Alterations in pharmacokinetics and protein binding behavior of cefazolin in endotoxemic rats

Inflammation Induces Changes in the Functional Expression of P-gp, BCRP, and MRP2: An Overview of Different Models and Consequences for Drug Disposition

The ATP-binding cassette (ABC) transporters play a key role in drug pharmacokinetics. These membrane transporters expressed within physiological barriers can be a source of pharmacokinetic variability. Changes in ABC transporter expression and functionality may consequently affect the disposition of substrate drugs, resulting in different drug exposure. Inflammation, present in several acute and chronic diseases, has been identified as a source of modulation in drug transporter expression leading to variability in drug response. Its regulation may be particularly dangerous for drugs with a narrow therapeutic index. In this context, numerous in vitro and in vivo models have shown up- or downregulation in the expression and functionality of ABC transporters under inflammatory conditions. Nevertheless, the existence of contradictory data and the lack of standardization for the models used have led to a less conclusive interpretation of these data.

Reductively modified albumin attenuates DSS-Induced mouse colitis through rebalancing systemic redox state

Albumin (Alb) is the most abundant plasma protein with multiple biological functions, including antioxidative property through its thiol activity. Given that inflammatory bowel disease is associated with a decreased level of Alb and an increased level of Alb oxidation, we asked whether Alb could have a therapeutic effect on colitis. Here we tested this possibility. Bovine serum albumin (BSA) was reductively modified with dithiothreitol (DTT) and administrated via gavage or intraperitoneal injection. Dextran sulfate sodium (DSS)-induced mice colitis was associated with massive oxidative stress, as indicated by the elevated sulfenic acid formation in blood, colon tissues, and feces. Treatment of mice with the reductively modified albumin (r-Alb) attenuated the oxidative stress and reduced local inflammation and tissue injury. These effects of r-Alb were only partially achieved by unmodified Alb and wholly lost after blocking the -SH groups with maleimide. In cultured colon epithelial cells, r-Alb prevented DSS- and H2O2-induced ROS elevation and barrier dysfunction, preceded by inhibition of sulfenic acid formation and P38 activation. Further analysis revealed that Alb was susceptible to H2O2-induced oxidation, and it detoxified H2O2 in a -SH group-dependent way. Moreover, Alb reacted with GSH/GSSG via thiol-disulfide exchange and reciprocally regulated the availability of -SH groups. Collectively, our study shows that r-Alb effectively attenuates DSS colitis via -SH group-mediated antioxidative action. Given that the oxidative stress underlies many life-threatening diseases, r-Alb, functioning as a potent antioxidant, could have a wide range of applications.

Metabolism and pharmacokinetics of pharmaceuticals in cats (Felix sylvestris catus) and implications for the risk assessment of feed additives and contaminants

In animal health risk assessment, hazard characterisation of feed additives has been often using the default uncertainty factor (UF) of 100 to translate a no-observed-adverse-effect level in test species (rat, mouse, dog, rabbit) to a 'safe' level of chronic exposure in farm and companion animal species. Historically, both 10-fold factors have been further divided to include chemical-specific data in both dimensions when available. For cats (Felis Sylvestris catus), an extra default UF of 5 is applied due to the species' deficiency in particularly glucuronidation and glycine conjugation. This paper aims to assess the scientific basis and validity of the UF for inter-species differences in kinetics (4.0) and the extra UF applied for cats through a comparison of kinetic parameters between rats and cats for 30 substrates of phase I and phase II metabolism. When the parent compound undergoes glucuronidation the default factor of 4.0 is exceeded, with exceptions for zidovudine and S-carprofen. Compounds that were mainly renally excreted did not exceed the 4.0-fold default. Mixed results were obtained for chemicals which are metabolised by CYP3A in rats. When chemicals were administered intravenously the 4.0-fold default was not exceeded with the exception of clomipramine, lidocaine and alfentanil. The differences seen after oral administration might be due to differences in first-pass metabolism and bioavailability. Further work is needed to further characterise phase I, phase II enzymes and transporters in cats to support the development of databases and in silico models to support hazard characterisation of chemicals particularly for feed additives.

