Effects of cysteine on the pharmacokinetics and pharmacodynamics of intravenous and oral azosemide in rats with protein-calorie malnutrition

Effect of low-protein diet on anthracycline pharmacokinetics and cardiotoxicity

OBJECTIVES

Anthracyclines are broad spectrum anticancer drugs with dose-dependent cardiotoxicity. Protein malnutrition commonly occurs in cancer patients and is considered a risk factor for development of cardiotoxicity. This study was designed to assess the modulatory effect of protein malnutrition on the pharmacokinetics and drug disposition properties of a single dose of doxorubicin and epirubicin and how these possible changes will affect the degree of cardiotoxicity of these drugs.

METHODS

A single interperitoneal dose of 15 mg/kg of either doxorubicin or epirubicin was injected into rats fed with either normal protein diet or low-protein diet. The plasma concentration-time profiles of doxorubicin and epirubicin and their concentrations in different tissues were determined. Serum creatine kinase level was determined at different time intervals and histopathological examination of heart tissue was carried out.

KEY FINDINGS

Protein malnutrition significantly altered the pharmacokinetics of doxorubicin and epirubicin, with a significant decrease in their elimination, and prolonged the exposure of the heart to these drugs. Histopathological examination and serum creatine kinase measurements supported the role of protein malnutrition in enhancement of anthracycline cardiotoxicity.

CONCLUSIONS

If similar alteration in anthracyclines' pharmacokinetics occurs in malnourished cancer patients, protein malnutrition will be a risk factor for development of anthracycline cardiotoxicity and dose adjustment will be required in nutritionally deprived patients.

Effects of protein-calorie malnutrition on the pharmacokinetics of DA-7867, a new oxazolidinone, in rats

The pharmacokinetic parameters of DA-7867, a new oxazolidinone, were compared after intravenous and oral administration at a dose of 10mg kg−1 to control rats and rats with protein-calorie malnutrition (rats with PCM). After intravenous administration of 10mg kg−1 DA-7867 to rats, metabolism of the drug was not considerable and after 14 days approximately 85.0% of the dose was recovered as unchanged drug from urine and faeces. After intravenous administration to rats with PCM, the area under the plasma concentration-time curve from time zero to time infinity (AUC) was significantly smaller (10800 vs 6990μg min mL−1) compared with control rats. This may have been due to significantly faster total body clearance (CL, 0.930 vs 1.44mL min−1 kg−1). The faster CL in PCM rats could have been due to significantly faster non-renal clearance (0.842 vs 1.39mL min−1 kg−1 due to significantly greater gastrointestinal (including biliary) excretion; the amount of unchanged DA-7867 recovered from the entire gastrointestinal tract at 24h was significantly greater (1.19 vs 4.28% of intravenous dose)) because the renal clearance was significantly slower in PCM rats (0.0874 vs 0.0553mL min−1 kg−1). After oral administration to PCM rats, the AUC was significantly smaller compared with control rats (7900 vs 4310μgmin mL−1). This could have been due to a decrease in absorption from the gastrointestinal tract.

Effects of cysteine on the pharmacokinetic parameters of omeprazole in rats with protein-calorie malnutrition: partial restoration of some parameters to control levels by oral cysteine supplementation

BACKGROUND

It has been reported that omeprazole is mainly metabolized via the hepatic cytochrome (CYP) 1A1/2, 3A1/2, and 2D1, and the expressions and mRNA levels of CYP1A2, 2C11, and 3A1/2 decreased in protein-calorie malnutrition (PCM) rats compared with controls. Interestingly, the decreased CYP1A2, 2C11, and 3A1/2 in PCM rats returned fully or partially to control levels by oral cysteine supplementation (PCMC rats). Hence, it could be expected that some pharmacokinetic parameters of omeprazole might change in PCM rats and partially restore to control levels in PCMC rats. The purpose of this study is to investigate the pharmacokinetic changes of omeprazole in PCM rats and restoration of the parameters in PCMC rats to control levels.

METHODS

Omeprazole was administered intravenously (20 mg/kg) and orally (40 mg/kg) to control, PCM, and PCMC rats.

