Pharmacokinetic changes of drugs in a rat model of liver cirrhosis induced by dimethylnitrosamine, alone and in combination with diabetes mellitus induced by streptozotocin

Rats with liver cirrhosis induced by N-dimethylnitrosamine (LC) and rats with LC with diabetes mellitus induced by streptozotocin (LCD) have been developed as animal models for human liver cirrhosis and liver cirrhosis with diabetes mellitus, respectively. Changes in the pharmacokinetics of drugs (mainly non-renal clearance, CLNR) in LC and LCD rats reported in the literature compared with respective control rats were reviewed. This review mainly explains the changes in the CLNRs of drugs (which are mainly metabolized via hepatic microsomal cytochrome P450s, CYPs) in LC and LCD rats, in terms of the changes in in vitro hepatic intrinsic clearance (CLint; mainly due to the changes in CYPs in the disease state), free (unbound) fraction of a drug in the plasma (fp) and hepatic blood flow rate (QH) depending on the hepatic excretion ratio of the drug. Generally, changes in the CLNRs of drugs in LC and LCD rats could be well explained by the above-mentioned three factors. The mechanism of urinary excretion of drugs (such as glomerular filtration or renal active secretion or reabsorption) in LC and LCD rats is also discussed. The pharmacokinetics of the drugs reported in the LC and LCD rats were scarce in humans. Thus, the present rat data should be extrapolated carefully to humans.

Pharmacokinetics of drugs in mutant Nagase analbuminemic rats and responses to select diuretics

OBJECTIVES

To report (1) the pharmacokinetics of drugs that are mainly metabolized via hepatic cytochrome P450s (CYPs) or mainly excreted via the urine and bile, (2) the mechanism for the urinary excretion of drugs (such as glomerular filtration or renal active secretion or re-absorption), and (3) the diuretic effect of some loop diuretics in mutant Nagase analbuminaemic rats (NARs), an animal model for human familial analbuminaemia based on the pharmacokinetics of drugs reported in the literatures.

KEY FINDINGS

In NARs, the changes in the time-averaged non-renal clearances (CL(NR)s) of drugs that are mainly metabolized via CYPs were explained in terms of changes in the hepatic intrinsic clearance (mainly because of changes in CYPs), free (unbound) fractions of drugs in the plasma (fp) and hepatic blood-flow rate (QH) depending on the hepatic excretion ratios of drugs.

SUMMARY

The CL(NR) changes of drugs mainly metabolized via hepatic CYPs can be sufficiently explained by the three earlier mentioned factors. The plasma albumin (furosemide) or globulin (azosemide, bumetanide and torasemide) binding affects their diuretic effects.

Pharmacokinetic and pharmacodynamic interaction between nifedipine and metformin in rats: competitive inhibition for metabolism of nifedipine and metformin by each other via CYP isozymes

It has been reported that hypertension exponentially increases in the patients with type 2 diabetes mellitus. Thus, this study was performed to investigate the pharmacokinetic and pharmacodynamic interactions between nifedipine and metformin, since both drugs were commonly metabolized via hepatic CYP2C and 3A subfamilies in rats. Nifedipine (3 mg/kg) and metformin (100 mg/kg) were simultaneously administered intravenously or orally to rats. Concentrations (I) of each drug in the liver and intestine, maximum velocity (V(max)), Michaelis-Menten constant (K(m)), and intrinsic clearance (CL(int)) for the disappearance of each drug, apparent inhibition constant (K(i)) and [I]/K(i) ratios of each drug in liver and intestine were determined. Also the metabolism of each drug in rat and human CYPs and blood pressure were also measured. After the simultaneous single intravenous administration of both drugs together, the AUCs of each drug were significantly greater than that in each drug alone due to the competitive inhibition for the metabolism of nifedipine by metformin via hepatic CYP3A1/2 and of metformin by nifedipine via hepatic CYP2C6 and 3A1/2. After the simultaneous single oral administration of both drugs, the significantly greater AUCs of each drug than that in each drug alone could have mainly been due to the competitive inhibition for the metabolism of nifedipine and metformin by each other via intestinal CYP3A1/2 in addition to competitive inhibition for the hepatic metabolism of each drug as same as the intravenous study.

Effects of cytochrome P450 inducers and inhibitors on the pharmacokinetics of intravenous furosemide in rats: involvement of CYP2C11, 2E1, 3A1 and 3A2 in furosemide metabolism

Objectives

It has been reported that the non-renal clearance of furosemide was significantly faster in rats pretreated with phenobarbital but was not altered in rats pretreated with 3-methylcholanthrene. However, no studies on other cytochrome P450 (CYP) isozymes have yet been reported in rats.

Method

Furosemide 20 mg/kg was administered intravenously to rats pretreated with various CYP inducers –3-methylcholanthrene, orphenadrine citrate and isoniazid, inducers of CYP1A1/2, 2B1/2 and 2E1, respectively, in rats – and inhibitors – SKF-525A (a nonspecific inhibitor of CYP isozymes), sulfaphenazole, cimetidine, quinine hydrochloride and troleandomycin, inhibitors of CYP2C6, 2C11, 2D and 3A1/2, respectively, in rats.

