could be identified from TMP. However, the TP formation was influenced by the spike concentration. At an initial concentration of 500 μg/L TMP, only two TPs were found, whereas at 5 μg/L a completely different transformation pathway led to four further TPs. At low concentrations, TMP was demethylated forming 4-desmethyl-TMP, which was then quickly hydroxylated, oxidized and cleaved forming 2,4-diaminopyrimidine-5-carboxylic acid (DAPC) via two intermediate TPs. DAPC was detected in the SBR effluent in a 3-d composite sample with 61 ng/L, which accounts for 52% of the attenuated TMP. The primary degradation at low spiking levels was best modelled by a pseudo-first order kinetic. Considering the SBR, the model predicted a TMP removal of 88-94% for the reactor, consistent with a monitoring campaign exhibiting an average removal of >83%. Both the TP formation profiles and kinetic modelling indicated that only the results from the bioreactor tests at low spike concentrations were representative of the transformation in the SBR.

An immunochromatographic assay for rapid and direct detection of 3-amino-5-morpholino-2-oxazolidone (AMOZ) in meat and feed samples

BACKGROUND

Furaltadone (FTD) is a type of nitrofuran and has been banned in many countries as a veterinary drug in food-producing animals owing to its potential carcinogenicity and mutagenicity. FTD is unstable in vivo, rapidly metabolizing to 3-amino-5-methylmorpholino-2-oxazolidinone (AMOZ); thus AMOZ can be used as an indicator for illegal usage of FTD. Usually, for the determination of nitrofurans, the analyte is often a derivative of the metabolite rather than the metabolite itself. In this study, based on the monoclonal antibody (mAb) against AMOZ, a competitive immunochromatographic assay (ICA) using a colloidal gold-mAb probe for rapid and direct detection of AMOZ without a derivatization step in meat and feed samples was developed.

RESULTS

The intensity of red color in the test line is inversely related to the analyte concentration and the visual detection limit was found to be 10 ng mL⁻¹. The performance of this assay was simple and convenient because the tedious and time-consuming derivatization step was avoided. The ICA detection was completed within 10 min. The ICA strips could be used for 7 weeks at room temperature without significant loss of activity. The AMOZ spiked samples were detected by ICA and confirmed by enzyme-linked immunosorbent assay. The results of the two methods were in good agreement.

CONCLUSION

The proposed ICA provides a feasible tool for simple, sensitive, rapid, convenient and semi-quantitative detection of AMOZ in meat and feed samples on site. To our knowledge, this is the first report of the ICA for direct detection of AMOZ.

Inhibition of Nitrofurantoin Reduction by Menthol Leads to Enhanced Antimicrobial Activity

Nitrofurantoin is a nitroaromatic compound used for the treatment of urinary tract infections. Nitrofurantoin activity is regulated by a nitroreduction process. It is first reduced by bacterial nitroreductases to active short-life intermediates, which are further converted to non-toxic molecules, which negatively affect its antibacterial activity. In this study we have shown that resistant strains of Klebsiella sp. inactivate the bactericidal activity of nitrofurantoin. Also we demonstrated a synergistic effect between menthol and nitrofurantoin bactericidal activities against nitrofurantoin susceptible Enterobacteriaceae.

Stability studies of the metabolites of nitrofuran antibiotics during storage and cooking

Nitrofuran antibiotics cannot be used in food production within the European Union because of their potential health risks to consumers. The recent discovery of their widespread use in global food industries and the finding of semicarbazide in baby food as a result of packaging contamination have focused attention on the toxicity and stability of these drugs and their metabolites. The stability of the nitrofuran marker residues 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidone (AMOZ), 1-aminohydantoin (AHD) and semicarbazide (SEM) were tested. Muscle and liver of nitrofuran treated pigs were cooked by frying, grilling, roasting and microwaving. Between 67 and 100% of the residues remained after cooking, demonstrating that these metabolites are largely resistant to conventional cooking techniques and will continue to pose a health risk. The concentration of metabolites in pig muscle and liver did not drop significantly during 8 months of storage at -20 degrees C. Metabolite stock and working standard solutions in methanol were also stable for 10 months at 4 degrees C. Only a 10 ng ml(-1) solution of SEM showed a small drop in concentration over this extended storage period.

Depletion of four nitrofuran antibiotics and their tissue-bound metabolites in porcine tissues and determination using LC-MS/MS and HPLC-UV

Depletion of the nitrofuran antibiotics furazolidone, furaltadone, nitrofurantoin and nitrofurazone and their tissue-bound metabolites AOZ, AMOZ, AHD and SEM from pig muscle, liver and kidney tissues is described. Groups of pigs were given feed medicated with one of the nitrofuran drugs at a therapeutic concentration (400?mg?kg(-1)) for ten days. Animals were slaughtered at intervals and tissue samples collected for analysis for six weeks following withdrawal of medicated feed. These samples were analysed both for parent nitrofurans (using LC-MS/MS and HPLC-UV), and for tissue-bound metabolites (using LC-MS/MS). The parent drugs were detectable only sporadically and only in pigs subjected to no withdrawal period whatsoever. This confirms the instability of the four major nitrofuran antibiotics in edible tissues. In contrast, the metabolites accumulated to high concentrations in tissues (ppm levels) and had depletion half lives of between 5.5 and 15.5 days. The metabolites of all four drugs were still readily detectable in tissues six weeks after cessation of treatment. This emphasizes the benefits of monitoring for the stable metabolites of the nitrofurans.

