Therapeutic potential of dithiolethiones for hepatic diseases

Comprehensive studies support the notion that oltipraz [4-methyl-5-(2-pyrazynyl)-1,2-dithiole-3-thione] and its congeners exert cancer chemopreventive effects by the prevention, inhibition or reversal of carcinogenic processes. Recently, it was found that dithiolethione compounds had the activities to prevent or treat fibrosis, insulin resistance, and mitochondrial protective effects in the liver by a mechanism involving AMP-activated protein kinase (AMPK) and/or 70-kDa ribosomal protein S6 kinase 1 (S6K1). Moreover, chemical regulation of the AMPK-S6K1 pathway was found to affect Liver X receptor (LXR) activity and lipogenesis, leading to the identification of AMPK and S6K1 as targets for treating hepatic steatosis. These biological activities of dithiolethiones may offer a novel approach to pharmaceutical intervention. This review focuses on the interaction between oltipraz and the AMPK-mTOR-S6K1 pathway, which regulates genes that confer hepatocyte protection from intoxication, disrupted energy metabolism, and inflammation. In terms of therapeutic potential, the findings reviewed here demonstrate a new therapeutic potential for dithiolethiones, which function in a unique manner, and offer the possibility of new treatments for hepatic diseases.

Pharmacokinetic interaction between tamoxifen and ondansetron in rats: non-competitive (hepatic) and competitive (intestinal) inhibition of tamoxifen metabolism by ondansetron via CYP2D subfamily and 3A1/2

PURPOSE

Tamoxifen and ondansetron were commonly metabolized via rat hepatic CYP2D subfamily and 3A1/2, and ondansetron is used to treat chemotherapy-induced nausea. The purpose of this study was to report the pharmacokinetic interaction between tamoxifen and ondansetron in rats.

METHODS

The pharmacokinetics of tamoxifen and ondansetron were evaluated after the intravenous and oral administration of tamoxifen, ondansetron, and both drugs together to rats. The Vmax (maximum velocity), Km (apparent Michaelis-Menten constant), CLint (intrinsic clearance), Ki (inhibition constant), and [I] (concentration of inhibitor in the liver and intestine)/Ki ratio of ondansetron were also measured.

RESULTS

The AUC0-infinitys of tamoxifen were significantly greater after both intravenous and oral administration with ondansetron compared to those of tamoxifen alone. The significantly slower hepatic and intestinal CLints for the disappearance of tamoxifen with both drugs together were due to inhibition of metabolism of tamoxifen by ondansetron via CYP2D subfamily and 3A1/2.

CONCLUSIONS

The significantly greater AUC0-infinity of tamoxifen after the intravenous administration of both drugs together could have possibly been attributable to a non-competitive (hepatic) inhibition of CYP2D subfamily- and 3A1/2-mediated tamoxifen metabolism by ondansetron. The significantly greater AUC0-infinity of tamoxifen after the oral administration of both drugs together could have been attributable to a competitive (intestinal) inhibition of CYP2D subfamily- and 3A1/2-mediated tamoxifen metabolism by ondansetron in addition to non-competitive inhibition in the liver.

A national survey on the practice and outcomes of mechanical ventilation in Korean intensive care units

A study was undertaken to describe the practice and outcomes of mechanical ventilation throughout Korea. This prospective cohort study was conducted over a three-month period enrolling patients (n = 519) who received mechanical ventilation for more than 72 hours in 21 university hospital intensive care units throughout Korea. The most common indication for mechanical ventilation was acute respiratory failure. The most common cause of acute-on-chronic respiratory failure was tuberculous lung disease. The most common initial mode for ventilation was volume-controlled ventilation. The mean tidal volume of acute respiratory distress syndrome patients was 7.6 ml/kg of the predicted body weight and the mean positive end-expiratory pressure was 9.4 cmH20. The weaning success rate at 28 days was 50.3%. Pressure support and the T-piece were most commonly used as initial and final weaning modes respectively. Preventive measures against deep vein thrombosis during mechanical ventilation were performed more frequently in intensive care units with full-time critical care physicians than those without such physicians. Multivariate analysis showed that the APACHE II score, indication for mechanical ventilation, respiratory rate at 72 hours, enteral feeding and prophylaxis of deep vein thrombosis were prognostic factors for survival. In Korean intensive care units, tuberculous lung disease remains an important cause for mechanical ventilation. The practice of mechanical ventilation in Korean intensive care units in general appeared to comply with the current international recommendations with regard to lung protection and weaning. However, intensive care units lacking critical care physicians seemed to be adopting fewer ancillary measures, such as deep vein thrombosis prophylaxis.