Key findings

The non-renal clearance of furosemide was significantly faster (55.9% increase) in rats pretreated with isoniazid, but slower in those pretreated with cimetidine or troleandomycin (38.5% and 22.7% decreases, respectively), than controls. After incubation of furosemide with baculovirus-infected insect cells expressing CYP2C11, 2E1, 3A1 or 3A2, furosemide was metabolized via CYP2C11, 2E1, 3A1 and 3A2.

Conclusions

These findings could help explain possible pharmacokinetic changes of furosemide in various rat disease models (where CYP2C11, 2E1, 3A1 and/or CYP3A2 are altered) and drug–drug interactions between furosemide and other drugs (mainly metabolized via CYP2C11, 2E1, 3A1 and/or 3A2).

Pharmacokinetics of drugs in rats with diabetes mellitus induced by alloxan or streptozocin: comparison with those in patients with type I diabetes mellitus

Objectives

In rats with diabetes mellitus induced by alloxan (DMIA) or streptozocin (DMIS), changes in the cytochrome P450 (CYP) isozymes in the liver, lung, kidney, intestine, brain, and testis have been reported based on Western blot analysis, Northern blot analysis, and various enzyme activities. Changes in phase II enzyme activities have been reported also. Hence, in this review, changes in the pharmacokinetics of drugs that were mainly conjugated and metabolized via CYPs or phase II isozymes in rats with DMIA or DMIS, as reported in various literature, have been explained. The changes in the pharmacokinetics of drugs that were mainly conjugated and mainly metabolized in the kidney, and that were excreted mainly via the kidney or bile in DMIA or DMIS rats were reviewed also. For drugs mainly metabolized via hepatic CYP isozymes, the changes in the total area under the plasma concentration–time curve from time zero to time infinity (AUC) of metabolites, AUCmetabolite/AUCparent drug ratios, or the time-averaged nonrenal and total body clearances (CLNR and CL, respectively) of parent drugs as reported in the literature have been compared.

Key findings

After intravenous administration of drugs that were mainly metabolized via hepatic CYP isozymes, their hepatic clearances were found to be dependent on the in-vitro hepatic intrinsic clearance (CLint) for the disappearance of the parent drug (or in the formation of the metabolite), the free fractions of the drugs in the plasma, or the hepatic blood flow rate depending on their hepatic extraction ratios. The changes in the pharmacokinetics of drugs that were mainly conjugated and mainly metabolized via the kidney in DMIA or DMIS rats were dependent on the drugs. However, the biliary or renal CL values of drugs that were mainly excreted via the kidney or bile in DMIA or DMIS rats were faster.

Summary

Pharmacokinetic studies of drugs in patients with type I diabetes mellitus were scarce. Moreover, similar and different results for drug pharmacokinetics were obtained between diabetic rats and patients with type I diabetes mellitus. Thus, present experimental rat data should be extrapolated carefully in humans.

Time-dependent effects of Klebsiella pneumoniae endotoxin on the telithromycin pharmacokinetics in rats; restoration of the parameters in 96-hour KPLPS rats to the control levels

OBJECTIVES

It has been reported that telithromycin is primarily metabolized via hepatic CYP3A4 and 3A1/2 in humans and rats, respectively, and that the protein expression of hepatic CYP3A subfamily significantly decreased (59.1% decrease) in 24-h KPLPS rats (lipopolysaccharide derived from Klebsiella pneumoniae; the protein expression was measured 24h after KPLPS administration) compared with that in control rats, but restored to that in control rats in 96-h KPLPS rats.

METHODS

The pharmacokinetic parameters of telithromycin were compared after intravenous and oral administration at a dose of 50mg/kg to control, 24-h KPLPS, and 96-h KPLPS rats.

RESULTS

After both intravenous and oral administration of telithromycin to 24-h KPLPS rats, the AUC of telithromycin became significantly greater (68.2% and 88.7% increase for intravenous and oral administration, respectively) and this could have been due to the significantly slower CL(NR) (45.7% decrease). Because telithromycin is a low hepatic extraction ratio drug, the slower CL(NR) could have been due to the decreased protein expression of the hepatic CYP3A subfamily compared with that in control rats, and was supported by the significantly slower in vitro CL(int) in hepatic microsomes (13.1% decrease). However, in 96-h KPLPS rats, the pharmacokinetic parameters of telithromycin restored fully to those in control rats due to restoration of the protein expression of the hepatic CYP3A subfamily to that in control rats. The protein expression of the intestinal CYP3A subfamily was comparable among three groups of rats.

CONCLUSIONS

These findings indicate the existence of the time-dependent effects of KPLPS on the pharmacokinetics of telithromycin in rats.