Application of Ion Trap-MS with H/D Exchange and QqTOF-MS in the Identification of Microbial Degradates of Trimethoprim in Nitrifying Activated Sludge

In this work, the identification of two microbial degradation products of the antimicrobial trimethoprim (290 Da) is described. The structural elucidation of the metabolites, which were produced by nitrifying activated sludge bacteria in a small-scale laboratory batch reactor, was accomplished by electrospray ionization-ion trap mass spectrometry conducting consecutive fragmentation steps (MS(n)) combined with H/D-exchange experiments. Although one metabolite corresponded to alpha-hydroxytrimethoprim (306 Da), oxidation of the aromatic ring within the diaminopyrimidine substructure was determined for the second degradate (324 Da). Accurate mass measurements of the two metabolites were provided by a hybrid quadrupole time-of-flight-mass spectrometer operated in MS/MS mode. With absolute mass errors of <5 mDa, it allowed us to confirm the proposed elemental composition for the protonated precursor ions as well as for a series of fragment ions that were previously identified by ion trap mass spectrometry. The study emphasized the potential of nitrifying activated sludge bacteria for breaking down an environmentally relevant pharmaceutical that is otherwise poorly degradable by a bacterial community encountered in conventional activated sludge.

Complexes of Ni(II) and Cu(II) with ofloxacin. Crystal structure of a new Cu(II) ofloxacin complex

Several coordination compounds formed between Ni(II) or Cu(II) with ofloxacin have been synthesised and characterised. According to elemental chemical analysis and FT-IR spectroscopy data, direct reaction of Ni(II) and Cu(II) salts with ofloxacin leads to formation of precipitates for which mass spectrometry demonstrates their polymeric nature. However, crystalline [Cu(oflo)2(H2O)].2H2O is formed if the reaction is carried out in the presence of ammonia. This complex crystallises in the triclinic system, space group P-1 with a=9.2887(12), b=11.2376(14), c=17.874(2) A, alpha=92.12(3), beta=95.39(3), gamma=91.71(3) degrees and Z=2. The local geometry around the Cu(II) ion is a slightly distorted square base pyramid. Electronic spectra, magnetic susceptibility measurements and EPR spectra of the synthesised complexes indicate a tetragonal environment.

Isolation of nitrofurantoin-resistant mutants of nitroreductase-producing Clostridium sp. strains from the human intestinal tract

Five spontaneous nitrofurantoin-resistant mutants (one each of Clostridium leptum, Clostridium paraputrificum, two other Clostridium spp. strains from the human intestinal microflora, and Clostridium perfringens ATCC 3626) were selected by growth on a nitrofurantoin-containing medium. All of the Clostridium wild-type and mutant strains produced nitroreductase, as was shown by the conversion of 4-nitrobenzoic acid to 4-aminobenzoic acid. High-performance liquid chromatography (HPLC) analysis of the mutants during incubation with 50 microg of nitrofurantoin per ml showed the gradual disappearance of the nitrofurantoin peak. The nitrofurantoin peak also disappeared when cell-free supernatants instead of cultures of each of the resistant and wild-type bacteria were used, but it persisted if the cell-free supernatants had been inactivated by heat. At least two of the mutants converted nitrofurantoin to metabolites without antibacterial activity, as was shown by a bioassay with a nitrofurantoin-susceptible Bacillus sp. strain. Nitrofurantoin at a high concentration (50 microg/ml) continued to exert some toxicity, even on the resistant strains, as was evident from the longer lag phases. This study indicates that Clostridium strains can develop resistance to nitrofurantoin while retaining the ability to produce nitroreductase; the mutants metabolized nitrofurantoin to compounds without antibacterial activity.

Pharmacokinetics of flumequine in sheep after intravenous and intramuscular administration: bioavailability and tissue residue studies

The pharmacokinetic properties of flumequine and its metabolite 7-hydroxyflumequine were determined in six healthy sheep after single intramuscular (i.m.) and intravenous (i.v) injections at a dose of 6 mg/kg body weight. The tissue residues were determined in 20 healthy sheep after repeated i.m. administration with a first dose of 12 mg/kg and nine doses of 6 mg/kg. The flumequine formulation used was Flumiquil 3% Suspension Injectable. The mean plasma concentrations of flumequine after i.v. administration were described by a three-compartment open model with a rapid distribution and a relatively slow elimination phase. The low value of volume of distribution at steady state (Vdss) (0.52 +/- 0.24 L/kg) and high value of volume of distribution (Vdlambda3) (5.05 +/- 3.47 L/kg) emphasized the existence of a small compartment with a slow rate of return to the central compartment. The mean elimination half-life was 11.5 h. The 7-hydroxyflumequine plasma levels represented 2.3% of the total area under the curve. The mean plasma concentrations of flumequine after i.m. administration were characteristic of a two-compartment model with a first order absorption. The mean maximal plasma concentration (1.83 +/- 1.15 microg/mL) was obtained rapidly, i.e. 1.39 +/- 0.71 h after the i.m. administration. The fraction of dose absorbed from the injection site was 85.00 +/- 30.13%. The minimal concentrations of flumequine during repeated treatment were significantly lower in females than in males. Eighteen hours after the last repeated i.m. administration, the highest concentration of flumequine was observed at the injection sites followed by kidney, liver, muscle and fat. The highest concentration of 7-hydroxyflumequine was observed in the kidney and was ten times lower than the flumequine concentration. The longest flumequine elimination half-life was observed in the fat.

[Interaction between warfarin and nalidic acid]

A case of presumed interaction between warfarin and nalidixic acid is reported in an 84 year-old female in whom INR rose from 1.9 to 9.6 after start of treatment with nalidixic acid. The interaction may be caused by several factors: 1) Nalidixic acid may displace warfarin from plasma proteins and thereby increase the anticoagulant effect. 2) The fluoroquinolone drug enoxacin reduces the hepatic clearance of the R-stereomere of warfarin but without prolongation of the prothrombin time ratio. 3) Fluoroquinolones may affect the vitamin-K producing bacteria in the gut and thereby influence the vitamin-K: warfarin ratio in plasma. Only some patients develop hypoprothrombinaemia during concomitant therapy with warfarin and quinolone antimicrobials. It is hypothesized that the interaction may partly be related to age, sex or concomitant disease. Frequent control of INR in patients treated with both warfarin and quinolone antimicrobials is recommended.

