Cumulative Urine Samples Research Articles

Urinary Excretion of Iohexol as a Permeability Marker in a Mouse Model of Intestinal Inflammation: Time Course, Performance and Welfare Considerations.

Simple SummaryIn mammals, different diseases are associated with intestinal changes that may cause an increase in gut permeability. Intestinal permeability tests allow the evaluation of intestinal damage in humans, veterinary patients and laboratory animal models. When used in mouse models, these tests require that animals are singly housed in metabolic cages with a wire-grid floor to collect urine samples. This raises welfare concerns. Iohexol meets several criteria for an ideal intestinal permeability marker and has recently been used in several species. Here, we examined the performance of an intestinal permeability test using iohexol administered by mouth and following excretion over 24 h in urine. As a model, we chose immunodeficient mice with intestinal inflammation induced by adoptive transfer of effector/memory T cells. We collected urine samples at seven time points to profile the urinary excretion of iohexol, in addition to intestinal tissue samples for histological assessment. We conclude that a 6 h cumulative urine sample may be sufficient to evaluate small intestinal permeability in this mouse model and increased urinary excretion of iohexol is correlated with increased severity of duodenitis. The welfare of mice housed in metabolic cages could be improved by reducing the cage periods from 24 to 6 h.Intestinal permeability (IP) tests are used to assess intestinal damage in patients and research models. The probe iohexol has shown advantages compared to 51Cr-EDTA or absorbable/nonabsorbable sugars. During IP tests, animals are housed in metabolic cages (MCs) to collect urine. We examined the performance of an iohexol IP test in mice. Rag1-/- (C57BL/6) mice of both sexes were divided into controls or treatment groups, the latter receiving injections of effector/memory T cells to induce intestinal inflammation. After two, four and five weeks (W), a single dose of iohexol was orally administered. Urine was collected seven times over 24 h in MCs. Iohexol concentration was measured by ELISA. Intestinal histological damage was scored in duodenal sections. In control and treated mice of both sexes, urinary excretion of iohexol peaked at 4 h. From W2 to W4/W5, urinary iohexol excretion increased in treated mice of both sexes, consistent with development of duodenitis in this model. Positive correlations were observed between the urinary excretion of iohexol in W4/W5 and the histological severity of duodenitis in treated male mice. We conclude that a 6 h cumulative urine sample appears sufficient to evaluate small IP to iohexol in this mouse model, improving animal welfare by reducing cage periods.

Evaluation of vanillin as a probe drug for aldehyde oxidase and phenotyping for its activity in a Western Indian Cohort.

BACKGROUND:Aldehyde oxidase (AO), a molybdoflavoenzyme, is emerging as a key player in drug discovery and metabolism. Despite having several known substrates, there are no validated probes reported for studying the activity of AO in vivo. Vanillin (4-hydroxy 3-methoxy benzaldehyde) is an excellent substrate of AO, in vitro. In the present study, vanillin has been validated as an in vivo probe for AO. Subsequently, a phenotyping study was carried out using vanillin in a subset of Indian population with 100 human volunteers.METHODS:For the purposes of in vitro probe validation, initially the metabolism of vanillin was characterized in partially purified guinea pig AO fraction. Further, vanillin was incubated with partially purified xanthine oxidase fraction and AO fractions, and liver microsomes obtained from different species (in presence and absence of specific inhibitors). For the phenotyping study, an oral dose of 500 mg of vanillin was administered to the participants in the study and cumulative urine samples were obtained up to 8 h after giving the dose. The samples were analyzed by high-performance liquid chromatography and metabolic ratios were calculated as peak area ratio of vanillic acid/vanillin.RESULTS:(a) The results of the in vitro validation studies clearly indicated that vanillin is preferentially metabolized by AO. (b) Normal distribution tests and probit analysis revealed that AO activity was not normally distributed and that 73.72% of the participants were fast metabolizers, 24.28% intermediate metabolizers, and 2% were slow metabolizers.CONCLUSIONS:Data of the phenotyping study suggest the existence of AO polymorphism, in a Western Indian cohort.