RESULTS

The following pharmacokinetic parameters were changed in PCM rats and partially returned to control levels in PCMC rats: the area under the plasma concentration-time curve (AUC; 387, 762, and 539 microg min/mL for control, PCM, and PCMC rats, respectively, after intravenous [IV] administration, and the corresponding values after oral administration: 115, 304, and 201 microg min/mL), total body clearance (51.7, 25.5, and 37.1 mL/min/kg, respectively), nonrenal clearance (51.5, 25.4, and 36.1 mL/min/kg, respectively), and in vitro intrinsic clearance (0.158, 0.118, and 0.138 mL/min/mg protein).

CONCLUSIONS

PCM was associated with significant changes in some omeprazole pharmacokinetics and the pharmacokinetic parameters restored to control levels by oral cysteine.

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.

Effects of cysteine on the pharmacokinetics of intravenous torasemide in rats with protein−calorie malnutrition

Effects of cysteine on the pharmacokinetics of torasemide were investigated after intravenous administration at a dose of 2 mg/kg to control rats and rats with PCM and PCMC. Torasemide was reported to be mainly metabolized via hepatic CYP2C9 in humans, and human CYP2C9 and male rat CYP2C11 proteins have 77% homology. It has also been reported that in male rats with PCM, the CYP2C11 level decreased to approximately 20% of the control level, but the decreased CYP2C11 level in rats with PCM partially returned to the control level by oral cysteine supplementation (rats with PCMC). Hence, it could be expected that in rats with PCM, some pharmacokinetic parameters of torasemide could be significantly different compared with those in control rats and rats with PCMC; however, they could be not significantly different between control rats and rats with PCMC. This was proven by the following parameters; the AUC (1880, 4080, and 2290 microg x min/mL for control rats and rats with PCM and PCMC, respectively), terminal half-life (188, 277, and 139 min), MRT (154, 323, and 155 min), CL (1.06, 0.491, and 0.943 mL/min/kg), CL(NR) (0.992, 0.430, and 0.874 mL/min/kg), and in vitro intrinsic torasemide disappearance clearance, CL(int) (0.102, 0.0842, and 0.0997 mL/min/mg protein).

Pharmacokinetic changes in drugs during protein-calorie malnutrition: correlation between drug metabolism and hepatic microsomal cytochrome p450 isozymes

The rats with protein-calorie malnutrition (PCM, 5% casein diet for a period of 4-week) were reported to exhibit 60 and 80% suppression in the hepatic microsomal cytochrome P450 (CYP) 1A2 and CYP2C11 levels, respectively, and 40-50% decreases in CYP2E1 and CYP3A1/2 levels compared to control (23% casein diet for a period of 4-week) based on Western blot analysis. In addition, Northern blot analysis showed that CYP1A2, CYP2E1, CYP2C11, and CYP3A1/2 mRNAs decreased in the state of PCM as well. Hence, pharmacokinetic changes of the drugs in rats with PCM [especially the area under the plasma concentration-time curve from time zero to time infinity (AUC) changes of metabolite(s)] reported from literatures were tried to explain in terms of CYP isozyme changes in the rats. Otherwise, the time-averaged nonrenal clearance (CL NR) of parent drug was compared. Pharmacokinetic changes of the drugs in other types of malnutritional state, such as kwashiorkor and marasmus, in both human and animal models were also compared. The drugs reviewed are as follows: diuretics, antibiotics, anticancer agents, antiepileptics, antiarrythmics, analgesics, xanthines, antimalarials, and miscellaneous.

Effects of cysteine on the pharmacokinetics of intravenous clarithromycin in rats with protein-calorie malnutrition