In vitro and in vivo binding of trimethoprim and sulphachlorpyridazine to equine food and digesta and their stability in caecal contents

Binding of antibiotics to food has received little attention in equine medicine, although such binding could potentially reduce the bioavailability and clinical efficacy. In the present study, binding of trimethoprim (TMP) and sulphachlorpyridazine (SCP) to hay, grass silage and concentrate was investigated in vitro in buffer at pH 6.8 at different concentrations. The binding of TMP and SCP to caecal contents was also studied. In addition, the degradation of TMP and SCP by the caecal microflora was investigated by incubating sterilized and non-sterilized caecal contents for 3 h at 37 degrees C under anaerobic conditions and comparing the TMP and SCP contents. Further, a TMP/SCP powder formulation was adminstered orally with concentrate at a dose rate of 5 mg/kg TMP and 25 mg/kg SCP to three ponies with a caecum fistula; the animals were deprived of food for 8 h before administration. Blood samples, caecal contents samples and faecal samples were collected and analysed for TMP and SCP concentrations by means of high performance liquid chromatography (HPLC). Three non-fistulated ponies, acting as control animals, were fed the same dose of TMP/SCP with concentrate after 8 h of food deprivation and blood samples were taken. The percentage of in vitro binding of TMP as well as SCP to hay, grass silage and concentrate at concentrations of 4 micrograms/mL to 10 micrograms/mL was high (60-90%). TMP and SCP were also extensively bound to caecal contents (50-70%). At spiking concentrations above 10 micrograms/mL the percentage of binding decreased. There was no evidence of biodegradation of TMP or SCP in caecal contents. In vivo, both drugs could be detected in the caecal contents and in the faeces of three fistulated ponies. However, the fistulated ponies differed from the control ponies in that their TMP and SCP plasma concentrations were higher, and two fistulated ponies did not show double peaks in their plasma concentration-time curves. Therefore, the fistulated ponies did not provide an optimal model for in vivo binding studies. Despite this limitation, it can be concluded that binding of TMP and SCP to food is a major cause of the limited bioavailability of these drugs in the horse. It is hypothesized that the binding is reversible, and that a second absorption phase occurs in the large intestine, but part of the administered dose remains bound as both drugs were found in the faeces.

Chitosan/calcium alginate microcapsules for intestinal delivery of nitrofurantoin

A new sustained-release dosage form of nitrofurantoin (NF) as microcapsules has been prepared by a mild chitosan/calcium alginate microencapsulation process. These microcapsules have been prepared by adding, dropwise, a solution of sodium alginate containing NF into a chitosan-CaCl(2) system. About 70-80% of the drug is released into phosphate buffer, pH = 7.4 within 6 h. Drug release into the gastric medium is found to be relatively slow compared to that into the intestinal medium. From scanning electron microscopic studies, it appears that the chitosan modifies the NF-alginate microspheres. These findings suggest the possibility of modifying the formulation to obtain the controlled release of NF in an oral sustained-delivery system.

[Study of the elimination of residues and local tissue injury following intramuscular injection of a solution of the combination trimethoprim/sulfatroxazole in pigs]

Two different studies are described. The first study deals with the elimination of residues of trimethoprim (TMP), sulfatroxazole (STX) and its main metabolite N4-acetyl-sulfatroxazole (N4-acetyl-STX) in pigs. Thirty -six pigs were treated with trimethoprim/sulfatroxazole IM in the nec k at a dosage of 16 mg/kg body weight for five days. Groups of four pig s were slaughtered at different time intervals. The study showed that concentration of STX, N4-acetyl-STX and TMP in edible tissues and at the injection sites were below 0.1 ppm on day nine after the last injection. S TX was eliminated the slowest, and STX can therefore be selected as a marker for residues of the trimethoprim/sulfatroxazole formulation in the tissues. The second study deals with irritation aspects of this trimethoprim /sulfatroxazole formulation. Four pigs of 32-35 kg were treated IM w with trimethoprim/sulfatroxazole and benzylpenicillin sodium. Each pig received the same injection volume, namely four trimethoprim/sulfatroxazole injections (16 mg/kg body weight per injection site), two in the back and two in the neck muscle, and two benzylpenicillin sodium injections (20,000 I.U./kg body weight per injection site), in the back muscle. All pigs were slaughtered 14 days after treatment and the extent of the irritation was compared. There were no differences between trimethoprim/sulfatroxazole and benzylpenicillin sodium with regard to irritation at the injection site in the back muscle. The irritation in the neck site was statistically less prominent than that in the back muscle and was considered not to affect the quality of the meat.

3(3) factorial design-based optimization of the formulation of nitrofurantoin microcapsules

A microcapsule form of nitrofurantoin was prepared by a simple coacervation method with carboxymethylcellulose and aluminium sulfate. 3(3) factorial design was performed for three independent variables, namely, the particle size of the drug, the size of the microcapsules and the pH of the dissolution medium. The dissolution tests with the formulated microcapsules were carried out according to the United States Pharmacopeia XXII rotating basket method at pH 1.2, 5, and 7.5, which represent the pH of gastrointestinal fluids. Release data were examined kinetically and the ideal kinetic models were estimated and t(63.2) values obtained from RRSBW distribution were used in the factorial design experiment. The influence of the independent variables on the dissolution of nitrofurantoin microcapsules could be expressed as the pH of the dissolution medium > particle size of the microcapsule > particle size of nitrofurantoin. The other aim of this study was to evaluate microcapsule formulation in terms of the United States Pharmacopeia criteria with a minimum of experiments. Our findings suggest that dosage forms which comply with the pharmacopoeia criteria for dissolution can be prepared and selected by factorial design.