A case-control study to assess the ability of the thymine challenge test to predict patients with severe to life threatening fluoropyrimidine-induced gastrointestinal toxicity.

A previous study suggested that a thymine (THY) challenge dose could detect aberrant pharmacokinetics in known cases of fluoropyrimidine toxicity compared with healthy volunteers. The preliminary data suggested that urine sampling also could detect this aberrant disposition. The aim of this case-control study was to assess the ability of the urinary THY challenge test to discriminate cases of severe gastrointestinal toxicity in a cohort of patients treated with 5-fluorouracil or capecitabine. Patients (n=37) received a 250mg (per os) dose of THY and a cumulative urine sample was collected for 0-4h. The urinary amounts of THY and metabolite dihydrothymine (DHT) were determined by liquid chromatography/mass spectrometry. Genomic DNA was analysed for DPYD gene variants. Renal function was estimated from blood creatinine levels. Cases (n=9) and noncases (n=23) of severe (grade≥3) gastrointestinal toxicity were defined based on Common Terminology Criteria for Adverse Events. The median THY/DHT ratios were 6.2 (interquartile range 2.9-6.4) in cases, including the 2 patients who were DPYD heterozygous carriers. However, this was not significantly different (P=.07) from the THY/DHT in noncases (median 2.6, interquartile range 2.8-4.2). Although creatinine clearance was lower (P=.001) in cases, renal function could not discriminate cases from noncases. However, logistic regression analysis using both of these explanatory variables could discriminate most cases (receiver operating characteristic area 0.8792, 95% confidence interval 0.72-1.00). The THY challenge test combined with a patient's renal function may be useful as a phenotypic diagnostic test to detect risk of life-threatening fluoropyrimidine gastrointestinal toxicity.

Lower urine sodium predicts longer length of stay in acute heart failure patients: Insights from the ROSE AHF trial.

BackgroundIn patients hospitalized with acute heart failure (AHF), low urine sodium concentration (U Na) after diuretic treatment may identify patients at risk for longer length of stay (LOS) and adverse events. We investigated the prognostic significance of 24‐hour cumulative postdiuretic urine sodium concentration in a multicenter clinical trial population.MethodsThe Renal Optimization Strategies Evaluation AHF (ROSE AHF) trial randomized 360 patients with AHF and renal dysfunction receiving intravenous diuretic to dopamine, nesiritide, or placebo. Sodium concentration was measured in cumulative urine sample collected during the first 24 hours after randomization in 298 patients. Based on prior studies, lower U Na was defined as ≤60 mmol/L.ResultsLower U Na was present in 142 (48%) patients, who had longer LOS (7 days vs 5 days, P < .001) and less 72‐hour weight loss (5.7 lb vs 9.0 lb, P < .001). These associations persisted after controlling for baseline estimated glomerular filtration rate and outpatient furosemide dose. Lower U Na did not modify the null effects of dopamine or nesiritide on clinical outcomes. Results were similar for spot rather than cumulative 24‐hour U Na concentration.ConclusionIn patients hospitalized for AHF and renal dysfunction, U Na ≤ 60 mmol/L during the first 24 hours of diuresis identifies patients at risk for prolonged hospitalization but does not provide an indication for adjunctive dopamine or nesiritide.

Spot and Cumulative Urine Samples Are Suitable Replacements for 24-Hour Urine Collections for Objective Measures of Dietary Exposure in Adults Using Metabolite Biomarkers