Effect of supportive therapy on the pharmacokinetics of intravenous marbofloxacin in endotoxemic sheep

The purpose of this study was to determine the influences of supportive therapy (ST) on the pharmacokinetics (PK) of marbofloxacin in lipopolysaccharide (LPS)-induced endotoxemic sheep. Furthermore, minimum inhibitory concentration (MIC) of marbofloxacin against Escherichia coli, Mannheimia haemolytica, Pasteurella multocida, Klebsiella pneumoniae, Salmonella spp., and Staphylococcus aureus was determined. The study was performed using a three-period cross PK design following a 15-day washout period. In the first period, marbofloxacin (10 mg/kg) was administered by an intravenous (IV) injection. In the second and third periods, marbofloxacin was co-administered with ST (lactated ringer + 5% dextrose + 0.45% sodium chloride, IV, 20 ml/kg, dexamethasone 0.5 mg/kg, SC) and ST + LPS (E. coli O55:B5, 10 µg/kg), respectively. Plasma marbofloxacin concentration was measured using HPLC-UV. Following IV administration of marbofloxacin alone, the t 1 / 2 λ z , AUC_0-∞ , Cl_T , and V_dss were 2.87 hr, 34.73 hr × µg/ml, 0.29 L hr^-1  kg^-1 , and 0.87 L/kg, respectively. While no change was found in the MBX + ST group in terms of the PK parameters of marbofloxacin, it was determined that the Cl_T of marbofloxacin decreased, AUC_0-∞ increased, and t 1 / 2 λ z and MRT prolonged in the MBX + ST + LPS group. MIC values of marbofloxacin were 0.031 to >16 µg/ml for E. coli, 0.016 to >16 µg/ml for M. haemolytica, 0.016-1 µg/ml for P. multocida, 0.016-0.25 µg/ml for K. pneumoniae, 0.031-0.063 µg/ml for Salmonella spp., and 0.031-1 µg/ml for S. aureus. The study results show the necessity to make a dose adjustment of marbofloxacin following concomitant administration of ST in endotoxemic sheep. Also, the PK and pharmacodynamic effect of marbofloxacin needs to be determined in naturally infected septicemic sheep following concomitant administration of single and ST.

A pilot and feasibility study of the plasma and tissue pharmacokinetics of cefazolin in an immature porcine model of pediatric cardiac surgery

BACKGROUND

Surgical site infection (SSI) prevention for children with congenital heart disease is imperative and methods to assess and evaluate the tissue concentrations of prophylactic antibiotics are important to help maximize these efforts.

AIM

The purposes of this study were to determine the plasma and tissue concentrations with standard of care, perioperative cefazolin dosing in an immature porcine model of pediatric cardiac surgery, and to determine the feasibility of this model.

METHODS

Piglets (3-5 days old) underwent either median sternotomy (MS) or cardiopulmonary bypass with deep hypothermic circulatory arrest (CPB + DHCA) and received standard of care prophylactic cefazolin for the procedures. Serial plasma and microdialysis sampling of the skeletal muscle and subcutaneous tissue adjacent to the surgical site was performed. Cefazolin concentrations were measured, noncompartmental pharmacokinetic analyses were performed, and tissue penetration of cefazolin was assessed.

RESULTS

Following the first intravenous dose, maximal cefazolin concentrations in the subcutaneous tissue and skeletal muscle were similar between groups with peak tissue concentrations 15-30 min after administration. After the second cefazolin dose given with the initiation of CPB, total plasma cefazolin concentrations remained relatively constant until the end of DHCA and then decreased while muscle- and subcutaneous-unbound cefazolin concentrations showed a second peak during or after rewarming. For the MS group, 60-67% of the intraoperative time showed subcutaneous and skeletal muscle concentrations of cefazolin >16 μg·ml(-1) while this percentage was 78-79% for the CPB + DHCA group. There was less tissue penetration of cefazolin in the group that underwent CBP + DHCA (P = 0.03).

