Population pharmacokinetics of nevirapine in an unselected cohort of HIV-1-infected individuals

AIMS: To study the population pharmacokinetics of nevirapine and to identify relationships between patient characteristics and pharmacokinetics in an unselected population of patients attending our outpatient clinic. METHODS: Ambulatory HIV-1-infected patients from the outpatient clinic of the Slotervaart Hospital who were being treated with a nevirapine-containing regimen were included. During each visit, blood samples were collected for the determination of nevirapine plasma concentrations and clinical chemistry parameters. Variables that were collected at baseline were serology for hepatitis B (HBV) and C (HCV) viruses, liver enzymes, and total bilirubin (TBR). In addition, information about concomitant use of St John's wort and patient demographics were included. The pharmacokinetics of nevirapine were described by first-order absorption and elimination using nonlinear mixed effect modelling (NONMEM V1.1). Population pharmacokinetic parameters (apparent clearance (CL/F), volume of distribution (V/F), absorption rate constant (k a)) were estimated, as were interindividual, interoccasion, and residual variability in the pharmacokinetics. The influence of patient characteristics on the pharmacokinetics of nevirapine was determined. RESULTS: From 173 outpatients a total number of 757 nevirapine plasma concentrations at a single random time point and full pharmacokinetic curves for 13 patients were available resulting in a database of 1329 nevirapine plasma concentrations. Mean CL/F, V/F, and k a were 3.27 l h-1, 106 l, and 01.66 h-1, respectively. CL/F of nevirapine was correlated with weight, chronic HCV infection, and baseline aspartate aminotransferase (ASAT). Chronic HCV and baseline ASAT> 1.5 x upper limit of normal (ULN) decreased CL/F by 27.4% and 13.2%, respectively, whereas an increase in body weight of 10 kg increased CL/F by 0.14 l h-1. A trend towards a lower CL/F in patients of the Negroid race was observed. No significant covariates were found for V/F. CONCLUSIONS: The pharmacokinetics of nevirapine were adequately described by our population pharmacokinetic model. Weight, chronic HCV infection, and baseline ASAT were found to be significant covariates for CL/F of nevirapine. The model incorporating these significant covariates may be an important aid in further optimizing nevirapine-containing therapy.     

No relationship between high nevirapine plasma concentration and hepatotoxicity in HIV-1-infected patients naive of antiretroviral treatment or switched from protease inhibitors

Objective A prospective population pharmacokinetic study of nevirapine (NVP) was performed to test the relationship between hepatotoxicity and NVP trough plasma concentration and to identify which covariates could influence NVP pharmacokinetics.Methods All patients [77 HIV-1 (human immunodeficiency virus type 1)-infected patients (128 samples)] were either on first-line antiretroviral therapy or switched from successful therapy containing protease inhibitor. Population pharmacokinetic parameters were estimated by a non-linear mixed-effect modelling method. Hepatotoxicity was evaluated by ASAT (aspartate aminotransferase) plasma level.Results No correlation was found between high NVP trough plasma concentration and high ASAT level or the increase of ASAT level on NVP therapy. Age and Caucasian race were found to be significant covariates of NVP clearance (Cl/F). Population pharmacokinetic parameters (rate absorption constant=1.04 h^–1; Cl/F=3.31 h^–1; apparent volume of distribution=92 l) are consistent with previous studies.Conclusion High NVP trough plasma concentrations are not correlated with hepatotoxicity in our population. NVP clearance is decreased in the elderly patients, suggesting a potential increase of NVP plasma level and the interest of therapeutic drug monitoring for this population.     

Observations of alanine aminotransferase and aspartate aminotransferase in THRIVE studies treated orally with ximelagatran

