Dose-finding results in an adaptive, seamless, randomized trial of once-weekly dulaglutide combined with metformin in type 2 diabetes patients (AWARD-5).

AIMS: AWARD-5 was an adaptive, seamless, double-blind study comparing dulaglutide, a once-weekly glucagon-like peptide-1 (GLP-1) receptor agonist, with placebo at 26 weeks and sitagliptin up to 104 weeks. The study also included a dose-finding portion whose results are presented here. METHODS: Type 2 diabetes (T2D) patients on metformin were randomized 3 : 1 : 1 to seven dulaglutide doses, sitagliptin (100 mg), or placebo. A Bayesian algorithm was used for randomization and dose selection. Patients were adaptively randomized to dulaglutide doses using available data on the basis of a clinical utility index (CUI) of glycosylated haemoglobin A1c (HbA1c) versus sitagliptin at 52 weeks and weight, pulse rate (PR) and diastolic blood pressure (DBP) versus placebo at 26 weeks. The algorithm randomly assigned patients until two doses were selected. RESULTS: Dulaglutide 1.5 mg was determined to be the optimal dose. Dulaglutide 0.75 mg met criteria for the second dose. Dulaglutide 1.5 mg showed the greatest Bayesian mean change from baseline (95% credible interval) in HbA1c versus sitagliptin at 52 weeks -0.63 (-0.98 to -0.20)%. Dulaglutide 2.0 mg showed the greatest placebo-adjusted mean change in weight [-1.99 (-2.88 to -1.20) kg] and in PR [0.78 (-2.10 to 3.80) bpm]. Dulaglutide 1.5 mg showed the greatest placebo-adjusted mean change in DBP [-0.62 (-3.40 to 2.30) mmHg]. CONCLUSIONS: The Bayesian algorithm allowed for an efficient exploration of a large number of doses and selected dulaglutide doses of 1.5 and 0.75 mg for further investigation in this trial.

Direct observation therapy with appropriate treatment regimens was associated with a decline in second-line drug-resistant tuberculosis in Taiwan.

The resistance of Mycobacterium tuberculosis (MTB) to second-line drugs (SLDs) is growing worldwide; however, associations between the appropriateness of treatment for tuberculosis (TB) and whether the directly observed treatment, short course (DOTS)/DOTS-plus programs had an impact on the prevalence of SLD-resistant MTB are still uncertain. We performed a retrospective analysis of resistance profiles among MTB isolates obtained from 6,035 consecutive patients from 2004 to 2011 at two TB referral hospitals in Taiwan. There was a significant decrease (all p-values <0.01) in the prevalence of MTB isolates that were resistant to fluoroquinolones, injectable SLDs, and orally administered SLDs, and multidrug-resistant (MDR) and extensively drug-resistant (XDR) MTB isolates over time. There was a significant increase in the coverage rate of DOTS/DOTS-plus programs and that of administering appropriate first-line and second-line regimens (all p < 0.01). Compared with isoniazid-susceptible isolates, high-level (1.0 mg/L) isoniazid-resistant and MDR isolates showed extensive cross resistance to ofloxacin (5.9%, p < 0.01 and 33.6%, p < 0.01), levofloxacin (9.6%, p < 0.01 and 38.1%, p < 0.01), moxifloxacin (11.1%, p < 0.01 and 26.5%, p < 0.01), kanamycin (6.8 %, p < 0.01 and 16.7 %, p < 0.01), ethionamide (6.4%, p < 0.01 and 16.2%, p < 0.01), and para-aminosalicylic acid (13.1%, p < 0.01 and 20.4%, p < 0.01), but not to capreomycin (2.0%, p = 0.06 and 1.6%, p = 0.08). The decline in prevalence of resistance to SLDs was negatively correlated with the rise in rates of administering appropriate regimens as well as the DOTS/DOTS-plus programs, but not with the increase in usage of second-line regimens. The implementation of DOTS/DOTS-plus programs with appropriate regimens was associated with a decrease in the prevalence of SLD-resistant and XDR TB.

