Determination of Oltipraz in serum by high-performance liquid chromatography with optical absorbance and mass spectrometric detection

Quantification of oltipraz using liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic study in rat plasma

An assay method for the determination of oltipraz, a candidate drug for the treatment of liver fibrosis and liver cirrhosis, was developed in rat plasma using a fast-flow protein precipitation (FF-PPT) method coupled with LC-MS/MS for quantification to reduce the labor and to improve the speed of analysis. The applicability of the assay to pharmacokinetic studies was also evaluated. Oltipraz and ethyl-oltipraz, an internal standard (IS), were analyzed by multiple reaction monitoring (MRM) at m/z transitions of 227→193 and 241→174, respectively. A lower limit of quantification (LLOQ) of 20 ng/mL was observed, with a linear dynamic range from 20 to 4000 ng/mL (R>0.997). The accuracy, precision, dilution, recovery, and stability of the assay were deemed acceptable according to FDA guidelines. Oltipraz concentrations were measured successfully in plasma samples up to 12h post-dose in rats that had received an oral dose of 60 mg/kg. The findings indicate that the assay method is rapid and sensitive to oltipraz, showing applicability for pharmacokinetics (PK) studies of oltipraz in other small animals, including rats.

Effect of enzyme inducers and inhibitors on the pharmacokinetics of oltipraz in rats

A series of in-vitro and in-vivo experiments, using various inducers and inhibitors of hepatic microsomal cytochrome P450 (CYP) isozymes, was conducted to study oltipraz pharmacokinetics in rats. In in-vivo studies, oltipraz at a dose of 10 mg kg−1 was administered intravenously to rats. In rats pretreated with SKF 525-A (a nonspecific CYP isozyme inhibitor in rats; n = 9), the time-averaged total body clearance (CL) of oltipraz was significantly slower (56.6% decrease) than that in untreated rats (n = 9). This indicated that oltipraz is metabolized via CYP isozymes in rats. Hence, various enzyme inducers or inhibitors were used in in-vitro and in-vivo studies in rats. In rats pretreated with 3-methylcholanthrene (n = 9 and 8 for untreated and treated groups, respectively), phenobarbital (n = 7 and 10 for untreated and treated groups, respectively) or dexamethasone (n = 7 and 12 for untreated and treated groups, respectively) (main inducers of CYP1A1/2, 2B1/2 and 3A1/2 in rats, respectively), the CL values were significantly faster (38.4, 94.4 and 33.6% increase, respectively). In rats pretreated with sulfaphenazole (n = 8 and 9 for untreated and treated groups, respectively), quinine (n = 7 and 9 for untreated and treated groups, respectively) or troleandomycin (n = 8 and 9 for untreated and treated groups, respectively) (main inhibitors of CYP2C11, 2D1 and 3A1/2 in rats, respectively), the CL values were significantly slower (31.0, 27.6 and 36.3% decrease, respectively). The in-vivo results with various enzyme inhibitors correlated well with the in-vitro intrinsic clearance for disappearance of oltipraz (CLint) (n = 5, each). The above data suggested that oltipraz could be metabolized in male rats mainly via CYP1A1/2, 2B1/2, 2C11, 3A1/2 and 2D1.

Pharmacokinetic interaction between oltipraz and dimethyl-4,4‘-dimethoxy-5,6,5′,6’-dimethylene dioxybiphenyl-2,2′-dicarboxylate (DDB) after single intravenous and oral administration to rats

The aim of this study was to report the pharmacokinetic interaction between oltipraz (50 mg kg−1) and dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene dioxybiphenyl-2,2′-dicarboxylate (DDB, 10 mg kg−1) after single intravenous and oral administration to rats. After intravenous administration of oltipraz plus DDB, the area under the plasma concentration–time curve from time zero to time infinity (AUC) of oltipraz was significantly greater (1440 vs 1740 μg min mL−1) than that after oltipraz alone. This was not due to slower clearances of oltipraz after oltipraz plus DDB since the total body, renal and nonrenal clearances were comparable between the two groups of rats. It could be due to a decrease in tissue binding of oltipraz by DDB. The apparent volume of distribution at steady state (Vdss) of DDB was significantly smaller (7060 vs 4650 mL kg−1) than after oltipraz alone. After oral administration of oltipraz plus DDB, the AUC of olitpraz was also significantly greater (479 vs 583 μg min mL−1) than that after oltipraz alone. This was not due to increased absorption of oltipraz from the rat gastrointestinal tract after oltipraz plus DDB but again could be due to a decrease in Vdss of oltipraz by DDB. However, after both intravenous and oral administration, the pharmacokinetic parameters of DDB were comparable between DDB alone and DDB plus oltipraz, indicating that oltipraz did not greatly affect the pharmacokinetics of DDB in rats.