Interaction between udenafil and tamsulosin in rats: non-competitive inhibition of tamsulosin metabolism by udenafil via hepatic CYP3A1/2

BACKGROUND AND PURPOSE

Orthostatic hypotension has been observed when PDE 5 (cGMP-specific phosphodiesterase type 5) inhibitors are co-administered with alpha-adrenoceptor antagonists. Here we assessed the pharmacokinetic and haemodynamic interactions between udenafil and tamsulosin in rats, as both drugs are metabolized via rat hepatic cytochrome P450 3A1/2.

EXPERIMENTAL APPROACH

Interactions between the two drugs were evaluated in rats after simultaneous 1 or 15 min i.v. infusion or after p.o. administration of udenafil (30 mg x kg(-1)) and/or tamsulosin (1 mg x kg(-1)). In vitro metabolism of tamsulosin with udenafil was measured to obtain the inhibition constant (K(i)) and [I]/K(i) ratio of udenafil.

KEY RESULTS

The total area under the plasma concentration-time curve from time zero to time infinity (AUC)s (or AUC(0-4 h)) of tamsulosin were significantly greater after 15 min of i.v. infusion or after oral administration with udenafil, compared with tamsulosin alone. The hepatic first-pass metabolism of tamsulosin was inhibited by udenafil, and the inhibition in vitro was in a non-competitive mode. The arterial systolic blood pressure was significantly lower at 5, 10 and 60 min after oral co-administration of the drugs.

CONCLUSIONS AND IMPLICATIONS

The significantly greater AUC of tamsulosin after i.v. and p.o. administration of both drugs may be attributable to non-competitive inhibition of cytochrome P450 3A1/2-mediated hepatic tamsulosin metabolism by udenafil. The inhibition was also observed in human liver S9 fractions, suggesting that a reassessment of the oral dosage of tamsulosin is necessary when udenafil and tamsulosin are co-administered to patients with benign prostatic hyperplasia.

Pharmacokinetic Interaction Between Oltipraz and Silymarin in Rats

ABSTRACT. Purpose: To evaluate the pharmacokinetic interaction between oltipraz and silymarin after intravenous and oral administration of both drugs to male Sprague–Dawley rats. Methods: Oltipraz (single doses of 10 and 30 mg/kg for intravenous and oral administration, respectively), silymarin (single doses of 50 and 100 mg/kg for intravenous and oral administration, respectively, and 14 days oral administration of 100 mg/kg), alone and together were administered to control rats. Results: The pharmacokinetic parameters of oltipraz did not significantly altered by silymarin. However, after intravenous administration of the drugs together, the AUCs of unconjugated, conjugated, and total (unconjugated plus conjugated) silibinin were significantly different (32.7% decrease, and 32.1% and 27.2% increase, respectively), and total and (CL) and non-renal (CLNR ) clearance of unconjugated silibinin were significantly faster (49.4% and 61.1% increase, respectively) than those of silymarin alone (without oltipraz). After oral administration of silymarin with or without oltipraz, however, the pharmacokinetic parameters of unconjugated, conjugated, and total silibinin were comparable. Conclusions: After single intravenous administration of the drugs together, the AUC of unconjugated silibinin was significantly smaller, but that of both conjugated and total silibinin was significantly greater. This could have been due to an increase in the formation of conjugates (glucuronidation and sulfation) of silibinin as induced by oltipraz. After simultaneous oral administration of the drugs, however, the AUCs (or AUC0−12 h) of unconjugated, conjugated, and total silibinin were comparable.