LY2189265, a long-acting glucagon-like peptide-1 analogue, showed a dose-dependent effect on insulin secretion in healthy subjects.

AIM: To assess the safety, tolerability, pharmacokinetics, pharmacodynamics and potential immunogenicity of single, escalating subcutaneous injections of a once-weekly glucagon-like peptide-1 analogue in healthy subjects. METHODS: This phase 1, three-period, crossover, double-blind, placebo-controlled study investigated single, escalating subcutaneous doses of LY2189265 (LY) ranging from 0.1 to 12 mg; approximately six subjects were randomized to each dose. Parameters of safety, including adverse events, were assessed. The pharmacokinetic profile was assessed over 14 days. Pharmacodynamic parameters (glucose and insulin concentrations) were measured following a step-glucose infusion (day 3) and as part of an oral glucose tolerance test (OGTT) (day 5). RESULTS: LY was generally well tolerated with some increase in gastrointestinal symptoms with escalating doses. There were small dose-dependent increases in pulse rate with doses ≥1.0 mg and diastolic blood pressure with doses ≥3.0 mg. The half-life of LY was approximately 90 h, with C(max) occurring between 24 and 48 h in most subjects. Evidence of increase in glucose-dependent insulin secretion and suppression of serum glucose excursions were observed during an OGTT at all doses compared to placebo; no episodes of hypoglycaemia occurred. No subjects developed antibodies to LY2189265. CONCLUSIONS: LY showed an acceptable safety profile and exhibited the expected glucagon-like peptide-1 pharmacological effects on glucose suppression and insulin secretion with a half-life that supports once-weekly dosing.

A 5-week study of the pharmacokinetics and pharmacodynamics of LY2189265, a novel, long-acting glucagon-like peptide-1 analogue, in patients with type 2 diabetes.

AIM: To investigate the safety, tolerability, pharmacokinetics and pharmacodynamics of LY2189265 (LY), a novel, long-acting glucagen-like peptide-1 analogue, administered once weekly to subjects with type 2 diabetes. METHODS: This was a placebo-controlled, parallel-group, subject- and investigator-blind study of LY in subjects (N = 43) with type 2 diabetes mellitus controlled with diet and exercise alone or with a single oral antidiabetic medication. Subjects taking metformin or thiazolidinediones continued on their therapy. Subjects receiving sulfonylurea, acarbose, repaglinide or nateglinide were switched to metformin prior to enrollment. Subjects received five once-weekly doses of 0.05, 0.3, 1, 3, 5 or 8 mg. Effects on glucose, insulin and C-peptide concentrations were determined during fasting and following standard test meals. The pharmacokinetics of LY and its effects on HBA1c, glucagon, body weight, gastric emptying and safety parameters were assessed. RESULTS: Once-weekly administration of LY significantly reduced (p < 0.01) fasting plasma glucose, 2-h post-test meal postprandial glucose and area under the curve (AUC) of glucose after test meals at doses ≥1 mg. These effects were seen after the first dose and were sustained through the weekly dosing cycle. Most doses produced statistically significant increases in insulin and C-peptide AUC when normalized for glucose AUC. Statistically significant reductions in HBA1c were observed for all dose groups except 0.3 mg. The most commonly reported adverse effects (AEs) were nausea (35 events), headache (20 events), vomiting (18 events) and diarrhoea (8 events). CONCLUSIONS: LY showed improvement in fasting and postprandial glycaemic parameters when administered once weekly in subjects with type 2 diabetes. The pharmacokinetics and safety profiles also support further investigation of this novel agent.

Impact of different subspecies on disease progression in initially untreated patients with Mycobacterium avium complex lung disease.