Treatment of acute venous thromboembolism (VTE) and prophylaxis of recurrent events has been investigated in the THRIVE (THRombin Inhibitor in Venous Thrombe Embolism) Treatment and the THRIVE III trial using the oral direct thrombin inhibitor ximelagatran. Alanine aminotransferase (ALAT) increased in 9.6% and 6.4% of patients in the THRIVE Treatment and THRIVE III trials, respectively. The authors analysed the time course of the ALAT and in additionally of aspartate aminotransferase (ASAT) in blood from 52 and 23 patients participating in the THRIVE Treatment and the THRIVE III trials in Germany. Analysis of variance for repeated measures and t test were performed. In the THRIVE Treatment trial, ALAT was significantly higher at week 2 for enoxaparin/warfarin (p => .0039, t test) and at months 3 and 6 for ximelagatran (p = .0453, p = .0014, respectively). ASAT and ASAT/ALAT ratio values did not increase and not differ for both groups. In the THRIVE III trial, ALAT and ASAT did not increase and did not differ compared to the comparator placebo. 2 x 36 mg Ximelagatran, induced higher ALAT values at months 3 and 6 compared to 2 x 24 mg ximelagatran (p = .0105, p = .0063, respectively). ASAT did not differ between the two doses of ximelagatran. The ASAT/ALAT ratios were lower at week 2 for enoxaparin/warfarin (t-test, p = .0032) and at month 3 and 6 for 2 x 36 mg versus warfarin or 2 x 24 mg Ximelagatran (p between .0187 and .0002). The authors conclude that ALAT increases dose dependently during therapy with ximelagatran. The less frequent and lower increase of ASAT values compared to ALAT values indicates a nontoxic effect of ximelagatran on liver cells.     

Analysis of severe hepatic events associated with nevirapine-containing regimens: CD4+ T-cell count and gender in hepatitis C seropositive and seronegative patients.

BACKGROUND: Nevirapine-containing regimens have been associated with a risk of significant elevations of liver transaminase levels. Higher risk in antiretroviral-naive populations has been related to gender and CD4+ T-cell count (women with CD4+ T-cell counts of > or =250/mm(3) or men with CD4+ T-cell counts of > or =400/mm(3), i.e. group at risk). However, recent studies do not confirm this association in HIV populations comprising patients who are antiretroviral-experienced. Moreover, the predictive value of gender and CD4+ T-cell count on the risk of raised transaminase levels has been poorly investigated in populations of patients co-infected with hepatitis C virus (HCV). METHODS: Analysis of HIV-positive patients receiving nevirapine-containing regimens for the first time was conducted. Grade > or =III hepatotoxicity (i.e. > or =5 x upper limit of normal in alanine aminotranferase or aspartate aminotransferase levels) was the primary endpoint. Univariate and multivariable Cox proportional hazard regression models were separately conducted among HCV-antibody (Ab)-positive and HCV-Ab-negative patients. RESULTS: Amongst 905 patients, 49% were HCV-Ab-positive and 79% were antiretroviral-experienced. Grade > or =III liver transaminase elevations developed in 7.1% of patients, accounting for an incidence of 2.47 (95% CI 1.97, 3.09) per 100 patient-years of follow-up. HCV-Ab reactivity was associated with a 3-fold increase in risk of developing relevant liver transaminase elevations (95% CI 1.75, 5.3; p < 0.001), whereas gender and CD4+ T-cell count did not impact significantly. When analysis was performed in HCV-Ab-negative patients, the outcome was independently correlated with the group at risk (hazard ratio [HR] 3.66; 95% CI 1.20, 11.14; p = 0.022). By contrast, in HCV-Ab-positive patients, the group at risk was not significantly associated with the outcome. CONCLUSIONS: Most of the excess rates of relevant raised transaminase levels in patients prescribed nevirapine-containing regimens could be attributed to HCV co-infection. Gender and CD4+ T-cell count appeared to have a statistically significant impact on the risk of relevant transaminase level elevations in HCV-negative, but not in HCV-positive patients, probably due to a diluting effect of HCV. Incidence of hepatic events after nevirapine-containing regimens did not appear to be a major concern in our cohort of patients who were mainly antiretroviral-experienced and negative for HCV-Ab. Preferably, nevirapine should be avoided in HCV co-infected patients and in males with CD4+ T-cell counts of > or =400/mm(3) or females with CD4+ T-cell counts of > or =250/mm(3).     

Controversies in the use of nevirapine for prevention of mother-to-child transmission of HIV

The use of nevirapine to prevent mother-to-child transmission of HIV has been controversial. Claims of high rates of toxicity have not been confirmed in clinical trials or extensive programme experience of use of the regimen. Whilst single-dose nevirapine can reduce transmission rates to approximately 10-15%, this can be halved by the addition of single-dose nevirapine to short-course regimens of zidovudine. The selection of resistant virus is reported in 20-50% of mothers and 50% of infants following one dose of nevirapine, although the impact of this on future treatment options is not fully understood. An increased risk of severe hepatotoxicity has been reported with long-term nevirapine-containing triple-therapy treatment regimens in women with CD4+ counts > 250 cells/mm3.     