Measurement of multiple food intake exposure biomarkers in urine may offer an objective method for monitoring diet. The potential of spot and cumulative urine samples that have reduced burden on participants as replacements for 24-h urine collections has not been evaluated. The aim of this study was to determine the utility of spot and cumulative urine samples for classifying the metabolic profiles of people according to dietary intake when compared with 24-h urine collections in a controlled dietary intervention study. Nineteen healthy individuals (10 male, 9 female, aged 21-65 y, BMI 20-35 kg/m2) each consumed 4 distinctly different diets, each for 1 wk. Spot urine samples were collected ∼2 h post meals on 3 intervention days/wk. Cumulative urine samples were collected daily over 3 separate temporal periods. A 24-h urine collection was created by combining the 3 cumulative urine samples. Urine samples were analyzed with metabolite fingerprinting by both high-resolution flow infusion electrospray mass spectrometry (FIE-HRMS) and proton nuclear magnetic resonance spectroscopy (1H-NMR). Concentrations of dietary intake biomarkers were measured with liquid chromatography triple quadrupole mass spectrometry and by integration of 1H-NMR data. Cross-validation modeling with 1H-NMR and FIE-HRMS data demonstrated the power of spot and cumulative urine samples in predicting dietary patterns in 24-h urine collections. Particularly, there was no significant loss of information when post-dinner (PD) spot or overnight cumulative samples were substituted for 24-h urine collections (classification accuracies of 0.891 and 0.938, respectively). Quantitative analysis of urine samples also demonstrated the relation between PD spot samples and 24-h urines for dietary exposure biomarkers. We conclude that PD spot urine samples are suitable replacements for 24-h urine collections. Alternatively, cumulative samples collected overnight predict similarly to 24-h urine samples and have a lower collection burden for participants.

Extracorporeal clearance of colistin methanesulphonate and formed colistin in end-stage renal disease patients receiving intermittent haemodialysis: implications for dosing.

Colistin, administered intravenously as its inactive prodrug colistin methanesulphonate (CMS), is being increasingly used. However, there is very limited information available on the impact of haemodialysis (HD) on the pharmacokinetics of CMS and formed colistin. A single 30 min intravenous dose of CMS (150 mg of colistin base activity) was administered to 10 patients undergoing HD. HD was performed from 1.5 to 5.5 h after the start of the CMS infusion. Serial blood samples were collected over 50 h, additional blood samples pre- and post-dialysis membrane at three timepoints during HD, dialysate samples at four timepoints during HD, and a cumulative urine sample over 24 h. CMS and colistin were determined by HPLC. Population modelling and determination of HD clearance by multiple methods was conducted. The average amount of CMS recovered in the dialysate was 30.6% of the dose administered. The concentrations of CMS and colistin in the plasma and the amounts of CMS recovered in the dialysate were well described by the population disposition model. The clearance of CMS by dialysis as estimated by population analysis based on systemic plasma concentrations and amounts in the dialysate was 4.26 L/h (26% coefficient of variation). The dialysis clearance determined from the pre- and post-membrane plasma concentrations was 5.67 L/h (21%) for CMS and 3.99 L/h (44%) for colistin. Thus, CMS clearance by dialysis from trans-cartridge extraction was ∼30% higher than when calculated based on the amount in dialysate, suggesting adsorption to the membrane. Due to the extensive removal of CMS by dialysis, HD should be conducted at the end of a dosing interval and a supplemental dose should be administered.

Risk assessment visualization of rubidium compounds: comparison of renal and hepatic toxicities, in vivo.

Rubidium has been considered to be nontoxic. Its use includes thin film on glass deposition and as medical contrast medium. Recent technology innovations also involve the use of rubidium, but there is limited information about the biological effects of its various compounds. In the present risk assessment study, a series of rubidium compounds with different counter anions-acetate, bromide, carbonate, chloride, and fluoride-were orally administrated in a single dose to several groups of rats. Cumulative 24-h urine samples were obtained, and the levels of rubidium, fluoride, N-acetyl-β-D-glucosaminidase and creatinine were measured to evaluate possible acute renal effects. Daily samples of serum were also obtained to determine the levels of aspartate and alanine aminotransferases to assess possible acute hepatic effects. Urinary rubidium excretion recovery of 8.0-10.5% shows that urine can be a useful diagnostic tool for rubidium exposure. The present results reveal that rubidium shows different biological effects depending on the counter anion. A pattern of large significant NAG leakage and elevation of ALT observed in rats treated with anhydrous rubidium fluoride indicates renal and hepatic toxicities that can be attributed to fluoride. The techniques reported in this study will be of help to assess the potential risks of toxicity of rubidium compounds with a variety of anions.