Pharmacokinetics of oltipraz in diabetic rats with liver cirrhosis

BACKGROUND AND PURPOSE

The incidence of diabetes mellitus is increased in patients with liver cirrhosis. Oltipraz is currently in trials to treat patients with liver fibrosis and cirrhosis induced by chronic hepatitis types B and C and is primarily metabolized via hepatic cytochrome P450 isozymes CYP1A1/2, 2B1/2, 2C11, 2D1 and 3A1/2 in rats. We have studied the influence of diabetes mellitus on pharmacokinetics of oltipraz and on expression of hepatic, CYP1A, 2B1/2, 2C11, 2D and 3A in rats with experimental liver cirrhosis.

EXPERIMENTAL APPROACH

Oltipraz was given intravenously (10 mg x kg(-1)) or orally (30 mg x kg(-1)) to rats with liver cirrhosis induced by N-dimethylnitrosamine (LC rats) or with diabetes, induced by streptozotocin (DM rats) or to rats with both liver cirrhosis and diabetes (LCD rats) and to control rats, and pharmacokinetic variables measured. Protein expression of hepatic CYP1A, 2B1/2, 2C11, 2D and 3A was measured using Western blot analysis.

KEY RESULTS

After i.v. or p.o. administration of oltipraz to LC and DM rats, the AUC was significantly greater and smaller, respectively, than that in control rats. In LCD rats, the AUC was that of LC and DM rats (partially restored towards control rats). Compared with control rats, the protein expression of hepatic CYP1A increased, that of CYP2C11 and 3A decreased, but that of CYP2B1/2 and 2D was not altered in LCD rats.

CONCLUSIONS AND IMPLICATIONS

In rats with diabetes and liver cirrhosis, the AUC of oltipraz was partially restored towards that of control rats.

Pharmacokinetics and therapeutic effects of oltipraz after consecutive or intermittent oral administration in rats with liver cirrhosis induced by dimethylnitrosamine

Pharmacokinetics and therapeutic effects of oltipraz were evaluated after consecutive (once per day at 30 mg/kg/day for 7 and 14 days) or intermittent (once per week at 100 mg/kg/week for 1-3 weeks) oral administration to rats with liver cirrhosis induced by dimethylnitrosamine. The AUC of oltipraz was significantly greater in cirrhotic rats than controls (890 compared with 270 microg . min/mL) due to impaired liver function in cirrhotic rats. However, the AUC values after consecutive 7 (421 compared with 753 microg . min/mL) and 14 (309 compared with 821 microg . min/mL) days oral administration of oltipraz in cirrhotic rats were significantly smaller than those in respective vehicle-treated cirrhotic rats. Moreover, the AUC values after intermittent 2 and 3 weeks in cirrhotic rats were also significantly smaller than that in 1 week vehicle-treated cirrhotic rats (2370 and 1690 compared with 4760 microg . min/mL). This could be due to induction of CYP isozymes and considerably greater numbers of normal liver cells in cirrhotic rats by oral administration of oltipraz. Improved liver function by oltipraz in cirrhotic rats was proved by liver microscopy; livers are free of significant fibrosis, although evidence of bridging necrosis is still present in many rats.

Pharmacokinetics of Oltipraz in Mutant Nagase Analbuminemic Rats

Pharmacokinetic parameters of oltipraz were compared after intravenous (10 mg/kg) and oral (50 mg/kg) administration to control male Sprague-Dawely rats and mutant Nagase analbuminemic rats (NARs). In NARs, the expression and mRNA level of CYP1A2 increased, and oltipraz was mainly metabolized via CYP1A1/2, 2B1/2, 2C11, 201, and 3A1/2 in male rats. Hence, it may be expected that the CL of oltipraz would be significantly faster in NARs. This was proven by the following results. After intravenous administration, the CL of oltipraz was significantly faster in NARs (125% increase) than controls due to significantly greater free fractions (unbound to plasma proteins) of oltipraz (197% increase) and significantly faster CL(int) for the disappearance of oltipraz (11.4% increase) in NARs, since oltipraz is an intermediate hepatic extraction ratio drug in rats. The V(ss) was significantly larger in NARs (109% increase) and this could be due to significant increase in free fractions of oltipraz in NARs. After oral administration, the AUC of oltipraz was also significantly smaller in NARs (61.9% decrease). This could also be due to significant increase in free fractions of oltipraz and significantly faster CL(int) in NARs. However, this was not due to decrease in absorption in NARs.