Roles of divalent cations and pH in mechanism of action of nitroxoline against Escherichia coli strains

The antibacterial activity of nitroxoline (NIT), an antibiotic used in the treatment of acute or recurrent urinary tract infections caused by Escherichia coli, is decreased in the presence of Mg2+ and Mn2+ but not Ca2+. In order to elucidate the interaction between this drug and the divalent cations, spectrophotometric studies based on the natural absorption of the nitroxoline moiety were conducted. In the presence of the divalent metal ions, a shift in the NIT A448 suggested the formation of drug-ion complexes, for which the stability followed the order Mn2+ > Mg2+ > Ca2+. A clear correlation was found between the chelating property and antibacterial activity of NIT; both were pH dependent. A convenient colorimetric method for the determination of NIT uptake by bacterial cells was also developed. Uptake was energy independent and showed biphasic kinetics: a rapid association with cells and then a slower increase in cell-associated NIT which reached a plateau. NIT uptake was reduced in the presence of magnesium. The implications of metal ion complexation and pH on the clinical efficacy of NIT are discussed.

First and second derivative spectrophotometric determination of cefoperazone and sulbactam in injections

A simple, spectrophotometric assay to measure the concentrations of cefoperazone and sulbactam in injectable formulations is described. Since zero-order spectra are subject to interference, derivative spectrophotometry was used to enhance the spectral details. A linear relationship between derivative amplitudes and the concentrations of the compounds was found. Beer's law is obeyed up to 75 and 80 micrograms ml-1 of cefoperazone in the first and second derivative modes, respectively, and up to 75 micrograms ml-1 of sulbactam in the second derivative mode. Detection limits were 0.64 and 0.88 microgram ml-1, respectively for cefoperazone in the first and second derivative modes and 0.30 micrograms ml-1 for sulbactam in the second derivative mode. The method is rapid, simple, does not require a separation step and has successfully been applied to the assay of commercial injections containing cefoperazone and sulbactam.

Determination of cefixime and its metabolites by high-performance capillary electrophoresis

Cefixime (CX), an oral cephalosporin antibiotic, and its metabolites in human digestive organs were separated by various modes of high-performance capillary electrophoresis. The zone electrophoresis mode in phosphate buffer (pH 6.8) containing 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulphonate gave the best separation, permitting the complete resolution of CX and all of five metabolites. On the other hand, the plain zone electrophoresis mode in phosphate buffer (pH 6.8) offered a simple procedure for the direct determination of urinary CX concentration using intact urine samples.

Activity of cefixime against Helicobacter pylori and affinities for the penicillin-binding proteins

Cefixime induced the formation of rounded cells from the spiral bacillary form of Helicobacter pylori at the MIC or less. Three main penicillin-binding proteins, called A, B and C, were separated from H. pylori. Cefixime had the strongest affinity to penicillin-binding protein B. The binding of cefixime to this protein may induce the formation of rounded H. pylori cells.

Pharmacokinetics of cefradine, sulfamethoxazole and trimethoprim and their metabolites in a patient with peritonitis undergoing continuous ambulatory peritoneal dialysis

Cefradine and co-trimoxazole pharmacokinetics were studied in a patient with peritonitis that complicated continuous ambulatory peritoneal dialysis (CAPD). Concentrations in the plasma reached after oral administration of 500 mg cefradine four times daily and 400/80 mg co-trimoxazole four times daily were for cefradine 100 micrograms/ml, for trimethoprim 15 micrograms/ml, and for sulfamethoxazole 100 micrograms/ml, respectively. In the dialysate concentrations were reached of 35-70 micrograms/ml cefradine, 2-5 micrograms/ml trimethoprim and 8-17 micrograms/ml sulfamethoxazole. The values for sulfamethoxazole are regarded too low to be clinically effective. Half-lives, protein binding values and CAPD clearances are presented. Low CAPD clearances were obtained during the night and high values during the day. The dosage yielded too high plasma trimethoprim concentrations, while sulfamethoxazole dialysate concentrations were too low. It seems questionable therefore whether co-trimoxazole can be used orally for the treatment of CAPD peritonitis.

The pharmacokinetics of enoxacin in elderly patients

Twenty-three patients of greater than 70 years of age, with proven urinary tract infections were treated with 200 mg of enoxacin twice daily. Serial blood samples were taken on day 1 and peak and trough levels on days 3 and 5. Enoxacin and oxo-enoxacin plasma levels were measured. The mean plasma half-lives of enoxacin and the oxo-metabolite were 6.1 h and 6.7 h respectively. The 2 h plasma level of enoxacin increased from a mean of 1.5 mg/l on day 1 to 2.65 mg/l on day 3 and 2.80 mg/l on day 5. No significant accumulation of the oxo-metabolite (as judged by the 2 h level) occurred. No alteration in enoxacin dosing in the elderly compared with that in younger patients is suggested. Eighty-five per cent of the patients were cured of their infection and no significant adverse advents were noted.

The microbiological and pharmacokinetic profile of an antibacterial agent useful for the single-dose therapy of urinary tract infection

Single-dose therapy of uncomplicated urinary tract infection (UTI) has been shown to be effective in many trials in adult women. The question which will be explored in this presentation is what properties constitute the ideal agent for the therapy of UTI. Important microbiological properties include spectrum of activity to include all common urinary pathogens, bactericidal action in urine and low prevalence of resistant bacteria. The vital feature of an antibacterial drug useful in the therapy of UTI is prolonged urinary concentrations. The agent must therefore be well absorbed and have slow renal excretion. Most beta-lactam drugs do not have these combined properties. Aminoglycosides are effective drugs but cannot be administered orally. Quinolones and the calcium salt of fosfomycin are useful but do not have an ideal pharmacokinetic profile. Cotrimoxazole, trimethoprim alone and the trometamol salt of fosfomycin all have good antibacterial activity combined with slow urinary excretion.