Liquiritigenin, a flavonoid aglycone from licorice, has a choleretic effect and the ability to induce hepatic transporters and phase-II enzymes

Liquiritigenin (LQ), an active component of licorice, has an inhibitory effect on LPS-induced inhibitory nitric oxide synthase expression. This study investigated the effects of LQ on choleresis, the expression of hepatic transporters and phase-II enzymes, and fulminant hepatitis. The choleretic effect and the pharmacokinetics of LQ and its glucuronides were monitored in rats. After intravenous administration of LQ, the total area under the plasma concentration-time curve of glucuronyl metabolites was greater than that of LQ in plasma, which accompanied elevations in bile flow rate and biliary excretion of bile acid, glutathione, and bilirubin. The expressions of hepatocellular transporters and phase-II enzymes were assessed by immunoblots, real-time PCR, and immunohistochemistry. In the livers of rats treated with LQ, the protein and mRNA levels of multidrug resistance protein 2 and bile salt export pump were increased in the liver, which was verified by their increased localizations in canalicular membrane. In addition, LQ treatment enhanced the expression levels of major hepatic phase-II enzymes. Consistent with these results, LQ treatments attenuated galactosamine/LPS-induced hepatitis in rats, as supported by decreases in the plasma alanine aminotransferase, liver necrosis, and plasma TNF-alpha. These results demonstrate that LQ has a choleretic effect and the ability to induce transporters and phase-II enzymes in the liver, which may be associated with a hepatoprotective effect against galactosamine/LPS. Our findings may provide insight into understanding the action of LQ and its therapeutic use for liver disease.

Estimating the market for tuberculosis drugs in industrialized and developing nations

BACKGROUND

The successful introduction of new drugs into low- and middle-income countries requires an understanding of the existing market size and market dynamics for the therapeutic area of interest. The drug markets in these countries are, however, less well understood than those in high-income countries.

METHODS

The global market for tuberculosis (TB) drugs was estimated by studying in detail six high-burden countries and four high-income countries, followed by extrapolation. Data were derived from existing pharmaceutical audit databases and interviews with government officials, medical staff and suppliers.

RESULTS

The use of qualitative inputs to inform the collection of quantitative information, notably to identify where the major flows of TB drugs are located, allowed a confident estimate of the global market for first-line TB drugs. Final ranges were US$261-316 million or US$310-418 million, depending on whether case notification rates or incidence were used for extrapolations.

CONCLUSIONS

An estimation of the global TB drug market is made more reliable by a qualitative understanding of TB drug distribution pathways, which differ greatly among countries. The understanding of this structure in key high-burden countries provides the basis for a simpler update of the market estimate in the future.

Effects of water deprivation on drug pharmacokinetics: correlation between drug metabolism and hepatic CYP isozymes

Male Sprague-Dawley rats deprived of water for 72 h (a rat model of dehydration) showed no change in protein expression of the hepatic microsomal cytochrome P450 (CYP) 1A2, 2B1/2, 2C11, or 3A1/2, but an increase in protein expression (3-fold) and mRNA level (2.6-fold) of CYP2E1. Glucose feeding instead of food normalized CYP2E1 protein expression during dehydration. Here, we review how dehydration can change the pharmacokinetics of drugs reported in the literature via changing CYP isozyme levels. We also discuss how dehydration changes the pharmacokinetics of drugs that are metabolized via renal DHP-I, or are mainly excreted in the urine and bile, and form conjugates.

Acetaminophen overdose in Jamaica

Acetaminophen is a dose dependent hepatotoxin which is frequently associated with intentional self-harm. Forty-nine cases of parasuicide attempts involving paracetamol only or in combination with another drug were treated at the UHWI, Jamaica, between 1994-2004. The majority were women (84%) and the mean age was 23 years. Acetaminophen was the only agent ingested in 71% of cases; 29% involved an additional drug. Patients presented an average of 6.5 hours after ingestion (range 1-45 hours). Serum transaminases were elevated in 18% of cases and N-acetylcysteine (NAC) therapy given in 55%. The mean duration of hospitalization was three days. One patient developed liver failure and there were no deaths. Education of the public and medical profession is needed to increase awareness of the potential toxic effects of acetaminophen overdose. N-acetylcysteine therapy should be given early in suspected cases.

Heterogeneity in the processing defect of SLC26A4 mutants

BACKGROUND

Mutations in the SLC26A4 gene are responsible for Pendred syndrome and non-syndromic hearing loss (DFNB4). This study analysed non-synonymous SLC26A4 mutations newly identified in East Asians, as well as three common mutations in Caucasians, to characterise their molecular pathogenic mechanisms and to explore the possibility of rescuing their processing defects.