CONCLUSIONS

The cefazolin dosing used in this study achieves plasma and tissue concentrations that should be effective against methicillin-sensitive Staphylococcus aureus but may not be effective against some gram-negative pathogens. The timing of the cefazolin administration prior to incision and a second dose given during cardiopulmonary bypass may be important factors for achieving goal tissue concentrations.

Protein binding of cefazolin is saturable in vivo both between and within patients

AIMS

The aims of the study were a) to determine if there is evidence of saturable protein binding of cefazolin in plasma across the range of concentrations achieved clinically (between patient variability) and b) to investigate whether saturable protein binding is also evident from trough and peak concentrations in the same patient (within patient variability).

METHODS

Unbound and total plasma concentrations were measured in patients who were treated with cefazolin intravenously by continuous infusion or intermittent injection. In study (i) single random samples were taken from one series of patients. In study (ii) paired samples (troughs and peaks) were taken from a second series of patients.

RESULTS

Thirty-one patients were included in study (i). Linear regression analysis of the percentage unbound vs. unbound plasma concentrations revealed a slope significantly different from zero, suggesting saturable protein binding. Mean values for percentage unbound ranged from 9% at low concentrations (8.5 mg l(-1)) to 51% at high concentrations (140 mg l(-1)). Twelve patients were investigated in study (ii). Values for protein binding ranged from 85% at low concentrations (2.7 mg l(-1)) to 52% at high concentrations (200.3 mg l(-1)). The percentage unbound was significantly higher (P < 0.0001) at high (peak) concentrations than at lower (trough) concentrations, confirming saturable protein binding.

CONCLUSIONS

The protein binding of cefazolin is saturable in vivo in humans, both between and within patients.

Effects of bacterial lipopolysaccharide on the pharmacokinetics of DA-7867, a new oxazolidinone, in rats

Pharmacokinetic parameters of DA-7867 were compared after intravenous and oral administration at a dose of 10 mg/kg to control rats and rats pretreated with Klebsiella pneumoniae lipopolysaccharide (KPLPS). After intravenous administration of DA-7867 at a dose of 10 mg/kg to 10 rats, metabolism of DA-7867 was minimal; however, the urinary and gastrointestinal excretion of DA-7867 were approximately 85% of intravenous dose when collected for up to 14 days. After intravenous administration to rats pretreated with KPLPS, the AUC was significantly greater (14,100 versus 9810 microg x min/mL), and this could be due to significantly slower total body clearance (CL, 0.709 versus 1.02 mL/min/kg). The slower CL in the rats could be due to significantly smaller fecal excretion of DA-7867 for up to 14 days (41.1 versus 58.8% of intravenous dose of DA-7867) because urinary excretion of DA-7867 was not significantly different between two groups of rats. After oral administration, the AUC values were not significantly different between two groups of rats and this was mainly due to decrease in absorption from the gastrointestinal tract in rats pretreated with the KPLPS (approximately 82 and 95% of oral dose were absorbed for rats with KPLPS and control rats, respectively).

Systemic Inflammation-Associated Glucocorticoid Resistance and Outcome of ARDS

Dysregulated systemic inflammation with excess activation of pro-inflammatory transcription factor nuclear factor-kappaB (NF-kappaB)-activated by inflammatory signals-compared to the anti-inflammatory transcription factor glucocorticoid receptor-alpha (GRalpha)-activated by endogenous or exogenous glucocorticoids (GCs)-is an important pathogenetic mechanism for pulmonary and extrapulmonary organ dysfunction in patients with acute respiratory distress syndrome (ARDS). Activation of one transcription factor in excess of the binding (inhibitory) capacity of the other shifts cellular responses toward increased (dysregulated) or decreased (regulated) transcription of inflammatory mediators over time. Recent data indicate that failure to improve in ARDS (unresolving ARDS) is frequently associated with failure of the activated GRs to downregulate the transcription of inflammatory cytokines despite elevated levels of circulating cortisol, a condition defined as systemic inflammation-associated acquired GC resistance; it is potentially reversible with prolonged GC supplementation. In the first part of this paper, after a brief description of inflammation in ARDS and our model of translational research, we review the two cellular signaling pathways that are central to the regulation of inflammation-the stimulatory NF-alphaB and the inhibitory GRalpha. In the second part, we review findings of recent studies indicating that excessive inflammatory activity in patients with unresolving ARDS may induce noncompensated GC resistance in target organs. In the third part, we review factors affecting cellular response to GC and potential mechanisms involved in inflammation-associated GC resistance.