Effects of cysteine on the pharmacokinetics of clarithromycin were investigated after intravenous administration of the drug at a dose of 20 mg/kg to control rats (4-week fed on 23% casein diet) and rats with PCM (protein-calorie malnutrition, 4-week fed on 5% casein diet) and PCMC (PCM treated with 250 mg/kg for oral cysteine twice daily during the fourth week). Clarithromycin has been reported to be metabolized via hepatic microsomal cytochrome P450 (CYP) 3A4 to 14-hydroxyclarithromycin (primary metabolite of clarithromycin) in human subjects. It has also been reported that in rats with PCM, CYP3A23 level decreased to 40-50% of control level, but decreased CYP3A23 level in rats with PCM completely returned to control level by oral cysteine supplementation (rats with PCMC). Human CYP3A4 and rat CYP3A23 proteins have 73% homology. In rats with PCM, the area under the plasma concentration-time curve from time zero to time infinity, AUC (567, 853 and 558 microg min/ml for control rats and rats with PCM and PCMC, respectively) and percentage of clarithromycin remaining after incubation with liver homogenate (69.6, 83.9 and 71.7%) were significantly greater than those in control rats and rats with PCMC. Moreover, in rats with PCM, the total body clearance, CL (35.3, 23.4 and 35.8 ml/min/kg), nonrenal clearance, CL(NR) (21.3, 15.2 and 24.1 ml/min/kg) and maximum velocity for the disappearance of clarithromycin after incubation with hepatic microsomal fraction, V(max) (351, 211 and 372 pmol/min/mg protein) were significantly slower than those in control rats and rats with PCMC. However, above mentioned each parameter was not significantly different between control rats and rats with PCMC. The above data suggested that metabolism of clarithromycin decreased significantly in rats with PCM as compared to control due to significantly decreased level of CYP3A23 in the rats. By cysteine supplementation (rats with PCMC), some pharmacokinetic parameters of clarithromycin (AUC, CL, CL(NR) and V(max)) were restored fully to control levels because CYP3A23 level was completely returned to control level in rats with PCMC.

The suppressed expression and functional activity of hepatic P-glycoprotein in rats with protein-calorie malnutrition

The effect of protein-calorie malnutrition (PCM) on the expression and functional activity of P-glycoprotein (P-gp) in the liver of rats was examined. Control protein diets and protein-restricted diets were fed to Sprague-Dawley rats for 4 weeks, and the expression of P-gp in the liver (Western blot), in vitro uptake of a representative substrate of P-gp, daunomycin, into canalicular liver plasma membrane (cLPM) vesicles, and in vivo canalicular excretion of daunomycin were compared between the control and PCM rats. The expression of P-gp in the cLPM vesicles was decreased (22%, p < 0.05) by PCM. Consistent with this result, the in vitro uptake rate (V(max)) was decreased (35%, p < 0.05) by PCM, with constant affinity (K(m)), for the carrier-mediated uptake of daunomycin into cLPM vesicles, resulting in a 33% (p < 0.05) decrease in the intrinsic uptake clearance (CL(int)). The in vivo canalicular excretion clearance (CL(exc)) of daunomycin was also decreased by 79% (p < 0.01) in PCM rats, but the degree was more severe than would be expected from the 22% decrease in the expression of P-gp and the 33% decrease in the uptake of daunomycin (CL(int)). The hepatic level of adenosine 5'-triphosphate, which was decreased by 60% (p < 0.01) in PCM rats, might have contributed to this severe decrease in CL(exc). In summary, the canalicular excretion of P-gp substrates, such as daunomycin, might be reduced in patients with PCM via a mechanism involving the suppression of the expression of P-gp.

Effects of cysteine on the pharmacokinetics of intravenous 2-(allylthio)pyrazine, a new chemoprotective agent, in rats with protein-calorie malnutrition

The effects of cysteine on the pharmacokinetics of 2-(allylthio)pyrazine (2-AP) were investigated after intravenous administration of the drug (50 mg/kg) to control (Sprague-Dawley) rats (4-week fed on 23% casein diet), and rats with protein-calorie malnutrition (PCM, 4-week fed on 5% casein diet) and PCMC (PCM with 250 mg/kg of oral cysteine, twice daily starting from the fourth week). In rats with PCM, the area under the plasma concentration-time curve from time zero to time infinity (AUC) of 2-AP was significantly smaller than that in control rats. However, in rats with PCMC, the AUC of 2-AP was significantly greater than that in control rats and rats with PCM. This could be due to significantly greater formation of M4 in rats with PCM and significantly smaller formation of M4 in rats with PCMC than that in control rats. In rats with PCMC, some pharmacokinetic parameters of 2-AP restored fully or more than the levels of control rats. For example, in rats with PCMC, the apparent volume of distribution at steady state of 2-AP (7290, 16,600, and 7050 ml/kg for control rats, and rats with PCM and PCMC, respectively), the percentage of dose excreted in 24-h urine as unchanged 2-AP (0.242, 0.727, and 0.130%), and 'the amount' excreted in 24-h urine as M4 (100, 228, and 51%) were comparable to those in control rats. However, the AUC (739, 434, and 1240 microg/min/ml) and total body clearance (67.7, 115, and 40.2 ml/min/kg) of 2-AP were significantly greater and slower, respectively, than those in control rats. This could be at least partly due to increase in S-methyltransferase activity (to form M4) in rats with PCM and greater restoration of its activity (decrease in its activity) in rats with PCMC.