Novel Sources of Mammalian C-S Lyase Activity

The C-S lysis of L-cysteine conjugates is one biotransformation pathway which is responsible for the generation of mutagenic and cytotoxic metabolic species. Thirteen cysteine S-conjugates were synthesized in our laboratories and incubated with aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) enzymes from porcine heart tissue. The C-S lyase (CSL) activity for each enzyme-substrate combination was determined. ASAT and ALAT were shown to exhibit CSL activity and it was also demonstrated that this activity was inhibited in the presence of the pyridoxal phosphate-dependent enzyme inhibitor amino(oxyacetic acid) confirming the pyridoxal phosphate-dependent mechanism by which C-S lysis is known to take place. This finding has potentially important implications for the risk assessment of compounds which produce L-cysteine conjugates during their biotransformation.     

Comparison of the effects of ascorbyl palmitate and L-ascorbic acid on paracetamol-induced hepatotoxicity in the mouse

The effects of ascorbyl palmitate (ASCP) and free L-ascorbic acid (LAA) on the hepatotoxicity of paracetamol (acetaminophen) and the in vivo covalent binding of reactive paracetamol metabolites to hepatic proteins has been studied in male MF1 mice. The oral administration of [3H(G)]paracetamol (600 mg/kg) resulted in covalent binding to hepatic proteins, a depletion of hepatic non-protein sulphydryl (NPS) groups after 2 h, and a marked elevation of plasma alanine aminotransferase (ALAT) activity after 24 h. The co-administration of paracetamol and ASCP (1412 mg/kg, equivalent to 600 mg/kg free LAA), but not paracetamol and LAA (600 mg/kg), significantly reduced covalent binding of paracetamol metabolites at 2 and 4 h after treatment. In addition ASCP, but not LAA, significantly reduced the depletion of NPS groups and the elevation of plasma ALAT activity. ASCP also completely prevented the 35% mortality observed at 24 h in paracetamol treated mice. These results demonstrate that ASCP, but not LAA, when co-administered orally with the analgesic is an effective inhibitor of paracetamol-induced hepatotoxicity in the mouse. The mechanism by which ASCP prevents liver injury appears to involve destruction of reactive paracetamol metabolites which is associated with a sparing action on hepatic reduced glutathione levels.     

Trimetazidine ameliorates the hepatic injury associated with ischaemia-reperfusion in rats.

Ischaemia-reperfusion induces structural and functional damage to hepatocytes. The purpose of this study was to evaluate the protective effect of trimetazidine, an anti- ischaemic drug, in a rat liver model of ischaemia-reperfusion. Male Wistar rats were divided into groups pretreated with different doses of trimetazidine (1, 5, 10 or 20 mg kg-1 day-1) or saline for 7 days. Liver ischaemia was induced for 120 min and blood reflow was subsequently restored for 30, 60, 90 or 120 min. The activities of alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) as well as the bile flow and the liver ATP content were determined. Ischaemia-reperfusion induced major alterations of hepatic functions involving increases of ASAT and ALAT activities, a drop of ATP content and a sharp decrease in bile flow. Trimetazidine pretreatment reduced the liver injury. Indeed, it lowered the increase in ALAT and ASAT activities observed immediately after reperfusion and maintained higher concentrations of hepatic ATP. Simultaneously, bile flow was increased. These effects were dose-dependent and 5 mg kg-1 day-1 seemed to be the lowest effective dose. In this experimental model trimetazidine pretreatment reduced the liver damage induced by ischaemia-reperfusion. Our data suggest that trimetazidine may be a useful drug in liver surgery to prevent ischaemia-reperfusion injury.     

The effects of moderate drinking and abstinence on serum and urinary beta-hexosaminidase levels

The effects of moderate alcohol intake on serum (SHEX)- and urinary beta-hexosaminidase (UHEX) were studied in ten healthy volunteers, who ingested 60 g of 100% ethanol daily for 10 days. The drinking period was preceded and followed by an abstinence period. Moderate drinking and abstinence were rapidly and significantly reflected on SHEX, while UHEX levels did not change significantly during the study. Gramma-glutamyl transpeptidase (GGT), aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) decreased during the first abstinence period (P less than 0.05), but stayed thereafter at a constant level. It is concluded that SHEX may better reflect recent alcohol consumption than UHEX, GGT, ASAT or ALAT.     