Down-regulation of cytochrome P450 proteins and its activities by Shiga-like toxin II from Escherichia coli O157:H7

Escherichia coli O157:H7 infection frequently induces clinical complications such as hemolytic uremic syndromes and intestinal dysfunctions. These changes could alter the disposition of drugs, consequently changing their efficacy. However, the possible changes of drug-metabolizing activities by E. coli O157:H7 infection have not been addressed. Thus, we have investigated the effect of Shiga-like toxin type II (SLT-II), derived from E. coli O157:H7, on the hepatic cytochrome P450 (CYP) content and its activity in rats. SLT-II (2microg per animal, i.v.) time-dependently decreased total CYP content and the contents of CYP2C11 and CYP3A2 in hepatic microsomal preparations up to 24hr following injection. Consistently, SLT-II time-dependently decreased CYP activity in vivo, as represented by systemic clearance of antipyrine. An inhibitor of inducible nitric oxide synthase, S-methylisothiourea, restored the decreased systemic clearance of antipyrine by SLT-II, suggesting the involvement of the overproduction of nitric oxide by SLT-II. Moreover, dexamethasone restored the decreased systemic clearance of antipyrine by SLT-II. In the hepatic microsomal preparation, dexamethasone restored the SLT-II-induced decrease of CYP3A2 whereas S-methylisothiourea did not affect both CYP subtypes. Taken together, these results suggest that SLT-II might alter hepatic drug-metabolizing function during E. coli O157 infection and that more than one cytokines induced by SLT-II, including nitric oxide, might make a critical contribution to the decrease of CYP content and its activity.

Effect of endotoxin on doxorubicin transport across blood-brain barrier and P-glycoprotein function in mice

The aim of this study was to investigate whether Klebsiella pneumoniae endotoxin modifies transport of doxorubicin, a P-glycoprotein substrate, across the blood-brain barrier and P-glycoprotein function in mice. Doxorubicin (30 mg/kg) was administered into the tail vein or fluorescein isothiocyanate-labeled dextran (FD-4) was infused (20 microg/min) into the right jugular vein of mice intravenously injected with endotoxin (10 mg/kg) 6 or 24 h earlier. Blood and brain samples were collected 4 h after injection of doxorubicin or 1 h after infusion of FD-4. We examined using Western blotting the influence of endotoxin on the expression of P-glycoprotein in brains obtained 6, 12 and 24 h after injection. Endotoxin did not change the plasma and brain concentrations and brain-to-plasma concentration ratio (K(p) value) of FD-4. No histopathological changes in brain capillaries were observed. These results suggest that endotoxin does not cause damage to brain capillaries. Plasma and brain concentrations of doxorubicin in mice treated 6 h earlier with endotoxin were significantly higher than those in control and mice treated 24 h earlier. However, endotoxin did not significantly change the K(p) value of doxorubicin. The protein level of P-glycoprotein was significantly, but slightly down-regulated 6 h after endotoxin treatment. However, the levels remained almost unchanged after 12 and 24 h. The present results suggest that Klebsiella pneumoniae endotoxin has no effect on the brain capillary integrity and doxorubicin transport across the blood-brain barrier in mice. It is likely that P-glycoprotein function might be sufficient to transport doxorubicin in spite of decreased levels of P-glycoprotein in the brain.