OBJECTIVE: Disease progression is a strong indicator of treatment for Mycobacterium avium complex lung disease (MAC-LD). The impact of MAC subspecies on the risk of disease progression remains uncertain in MAC-LD patients. METHODS: In this cohort study, we included MAC-LD patients from 2013 to 2018 and classified them into M. intracellulare, M. avium, M. chimaera and other subspecies groups by genotype. We observed the disease progression of MAC-LD, indicated by antibiotic initiation and/or radiographic progression. We used Cox regression analysis to assess predictors for disease progression. RESULTS: Of 105 MAC isolates from unique MAC-LD patients, 35 (33%) were M. intracellulare, 41 (39%) M. avium, 16 (15%) M. chimaera and 13 (12%) other subspecies. After a mean follow-up time of 1.3 years, 56 (53%) patients developed disease progression: 71% (25/35), 54% (22/41), 31% (4/13) and 31% (5/16) in patients with M. intracellulare, M. avium, others and M. chimaera, respectively. The independent predictors for disease progression were M. chimaera subspecies (HR 0.356, 95% CI (0.134-0.943)), compared with the reference group of M. intracellulare, body mass index ≤20 kg/m2 (HR 1.788 (1.022-3.130)) and initial fibrocavitary pattern (HR 2.840 (1.190-6.777)) after adjustment for age, sex and sputum smear positivity. Among patients without fibrocavitary lesions (n = 94), the risk of disease progression significantly decreased in patients with other subspecies (HR 0.217 (0.050-0.945)) and remained low in those with M. chimaera (HR 0.352 (0.131-0.947)). CONCLUSIONS: Mycobacterium chimaera was not uncommon in this study; unlike M. intracellulare, it was negatively correlated with disease progression of MAC-LD, suggesting a role of MAC subspecies identification in prioritizing patients.

Age-dependent tetrahydrothiophenium ion formation in young children and adults receiving high-dose busulfan.

Busulfan, a bifunctional alkylating agent, is a mainstay of myeloablative preparative regimens before hematopoietic stem cell transplantation. The apparent oral clearance of busulfan expressed relative to body surface area is 2-3-fold higher in children 1-4 years old than it is in adults. The first step in busulfan elimination is the formation of a tetrahydrothiophenium ion (THT+) in a glutathione S-transferase-catalyzed reaction. We present computer simulations that demonstrate that the ratio of the AUC of THT+ to that of busulfan over 6 h [(AUC(THT+)/AUC(BU))(0-->6)] is highly correlated (r2 = 0.805) with the determinants of THT+ formation and is virtually independent of the determinants of its elimination (r2 = 0.0201). We compared (AUC(THT+)/AUC(BU))(0-->6) determined in 14 children (0.5-4 years) to that of 11 adults (12-54 years) and found a 1.5-fold elevation in the area ratio (P = 0.0098) and a similarly significant increase in busulfan apparent oral clearance expressed relative to body surface area (P = 0.042). The only common explanation for the elevated busulfan apparent oral clearance and (AUC(THT+)/AUC(BU))(0-->6) is an enhanced ability of children to metabolize busulfan through glutathione conjugation.

αTAT1 downregulation induces mitotic catastrophe in HeLa and A549 cells.

α-Tubulin acetyltransferase 1 (αTAT1) controls reversible acetylation on Lys40 of α-tubulin and modulates multiple cellular functions. αTAT1 depletion induced morphological defects of touch receptor neurons in Caenorhabditis elegans and impaired cell adhesion and contact inhibition in mouse embryonic fibroblasts, however, no morphological or proliferation defects in human RPE-hTERT cells were found after αTAT1-specific siRNA treatment. Here, we compared the effect of three αTAT1-specific shRNAs on proliferation and morphology in two human cell lines, HeLa and A549. The more efficient two shRNAs induced mitotic catastrophe in both cell lines and the most efficient one also decreased F-actin and focal adhesions. Further analysis revealed that αTAT1 downregulation increased γ-H2AX, but not other DNA damage markers p-CHK1 and p-CHK2, along with marginal change in microtubule outgrowth speed and inter-kinetochore distance. Overexpression of αTAT1 could not precisely mimic the distribution and concentration of endogenous acetylated α-tubulin (Ac-Tu), although no overt phenotype change was observed, meanwhile, this could not completely prevent αTAT1 downregulation-induced deficiencies. We therefore conclude that efficient αTAT1 downregulation could impair actin architecture and induce mitotic catastrophe in HeLa and A549 cells through mechanisms partly independent of Ac-Tu.