Pharmacokinetics of oltipraz in rat models of diabetes mellitus induced by alloxan or streptozotocin

Pharmacokinetic parameters of oltipraz were compared after intravenous (10 mg/kg) and oral (30 mg/kg) administration in rat model of diabetes mellitus induced by alloxan (rat model of DMIA) or streptozotocin (rat model of DMIS) and their respective control male Sprague-Dawley rats. In rat models of DMIA and DMIS, the expressions and mRNA levels of CYP1A2, 2B1/2, and 3A1(23) increased, and oltipraz was metabolized mainly via CYP1A1/2, 2B1/2, 2C11, 2D1, and 3A1/2 in male Sprague-Dawley rats. Hence, it would be expected that the AUC and CL values of oltipraz would be significantly smaller and faster, respectively, in rat models of diabetes. This was proven by the following results. After intravenous administration, the AUC values were significantly smaller in rat models of DMIA (40.1% decrease) and DMIS (26.0% decrease) than those in respective control rats, and this could be due to significantly faster CL values in rat models of DMIA (40.1% increase) and DMIS (26.0% increase). The faster CL could be due to increase in hepatic blood flow rate and significantly faster CL(int) in rat models of diabetes, since oltipraz is an intermediate hepatic extraction ratio drug in male Sprague-Dawley rats. After oral administration, the AUC values of oltipraz were also significantly smaller in rat models of DMIA (54.0% decrease) and DMIS (63.2% decrease). This could be due to increase in hepatic blood flow rate, significantly faster CL(int), and changes in the intestinal first-pass effect in rat models of diabetes. However, this was not due to decrease in absorption in rat models of diabetes.

Effects of cysteine on the pharmacokinetics of oltipraz in rats with protein–calorie malnutrition

Effects of cysteine on the pharmacokinetics of oltipraz were investigated after iv (10 mg/kg) and oral (30 mg/kg) administration to male control, protein-calorie malnutrition (PCM), and PCM with oral cysteine supplementation (PCMC) rats. It was reported that oltipraz was mainly metabolized via hepatic CYP1A1/2, 2B1/2, 2C11, 3A1/2, and 2D1 in male rats. The expression and mRNA levels of CYP1A2, 2C11, and 3A1/2 were also reported to decrease in male PCM rats compared with controls. Interestingly, the decreased CYP isozymes in PCM rats returned fully or partially to controls by oral cysteine supplementation (PCMC rats). Hence, it would be expected that in PCM rats, some pharmacokinetic parameters of oltipraz are fully or partially returned to controls by cysteine. This was proven by the following parameters in PCMC rats: the AUC (328, 782, and 416 mug min/mL for control, PCM, and PCMC rats, respectively, after iv administration, and 223, 456, and 242 mug min/mL after oral administration), terminal half-life (130, 212, and 143 min), mean residence time (MRT) (149, 299, and 189 min), and in vitro CL(int) (0.181, 0.107, and 0.153 mL/min/mg protein) were fully returned to controls, and CL and CL(NR) values were partially returned to controls.

Pharmacokinetics of oltipraz after intravenous and oral administration in rats with dehydration for 72 hours

Pharmacokinetic parameters of oltipraz were compared after intravenous and oral administration at a dose of 30 mg/kg to control rats and rats with water deprivation for 72 h (rats with dehydration). The plasma protein binding of oltipraz was measured in both groups of rats using an equilibrium dialysis technique. The concentrations of oltipraz were measured by the reported HPLC analysis. After intravenous administration, the total area under the plasma concentration-time curve from time zero to time infinity (AUC), terminal half-life, time-averaged total body and nonrenal clearances, and apparent volume of distribution at steady state were not significantly different between the two groups of rats. However, after oral administration to rats with dehydration, the AUC was significantly smaller than that in control rats (180 versus 316 microg min/ml) mainly due to decrease in absorption. In rats with dehydration, plasma protein binding was significantly greater than that in control rats (91.5 +/- 0.309 versus 81.3 +/- 2.79%).

Hepatic and intestinal first-pass effects of oltipraz in rats

It was reported that the mean value of the extent of absolute oral bioavailability (F) of oltipraz at a dose of 20 mg/kg was 41.2% and only 2.68% of the oral dose was unabsorbed from the gastrointestinal tract in rats. Hence, the low F in rats could be due to considerable first-pass (gastric, intestinal and hepatic) effects. Hence, the first-pass effects of oltipraz were measured after intravenous, intraportal, intragastric and intraduodenal administration of the drug at a dose of 20 mg/kg to rats. The total area under the plasma concentration-time curve from time zero to time infinity (AUC) values between intragastric and intraduodenal administration (213 and 212 microg min/ml) in rats were almost similar, but the values were significantly smaller than that after intraportal administration (316 microg min/ml) in rats, indicating that gastric first-pass effect was almost negligible (due to negligible absorption of oltipraz from rat stomach), but the intestinal first-pass effect of oltipraz was considerable, approximately 32% of the oral dose. The hepatic first-pass effect of oltipraz was approximately 40% based on AUC values between intravenous and intraportal administration (319 versus 536 microg min/ml). Since approximately 65% of the oral oltipraz was absorbed into the portal vein, the value of 40% was equivalent to 25% of the oral dose. The low F of oltipraz in rats was mainly due to considerable hepatic and intestinal first-pass effects.