Pharmacokinetics of co-trimazine after single and multiple doses

Plasma and urinary levels of trimethoprim (TMP), sulfadiazine (SDZ) and N4-acetylsulfadiazine (N4-SDZ) were determined after administration of 1 g co-trimazine (equivalent to 180 mg TMP and 820 mg SDZ) (Kombinax) as a single dose and again once daily for 7 days to 6 normal subjects. Both TMP and SDZ were rapidly absorbed from the gastrointestinal tract with peak plasma levels being achieved within 4 h in all subjects. Elimination half-lives ranged from 8 to 13 h for TMP and from 9 to 15 h for SDZ. Approximately 50% of the administered dose of SDZ was recovered in urine within 24 h of the single dose (32% as unchanged drug and 17% as the N4-acetylmetabolite). For TMP, the urinary recovery during the 24 h following the single dose averaged 39%. Mean plasma levels of TMP, SDZ and N4-SDZ at steady state were moderately higher than those observed after a single dose, but no change in absorption or disposition kinetics of these compounds was seen after repeated dosing.

Disposition of radiolabeled flumequine in rat and dog

Single doses of 14C-flumequine (a urinary tract antibacterial) were given to rats and dogs. Unchanged drug accounted for more than 80% of the drug in plasma of rats but only 25-50% in plasma of dogs. Although only a small percentage of the dose was excreted in the urine of each species as unchanged drug, a wide differentiation in the urinary metabolite profiles was observed. No significant tissue retention was seen in rats or dogs.

Pharmacokinetics of co-trimazine (sulphadiazine plus trimethoprim) in geriatric patients

The study was aimed at analyzing the pharmacokinetics of sulphadiazine (SDZ) and trimethoprim (TMP) in geriatric patients and was carried out in two stages. The first stage compared 11 geriatric patients (68-89 years old) and 9 healthy volunteers (21-34 years old). Serum concentration and urine elimination were determined on day 4 after 12-hourly administration of 1 tablet of co-trimazine containing 410 mg sulphadiazine (SDZ) plus 90 mg trimethoprim (TMP). The mean serum concentrations of SDZ were significantly higher in the older subjects than in the volunteers after 1, 8 and 12 h (p less than 0.05, 0.01, 0.01), but were not differentiable after 2 or 4 h. For TMP, the serum levels were higher (p less than 0.05) in the patients only after 8 h. The amounts collected in urine were higher in the normal volunteers for SDZ during the intervals 0-2 h (p less than 0.05), 2-4 h (p less than 0.01), and 4-8 h (p less than 0.01), but not for 8-12 h. The 12-hour recovery was 69% SDZ + acetyl-SDZ recovered in the patients compared to 66.0% in the volunteers. Indistinguishable amounts of TMP were recovered during each interval in the two groups of subjects, 59.2% in the patients compared to 70.0% in the volunteers. The second stage of the study comprised 9 geriatric patients of mean age 83.6 years and creatinine clearance 59.2 ml/min who were followed for 11 days. A steady increase in serum levels was observed. The mean peak serum concentration for SDZ was 16.7 +/- 4.2 mg/l after the first dose and 44.7 +/- 11.3 mg/l on day 10. For acetyl-SDZ, the respective concentrations were 2.1 +/- 0.9 and 7.1 +/- 3.1 mg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

[In vitro activity, serum, urine and prostatic adenoma concentrations of ofloxacin in urologic patients with complicated urinary tract infections]

The minimal inhibitory concentrations (MIC) of ofloxacin against 400 isolates cultured from the urine of urological patients with complicated urinary tract infections (UTI) resulted in an inhibition of 94% (99%) of the gram-negative strains at a concentration of 1 mg/l (2 mg/l) and an inhibition of 59% (100%) of the gram-positive strains at a concentration of 1 mg/l (4 mg/l). According to the MIC 90% values, the corresponding grade of activity was as follows: ciprofloxacin, ofloxacin, norfloxacin, pefloxacin, enoxacin, pipemidic acid, enoxacin and nalidixic acid. After an oral dose of 400 mg of ofloxacin, the mean peak serum concentration of ten patients was 5.5 mg/l. The mean renal excretion during 24 hours was 41%. In ten patients undergoing transurethral resection of the prostate, the median serum concentration was 1.87 mg/l and the median prostatic adenoma tissue concentration 1.20 mg/kg 14.5 to 19 hours after oral administration of 400 mg ofloxacin. Due to the in vitro activity and the concentrations obtained in serum, urine and tissue, ofloxacin appears to be well suited for treatment of complicated UTI.

Pharmacokinetics of oral co-trimazine and the penetration of its components sulfadiazine and trimethoprim into peripheral human lymph

Five healthy informed male volunteers received oral doses of 820 mg sulfadiazine (SDZ) plus 180 mg trimethoprim (TMP) (co-trimazine) every 24 h. Concentrations in serum, peripheral lymph from the leg and urine were determined after the first dose, and on the 4th day to reflect approximate steady-state conditions. TMP was assayed microbiologically and unchanged SDZ by high-pressure liquid chromatography. There was a rise in concentrations from the first dose to the 4th day. The rise for SDZ was by a factor of 1.6 in both serum and lymph; the rise for TMP was also 1.6 in serum, but 1.5 in lymph. The peak concentrations at steady state were 27.7 mg/l (SD) +/- 4.3 SDZ, and 1.6 +/- 0.68 mg/l TMP. The serum values at that time were 31.7 +/- 5.8 mg/l SDZ and 2.3 +/- 0.51 mg/l TMP. The simultaneous concentrations of both SDZ and TMP were always somewhat lower in lymph than in serum, also at the end of the observation periods, i.e. 12 h after the first dose and 72 h after the final one. But the serum concentrations of both SDZ and TMP were only slightly higher than in lymph. After the final dose, the ratio between the 12-hour areas under the concentration curves of lymph and serum was 0.68 +/- 0.12 for SDZ and 0.59 +/- 0.14 for TMP. The values after the first dose were similar, 0.63 +/- 0.17 and 0.57 +/- 0.05, respectively. The elimination half-life in serum during steady state was 16.5 h for SDZ, 8.6 h for acetylated SDZ and 9.4 h for TMP. In lymph the corresponding values were 19.2, 19.2 and 8.9 h.