Treatment outcome of patients with isoniazid mono-resistant tuberculosis.

Isoniazid mono-resistance is the most common first-line drug resistance in tuberculosis (TB), but its treatment outcome remains unclear. From January 2004 to October 2011, 425 (5.1%) of 8414 patients with culture-confirmed pulmonary TB from four hospitals in Taiwan were identified as having isoniazid mono-resistant TB. Among them, 395 (92.9%) were included and followed up for 2 years after complete treatment. Although 328 (83.0%) patients were successfully treated, 67 (17.0%) had unfavourable outcomes, including death in 56 (14.2%) and treatment failure in 11 (2.8%). The treatment success rate was similar in patients with high-level and low-level isoniazid-resistant TB (82.2% versus 83.4%, p 0.785) and among those taking anti-TB treatment with and without isoniazid (83.1% versus 83.0%, p 1.000). Patients without rifampicin interruption had lower risk of unfavourable outcome (14.3% versus 37.0%, p <0.001), especially those with low-level isoniazid resistance (11.5% versus 56.5%, p <0.001). Supplementation with a new-generation fluoroquinolone improved treatment success (60.0% versus 12.5%, p 0.003). The presence of cavitary lesions was significantly associated with a higher relapse rate (4.1% versus 0.0%, p 0.006) and extended treatment of 7-9, 10-12 and >12 months had less relapse than 6-month treatment (3.2%, 0%, 3.7% and 25.0%, respectively, p 0.037). Multivariate Cox proportional hazards analysis revealed that co-morbidity with cancer (hazard ratio, 2.43) and rifampicin interruption (hazard ratio 1.91) were independent factors associated with unfavourable outcomes. Treatment throughout with rifampicin and extended treatment for cavitary disease are crucial for improving outcomes in patients with isoniazid mono-resistant TB.

Ethanol and production of the hepatotoxic metabolite of acetaminophen in healthy adults.

BACKGROUND: Recent case reports suggest that consumption of ethanol may increase the risk of liver injury induced by acetaminophen (INN, paracetamol). However, this possibility is at odds with previous clinical studies that showed that acute ethanol ingestion could protect against hepatotoxicity by inhibiting CYP-mediated acetaminophen oxidation. We tested the hypothesis that ethanol ingestion can increase susceptibility to acetaminophen toxicity if acetaminophen ingestion occurs shortly after ethanol is cleared from the body. METHODS: Ten healthy volunteers each received a 6-hour intravenous infusion of ethanol (to achieve a blood concentration of 100 mg/dL ethanol) or 5% dextrose in water, administered in random order. Acetaminophen (500 mg) was ingested 8 hours after the end of the infusion. Blood and urine were collected for assessment of formation of N-acetyl-p-benzoquinone imine (NAPQI), the hepatotoxic metabolite of acetaminophen. RESULTS: Mean NAPQI formation was enhanced by 22% (range, 2% to 38%; P < .03) when the acetaminophen dose was given after an ethanol infusion, compared with after 5% dextrose in water infusion. This mean increase was similar in magnitude to that predicted by a mathematical model describing the induction of CYP2E1, the main enzyme catalyzing NAPQI formation, by a mechanism of enzyme stabilization. CONCLUSIONS: Consumption of up to one 750-mL bottle of wine, six 12-ounce cans of beer, or 9 ounces of 80-proof liquor over the course of a single evening modestly increases the fraction of an acetaminophen dose converted to its toxic metabolite, NAPQI, when acetaminophen is ingested soon after ethanol has been cleared from the body. This change in acetaminophen metabolism may present an incremental increase in the risk of acetaminophen hepatotoxicity.