Interspecies pharmacokinetic scaling of oltipraz in mice, rats, rabbits and dogs, and prediction of human pharmacokinetics

Dose-independent pharmacokinetics of oltipraz after intravenous and/or oral administration at various doses to mice, rats, rabbits and dogs were evaluated. After both intravenous and/or oral administration of oltipraz to mice (5, 10 and 20 mg/kg for intravenous and 15, 30 and 50 mg/kg for oral administration), rats (5, 10 and 20 mg/kg for intravenous and 25, 50 and 100 mg/kg for oral administration), rabbits (5, 10 and 30 mg/kg for intravenous administration) and dogs (5 and 10 mg/kg for intravenous and 50 and 100 mg/kg for oral administration), the total area under the plasma concentration-time curve from time zero to time infinity (AUC) values of oltipraz were dose-proportional in all animals studied. Animal scale-up of some pharmacokinetics parameters of oltipraz was also performed based on the parameters after intravenous administration at a dose of 10 mg/kg to mice, rats, rabbits and dogs. Linear relationships were obtained between log time-averaged total body clearance (Cl) x maximum life-span potential (MLP) (1 year/h) and log species body weight (W) (kg) (r=0.999; p=0.0015), log Cl (l/h) and log W (kg) (r=0.979; p=0.0209), and log apparent volume of distribution at steady state (V(ss)) (l) and log W (kg) (r=0.999; p=0.0009). The corresponding allometric equations were ClxMLP=49.8 W(0.861), Cl=5.20 W(0.523) and V(ss)=4.46 W(0.764). Interspecies scale-up of plasma concentration-time data for the four species using pharmacokinetic time of dienetichron resulted in similar profiles. In addition, concentrations of oltipraz in a plasma concentration-time profile for humans predicted using the four animal data fitted to the dienetichron time transformation of animal data.

Effects of acute renal failure on the pharmacokinetics of oltipraz in rats

Pharmacokinetic parameters of oltipraz were compared after intravenous and oral administration at a dose of 30 mg/kg to control rats and rats with U-ARF. After intravenous administration to rats with U-ARF, the AUC was significantly greater (1100 versus 1730 microg x min/mL) than that in control rats, and this could be due to significantly slower CL (27.2 versus 17.3 mL/min/kg). The slower CL could be mainly due to significantly slower CL(NR) (27.2 versus 17.3 mL/min/kg), and this could be supported by significantly slower in vitro CL(int) (32.1 versus 13.2 mL/min/whole liver) in the rats. The Vss was significantly larger in rats with U-ARF (4050 versus 5680 mL/kg), and this was not due to a significant increase in free fractions (unbound in plasma proteins) of oltipraz in the rats because the free fractions were 17.0 and 15.7% for control rats and rats with U-ARF, respectively. Unexpectedly, after oral administration to rats with U-ARF, the AUC of oltipraz was significantly smaller than that in control rats (329 versus 149 microg x min/mL), and this could be mainly due to a decrease in the absorption of oltipraz from the gastrointestinal tract in the rats (95 and 72% of the oral dose were absorbed in control rats and rats with U-ARF, respectively).

Pharmacokinetic changes of oltipraz after intravenous and oral administration to rats with liver cirrhosis induced by dimethylnitrosamine

Pharmacokinetic changes of oltipraz were investigated after intravenous and oral administration at a dose of 30 mg/kg to control Sprague-Dawley rats and rats with liver cirrhosis induced by dimethylnitrosamine. After intravenous administration in rats with liver cirrhosis, the area under the plasma concentration-time curve from time zero to time infinity (AUC) was significantly greater (1490 microg min/ml versus 2840 microg min/ml) than that in control rats. This was due to significantly slower total body clearance (CL) (20.2 ml/(min kg) versus 10.6 ml/(min kg)) in the rats. The slower CL was due to significantly slower CL(NR) (20.1 ml/(min kg) versus 10.5 ml/(min kg)) in rats with liver cirrhosis. The significantly slow CL(NR) was due to slower hepatic blood flow rate and significantly slower in vitro intrinsic oltipraz disappearance clearance (CL(int), 77.2 ml/min per whole liver versus 11.5 ml/min per whole liver) because the free (unbound in serum proteins) fraction of oltipraz was significantly greater (15.1% versus 31.3%) in the rats. After oral administration in rats with liver cirrhosis, the AUC was also significantly greater (354 microg min/ml versus 812 microg min/ml) and this was not due to increased absorption in the rats. This also could be due to slower hepatic blood flow rate and significantly slower CL(int) in the rats.