METHODS

A total of 11 non-synonymous disease associated mutations were generated and their effects on protein processing and on ion transporting activities were examined.

RESULTS

Most of the mutations caused retention of the SLC26A4 gene product (pendrin) in the intracellular region, while wild-type pendrin reached the plasma membrane. Accordingly, these mutations abolished complex glycosylation and Cl(-)/HCO(3)(-) exchange activities of pendrin. However, significant heterogeneity in the processing of mutant pendrin molecules was observed. Each mutant protein exhibited a different cellular localisation, a different degree of N-glycosylation, and a different degree of sensitivity to the treatments that rescue processing defects. For example, H723R-pendrin, the most common mutation in East Asians, was mostly expressed in endoplasmic reticulum (ER), and its defects in protein processing and ion transporting activities were restored considerably by low temperature incubation. On the other hand, L236P-pendrin, the most common mutation in Caucasians, was mainly in the centrosomal region and was temperature insensitive.

CONCLUSION

These results indicate that the processing of pendrin mutant protein is determined by mutant specific mechanisms, and that a mutant specific method would be required to rescue the conformational defects of each folding mutant.

Pharmacokinetic interaction between DA-8159, a new erectogenic, and metformin in rats: competitive inhibition of metabolism via hepatic CYP3A1/2

BACKGROUND AND PURPOSE

Erectile dysfunction is highly prevalent in diabetic patients and PDE V inhibitors are effective and safe for the treatment of erectile dysfunction in men with diabetes. Therefore, in this study we investigated whether a pharmacokinetic interaction occurs between DA-8159 and metformin, as both drugs are metabolized via hepatic CYP3A1/2 in rats.

EXPERIMENTAL APPROACH

DA-8159 (30 mg kg(-1)) and metformin (100 mg kg(-1)), both separately and together, were administered to rats either intravenously or orally. The V (max), K (m), CL(int), apparent inhibition constants (K (i)), [I]/K (i) and concentrations of each drug in the liver and intestine were then measured.

KEY RESULTS

After i.v. administration of both drugs simultaneously, the AUC of DA-8159 and metformin was significantly greater (21.2 and 33.9% increase for DA-8159 and metformin, respectively) than that of each drug alone. After p.o. administration of the drugs, the AUC of metformin was also significantly greater (20.7% increase) in the presence of DA-8159 than in its absence. However, the AUC of DA-8159 was similar in the absence and presence of metformin.

CONCLUSIONS AND IMPLICATIONS

The significantly greater AUC of metformin and DA-8159 after i.v. administration of both drugs and of metformin after p.o. administration of both drugs is probably due to competitive inhibition for the metabolism of these drugs via hepatic CYP3A1/2. However, the similar AUCs of DA-8159 in the absence and presence of metformin, after p.o. administration, indicates that the dose of metformin used was insufficient to inhibit the hepatic and intestinal metabolism of DA-8159.

Steatohepatitis due to antiretroviral therapy

Jamaica has recorded the largest increase in the rate of HIV/AIDS infection in the English-speaking Caribbean since 1985. Treatment has significantly improved recently with approximately 50% availability of antiretrovirals (ARVs) to patients. The incidence of drug induced hepatotoxicity is not well known for most ARV drugs and few studies have assessed adverse drug effects in clinical practice. A patient with HIV on highly active antiretroviral therapy (HAART) presented with a one year history of progressive abdominal distension. Abdominal examination revealed a 17 cm, smooth, non-tender liver with a rounded edge; 12 cm of which was below the right costal margin. Liver enzymes were grossly abnormal. The liver biopsy revealed parenchymal distortion by fibrosis with macrovesicular fatty change and Mallory's hyaline in keeping with steatohepatitis. Follow-up studies after discontinuation of stavudine revealed that the liver enzymes improved within four months. Physicians should be mindful of the hepatotoxic potential of ARVs and monitor liver enzymes in HIV-infected patients on therapy.