Controversies in the use of nevirapine for prevention of mother-to-child transmission of HIV

The use of nevirapine to prevent mother-to-child transmission of HIV has been controversial. Claims of high rates of toxicity have not been confirmed in clinical trials or extensive programme experience of use of the regimen. Whilst single-dose nevirapine can reduce transmission rates to ～ 10 – 15%, this can be halved by the addition of single-dose nevirapine to short-course regimens of zidovudine. The selection of resistant virus is reported in 20 – 50% of mothers and 50% of infants following one dose of nevirapine, although the impact of this on future treatment options is not fully understood. An increased risk of severe hepatotoxicity has been reported with long-term nevirapine-containing triple-therapy treatment regimens in women with CD4⁺ counts > 250 cells/mm³.     

Biochemical Changes Induced in Liver and Serum of Diplodiatoxin (Stenocarpella maydis) Treated Male and Female Rats

Abstract

Present study was conducted to investigate the acute and sub-acute toxic effect of diplodiatoxin with special reference to biochemical membrane bound enzymes like aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and RBC acetylcholinesterase (AChE) in male and female rats. For acute study, rats were treated with a single oral dose of 5.7 mg/kg of diplodiatoxin, whereas for sub-acute study, the rats received 0.27 mg/kg/day for 21 days. Acute and sub-acute diplodiatoxin treatment caused loss in body weight and feed intake along with symptoms including irritation, dullness, tremors and convulsions. Diplodiatoxin caused a significant increase in serum ASAT and ALAT and a decrease in activity in the liver in both acute and sub-acute studies. This compound also significantly inhibited RBC AChE. Sexual dimorphism was observed when male rats were compared with female rats (p<0.05). The enzyme alterations observed in the affected enzymes recovered to the normal levels by day 7 post treatment (withdrawal study) in both acute and sub-acute treated rats. A negative correlation was observed with regard to these enzymes when serum was compared with liver. These enzyme profiles show increases in serum with parallel decrease in liver, indicating necrosis of liver. These results suggest that diplodiatoxin has potential to affect hepatic end-points.     

Biochemical changes induced in liver and serum of diplodiatoxin (Stenocarpella maydis) treated male and female rats

Present study was conducted to investigate the acute and sub-acute toxic effect of diplodiatoxin with special reference to biochemical membrane bound enzymes like aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and RBC acetylcholinesterase (AChE) in male and female rats. For acute study, rats were treated with a single oral dose of 5.7 mg/kg of diplodiatoxin, whereas for sub-acute study, the rats received 0.27 mg/kg/day for 21 days. Acute and sub-acute diplodiatoxin treatment caused loss in body weight and feed intake along with symptoms including irritation, dullness, tremors and convulsions. Diplodiatoxin caused a significant increase in serum ASAT and ALAT and a decrease in activity in the liver in both acute and sub-acute studies. This compound also significantly inhibited RBC AChE. Sexual dimorphism was observed when male rats were compared with female rats (p < 0.05). The enzyme alterations observed in the affected enzymes recovered to the normal levels by day 7 post treatment (withdrawal study) in both acute and sub-acute treated rats. A negative correlation was observed with regard to these enzymes when serum was compared with liver. These enzyme profiles show increases in serum with parallel decrease in liver, indicating necrosis of liver. These results suggest that diplodiatoxin has potential to affect hepatic end-points.     

The effect of chlorpromazine and carbamazepine on diagnostically relevant liver enzymes

No interactions related to the analytical method were observed between chlorpromazine (1) or carbamazepine (2) and activities of alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), glutamate dehydrogenase (GLDH) or lactate dehydrogenase (LDH). With respect to its cytotoxic potential 1 in cultures of isolated rat hepatocytes increased markedly the release of enzymes into the culture medium, whereas the overall activities of the enzymes were not influenced. 2 in cultured hepatocytes caused no significant effects on the activities of the enzymes investigated. Besides the investigation of methodically related interactions in pooled human serum the methodic procedure including the use of cultures of isolated hepatocytes allows to study also pharmacologically and toxicologically related interactions between drugs and diagnostically relevant liver enzymes.     