Shiga-like toxin II derived from Escherichia coli O157:H7 modifies renal handling of levofloxacin in rats

The effect of Shiga-like toxin II (SLT-II) (2 microg/animal), which was derived from Escherichia coli O157:H7, on renal handling of levofloxacin (LVX), a model drug for quinolone antimicrobial agents, was investigated in rats 24 h after intravenous injection. In histopathological examination, acute tubular injury was observed in SLT-II-treated rats, but the glomeruli were not injured. SLT-II significantly increased the steady-state concentration of LVX in plasma to 1.5-fold that of control rats. SLT-II induced significant decreases in the glomerular filtration rate (GFR) and renal clearance (CL(R)) of LVX. SLT-II slightly, but significantly, increased the unbound fraction and decreased renal plasma flow with no change in the extraction ratio of p-aminohippurate. SLT-II significantly increased concentrations of tumor necrosis factor alpha (TNF-alpha) and nitrite and nitrate (NOx) in plasma. The TNF-alpha inhibitor pentoxifylline partly, but significantly, inhibited SLT-II-induced decreases in the GFR and CL(R) of LVX; in contrast, S-methylisothiourea, a selective inhibitor of inducible nitric oxide synthase, did not. Western blotting analysis revealed that SLT-II did not alter the levels of multidrug resistance-associated protein 2 (Mrp2) and P-glycoprotein in kidneys 24 h after injection, assuming the lack of involvement of Mrp2 and P-glycoprotein in SLT-II-induced acute renal tubular injury and renal handling of LVX observed 24 h after SLT-II injection. The present study suggests that SLT-II impairs the renal handling of LVX by decreasing GFR and causing decreased renal plasma flow.

Effect of endotoxin on P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 in rats

The effects of Klebsiella pneumoniae endotoxin on the biliary excretion and renal handling of rhodamine-123 were investigated in rats at different times after intraperitoneal injection (1 mg/kg of body weight). The typical substrates for P glycoprotein, i.e., cyclosporine, colchicine, and erythromycin, inhibited the biliary clearance of rhodamine-123, whereas a substrate for organic cation transporter, cimetidine, did not inhibit clearance, suggesting that rhodamine-123 is transported mainly by P glycoprotein. The biliary, renal, and tubular secretory clearances of rhodamine-123 and the glomerular filtration rate significantly decreased 6 h after injection of endotoxin but returned to control levels by 24 h. These results suggest that endotoxin-induced decreases in P-glycoprotein-mediated biliary excretion and renal handling of rhodamine-123 were probably due to impairment of P-glycoprotein-mediated transport ability. Pretreatment with pentoxifylline (50 mg/kg) significantly inhibited endotoxin-induced increases in tumor necrosis factor alpha (TNF-alpha) levels in plasma, which ameliorated the endotoxin-induced reduction of the biliary excretion of rhodamine-123. It is likely that endotoxin-induced impairment of the transport of rhodamine-123 is caused, in part, by overproduction of TNF-alpha. The effect of endotoxin on the expression of P-glycoprotein mRNA in liver and kidneys of rats was investigated by using a reverse transcriptase PCR. The expression of Mdr1a mRNA in both liver and kidney decreased 6 h after endotoxin injection and returned to control levels after 24 h, whereas the expression of Mdr1b mRNA in liver increased at both times and that in kidney decreased at 24 h. These findings suggest that K. pneumoniae endotoxin dramatically decreases P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 probably by decreasing the expression of Mdr1a, which is likely due to increased plasma TNF-alpha levels.

Endotoxin impairs biliary transport of sparfloxacin and its glucuronide in rats

The effect of endotoxin on glucuronidation and hepatobiliary transport of quinolone antimicrobial agents was investigated in rats using sparfloxacin and p-nitrophenyl glucuronide as model drugs. The biliary clearance experiments were performed 24 h after a single intraperitoneal injection of endotoxin (1 mg/kg). Endotoxin significantly delayed the disappearance of sparfloxacin from plasma and increased plasma concentration of its glucuronide after intravenous injection of sparfloxacin (10 mg/kg). Significant decreases in the systemic clearance of sparfloxacin and the biliary clearance of sparfloxacin and the glucuronide were observed. Endotoxin had no effect on in vitro glucuronidation activity using p-nitrophenol as a substrate. When p-nitrophenyl glucuronide (8 mg/kg) was administered in endotoxin-pretreated rats, significant decreases in the systemic clearance, biliary clearance and renal clearance of p-nitrophenyl glucuronide were observed. These findings suggest that endotoxin decreases the biliary excretion of sparfloxacin and its glucuronide probably due to impairment of their hepatobiliary transport systems and renal handling.