Effects of cysteine on the pharmacokinetics of itraconazole in rats with protein-calorie malnutrition

The effects of cysteine on the pharmacokinetics of itraconazole were investigated after intravenous, 20 mg/kg, and oral, 50 mg/kg, administration of the drug to control rats (fed for 4 weeks on 23% casein diet) and rats with PCM (protein-calorie malnutrition, fed for 4 weeks on 5% casein diet) and PCMC (PCM with oral cysteine supplementation, 250 mg/kg, twice daily during the fourth week). After intravenous administration of itraconazole to rats with PCM, the area under the plasma concentration-time curve from time zero to time infinity (AUC) of itraconazole was significantly greater (3580 compared with 2670 and 2980 microg min/ml) than those in control rats and rats with PCMC (the values between control rats and rats with PCMC were not significantly different). The above data suggested that metabolism of itraconazole decreased significantly in rats with PCM due to suppression of hepatic microsomal cytochrome p450 (CYP) 3A23 in the rats. The results could be expected since in rats with PCM, the level of CYP3A23 decreased significantly as compared to control. Itraconazole was reported to be metabolized via CYP3A4 to several metabolites, including hydroxyitraconazole, in human subjects. Human CYP3A4 and rat CYP3A1 (CYP3A23) proteins have 73% homology. By cysteine supplementation (rats with PCMC), the AUC of itraconazole was restored fully to control levels.

Effects of cysteine on amino acid concentrations and transsulfuration enzyme activities in rat liver with protein-calorie malnutrition

The changes in amino acid concentrations and transsulfuration enzyme activities in liver were investigated after 4-week fed on 23% casein diet (control group) and 5% casein diet without (protein-calorie malnutrition, PCM group) or with (PCMC group) oral administration of cysteine, 250 mg/kg (twice daily, starting from the fourth week) using rats as an animal model. By supplementation with cysteine in PCM rats (PCMC group), cysteine level was elevated almost close to the control level, and glutathione (GSH), aspartic acid and serine levels were restored greater than the control levels. The measurement of transsulfuration enzyme activities exhibited that gamma-glutamylcysteine ligase (gamma-GCL) activity was up-regulated in rats with protein restriction (PCM group), and cysteine supplementation (PCMC group) down-regulated to the control level. One-week supplementation of cysteine (PCMC group) significantly down-regulated the cysteine sulfinate decarboxylase activity. These results indicate that the availability of sulfur amino acid(s) especially cysteine appears to play a role in determining the flux of cysteine between cysteine catabolism and GSH synthesis.

Pharmacokinetics and pharmacodynamics of azosemide

Azosemide is used in the treatment of oedematous states and hypertension. The exact mechanism of action is not fully understood, but it mainly acts on both the medullary and cortical segments of the thick ascending limb of the loop of Henle. Delayed tolerance was demonstrated in humans by homeostatic mechanisms (principally an increase in aldosterone secretion and perhaps also an increase in the reabsorption of solute in the proximal tubule). After oral administration to healthy humans in the fasting state, the plasma concentration of azosemide reached its peak at 3-4 h with an absorption lag time of approximately 1 h and a terminal half-life of 2-3 h. The estimated extent of absolute oral bioavailability in humans was approximately 20.4%. After oral administration of the same dose of azosemide and furosemide, the diuretic effect was similar between the two drugs, but after intravenous administration, the effect of azosemide was 5.5-8 times greater than that in furosemide. This could be due to the considerable first-pass effect of azosemide. The protein binding to 4% human serum albumin was greater than 95% at azosemide concentrations ranging from 10 to 100 microg/ml using an equilibrium dialysis technique. The poor affinity of human tissues to azosemide was supported by the relatively small value of the apparent post-pseudodistribution volume of distribution (Vdbeta), 0.262 l/kg. Eleven metabolites (including degraded products) of azosemide including M1, glucuronide conjugates of both M1 and azosemide, thiophenemethanol, thiophencarboxylic acid and its glycine conjugate were obtained in rats. Only azosemide and its glucuronide were detected in humans. In humans, total body clearance, renal clearance and terminal half-life of azosemide were 112 ml/min, 41.6 ml/min and 2.03 h, respectively. Azosemide is actively secreted in the renal proximal tubule possibly via nonspecific organic acid secretory pathway in humans. Thus, the amount of azosemide that reaches its site of action could be significantly modified by changes in the capacity of this transport system. This capacity, in turn, could be predictably changed in disease states, resulting in decreased delivery of the diuretic to the transport site, as well as in the presence of other organic acids such as nonsteroidal anti-inflammatory drugs which could compete for active transport of azosemide. The urinary excretion rate of azosemide could be correlated well to its diuretic effects since the receptors are located in the loop of Henle. The diuretic effects of azosemide were dependent on the rate and composition of fluid replacement in rabbits; therefore, this factor should be considered in the evaluation of bioequivalence assessment.