Formation of GSH-derivatives as a pathway for inactive intermediates in vinylidene chloride-treated rats

The two conjugates, S-[N-(2-hydroxyethyl)carbamoylmethyl]glutathione (GSAAE), and its corresponding mercapturic derivative N-acetyl-S-[N-(2-hydroxyethyl)carbamoylmethyl]cysteine (NCySAAE) were administered to fasted Sprague-Dawley rats as putative metabolites of vinylidene chloride (VDC). Methylthioacetylaminoethanol (MAAE) was identified in the urine of GSAAE- or NCySAAE-treated rats (0.5–2.0 mmol/kg i.p.), as well as in the urine of VDC-treated rats (0.5–2.0 mmol/kg p.o.). The effects of VDC, GSAAE and NCySAAE on the kidney and liver were also examined using aspartate aminotransferase (ASAT), N-acetyl-β-d-glucosaminidase (NAG) and β₂-microglobulin (β₂-m) as urinary parameters of nephrotoxicity, and glutamate dehydrogenase (GLDH), sorbitol dehydrogenase (SDH) and alanine aminotransferase (ALAT) as serum parameters of hepatotoxicity. Unlike treatment with VDC, treatment with both GSAAE and NCySAAE failed to cause kidney and liver toxicity. The results support the hypothesis that MAAE originates from the formation of GSAAE and further metabolization to NCySAAE, and that MAAE excretion does not reveal a pathway of reactive intermediates.     

Protective effect of s-allyl cysteine and s-propyl cysteine on acetaminophen-induced hepatotoxicity in mice.

In vivo protective effects of s-allyl cysteine (SAC) and s-propyl cysteine (SPC) against acetaminophen-induced hepatotoxicity in Balb/cA mice were studied. SAC and SPC at 1g/L were added into drinking water for four weeks and followed by acetaminophen treatment. Acetaminophen treatment significantly depleted glutathione content, increased oxidation stress and elevated alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities (P < 0.05); however, the intake of SAC or SPC significantly alleviated glutathione depletion and the elevation of ALT and AST, enhanced glutathione peroxidase activity, and lowered malondialdehyde formation (P < 0.05). Plasma levels of C-reactive protein (CRP), von Willebrand factor (vWF), IL-6, IL-10 and TNF-alpha were significantly increased by acetaminophen treatment (P < 0.05); and SAC or SPC intake significantly suppressed acetaminophen-induced elevation of CRP, vWF and the three cytokines (P < 0.05). Acetaminophen treatment also significantly increased plasminogen activator inhibitor-1 (PAI-1) activity and plasma fibrinogen level, and decreased antithrombin III (AT-III) and protein C activities (P < 0.05). SAC or SPC intake alleviated AT-III and protein C reduction (P < 0.05); but did not affect PAI-1 activity and plasma fibrinogen level (P > 0.05). These data suggest that SAC and SPC are potential multiple-protective agents against acetaminophen-induced hepatotoxicity.     

Early biochemical and histological changes in rats exposed to a single injection of thioacetamide

Liver injury was induced by one subcutaneous administration of thioacetamide (200 mg/kg b.wt.) and studied 24 and 48 hrs later. Levels of aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) increased after 24 and 48 hrs. The lysosomal enzymes beta-hexosaminidase (beta-NAG) and beta-glucuronidase (beta-GLU) increased significantly after 24 hrs, while the level of beta-GLU returned to normal after 48 hrs, but the activity of beta-NAG remained significantly high even after 48 hrs. Histopathological examination showed necrotic hepatocytes around the central vein with infiltration of macrophages, neutrophils and eosinophils. The plasma zinc level decreased after 24 hrs and returned to normal after 48 hrs. Liver zinc content increased simultaneously at 24 hrs, returning to normal after 48 hrs. No alterations of plasma copper were observed after 24 and 48 hrs. Copper content of the liver increased significantly after 24 and 48 hrs. The present study thus shows that one dose of thioacetamide results in profound liver injury and supplementation of zinc prior to and simultaneously with thioacetamide normalized plasma zinc, increased liver zinc content and reduced the increase of beta-NAG, but did not influence the histological changes.     