Time-variant increase in methylprednisolone clearance in patients with acute respiratory distress syndrome: a population pharmacokinetic study

Methylprednisolone (MP) disposition was evaluated in 20 individuals who participated in an ongoing randomized, double-blind, placebo-controlled study designed to evaluate the efficacy of MP in the treatment of acute respiratory distress syndrome (ARDS). MP (1 mg/kg) was given as a loading infusion over 30 minutes followed by a 1 mg/kg/day continuous i.v. infusion. Patients were switched to oral MP upon restoration of oral intake. MP plasma concentrations (n = 110) were determined using a specific HPLC method. Population pharmacokinetic analysis was performed using nonlinear mixed-effects models, implemented in NONMEM, version V. MP plasma concentration data were described by a one-compartment open model with a time-dependent, non-linear increase in the clearance (CL) of MP during the course of therapy. Initial clearance of MP (CLo) in ARDS patients at the start of therapy increased to a maximal value (CLmax) after approximately 7 days. The estimate of CLmax was similar to the CL of MP in healthy individuals reported previously. Population mean estimates (+/- SE) of parameters in the model were as follows: CLo = 13.2 +/- 2.4 L/h, CLmax = 25.0 +/- 3.6 L/h, time of half-maximal increase in CL (T50) = 41.1 +/- 8.2 h, gamma (Hill coefficient) = 3.8 +/- 0.6, and volume of distribution (Vd) = 137 +/- 30.2 L. Disease progression indices and patient demographics were evaluated as covariates, and no significant correlation was found. Means (+/- SD) of plasma protein binding differed between healthy individuals (72% +/- 4%) and ARDS patients (46% +/- 11%) (p < 0.001). The pharmacokinetics of MP in ARDS patients has not been described previously.

Dexamethasone coupled to albumin is selectively taken up by rat nonparenchymal liver cells and attenuates LPS-induced activation of hepatic cells

BACKGROUND/AIMS

The human serum albumin (HSA) conjugate Dexa10-HSA was designed to specifically deliver the anti-inflammatory drug dexamethasone (Dexa) to nonparenchymal cells (NPC) in the rat liver. NPC play an important role in the pathogenesis of acute and chronic inflammatory liver diseases like fibrosis. Targeting Dexa to these cells might reduce its adverse effects and increase the efficacy.

METHODS

Tissue and intrahepatic distributions of Dexa10-HSA were assessed in normal and fibrotic rats with 125I-labelled conjugate and by immunohistochemistry. The effect of the conjugate on lipopolysaccharide (LPS)-induced inflammation and cell activation was studied in vitro with precision-cut liver slices and in vivo.

RESULTS

Ten minutes after i.v. injection 72+/-13% and 65+/-12% of a tracer dose of Dexa10-HSA had been taken up in normal and fibrotic livers, respectively. Unconjugated Dexa also accumulated in livers, but cellular distribution studies revealed an accumulation in parenchymal cells (NPC vs. parenchymal cell (PC) ratio=0.29+/-11, p<0.005) whereas Dexa10-HSA accumulated in nonparenchymal cells (NPC/PC ratio=7.9+/-3.1). Both coupled and uncoupled Dexa showed effective inhibition of LPS-induced NOx and TNFalpha production in precision-cut liver slices. At low concentrations (0.02 microM), however, Dexa10-HSA was more efficient at inhibiting TNFalpha production than uncoupled Dexa. In fibrotic rats Dexa10-HSA (3 mg/kg) and an equimolar amount of uncoupled Dexa (0.22 mg/kg) both significantly promoted survival after LPS-induced acute inflammation.

CONCLUSION

Dexa10-HSA was at least as effective as uncoupled Dexa at inhibiting LPS-induced effects, which indicates that HSA-bound Dexa is pharmacologically active. Coupling Dexa to HSA shifted the accumulation of Dexa from the PC to the NPC of livers. Since mediator release from NPC is crucial in the initiation and propagation of the fibrotic process, selective delivery of Dexa in NPC may improve the efficacy and safety of corticosteroid treatment of liver fibrosis.