Influence of polymorphic N-acetyltransferase phenotype on the inhibition and induction of acetaminophen bioactivation with long-term isoniazid.

OBJECTIVE: To determine in patients receiving isoniazid prophylaxis whether an increase in the CYP2E1 dependent formation clearance of acetaminophen (paracetamol) to N-acetyl-p-benzoquinone imine (NAPQI) occurs during a normal 24-hour isoniazid dose interval and whether the interaction is dependent on acetylation status. METHODS: Acetaminophen elimination kinetics were determined on four different occasions. Ten subjects were assigned to receive acetaminophen either simultaneously with the 8 am dose of isoniazid or 12 hours after the isoniazid dose. One week later, on the last day of isoniazid therapy, subjects received acetaminophen at the alternate time of day. The control phase acetaminophen administrations were repeated 1 and 2 weeks later, following the initial randomization. Isoniazid acetylation (NAT2) genotype was determined by analysis of genomic DNA obtained from peripheral blood leukocytes. RESULTS: The mean NAPQI formation clearance was inhibited 57% when acetaminophen and isoniazid were coadministered but was unchanged compared with time-matched control when acetaminophen was given 12 hours after the isoniazid dose. However, when data from subjects was segregated according to isoniazid (INH) acetylation phenotype, the mean ratio of NAPQI formation clearances (+INH/-INH) with 8 PM acetaminophen was significantly higher for fast acetylators compared with slow acetylators (1.36 versus 0.68; p = 0.006). CONCLUSIONS: Fast metabolizers of isoniazid appeared to clear the inducer or inhibitor from the active site of CYP2E1 more rapidly, which resulted in an increased formation of NAPQI 12 hours after the isoniazid dose. In contrast, formation of NAPQI for slow isoniazid metabolizers remained inhibited.

Physiological approaches to the prediction of drug-drug interactions in study populations.

The prediction of metabolic drug-drug interactions should include quantitative attributes, such as variability in the study populations, and the results should be presented in terms of probability and uncertainty. The simple algebraic equations used to calculate one mean value for the extent of drug-drug interaction are adequate for qualitative or semi-quantitative risk assessment. However, truly quantitative predictions continue to fail. The success of drug-drug interaction predictions requires understanding of the relationship between drug disposition and quantifiable influential factors on the change in systemic exposure. The complex interplay of influential factors, including variability estimates, on successful prediction of drug interaction have not been systematically examined. Therefore, physiologically relevant models of metabolic drug-drug interaction will likely play increasingly important roles in improving quantitative predictions and in the assessment of the influential factors underlying the interactions. The physiologically-based approach, with stochastic considerations, offers a powerful alternative to the empirical calculation of mean values. In addition to quantitative estimation of the interaction for assessing probability of risk, a reasonably validated predictive model is useful for prospective optimization of study designs. As a consequence, the definitive clinical trial would yield more meaningful information to support dosing recommendations. This review focuses on illustrating the importance of an integrated approach to building useful models for prediction of metabolism-based drug-drug interactions in human subjects.

Evaluation of various static in vitro-in vivo extrapolation models for risk assessment of the CYP3A inhibition potential of an investigational drug.