Comparative pharmacokinetic study of four different sulfonamides in combination with trimethoprim in human volunteers

The pharmacokinetics of four different sulfonamides i. e., sulfamethoxazole (SMZ). Sulfamoxole (SMO), Sulfadiazine (SDZ) and Sulfadimidine (SDD) in combination with trimethoprim (TMP) were studied in 12 healthy volunteers. Plasma and urine concentrations of sulfonamides were measured at different time intervals. No significant difference was observed in the area under the plasma curve (AUC) of SMZ, SMO and SDZ, while AUC of SMO was significantly higher than SDD only. Free (unmetabolized) SDZ urinary excretion during a 10-25 h period was significantly higher than SMZ, SMO and SDD. The results suggest that SDZ alone or in combination with TMP would be more effective in urinary tract infections as compared to other sulfonamides studied.

The pharmacokinetics and serum and urine bactericidal activity of ciprofloxacin

Ciprofloxacin is an investigational quinolone agent possessing an impressive antibacterial spectrum. Its pharmacokinetics were studied in six volunteers after 250-mg and 500-mg single oral doses, and its bactericidal activity compared to that of trimethoprim-sulfamethoxazole given to the same volunteers. Mean peak serum levels were 1.45 micrograms/mL and 2.46 micrograms/mL for 250-mg and 500-mg doses, and time to peak was 1 and 1.3 hours. The 12-hour levels were 0.12 micrograms and 0.22 microgram. Half-life (T1/2)alpha were 0.32 and 0.43 with T1/2 beta were 3.97 and 4.15 and volume of distribution (area) were 80L and 90L, respectively. Area under the concentration curve (AUC) was 5.65 h X micrograms/mL and 10.37h X micrograms/mL. Serum clearance was 23L for both doses. Approximately 49% of the 250-mg dose and 43% of the 500-mg dose was recovered in the urine. Bactericidal levels were determined against clinical isolates. Sera at 1.5 hours after the 500-mg dose averaged bactericidal levels of 1:20 or better for an Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and beta-lactamase producing Haemophilus influenzae and Branhamella catarrhalis. Urinary bactericidal levels at eight to 12 hours were greater than or equal to 1:157 for E coli, K pneumoniae, gentamicin-piperacillin resistant P aeruginosa, Staphylococcus aureus, and 1:20 for Streptococcus faecalis. Serum bactericidal levels were superior, and urine bactericidal levels were superior or equal to the bactericidal levels obtained with trimethoprim-sulfamethoxazole.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraprostatic concentration of ciprofloxacin and its activity against urinary pathogens

The in-vitro activity of ciprofloxacin against 376 urinary pathogens was determined. The minimal inhibitory concentrations for 90% of the Enterobacteriaceae were 0.03-0.23 mg/l, for Pseudomonas aeruginosa 0.37 mg/l, for Streptococcus faecalis 0.75 mg/l and for Staphylococcus aureus 0.92 mg/l. A 100 mg dose of ciprofloxacin was administered intravenously to 25 patients undergoing prostatectomy. The concentrations in prostate and serum were measured at different intervals. Peak levels in prostate were 3.0 micrograms/g attained 20 min after administration. Peak serum levels were 1.2 mg/l attained 20 min after administration. Serum and prostate elimination was slowly. The overall serum: prostate ratio 1:2.1.

Trimethoprim-sulfamethoxazole pharmacokinetics during continuous ambulatory peritoneal dialysis

Eight adult patients without peritonitis maintained on chronic ambulatory peritoneal dialysis (CAPD) were administered a single oral dose of 320 mg trimethoprim (TMP) and 1600 mg sulfamethoxazole (SMX) to characterize the pharmacokinetics of TMP and SMX. Ten blood samples were drawn following the dose. TMP and SMX-active (SMXA) concentrations were quantified in serum and dialysate. The half-life of TMP and SMXA determined by model independent methods were 33.7 +/- 10.5 h (mean +/- SD) and 13.8 +/- 2.2 h respectively. Total body clearance of TMP was 32.8 +/- 10.1 ml/min and SMXA was 21.9 +/- 6.4 ml/min. CAPD clearance of TMP was 2.27 +/- 0.81 ml/min and SMXA was 1.72 +/- 0.93 ml/min. The average peritoneal dialysate concentrations over the 72-hour collection period of TMP and SMXA were 0.9 +/- 0.1 mg/l and 5.3 +/- 0.8 mg/l respectively. A dose of 320 mg TMP and 1600 mg SMX every 48 hours is recommended for CAPD patients with mild to moderate systemic infections.

Diffusion of ciprofloxacin into prostatic fluid

To determine whether ciprofloxacin might be efficacious in therapy for chronic bacterial prostatitis, its diffusion into prostatic fluid was studied in ten healthy volunteers. One hour after administering 500 mg ciprofloxacin, the concentration of ciprofloxacin was measured by the agar diffusion method and bioassay. Serum levels were twice as high as in seminal fluid; however, 12 and 24 hours later concentration in seminal fluid was tenfold higher than in serum. Split ejaculates were examined to determine the secretory pattern of ciprofloxacin into seminal fluid. The two fractions also showed tenfold concentration. Ciprofloxacin concentration in expressed prostatic secretion ranged from 15 to 0.9 mg/l, thus indicating pronounced diffusion of ciprofloxacin into the prostatic fluid.