Influence of fever on cefazolin pharmacokinetics

The influence of fever on the pharmacokinetics of cefazolin was investigated in patients with acute febrile diseases. Nine patients were included in the study. Antibiotic serum concentrations were determined using high performance liquid chromatograpy (HPLC). An analog computer and the SIMULINK software package were used to identify the pharmacokinetic model and PCNONLIN software package to obtain the secondary parameters. In 6 patients a two-compartment pharmacokinetic model of cefazolin was observed during fever and after defervescence. In 2 patients a two-compartment model changed to a one-compartment after defervescence, and a one-compartment model was observed in one patient during both periods. Cefazolin-treated patients with a two-compartment model (6/9) had higher Cmax, mean steady state serum concentrations (Css), and area under the plasma concentration-time curve (AUC(0-->infinity)), smaller central compartment volume (V1), and lower clearance (Cl) during fever. The varying distribution of antibiotics during fever probably reflects different hemodynamic responses to fever.

Influence of fever on the pharmacokinetics of ciprofloxacin

The influence of fever on the pharmacokinetics of ciprofloxacin was investigated in seven patients with acute febrile diseases. Antibiotic serum concentrations were determined using high-performance liquid chromatograpy (HPLC). The analog computer and the Simulink software package were used to identify the pharmacokinetic model and Penoclin software package to obtain the secondary parameters. During fever, higher maximum serum concentrations (Cmax) of ciprofloxacin were observed in six out of seven patients. The result suggests that the influence of fever on the pharmacodynamics of ciprofloxacin is favorable.

Granulocyte colony-stimulating factor enhances endotoxin-induced decrease in biliary excretion of the antibiotic cefoperazone in rats

We have recently reported that endotoxin (lipopolysaccharide [LPS]) derived from Klebsiella pneumoniae dramatically decreased the biliary excretion of the beta-lactam antibiotic cefoperazone (CPZ), which is primarily excreted into the bile via the anion transport system, in rats. The present study was designed to investigate the effect of human recombinant granulocyte colony-stimulating factor (G-CSF), which is reported to be beneficial in experimental models of inflammation, on the pharmacokinetics and biliary excretion of CPZ in rats. CPZ (20 mg/kg of body weight) was administered intravenously 2 h after the intravenous injection of LPS (250 microgram/kg). G-CSF was injected subcutaneously at 12 microgram/kg for 3 days and was administered intravenously at a final dose of 50 microgram/kg 1 h before LPS injection. Peripheral blood cell numbers were also measured. LPS dramatically decreased the systemic and biliary clearances of CPZ and the bile flow rate. Pretreatment with G-CSF enhanced these decreases induced by LPS. The total leukocyte numbers were increased in rats pretreated with G-CSF compared to the numbers in the controls, while the total leukocyte numbers were decreased (about 3,000 cells/microliter) by treatment with LPS. Pretreatment with G-CSF produces a deleterious effect against the LPS-induced decrease in biliary secretion of CPZ, and leukocytes play an important role in that mechanism.

Time-dependent effects of Klebsiella pneumoniae endotoxin on hepatic drug-metabolizing enzyme activity in rats