Molecular and functional expression of anion exchangers in cultured normal human nasal epithelial cells

Aims

Anions have an important role in the regulation of airway surface liquid (ASL) volume, viscosity and pH. However, functional localization and regulation of anion exchangers (AEs) have not been clearly described. The aim of this study was to investigate the regulation of AE mRNA expression level in accordance with mucociliary differentiation and the functional expression of AEs cultured normal human nasal epithelial (NHNE) cells.

Methods

Nasal mucosal specimens from three patients are obtained and serially cultured cells are subjected to morphological examinations, RT-PCR, Western blot analysis and immunocytochemistry. AE activity is assessed by pHi measurements.

Results

Expression of ciliated cells on the apical membrane and expression of MUC5AC, a marker of mucous differentiation, increased with time. AE2 and SLC26A4 mRNA expression decreased as mucociliary differentiation progressed, and AE4, SLC26A7 and SLC26A8 mRNA expression increased on the 14th and 28th day after confluence. Accordingly, AE4 protein expression also progressively increased. AE activity in 100 mm K⁺ buffer solutions was nearly twofold higher than that in 5 mm K⁺ buffer solutions. Moreover, only luminal AE activity increased about fourfold over the control in the presence of 5 μm forskolin. In the presence of 100 μm adenosine-5′-triphosphate (ATP) which evokes intracellular calcium signalling through activation of purinergic receptors, only luminal AE activity was again significantly increased. On the other hand, 500 μm 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS), an inhibitor of most SLC4 and SLC26AE isoforms, nearly abolished AE activity in both luminal and basolateral membranes. We found that AE activity was affected by intracellular cAMP and calcium signalling in the luminal membrane and was DIDS-sensitive in both membranes of cultured NHNE cells.

Conclusion

Our findings through molecular and functional studies using cultured NHNE cells suggest that AEs may have an important role in the regulation of ASL.

Influence of OATP1B1 genotype on the pharmacokinetics of rosuvastatin in Koreans

This study was carried out to determine whether polymorphisms of organic anion-transporting polypeptide 1B1 (OATP1B1) have an effect on rosuvastatin pharmacokinetics in Koreans. Among 200 subjects genotyped for OATP1B1 c.388A>G, and c.521T>C, 30 subjects were selected for the rosuvastatin pharmacokinetic study. The area under the concentration-time curve for 0 to infinity (AUC(0-infinity)) of rosuvastatin for group 1 (*1a/*1a, *1a/*1b, *1b/*1b), group 2 (*1a/*15, *1b/*15), and group 3 (*15/*15) were 111+/-49.3, 126+/-45.2, and 191+/-31.0 ng h/ml, respectively, with significant differences among the three groups (P=0.0429) and between *15/*15 and the other groups (P=0.0181). The maximum plasma concentration (Cmax) also showed a significant difference between *15/*15 and the other groups (P=0.0181). There were no significant differences in rosuvastatin-lactone pharmacokinetics among the three groups. The pharmacokinetic exposure of rosuvastatin was higher in the OATP1B1*15/*15 subjects than the others, suggesting a potential association between the OATP1B1 genetic polymorphisms and altered rosuvastatin pharmacokinetics in Korean populations.

Pharmacokinetic and pharmacodynamic consequences of inhibition of terazosin metabolism via CYP3A1 and/or 3A2 by DA-8159, an erectogenic, in rats

BACKGROUND AND PURPOSE

Recently, orthostatic hypotension was observed in patients with benign prostatic hyperplasia who are taking vardenafil (a PDE 5 inhibitor) and terazosin (a long acting alpha blocker). Therefore, this study was performed with DA-8159 (a long acting PDE 5 inhibitor) and terazosin in rats to find whether or not pharmacokinetic and pharmacodynamic interactions between the two drugs were observed.

EXPERIMENTAL APPROACH

Pharmacokinetic and pharmacodynamic (changes in blood pressure) interactions between DA-8159 and terazosin were evaluated after simultaneous i.v. and p.o. administration of DA-8159 (30 mg kg(-1)) and terazosin (5 mg kg(-1)) to male Sprague-Dawley rats.

KEY RESULTS

After simultaneous i.v. and p.o. administration of terazosin and DA-8159, the total area under the plasma concentration-time curve from time zero to time infinity (AUC) of terazosin became significantly greater (57.4 and 75.4% increase for i.v. and p.o. administration, respectively) than those of without DA-8159. The blood pressure dropping effect was considerable after simultaneous p.o. administration of DA-8159 and terazosin compared with each drug alone.