Urinary Monitoring of Exposure to Yttrium, Scandium, and Europium in Male Wistar Rats

On the assumption that rare earth elements (REEs) are nontoxic, they are being utilized as replacements of toxic heavy metals in novel technological applications. However, REEs are not entirely innocuous, and their impact on health is still uncertain. In the past decade, our laboratory has studied the urinary excretion of REEs in male Wistar rats given chlorides of europium, scandium, and yttrium solutions by one-shot intraperitoneal injection or oral dose. The present paper describes three experiments for the suitability and appropriateness of a method to use urine for biological monitoring of exposure to these REEs. The concentrations of REEs were determined in cumulative urine samples taken at 0-24h by inductively coupled plasma atomic emission spectroscopy, showing that the urinary excretion of REEs is <2%. Rare earth elements form colloidal conjugates in the bloodstream, which make high REEs accumulation in the reticuloendothelial system and glomeruli and low urinary excretion. The high sensitivity of inductively coupled plasma-argon emission spectrometry analytical methods, with detection limits of <2μg/L, makes urine a comprehensive assessment tool that reflects REE exposure. The analytical method and animal experimental model described in this study will be of great importance and encourage further discussion for future studies.

Using a physiologically based pharmacokinetic model to link urinary biomarker concentrations to dietary exposure of perchlorate

Exposure to perchlorate is widespread in the United States and many studies have attempted to character the perchlorate exposure by estimating the average daily intakes of perchlorate. These approaches provided population-based estimates, but did not provide individual-level exposure estimates. Until recently, exposure activity database such as CSFII, TDS and NHANES become available and provide opportunities to evaluate the individual-level exposure to chemical using exposure surveillance dataset. In this study, we use perchlorate as an example to investigate the usefulness of urinary biomarker data for predicting exposures at the individual level. Specifically, two analyses were conducted: (1) using data from a controlled human study to examine the ability of a physiologically based pharmacokinetic (PBPK) model to predict perchlorate concentrations in single-spot and cumulative urine samples; and (2) using biomarker data from a population-based study and a PBPK model to demonstrate the challenges in linking urinary biomarker concentrations to intake doses for individuals. Results showed that the modeling approach was able to characterize the distribution of biomarker concentrations at the population level, but predicting the exposure–biomarker relationship for individuals was much more difficult. The type of information needed to reduce the uncertainty in estimating intake doses, for individuals, based on biomarker measurements is discussed.

A comparison of the natriuretic and kaliuretic effects of cicletanine and hydrochlorothiazide in prehypertensive and hypertensive humans

The aim of this study was to compare the single-dose effects of thiazide-type diuretics cicletanine and hydrochlorothiazide (HCTZ), on natriuresis and kaliuresis in prehypertensive and treatment-naïve, stage 1 hypertensive patients and to explore the impact of GRK4 gene polymorphisms on thiazide-induced urinary electrolyte excretion. The study was a randomized, double-blind, placebo-controlled, three-period, four-treatment, balanced incomplete block, cross-over study in male patients assigned to treatment sequences consisting of placebo, cicletanine 50 mg, cicletanine 150 mg, and HCTZ 25 mg, doses used to treat hypertension. Cumulative urine samples were collected predosing and over 24 h after dosing in each period to compare urine electrolyte excretion profiles of potassium (UKV), sodium (UNaV), magnesium, calcium, phosphate, chloride, and pH among groups. Each treatment was administered to 18 different patients in each period, and an equal number of patients had less than and at least three GRK4 allele variants. Compared with placebo, mean UKV was significantly increased with HCTZ 25 mg (12.7 mmol/day; P ≤ 0.001), cicletanine 50 mg (4.6 mmol/day; P = 0.026), and cicletanine 150 mg (5.5 mmol/day; P = 0.011), and mean UNaV was significantly increased with HCTZ 25 mg (102.2 mmol/day; P ≤ 0.001), cicletanine 50 mg (21.7 mmol/day; P = 0.005), and cicletanine 150 mg (57.9 mmol/day; P ≤ 0.001). All treatments had more natriuresis, diuresis, and kaliuresis than placebo, and both doses of cicletanine had less kaliuresis than HCTZ. These findings suggest that cicletanine is a favorable and well tolerated option for the treatment of hypertension with an improved safety profile compared with HCTZ.