Population pharmacokinetics of nevirapine in combination with rifampicin-based short course chemotherapy in HIV- and tuberculosis-infected South African patients

Objective  The aim was to develop a model to describe the population pharmacokinetics of nevirapine in South African human immunodeficiency virus (HIV)-infected patients who were taking nevirapine-based antiretroviral therapy concomitantly or in the absence of rifampicin-based tuberculosis therapy. Methods  Patients were divided into two groups: (1) patients receiving nevirapine-containing antiretroviral regimen (200 mg twice daily) and continuation phase rifampicin-containing tuberculosis therapy (n = 27) in whom blood samples were obtained before and not less than 14 days after they completed tuberculosis therapy; (2) patients without tuberculosis who were receiving a nevirapine-containing antiretroviral regimen for at least 3 weeks (n = 26). The population pharmacokinetics of nevirapine was described using nonlinear mixed effects modelling with NONMEM software. Based on the developed model, plasma concentration profiles after 300, 400 and 500 mg of nevirapine twice daily were simulated. Results  Concomitant administration of rifampicin increased nevirapine oral clearance (CL/F) by 37.4% and reduced the absorption rate constant (k_a) by almost sixfold. Rifampicin reduced the nevirapine average minimum concentration by 39%. Simulated doses of 300 mg twice daily elevated nevirapine concentrations above subtherapeutic levels in most patients, with minimum exposure above the recommended maximum concentration. The area under the concentration–time curve of 12-hydroxynevirapine was not different in the presence of rifampicin. 2-, 3- and 8-Hydroxynevirapine were not detectable (LLOQ = 0.025 mg/L). Conclusion  The developed model adequately describes nevirapine population pharmacokinetics in a South African population when taken with/and in the absence of rifampicin treatment. The simulations suggest that an increased dose of 300 mg twice daily would achieve adequate nevirapine concentrations in most patients during rifampicin-containing treatment for tuberculosis.     

Fumonisin B1-induced DNA damage in rat liver and spleen: effects of pretreatment with coenzyme Q10, L-carnitine, alpha-tocopherol and selenium.

Active oxygen radical species are reported to cause organ damage. This study was designed to determine whether oxidative stress contributed to the initiation or progression of hepatic and splenic cell DNA damage induced by fumonisin B1 (FB1) in rats. Another aim was to investigate the protective effects of the antioxidants coenzyme Q10 (CoQ10), L-carnitine, vitamin E (alpha-tocopherol) and selenium against DNA damage in the liver and spleen of rats treated with FB1. Fasted rats were injected intravenously with a single dose of fumonisin B1 at 1.55 mg kg-1 body wt. into the tail vein. Treatment with FB1 led to splenic and hepatic DNA fragmentation in 85% of the test animals. DNA fragmentation was investigated as a critical event in toxic cell death by testing total Ca2+ in liver. FB1 administration caused total Ca2+ in liver to increase within 4 h (204% of control). Measurement of liver enzyme activities showed an increase in aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT). FB1 also markedly decreased splenic and hepatic glutathione (GSH) levels. Pretreatment with CoQ10 (30 mg CoQ10 kg-1 diet) together with L-carnitine (2.8 mg carnitine kg-1 diet), alpha-tocopherol (30 IU vitamin E kg-1 diet) and selenium (1 mg selenium as sodium selenite kg-1 diet), decreased DNA damage and the activities of Ca2+, ASAT and ALAT in the liver. On the other hand, the level of GSH was slightly increased. The CoQ10 alone did not significantly protect against toxic cell death and glutathione depletion caused by FB1. Oxidative damage caused by FB1 may be one of the underlining mechanisms of FB1-induced cell injury and DNA damage.     

Ticlopidine-induced hepatotoxicity in a GSH-depleted rat model

We investigated hepatotoxicity induced by ticlopidine (TIC) in glutathione (GSH)-depleted rats by pre-treatment of a well-known GSH synthesis inhibitor, l-buthionine-S,R-sulfoxinine (BSO). Although sole administration of either TIC or BSO showed no signs of hepatotoxicity, combined administration of TIC with BSO induced hepatotoxicity, which was characterized by centrilobular necrosis of the hepatocytes and an elevation of plasma alanine aminotransferase activity. Administration of radio-labeled TIC in combination with BSO resulted in significantly higher covalent binding to rat liver proteins than that observed after sole dosing of radio-labeled TIC. Pre-treatment of 1-Aminobenzotriazole, a non-specific inhibitor of P450s, completely suppressed both hepatotoxicity and the increased hepatic covalent binding caused by TIC co-treatment with BSO. The results obtained in this animal model suggest that GSH depletion and covalent binding may be involved in hepatotoxicity induced by TIC. These observations may help to understand the risk factors and the mechanism of hepatotoxicity of TIC in humans.