Pharmacokinetics of norfloxacin (MK 366) in patients with impaired kidney function--some preliminary results

The concentration of norfloxacin in serum and urine was measured in five healthy volunteers and eleven patients with renal impairment following a 400 mg oral dose of norfloxacin. In impaired renal function the elimination rate of norfloxacin is decreased considerably whereupon the area under the curve (AUC) rises rapidly. The urinary concentration of norfloxacin decreases with renal function but therapeutic levels are still obtained for sensitive organisms. Patients with a glomerular filtration rate of less than 30 ml/min require dosage reduction and we would recommend a reduction to half the usual dosage.

Norfloxacin--a review of pharmacology and tissue penetration

A review of the pharmacokinetics of the highly active quinoline derivative, norfloxacin, is presented. The compound appears to be rapidly absorbed. The serum half-life is about 3 X 5 h and 30% of a given dose is recovered in the urine. Rapid penetration of an inflammatory exudate occurs. The compound is metabolized to a modest extent, probably in the liver, six metabolites being recognized. The serum half-life is prolonged in severe renal impairment. Probenecid would appear to decrease the renal elimination. The possibility of treating both urinary and tissue infections with this compound is raised.

In-vitro studies with ciprofloxacin, a new 4-quinolone compound

Ciprofloxacin is a new antibacterial agent of the 4-quinolone group. With an agar dilution technique we compared its activity on 365 clinical isolates with those of norfloxacin, nalidixic acid, ampicillin, mezlocillin, cefadroxil, cefuroxime, ceftazidime, ceftriazone , cefotaxime, latamoxef (moxalactam), and gentamicin. Ciprofloxacin was overall the most active agent tested against aerobic Gram-negative species, with the MIC90 values for all species being below 1 mg/l (excepting Providencia stuartii with 4 mg/l), and the large majority being below 0.12 mg/l. Many of the strains were selected on the basis of resistance to beta-lactam agents or gentamicin, and ciprofloxacin was also active against these. There was little difference in the activity of ciprofloxacin at inocula of 10(4) or 10(6) cfu. Strains with higher MIC's of the related agents norfloxacin and nalidixic acid were less susceptible to ciprofloxacin . Ciprofloxacin was less active against Gram-positive species (typical MIC90 values were 0.5 or 1 mg/l) and obligate anaerobes (4 mg/l for Bacteroides fragilis). The activity of ciprofloxacin in broth dilution tests was little affected by pH over the range 6.0-8.0, or by human serum or tissue fluid; its activity was reduced by the presence of urine. Binding to human serum protein was 20-28%. Ciprofloxacin was rapidly bacterial in broth at concentrations near to its MICs. By exposure to subinhibitory concentrations of ciprofloxacin it was possible to increase its MIC for bacteria in daily subcultures. The final MIC values after ten days were often about 16-fold greater than those observed initially.

[Co-trimoxazole concentration in the prostatic fluid of patients with subacute and chronic prostatitis]

Plasma and prostatic fluid (PF) concentrations of co-trimoxazol (TMP/SMZ) were investigated on 16 patients with subacute or chronic prostatitis. Co-trimoxazol-forte was given perorally, 2X 1 tablet (2X 160 mg TMP/800 mg SMZ), daily. TMP-concentrations in PF were 3.3 micrograms/ml and 2.6 micrograms/ml three and six hours after peroral application (days two and three) respectively. Compared to the concentrations of TMP in plasma, there was an increase by the factor 2.0-3.7. The corresponding concentrations of SMZ in PF were 7.7 micrograms/ml and 10.4 micrograms/ml 3 and 6 hours after medication--i.e. 32% of the plasma concentrations.

Pharmacokinetic analysis of the level of sulfonamide-trimethoprim combination in calves

Pharmacokinetic parameters which describe biological availability (AUC, Cmax, tmax) and elimination (kel, t 1/2) of sulfonamides and trimethoprim were determined in calves. Pharmacokinetic analysis was based upon "one compartment model". The average +/- SD half-life in plasma was for sulfametoxazole 12.8 +/- 0.32 h, for sulfamerazine 17.0 +/- 0.75 h and for sulfachloropyridazine 13.1 +/- 0.86 h. The average half-life of trimethoprim in plasma was 11.3 +/- 0.56 h. In fasted calves the concentrations of sulfachloropyridazine and trimethoprim in plasma were higher as compared with fed group.

Pharmacological principles in the treatment of urinary tract infections

The ideal antibacterial drug for urinary tract infections should eliminate most urinary pathogens but not alter the colonic flora. Levels in the urine can be attained with the beta-lactam and aminoglycoside antibiotics which are up to several powers of 10 higher than the minimal inhibitory concentration values of the causative organisms. At these levels even penicillin G eliminates many Gram-negative urinary pathogens. Trimethoprim has a lesser propensity to select resistant organisms than most other antimicrobials. It occurs in vaginal secretions and reduces the number of Enterobacteriaceae surrounding the urethral orifice, thereby diminishing the chance of an ascending reinfection, and it is often effective in the treatment of bacterial prostatitis as it reaches therapeutic concentrations in prostatic secretions. Tetracycline therapy, however, carries a substantial chance of bacterial resistance at the next reinfection of the urinary tract, as these antibiotics produce almost uniform resistance in Escherichia coli in the faecal flora. Failure to respond to single-dose therapy actually implies the presence of antibody-coated bacteria in the urine, which in turn implies an upper tract or prostatic infection. This is an easy means of indicating which patients require further evaluation by intravenous pyelography or cystoscopy.