Adequacy of vitamin C supplementation in patients with gastrointestinal disorders receiving parenteral nutrition: A randomized trial

In Japan, supplemental vitamins are not always included during short-term peripheral parenteral nutrition (PPN) therapy. In addition, a dose of 100 mg/day of vitamin C shown in the 1975 AMA guideline for adult intravenous multi-vitamin formation, is inadequate to keep vitamin C levels in the normal range. We investigated the adequacy of 500 mg of supplemental vitamin C in patients with gastrointestinal disorders receiving short-term PPN therapy. We randomly assigned 16 in patients with gastrointestinal disorders who were scheduled to receive a 5 day continuous PPN intravenous infusion to a treatment group that received 500 mg/day of supplemental vitamin C or to a control group that received no vitamin C supplementation. Blood concentrations of vitamin C and indicators of inflammation were measured before and immediately after 3 and 5 days of vitamin C administration. Vitamin C and oxidative stress markers in 24 h, cumulative urine samples, collected and stored under light protection at 0 °C, were also measured before and on days 3 and 5 of supplementation. Mean blood vitamin C concentrations were below normal at baseline in both groups but returned to normal only in the treated group, on both days 3 and 5. Increases from the baseline were significantly larger in the treatment group than in the control group on both days. Mean urinary vitamin C excretion was above normal only in the treated group. Indications of inflammation and markers of oxidative stress did not differ markedly between-groups at any time. Poor vitamin C status in patients with gastrointestinal disorders receiving short-term PPN can be restored to normal with vitamin C supplementation at 500 mg/day.

Distribution, Elimination, and Renal Effects of Single Oral Doses of Europium in Rats

Single doses of europium (III) chloride hexahydrate were orally administered to several groups of rats. Cumulative urine samples were taken at 0-24 h, and blood samples were drawn after 24-h administration. The europium concentration was determined in these samples by inductively coupled plasma atomic emission spectroscopy. The volume, creatinine, ß-2-microglobulin, and N-acetyl-ß-D-glucosaminidase were measured in the urine samples to evaluate possible europium-induced renal effects. The blood samples showed low europium distribution, with an average of 77.5 μg/L for all groups. Although the urinary concentration and excretion showed dose-dependent increases, the percentage of europium excreted showed a dose-dependent decrease, with an average of 0.31% in all groups. The administration of europium resulted in a significant decrease of creatinine and a significant increase of urinary volume, N-acetyl-ß-D-glucosaminidase, and ß-2-microglobulin. Rare earth elements, including europium, are believed to form colloidal conjugates that deposit in the reticuloendothelial system and glomeruli. This specific reaction may contribute to low europium bioavailability and renal function disturbances. Despite low bioavailability, the high performance of the analytical method for determination of europium makes the blood and urine sampling suitable tools for monitoring of exposure to this element. The results presented in this study will be of great importance in future studies on the health impacts of rare earth elements.

Vitamin C supplementation in patients receiving peripheral parenteral nutrition after gastrointestinal surgery

Objective We investigated an adequate vitamin C dose during peripheral parenteral nutrition therapy in patients after gastrointestinal surgery by measuring blood concentrations and urine excretions of vitamin C. We also sought to identify the effects of vitamin C on the oxidative status. Methods In a randomized trial, 2 d after undergoing gastrointestinal surgery, 16 patients started to receive a 5-d continuous intravenous infusion of vitamin C, either 100 or 500 mg/d. Blood concentrations of vitamin C and inflammatory and immunologic parameters were measured preoperatively, the day after surgery, and 3 and 5 d after starting administration of vitamin C (day 3 and day 5). Also, excretions of vitamin C and oxidative stress markers in 24-h, cumulative urine samples, collected and stored under light protection at 0°C, were measured on day 3 and day 5. Results Mean blood vitamin C concentration decreased markedly after surgery. The concentration returned to normal on day 3 and on day 5 in the 500-mg group and only on day 5 in the 100-mg group. Concentrations differed significantly between the groups on day 3 and on day 5 ( P < 0.001 for both days). Urinary vitamin C excretion was above normal on both days in the 500-mg group, but it never reached normal in the 100-mg group ( P < 0.001 for both days). Urinary excretion of 8-isoprostane, a marker of oxidative stress, was significantly lower in the 500-mg than in the 100-mg group on day 3 ( P = 0.002). Conclusion Vitamin C dose of 500 mg/d, not 100 mg/d, is adequate for patients undergoing gastrointestinal surgery and receiving peripheral parenteral nutrition therapy. Vitamin C may decrease postsurgical oxidative stress.