CONCLUSIONS AND IMPLICATIONS

The significantly greater AUC of terazosin after both simultaneous i.v. and p.o. administration of both drugs could be due to the hepatic (both i.v. and p.o.) and intestinal (p.o.) inhibition of the metabolism of terazosin via CYP3A1 and/or 3A2 by DA-8159, since both DA-8159 and terazosin are metabolized via CYP3A1 and/or 3A2 in rats. The blood pressure lowering effect after simultaneous p.o. administration of both drugs could be due to significant increase in plasma concentrations of terazosin.

Dose-dependent pharmacokinetics of telithromycin after intravenous and oral administration to rats: contribution of intestinal first-pass effect to low bioavailability

PURPOSE

To evaluate the pharmacokinetics of telithromycin after intravenous and oral administration and to find the reason for incomplete F value (first pass-effect) after intravenous, intraportal, intragastric, and intraduodenal administration to rats.

METHODS

Telithromycin was administered intravenously or orally at doses of 20, 50, and 100 mg/kg to rats. And hepatic, gastric, and intestinal first-pass effects of telithromycin were also measured after intravenous, intraportal, intragastric, and intraduodenal administration at a dose of 50 mg/kg to rats.

RESULTS

The dose-normalized AUC values of telithromycin were dose-dependent (increased with increasing doses) after both intravenous and oral dose ranges studied, possibly due to saturable metabolism of telithromycin. After oral administration (50 mg/kg), approximately 4.06% of oral dose was not absorbed, F was approximately 27.5%, and the intestinal first-pass effect was approximately 63.4% of oral dose. The first-pass effects of telithromycin in the lung, heart, stomach, and liver were almost negligible, if any, in rats.

CONCLUSIONS

The low F of telithromycin at a dose of 50 mg/kg was mainly due to considerable intestinal first-pass effect, approximately 63.4% of oral dose, in rats.

Effects of enzyme inducers and inhibitors on the pharmacokinetics of metformin in rats: involvement of CYP2C11, 2D1 and 3A1/2 for the metabolism of metformin

BACKGROUND AND PURPOSE

The types of hepatic microsomal cytochrome P450 (CYP) isozymes responsible for the metabolism of metformin in humans and rats have not been published to date. Therefore, a series of experiments using various inducers and inhibitors of CYP isozymes was conducted to find out what types of CYP isozymes are involved in the metabolism of metformin in rats.

EXPERIMENTAL APPROACH

Metformin at a dose of 100 mg kg(-1) was administered intravenously to rats. The rats were pretreated with CYP inducers such as 3-methylcholanthrene, orphenadrine, isoniazid, and dexamethasone (major inducers of CYP1A1/2, 2B1/2, 2E1, and 3A1/2, respectively, in rats), or CYP inhibitors such as SKF-525 (a non-specific inhibitor of CYP isozymes), and sulfaphenazole, quinine, and troleandomycin (major inhibitors of CYP2C11, 2D1, and 3A1/2, respectively, in rats). The time-averaged non-renal clearance (CLNR) of metformin was compared with that of controls.

KEY RESULTS

In rats pretreated with dexamethasone, the CLNR was significantly faster (57% increase) than for the controls. In rats pretreated with SKF-525-A, sulfaphenazole, quinine, and troleandomycin, the CLNR was significantly slower (24.3, 62.9, 77.6, and 78.7% decrease, respectively) than for the controls. However, the CLNR values did not significantly different in the rats pretreated with 3-methylencholanthrene, orphenadrine, and isoniazid compared with the controls.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that metformin was metabolized mainly via CYP2C11, 2D1, and 3A1/2 in rats. This result could contribute to understanding of the possible changes in metformin pharmacokinetics in disease models where CYP2C11 and/or 3A1/2 are altered.