Effects of cysteine on the pharmacokinetics of intravenous chlorzoxazone in rats with protein-calorie malnutrition

The effects of cysteine on the pharmacokinetics of chlorzoxazone (CZX) and one of its metabolites, 6-hydroxychlorzoxazone (OH-CZX), were investigated after intravenous administration of CZX, 25 mg/kg, to control rats (4-week fed on 23% casein diet) and rats with PCM (4-week fed on 5% casein diet) and PCMC (PCM with oral cysteine supplementation, 250 mg/kg, twice daily during the fourth week). In rats with PCM, the area under the plasma concentration-time curve from time zero to time infinity (AUC) of OH-CZX (436 compared with 972 microgmin/ml) and the percentages of intravenous dose of CZX excreted in 8-h urine as OH-CZX (20.2 compared with 38.5%) were significantly smaller than those in control rats. The above data indicated that the formation of OH-CZX from CZX decreased significantly in rats with PCM due to a significant decrease in chlorzoxazone-6-hydroxylase activity (328 compared with 895 pmol/min/mg protein) in the rats. The results were expected since in rats with PCM, hepatic CYP2E1 expression and its mRNA levels decreased significantly as compared to control, and CZX was metabolized to OH-CZX primarily by CYP2E1 in rats. By cysteine supplementation (rats with PCMC), some pharmacokinetic parameters restored fully (hepatic microsomal chlorzoxazone 6-hydroxylation activity based on both mg protein and nmol CYP450) or partially (total body clearance and apparent volume of distribution at steady state of CZX, and AUC, terminal half-life and 8-h urinary excretion of OH-CZX) to control levels.

Effects of cysteine on the pharmacokinetics of intravenous phenytoin in rats with protein-calorie malnutrition

The effects of cysteine on the pharmacokinetics of phenytoin and one of its metabolites, 5-(p-hydroxyphenyl)-5-phenylhydantoin (pHPPH) were investigated after intravenous administration of phenytoin, 25 mg/kg, to control rats (4-week fed on 23% casein diet) and rats with PCM (protein-calorie malnutrition, 4-week fed on 5% casein diet) and PCMC (PCM with oral cysteine supplementation, 250 mg/kg, twice daily starting from the fourth week). In rats with PCM and PCMC, the phenytoin hydroxylation (to form pHPPH) activities were significantly smaller (164, 103 and 95.3 pmol/min per mg protein for the control rats, and rats with PCM and PCMC, respectively) than that in control rats. In rats with PCMC, the intrinsic clearance of phenytoin, CL(int) was significantly slower than those in control rats and rats with PCM (0.175, 0.131 and 0.044 ml/min). The above data suggested that the formation of pHPPH could be reduced in rats with PCM and PCMC. This was supported by significantly smaller 24-h urinary excretion of pHPPH (54.7, 35.6 and 32.5% of intravenous dose of phenytoin) in rats with PCM and PCMC than that in control rats. In rats with PCM, the maximum velocity (0.344, 0.203 and 0.196 microg/min), apparent volume of distribution in central compartment (44.4, 65.4 and 72.2 ml/kg) of phenytoin, and total area under the plasma concentration-time curve from time zero to time infinity (609, 714 and 1210 microg min/ml), renal clearance (20.5, 13.4 and 4.67 ml/min per kg) and 24-h urinary excretion (54.7, 35.6 and 32.5% of intravenous dose of phenytoin) of pHPPH were not returned to control levels by cysteine supplementation (rats with PCMC). This could be mainly due to the fact that the phenytoin hydroxylation activity in rats with PCMC was not returned to control level.