OP033 BIOAVAILABILITY OF ANTIOXIDANTS VARIES WITH NUTRITIONAL STATUS IN ADOLESCENTS?

Rationale: The adequate dose and the effectiveness of vitamin C administration in postsurgical patients are not clear. We investigated an adequate vitamin C dose during PPN therapy in patients after gastrointestinal surgery by measuring blood concentrations and urine excretions of vitamin C. We also sought to identify the effects of vitamin C on the oxidative status. Methods: In a randomized trial, 2 days after undergoing gastrointestinal surgery, 16 patients started to receive a 5-day continuous intravenous infusion of vitamin C, either 100 or 500mg/day. Blood concentrations of vitamin C and inflammatory and immunological parameters were measured preoperatively, next day of surgery, and 3 and 5 days after starting administration of vitamin C (Day3 and Day5). Also, excretions of vitamin C and oxidative stress markers in 24-hour, cumulative urine samples, collected and stored under light protection at 0oC were measured on Day3 and Day5. Results: Mean blood vitamin C concentration decreased markedly after surgery. The concentration returned to normal on Day 3 and on Day 5 in the 500-mg group and only on Day 5 in the 100-mg group. Concentrations differed significantly between the groups on Day 3 and on Day 5 (P< 0.001 for both days). Urinary vitamin C excretion was above normal on both days in the 500mg group, but it never reached normal in the 100mg group (P< 0.001 for both days). Urinary excretion of 8-isoprostane, a marker of oxidative stress, was significantly lower in the 500-mg than in the 100-mg group on Day3 (P= 0.002). Conclusion: Vitamin C dose of 500mg/day, not 100mg/ day, is adequate for patients undergoing gastrointestinal surgery and receiving PPN therapy. Vitamin C may decrease postsurgical oxidative stress.

Effects of chlorophyll and chlorophyllin on low-dose aflatoxin B(1) pharmacokinetics in human volunteers.

Chlorophyll (Chla) and chlorophyllin (CHL) were shown previously to reduce carcinogen bioavailability, biomarker damage, and tumorigenicity in trout and rats. These findings were partially extended to humans, where CHL reduced excretion of aflatoxin B(1) (AFB(1))-DNA repair products in Chinese unavoidably exposed to dietary AFB(1). However, neither AFB(1) pharmacokinetics nor Chla effects were examined. We conducted an unblinded crossover study to establish AFB(1) pharmacokinetic parameters among four human volunteers, and to explore possible effects of CHL or Chla cotreatment in three of those volunteers. For protocol 1, fasted subjects received an Institutional Review Board-approved dose of 14C-AFB(1) (30 ng, 5 nCi) by capsule with 100 mL water, followed by normal eating and drinking after 2 hours. Blood and cumulative urine samples were collected over 72 hours, and 14C- AFB(1) equivalents were determined by accelerator mass spectrometry. Protocols 2 and 3 were similar except capsules also contained 150 mg of purified Chla or CHL, respectively. Protocols were repeated thrice for each volunteer. The study revealed rapid human AFB(1) uptake (plasma k(a), 5.05 + or - 1.10 h(-1); T(max), 1.0 hour) and urinary elimination (95% complete by 24 hours) kinetics. Chla and CHL treatment each significantly impeded AFB(1) absorption and reduced Cmax and AUCs (plasma and urine) in one or more subjects. These initial results provide AFB(1) pharmacokinetic parameters previously unavailable for humans, and suggest that Chla or CHL co-consumption may limit the bioavailability of ingested aflatoxin in humans, as they do in animal models.

Single dose and multiple dose pharmacokinetics of 2'-fluoro-2',3'-dideoxyadenosine and 2'-fluoro-2',3'-dideoxyinosine, anti-HIV agents, in rats.