Effects of glucose supplementation on the pharmacokinetics of intravenous chlorzoxazone in rats with water deprivation for 72 h

It was reported that in rats with water deprivation for 72 h with food (dehydration rat model), the expression of CYP2E1 was 3-fold induced with an increase in mRNA level and glucose supplementation instead of food during 72-h water deprivation (dehydration rat model with glucose supplementation) inhibited the CYP2E1 induction in dehydration rat model. It was also reported that chlorzoxazone (CZX) is metabolized to 6-hydroxychlorzoxazone (OH-CZX) mainly via CYP2E1 in rats. Hence, the effects of glucose supplementation on the pharmacokinetics of CZX and OH-CZX were investigated after intravenous administration of CZX at a dose of 25 mg/kg to control male Sprague-Dawley rats and dehydration rat model and dehydration rat model with glucose supplementation. Based on the above mentioned results of CYP2E1, it could be expected that increased formation of OH-CZX in dehydration rat model could decrease in dehydration rat model with glucose supplementation. This was proven by the following results. In dehydration rat model with glucose supplementation, the AUC of OH-CZX was significantly smaller (1900 versus 1050 microg min/ml), AUC(OH-CZX)/AUC(CZX) ratio was considerably smaller (105 versus 34.3%), C(max) was significantly lower (20.6 versus 8.08 microg/ml), total amount excreted in 24-h urine as unchanged OH-CZX was significantly smaller (62.3 versus 42.7% of intravenous dose of CZX), and in vitro V(max) (2.18 versus 1.20 nmol/min/mg protein) and CL(int) (0.0285 versus 0.0171 ml/min/mg protein) were significantly slower than those in dehydration rat model.

Pharmacokinetics of theophylline in diabetes mellitus rats: induction of CYP1A2 and CYP2E1 on 1,3-dimethyluric acid formation

Pharmacokinetic parameters of theophylline and one of its metabolites, 1,3-dimethyluric acid (1,3-DMU), were compared after intravenous and oral administration of aminophylline, 5mg/kg as theophylline, to diabetes mellitus rats induced by alloxan (DMIA) or streptozotocin (DMIS), and their respective control rats. In DMIA and DMIS rats, expression of CYP1A2 and 2E1 increased approximately three times. Theophylline was metabolized to 1,3-DMU by CYP1A2 and 2E1 in rats. Hence, it was expected that formation of 1,3-DMU increased in DMIA or DMIS rats. This was proven by the following results. First, after intravenous administration of theophylline, the AUC of 1,3-DMU was significantly greater in DMIA (110% increase) or DMIS (47.4% increase) rats. Second, the AUC of theophylline was significantly smaller in DMIA (26.1% decrease) or DMIS (30.1% decrease) rats because of significantly faster time-averaged total body clearance in DMIA (34.8% increase) or DMIS (42.7% increase) rats. Third, based on in vitro hepatic microsomal studies, intrinsic 1,3-DMU formation clearances were significantly faster in DMIA (20.4% increase) or DMIS (30.7% increase) rats than respective control rats. Similar results (AUC values of theophylline and 1,3-DMU) were also obtained after oral administration.

Effects of water deprivation on the pharmacokinetics of DA-8159, a new erectogenic, in rats

PURPOSE

To test the effect of 72 h water deprivation on the non-renal clearance (CL) of DA-8159 in a rat model of dehydration. DA-8159 is mainly metabolized via CYP3A1/2 and the expression and mRNA level of CYP3A1/2 are not affected by dehydration.

METHODS

DA-8159 (30 mg/kg) was administered intravenously or orally to male control Sprague Dawley rats and rat model of dehydration.

RESULTS

As expected, after intravenous administration, the CL(NR) values of DA-8159 were comparable between two groups of rats. This could be supported by comparable intrinsic CL of DA-8159 using hepatic microsomes for both groups of rats. However, the CL was significantly slower in rat model of dehydration due, at least in part, to significantly slower renal CL in rat model of dehydration. The slower CL(R) in rat model of dehydration could be due to urine flow ratedependent renal CL of DA-8159; the less urine output, the less the urinary excretion of unchanged DA-8159. After oral administration, the AUC values of DA-8159 were not significantly different between two groups of rats, although the AUC of DA-8159 in rat model of dehydration was significantly greater than controls after intravenous administration. This could be possibly due to changes in the intestinal first-pass effects in rat model of dehydration.

CONCLUSIONS

After intravenous administration of DA-8159, the non-renal CL values were comparable between two groups of rats due to the lack of effect of dehydration on CYP3A1/2.