Nine static models (seven basic and two mechanistic) and their respective cutoff values used for predicting cytochrome P450 3A (CYP3A) inhibition, as recommended by the US Food and Drug Administration and the European Medicines Agency, were evaluated using data from 119 clinical studies with orally administered midazolam as a substrate. Positive predictive error (PPE) and negative predictive error (NPE) rates were used to assess model performance, based on a cutoff of 1.25-fold change in midazolam area under the curve (AUC) by inhibitor. For reversible inhibition, basic models using total or unbound systemic inhibitor concentration [I] had high NPE rates (46-47%), whereas those using intestinal luminal ([I]gut) values had no NPE but a higher PPE. All basic models for time-dependent inhibition had no NPE and reasonable PPE rates (15-18%). Mechanistic static models that incorporate all interaction mechanisms and organ specific [I] values (enterocyte and hepatic inlet) provided a higher predictive precision, a slightly increased NPE, and a reasonable PPE. Various cutoffs for predicting the likelihood of CYP3A inhibition were evaluated for mechanistic models, and a cutoff of 1.25-fold change in midazolam AUC appears appropriate.

Hepatitis C virus infection increases hepatitis risk during anti-tuberculosis treatment.

OBJECTIVE: To study the impact of hepatitis B virus (HBV) and hepatitis C virus (HCV) co-infection on clinically significant transaminase elevation during short-course anti-tuberculosis treatment. DESIGN: Retrospective observation study. RESULTS: During standard anti-tuberculosis treatment of 295 patients with active pulmonary tuberculosis (TB) and normal baseline liver biochemical tests, 25 (8.5%) developed hepatitis and had a significantly higher mortality rate (32% vs. 7%, OR 6.22, 95%CI 2.0-17.6, P = 0.001). Multivariate analysis showed that HCV co-infected individuals were more likely to develop transaminase elevations (OR 3.43, 95%CI 1.14-10.35, P = 0.03) than those without HCV co-infection. They also had a longer duration of transaminase elevation than controls (43.3 +/- 40.4 vs. 13.5 +/- 8.6 days, P = 0.01). Co-infection with HBV was not associated with a higher rate of hepatitis but was associated with later onset (102 +/- 68.7 vs. 37.0 +/- 31.9 days, P = 0.01), higher peak alanine aminotransferase level and slower recovery (55.5 +/- 62.9 vs. 15.4 +/- 10.8 days, P = 0.01). CONCLUSION: Even with normal baseline liver biochemical tests, HCV co-infection had a higher incidence and longer exacerbations of hepatitis during anti-tuberculosis treatment. We suggest that screening for HCV infection before starting anti-tuberculosis treatment is helpful in planning the frequency of follow-up visits.

Pharmacokinetic consequences of induction of CYP2E1 by ligand stabilization.

Models of the time course of the effect of P450 induction on substrate clearance have previously only considered induction through enhanced synthesis of protein. Induction of CYP2E1 does not always conform to this model, in that many chemicals induce the enzyme through stabilization of the protein apparently by binding to the active site. While such binding protects the enzyme from degradation, it also results in competitive inhibition of substrate clearance. We present a model based on experimental studies of chemical induction of CYP2E1 by ligand stabilization through which this mechanism of induction can be translated into its pharmacokinetic consequence with regard to clearance of substrate. CYP2E1 is considered to be localized in two pools: Pool 1 at which two mechanisms of degradation, fast and slow, operate and pool 2, at which only the slower mechanism operates. Binding of substrate to enzyme in pool 1 stabilizes it from degradation by the fast process, leaving only the slow process. Ligand stabilization therefore results in induction of CYP2E1 as enzyme accumulates as a consequence of unchanged synthesis. Binding of ligand to the active site results in competitive inhibition of the clearance of substrate. Model-based computer simulations show that the time course of interaction between inhibitor/inducer and substrate can be predicted from knowledge of I/Ki and S/Km and the synthesis and degradation kinetics of CYP2E1. The simulations demonstrate further that as long as inhibitor/inducer administration is not interrupted, the clearance of substrate will always be less than the value observed at low concentration of substrate even if the substrate concentration is raised to displace inhibitor/inducer from the active site. On the other hand, the degree of inhibition of clearance is less than would be seen if induction had not taken place. Clearance of substrate is observed to rise above the value observed in the absence of the inhibitor/inducer only after the inhibitor/inducer concentration declines low enough for substrate to gain access to the active site of the enzyme. The model-based simulations agree with reports of the interaction between isoniazid and acetaminophen in humans.