A single and multiple dose pharmacokinetic (PK) study was conducted in rats following oral administration of 2'-fluoro-2',3'-dideoxyadenosine (FddA) and 2'-fluoro-2',3'-dideoxyinosine (FddI) at three dose levels. Six rats/gender were assigned to one of the three FddA or FddI dose levels: 40, 250, and 1000 mg/kg/day. Three rats/gender were assigned to the PK study on day 1, while the remaining 3 rats/gender were assigned to the PK study on day 14. The rats received the appropriate doses of either FddA or FddI orally by gavage once a day for 14 days. Serial blood samples up to 24 h and cumulative urine samples (0-24 h) were collected on both days 1 and 14. Plasma and urine samples were analyzed for the concentrations of intact FddA and/or FddI using a validated assay. The data were subjected to non-compartmental PK analyses. Over the dose range of 40-1000 mg/kg. both FddA and FddI exhibited dose dependent pharmacokinetics in rats. Following FddA administration, there was a rapid and extensive in vivo conversion of FddA to FddI; FddI was the major circulating moiety as reflected by Cmax and AUC values (generally 2-3-fold greater than those of FddA at each dose level) as well as the amount excreted (%UR) in the urine. In contrast, following FddI administration, Cmax, AUC, and %UR values were 2-5-fold lower as compared to the FddI generated from FddA administration at each dose level, which also suggested that FddI was not absorbed as extensively as FddA. Based on the findings of this study, FddA is an excellent prodrug of FddI.

Assessment of Renal Effects of Sevoflurane in Elderly Patients Using Urinary Markers

To the Editor: Although sevoflurane anesthesia has been shown not to cause nephrotoxicity in adults with normal renal function, its effect in patients with impaired renal function or in the elderly has not been thoroughly investigated. Recently, urinary albumin has gained attention as a marker of postanesthetic renal injury in surgical patients [1], but there is no agreement on how the results of studies should be interpreted. At our institution, we have investigated the effects of inhaled anesthetics on renal function in elderly patients. We present the data of our study, in which urinary albumin, alpha1 microglobulin (MG), beta2 MG, and N-acetyl- beta-D-glucosaminidase (NAG) were used as markers of renal injury in elderly patients anesthetized with sevoflurane. Thirteen patients aged >or=to70 yr undergoing gastrectomy were randomly assigned to receive either sevoflurane anesthesia (n = 7; mean age 77.6 yr) or isoflurane anesthesia (n = 6; mean age 78.5 yr). We used routine anesthetic techniques for our institution in this study, i.e., local epidural anesthesia combined with inhaled anesthesia (3 L/min air, 2 L/min oxygen, and either sevoflurane or isoflurane). A urine sample was collected via a catheter before anesthesia, and cumulative urine samples were then collected during and after anesthesia (immediately before surgery; 2 h after the start of surgery; at the end of surgery; and 3 h and Days 1, 3, and 7 after anesthesia). There were no significant differences in patient demographics. The mean minimum alveolar anesthetic concentration-hour was 5.1 for the sevoflurane group and 3.7 for the isoflurane group. The mean urinary albumin excretion was 65.0 mg/g creatinine (gCr) and 44.4 mg/gCr before anesthesia, which significantly increased to 147.9 mg/gCr and 196.9 mg/gCr 2 h after the start of surgery, sustained similar values 3 h after anesthesia, and returned to close to the preanesthetic values on Postanesthesia Day 1 in the sevoflurane group and the isoflurane group, respectively. No significant difference was found between the two groups, and the increase in urinary albumin excretion indicated that transient glomerular injury occurred with both anesthetics. The mean urinary alpha1 and beta2 MG levels were 9.3 mg/gCr and 0.81 mg/gCr in the sevoflurane group and 7.4 mg/gCr and 0.70 mg/gCr in the isoflurane group before anesthesia, showed a gradual but significant increase in both groups during anesthesia, and reached 31.4 mg/gCr and 6.20 mg/gCr in the sevoflurane group and 44.1 mg/gCr and 10.9 mg/gCr in the isoflurane group by 3 h after anesthesia. The values of alpha (1) and beta2 MG then temporally dropped on Postanesthesia Day 1, but they increased again on Day 3 in both groups and decreased again on Day 7 (cause unknown). The mean urinary NAG also began to increase during anesthesia to significantly higher levels than the preanesthetic values (18.9 mg/gCr in the sevoflurane group and 16.9 mg/gCr in the isoflurane group), reached a peak 3 h after anesthesia (40.6 mg/gCr in the sevoflurane group and 35.7 mg/gCr in the isoflurane group), but returned to almost the preanesthetic values on Postanesthesia Day 1. The changes in the urinary enzyme levels indicated the presence of transient renal tubular injury in both groups. In conclusion, using urinary markers, we found that sevoflurane and isoflurane anesthesia in combination with epidural anesthesia resulted in similar degrees of mild, transient, glomerular, and tubular functional impairment in elderly surgical patients undergoing gastrectomy. Kokichi Hase, MD Kazuko Meguro, MD Takako Nakamura, MD Department of Anesthesiology; Tokyo Metropolitan Geriatric Hospital; Tokyo 173-0015, Japan