Trimethoprim-sulfadiazine in the horse: serum, synovial, peritoneal, and urine concentrations after single-dose intravenous administration

Six healthy adult mares were given a single IV injection of trimethoprim (TMP)-sulfadiazine (SDZ) at a dosage rate of 2.5 mg of TMP/kg of body weight and 12.5 mg of SDZ/kg. Serum, synovial, peritoneal, and urine TMP-SDZ concentrations were measured serially over a 48-hour period. The highest measured mean concentrations of TMP and SDZ were found in the first (0.5 hour) sample of serum, synovial fluid, and peritoneal fluid. The mean peak concentrations of TMP and SDZ averaged 4.37 micrograms/ml and 21.81 micrograms/ml for serum, 2.95 micrograms/ml and 15.31 micrograms/ml for synovial fluid, and 3.88 micrograms/ml and 19.52 micrograms/ml for peritoneal fluid, respectively. Urine concentrations of the drugs were relatively high and peaked early. The elimination rate for TMP and SDZ averaged 0.41 and 0.26 hour-1, while the elimination half-life was 1.91 and 2.71 hours, respectively, and the volume of distribution averaged 0.59 and 0.52 L/kg, respectively.

Effect of physiological manipulations on the chemotherapy of experimentally induced renal infection

The belief that a favorable physiological milieu in the urinary tract may augment the effectiveness of antimicrobial agents used to treat urinary tract infections was examined by using an experimental model of Escherichia coli-induced renal infection in rats. The effect of manipulating urinary pH and flow on the antimicrobial activities of gentamicin, carbenicillin, ampicillin, nitrofurantoin and co-trimoxazole was assessed. In addition, a potential synergistic effect of the sequential administration of gentamicin and cephalothin in the eradication of renal infection was investigated. Although significant physiological alterations were achieved, these did not affect the efficacy of the antimicrobial agents studied, and therapeutic failures were common.

Concentrations of trimethoprim and sulphamethoxazole in the human prostate gland after intramuscular injection

Following intramuscular injection of co-trimoxazole (trimethoprim/sulphamethoxazole 1 : 5), concentrations of trimethoprim (TMP) and sulphamethoxazole (SMX) were measured in the prostatic tissue and serum of 30 men undergoing endoscopic prostatectomy. Tissue levels for TMP appeared to be higher than serum levels and probably reached the minimum inhibitory concentration (MIC) for most urinary pathogens. Administration of the drug at 4, 8 and 12 h prior to sampling produced no significant difference in tissue levels. It is concluded that TMP is concentrated in prostatic tissue following intramuscular injection. Tissue levels for SMX were apparently lower than serum levels.

[Co-tetroxazin levels in the prostatic secretion of patients with subacute and chronic prostatitis]

Plasma and prostatic fluid concentrations of co-tetroxacine (TXP/SDZ) were investigated on 12 patients with subacute or chronic prostatitis. Co-tetroxacine was given perorally, 2 x 2 tabl. daily. - Tetroxoprime-(TXP-)concentrations in prostatic fluid were 4.2 micrograms/ml and 4.5 micrograms/ml 3 and 6 hours after peroral application (days 2 and 3) respectively. Compared to the concentrations of TXP in the systemic fluid there was an increase by the factor 3 to 4.3. - The corresponding concentrations of sulfadiazine (SDZ) in prostatic fluid were 11.6 micrograms/ml and 10.0 micrograms/ml - i.e. 62-70% of the plasma concentrations.

The pharmacokinetics of antibiotic diffusion in chronic bacterial prostatitis

Historically chronic bacterial prostatitis in the male human has been relatively resistant to antimicrobial chemotherapy. The pharmacokinetic theory of drug diffusion into the prostate is reviewed. A brief description of the various canine models utilized to quantitate antimicrobial drug diffusion is presented. Specific data concerning the diffusion of various antimicrobial agents are abstracted followed by a brief discussion of mechanistic explanations for the success or failure of drug therapy.

Human prostatic tissue concentrations of rosoxacin

The corresponding concentrations of rosoxacin in serum (S) and prostatic tissue (PT) were determined in 15 patients undergoing transurethral resection of the prostate because of benign prostatic hyperplasia. Rosoxacin concentrations were determined employing both bioassay and a high-pressure liquid chromatography procedure, with excellent correlation between the two methods. Two dosage schedules were followed, resulting in median serum concentrations of 3.6 and 5.8 microgram/ml, respectively. The ratio of PT/S was found to be fairly constant and surprisingly high, the median values being 0.46 and 0.56. These results indicate that concentrations of rosoxacin are obtained in prostatic interstitial fluid in the range of the minimal inhibitory concentrations for most of the gram-negative pathogens causing bacterial prostatitis and urinary tract infections. Acceptable drug concentrations also were determined in urine and cerebrospinal fluid. The results obtained in this study warrant further clinical trials for rosoxacin in the treatment of bacterial prostatitis and urinary infections.

Pharmacokinetics of co-trimoxazole and co-tetroxazine in geriatric patients

Following a single dose of co-trimoxazole or co-tetroxazine, the plasma and urine levels of intact trimethoprim (TMP) and sulphamethoxazole (SMZ) and of tetroxoprim and sulphadiazine (SDZ) were determined in six geriatric patients in a cross-over design by high pressure liquid chromatography. The pharmacokinetic analysis showed a plasma elimination half-life in the terminal phase of 10.39 h for TMP, 11.79 h for SMZ, 6.55 h for TXP and 10.46 h for SDZ. The resulting distribution volumes Vd beta and total plasma clearance values corresponded with the data obtained in young patients or volunteers. Recovery in urine, measured for up to 96 h, was 49.2% (TMP), 19.8% (SMZ), 57.03% (TXP) and 61.1% (SDZ). In contrast to young volunteers, geriatric patients experienced a slight prolongation of renal excretion for both sulphonamides. In this group of patients the renal clearance was 2.42 ml/min for SMZ and 10.7 ml/min for SDZ.

Drug trials: treatment of urinary tract infection with multiple-dose intramuscular administration of cephamandole

Therapy with cephamandole (1.0 g, every eight hours) for five days was effective in eliminating cephamandole-sensitive microorganisms from the urinary tract. A 75% cure rate was achieved in a group of 20 patients, 45% of whom had abnormalities of the urinary tract. Local pain (despite addition of lignocaine) was sufficiently prolonged and severe to make multiple-dose intramuscular administration unacceptable. No other toxic effects were encountered.