Production of beta-fructofuranosidase with transfructosylating activity for fructooligosaccharides synthesis by Aspergillus japonicus NTU-1249.

Microbial beta-fructofuranosidases with transfructosylating activity can catalyze the transfructosylation of sucrose and synthesize fructooligosaccharides. Aspergillus japonicus NTU-1249 isolated from natural habitat was found to produce a significant amount of beta-fructofuranosidase with high transfructosylating activity and to have the potential for industrial production of fructooligosaccharides. In order to improve it's enzyme productivity, the medium composition and the cultivation conditions for A. japonicus NTU-1249 were studied. A. japonicus NTU-1249 can produce 83.5 units of transfructosylating activity per ml broth when cultivated in a shaking flask at 28 degrees C for 72 hours with a modified medium containing 80 g/l sucrose, 15 g/l soybean flour, 5 g/l yeast extract and 5 g/l NaCl at an initial pH of 6.0. The enzyme productivity was also optimized by submerged cultivation in a 5-litre jar fermentor with aeration at 1.5 vvm and agitation at 500 rpm. Under these operating conditions, the productivity of transfructosylating activity increased to 185.6 U/ml. Furthermore, the transfructosylating activity was improved to 256.1 U/ml in 1,000-litre pilot-scale fermentor. Enzymatic synthesis of fructooligosaccharides by beta-fructofuranosidase from A. japonicus NTU-1249 was performed in batch type by adding 5.6 units of transfructosylating activity per gram of sucrose to a 50% (w/v) sucrose solution at pH 5.0 and 50 degrees C. The yield of fructooligosaccharides was about 60% after reaction for 24 hours, and the syrup produced contained 29.8% (w/v) fructooligosaccharides, 15.2% (w/v) glucose and 5.0% (w/v) sucrose.

Saturable tissue binding and imirestat pharmacokinetics in rats.

To investigate the hypothesis that the pharmacokinetics of imirestat, an aldose reductase inhibitor, are influenced by saturable binding to tissues, three experiments were done. (1) The nature of the dose dependence was characterized in rats. Two groups of nine adult male Sprague-Dawley rats received iv 14C-imirestat at doses of 2 or 8 mg/kg. Serial blood samples were obtained over 15 days. Volume of distribution at steady-state was significantly different between the high- and the low-dose groups (0.744 +/- 0.103 l and 1.10 +/- 0.228 L, respectively). Clearance was independent of dose over this fourfold range (approximately 15 ml/hr). (2) The effect of either statil or AL3152, both aldose reductase inhibitors and potential competitors for aldose reductase binding, on the pharmacokinetics of a single 0.2-mg/kg iv dose of imirestat was assessed. A 2.4-mg/kg loading dose of statil was administered and a constant-rate infusion (56 micrograms/hr/kg) was begun 16 hr before imirestat. A 2-mg/kg loading dose of AL3152 and a constant-rate infusion (115 micrograms/kg/hr) were also administered 16 hr before imirestat. The infusions were maintained throughout the study. AL3152 administration decreased the imirestat steady-state volume of distribution by a mean of 63%. Statil administration decreased it by a mean of 39%. (3) The dosing regimen of the second study was repeated and, at two sampling times, nine tissues and plasma were obtained from four rats per sampling time for determination of imirestat tissue-to-plasma concentration ratio. The tissue/plasma imirestat concentration ratio in the adrenals 24 hr after imirestat administration was 56.9 +/- 20.0 in the imirestat group, 17.7 +/- 1.27 in the statil-coadministered group, and 12.3 +/- 2.59 in the AL3152-coadministered group.(ABSTRACT TRUNCATED AT 250 WORDS)