Clinical pharmacokinetics of 123I-IAZA in healthy volunteers.

123I-labelled iodoazomycin arabinoside (123I-IAZA) is an experimental radiopharmaceutical that has been shown to have clinical utility for imaging regional tissue hypoxia. We report the clinical pharmacokinetics of IAZA, the radiopharmacokinetics of 123I-IAZA and total radioactivity kinetics after injection of 123I-IAZA. Six healthy volunteers each received an intravenous bolus injection of 185 MBq of 123I-IAZA. Thirteen blood samples and a cumulative urine sample were collected over 28 h from each subject. A two-compartment open model best described the disposition characteristics of all three chemical components, with terminal phase half-lives of 179 +/- 24, 232 +/- 41 and 294 +/- 27 min for 123I-IAZA, IAZA and total radioactivity, respectively. 123I-IAZA had a steady-state volume of distribution (Vss) of 0.716 +/- 0.088 l.kg-1 and a systemic clearance (Cls) of 239 +/- 48 ml.min-1. Radioactive decay was responsible for about 37% of clearance; of the remaining radioactivity, about 92% was eliminated renally. Only about 12% of 123I-IAZA was eliminated unchanged in urine, indicating that renal excretion was the major route of elimination for the radioactive metabolites rather than for 123I-IAZA itself. The effective half-lives of 123I-IAZA and total radioactivity reported here are considerably shorter than previously estimated. Our results confirm that 123I-IAZA has appropriate pharmacokinetic and radiopharmacokinetic properties to support clinical hypoxia imaging.

Effects of cirrhosis on kinetics of aztreonam.

Aztreonam was administered as a single, 3-min, 1-g intravenous infusion to 18 subjects, including 6 with biopsy-proven, primary biliary cirrhosis, 6 with biopsy-proven, stable alcoholic cirrhosis, and 6 age- and sex-matched control subjects with normal hepatic functions. Aztreonam was well tolerated by all subjects. Multiple blood samples and timed, cumulative urine samples were taken for assay of aztreonam content and determination of pharmacokinetic profiles. Protein-free filtrates of serum were also assayed for drug levels. Analyses by microbiological and high-pressure liquid chromatographic procedures gave equivalent results. The kinetic data were described by an open, linear, two-compartment model. There were significant differences in elimination half-life (3.2 versus 1.9 h), serum clearance (0.8 versus 1.1 ml/min per kg), and nonrenal clearance (0.2 versus 0.4 ml/min per kg) between the alcoholic cirrhosis group and the normal control group and in elimination half-life (2.2 versus 1.9 h) between the primary biliary cirrhosis group and the normal control group. There was also a difference in nonrenal clearance between the alcoholic cirrhosis and primary biliary cirrhosis groups (0.2 versus 0.5 ml/min per kg). Although the handling of aztreonam differed in the three groups, the magnitude of the difference would warrant a change in aztreonam dosing only for the alcoholic cirrhosis group. In this group, dose adjustment might be required if long-term therapy with high doses of aztreonam is indicated.