The time-dependent effects of Klebsiella pneumoniae endotoxin on hepatic cytochrome P450-dependent drug-metabolizing capacity (cytochrome P450 and b5 content, activity of aminopyrine N-demethylase, p-nitroanisole O-demethylase, aniline hydroxylase and benzphetamine N-demethylase) and on the pharmacokinetics of antipyrine have been determined in rats. Measurement of enzyme activity and antipyrine (after intravenous injection of 20 mg kg(-1)) were performed 2, 24 and 96 h after a single intraperitoneal injection of endotoxin (1 mg kg(-1)) and after repeated doses (once daily for 4 days). The contribution of tumour necrosis factor alpha (TNFalpha) to the endotoxin-induced changes was also examined in rats pretreated with granulocyte colony-stimulating factor (G-CSF). The systemic clearance of antipyrine and the activity of hepatic cytochrome P450-dependent drug-metabolizing enzymes were dramatically reduced 24 h after a single injection of endotoxin, but had returned to control levels by 96h. The magnitudes of these decreases in these measurements after repeated doses of endotoxin were similar to those seen 24h after the single dose. The systemic clearance of antipyrine correlated significantly with cytochrome P450 content and aminopyrine N-demethylase activity. In histopathological experiments, moderate hypertrophy of Kupffer cells was observed, with no evidence of severe liver-tissue damage. G-CSF pretreatment suppressed the increased plasma concentrations of TNFalpha produced 2 h after single endotoxin injection, but did not eliminate the endotoxin-induced decrease in the systemic clearance of antipyrine, suggesting that TNFalpha is not the sole component responsible for the reduction of cytochrome P450-mediated drug-metabolizing enzyme activity. These results provide evidence that a single intraperitoneal injection of 1.0 mgkg(-1)K. pneumoniae endotoxin in rats reduces hepatic P450 and b5 levels, and reduces the activity of various cytochrome P450-mediated drug-metabolizing enzymes without causing severe liver-tissue damage. This suggests that the effect of endotoxin on hepatic cytochrome P450-mediated drug-metabolizing isozymes is non-selective.

Alterations in renal uptake kinetics of the xanthine derivative enprofylline in endotoxaemic mice

The pharmacokinetics and renal uptake of enprofylline, which is primarily excreted into the urine by an active tubular secretion mechanism, were investigated in endotoxaemic mice by lipopolysaccharide isolated from Klebsiella pneumoniae. Lipopolysaccharide (1 mg kg-1) was infused 2 h before starting the examination, thereby inducing a decrease in the systemic clearance and an increase in the steady-state volume of distribution of enprofylline while inducing no changes in the urinary recovery (> 90%). The protein binding of enprofylline significantly decreased in the presence of lipopolysaccharide. Both the systemic clearance for unbound enprofylline and glomerular filtration rate decreased in the treated mice. A nonlinear relationship was found in both groups between the steady-state unbound plasma concentration and renal uptake of enprofylline after constant infusion for 1 h. The renal uptake rate of enprofylline decreased in the treated mice. Lipopolysaccaharide caused increases in the apparent maximum capacity for renal uptake (Vmax) from 17.3 to 32.2 micrograms h-1 g-1 of kidney and in the Michaelis-Menten constant (Km) from 2.7 to 21.7 micrograms mL-1 and decrease in the nonsaturable uptake rate constant (K4) from 0.87 to 0.43 mL h-1 g-1 of kidney. These results indicate that lipopolysaccharide decreases the renal tubular secretion of enprofylline by inducing a decrease in the renal uptake ability.

Effect of a bacterial lipopolysaccharide on biliary excretion of a beta-lactam antibiotic, cefoperazone, in rats

Klebsiella pneumoniae O3 lipopolysaccharide (LPS) has been found to dramatically modify the pharmacokinetics of the beta-lactam antibiotic cefazolin in rats. This study investigated the effect of LPS on the biliary excretion of the beta-lactam antibiotic cefoperazone (CPZ) in rats. CPZ is known to be actively secreted into the bile by a carrier-mediated transport system. LPS (250 micrograms/kg of body weight) was infused for 20 to 30 min 2 h before an intravenous administration of CPZ (20 mg/kg). The pharmacokinetic parameters of CPZ were estimated by a noncompartment model. LPS induced a significant decrease in the systemic clearance (by approximately 50%) and an increase in the mean residence time of CPZ. Significant decreases were also seen in the bile flow rate and in the biliary recovery of unchanged CPZ in the LPS-treated rats. LPS tended to increase the proportion of urinary excretion of CPZ. LPS significantly decreased the biliary clearance (by approximately 55%) and renal clearance (by approximately 35%) of CPZ. However, no changes in the volume of distribution at steady state for CPZ were observed between the treatment groups. Our findings suggest that LPS induces changes in the pharmacokinetics of CPZ as a result of changes occurring in the biliary secretory system.