Increased hepatic lysosomal activity in biliary cirrhosis originates from hepatocytes rather than from macrophages

Pharmacokinetics of Micafungin in Healthy Volunteers, Volunteers With Moderate Liver Disease, and Volunteers With Renal Dysfunction

Micafungin is an antifungal agent metabolized by arylsulfatase with secondary metabolism by catechol-O-methyltransferase. The objectives of this study were to estimate the pharmacokinetic parameters and plasma protein binding of micafungin in volunteers with moderate hepatic dysfunction (n = 8), volunteers with creatinine clearance < 30 mL/min (n = 9), and matched controls (n = 8 and n = 9, respectively). Single-dose micafungin pharmacokinetics were estimated using noncompartmental techniques. There was a statistically lower area under the observed micafungin concentration-time curve (AUC) from time 0 to infinity for subjects with moderate hepatic dysfunction as compared to control subjects (97.5 +/- 19 microg.h/mL vs 125.9 +/- 26.4 microg.h/mL, P = .03), although there was no difference in micafungin weight-adjusted clearance (10.9 +/- 1.7 mL/h/kg vs 9.8 +/- 1.8 mL/h/kg, P = .2). The difference in area under the concentration-time curve may be explained by the differences in body weight between subjects and controls. Renal dysfunction did not alter micafungin pharmacokinetics.

[Micafungin for therapy of invasive candidiasis in solid organ transplant recipients]

BACKGROUND

Micafungin is an echinocandin approved for the prevention of Candida spp. infection in hematopoietic stem cell transplantation and therapy of oesophageal candidiasis, disseminated candidiasis and candidemia in adults, children and neonates.

AIMS

To evaluate the role of micafungin for candidiasis therapy in solid organ transplant recipients.

METHODS

A medical literature review according to micafungin role for candidiasis therapy in transplant patients is performed.

RESULTS

Micafungin has shown fungicide activity against Candida species, including strains resistant or poorly susceptible to fluconazole. No dose adjustment is required when micafungin is administered in combination with other drugs used in transplant patients, excluding sirolimus, nifedipine and itraconazol. With these drugs, a minimal dose reduction is recommended. The results observed in transplant patients included in clinical trials are favourable and similar to results obtained in other kind of patients.

CONCLUSIONS

The clinical results, its safety profile and the low grade of medical interactions permit micafungin to be considered for therapy in specific groups of transplant patients.

Micafungin sodium, the second of the echinocandin class of antifungals: theory and practice

Micafungin is a new drug in the echinocandin class and is currently being investigated in Phase III clinical trials. Like other echinocandins, it inhibits 1,3-beta-D-glucan synthesis, thus achieving fungicidal activity against virtually all Candida spp., including those resistant to fluconazole, and fungistatic activity against Aspergillus spp. Micafungin sodium is available for intravenous administration only. It has a favorable safety and drug-drug interaction profile. Micafungin has been approved by the US FDA for treatment of esophageal candidiasis and for antifungal prophylaxis during the pre-engraftment phase in patients undergoing hematopoietic stem cell transplantation. Considering the competitive pricing as well as the good tolerability and efficacy, at present micafungin seems to be another choice for both of these indications. Current research has proven micafungin sodium to add a rational and effective option to the antifungal armamentarium, especially in esophageal candidiasis refractory to fluconazole treatment, in those intolerant to triazoles or in patients needing concomitant therapy interacting with triazoles. In addition to the current indications, recent uncontrolled clinical trials have demonstrated a marked success in the treatment of candidemia and invasive candidiasis. Results from in vitro studies, animal models, small clinical trials, as well as the obvious comparison with the more established caspofungin, hint at possible future indications such as invasive aspergillosis and empirical antifungal therapy. However, preclinical data on micafungin is inconsistent and published well-designed clinical studies are scarce. More controlled and sufficiently scaled trials are imperative in order to establish micafungin as a reliable and safe option in clinical practice.

The Echinocandins

The changing pattern in fungal infections has driven the need to expand the targets of antifungal activity. The echinocandins are the newest addition to the arsenal against fungal infections. Three echinocandins have been approved by the United States Food and Drug Administration: caspofungin, micafungin, and anidulafungin. These agents have a broad spectrum of activity and are similar to each other with respect to in vitro activity against Candida sp, with micafungin and anidulafungin having similar minimum inhibitory concentrations (MICs) that are generally lower than the MIC of capsofungin. The MICs of the echinocandins are highest against Candida parapsilosis; however, whether this will affect clinical outcomes is unknown. Several case reports have identified clinical failure due to elevated MICs with caspofungin or micafungin against Candida albicans, Candida krusei, and C. parapsilosis. Resistance to the echinocandin class was present in some but not all of the isolates. Empiric therapy with one of the echinocandins for candidemia or invasive candidiasis in patients with neutropenia and those without neutropenia appears to be appropriate when one factors in mortality rate, the increasing frequency of non-albicans Candida infections, and the broad spectrum, safety, and fungicidal effect of the echinocandins. After speciation of the organism, continued therapy with an echinocandin can and should be reevaluated. The echinocandins demonstrate similar in vitro and in vivo activity against Aspergillus sp, but only caspofungin is approved for treatment in patients who are intolerant of or refractory to other therapies. Voriconazole and amphotericin B have demonstrated synergy with the echinocandins. The clinical response to combination therapy has been variable; however, the mortality rate appears to be lower with combination therapy than monotherapy. Large controlled trials are needed to determine the role of combination therapy for invasive aspergillosis. Micafungin and anidulafungin generally have a lower frequency of adverse reactions compared with caspofungin. Phlebitis (3.5-25% of patients) and elevated liver enzyme levels (1-15%) occur more often with caspofungin compared with micafungin and anidulafungin (< 8%). Overall, the three echinocandins are relatively safe and effective agents for the treatment of Candida infections.

Cationic drug pharmacokinetics in diseased livers determined by fibrosis index, hepatic protein content, microsomal activity, and nature of drug

The disposition kinetics of six cationic drugs in perfused diseased and normal rat livers were determined by multiple indicator dilution and related to the drug physicochemical properties and liver histopathology. A carbon tetrachloride (CCl(4))-induced acute hepatocellular injury model had a higher fibrosis index (FI), determined by computer-assisted image analysis, than did an alcohol-induced chronic hepatocellular injury model. The alcohol-treated group had the highest hepatic alpha(1)-acid glycoprotein, microsomal protein (MP), and cytochrome P450 (P450) concentrations. Various pharmacokinetic parameters could be related to the octanol-water partition coefficient (log P(app)) of the drug as a surrogate for plasma membrane partition coefficient and affinity for MP or P450, the dependence being lower in the CCl(4)-treated group and higher in the alcohol-treated group relative to controls. Stepwise regression analysis showed that hepatic extraction ratio, permeability-surface area product, tissue-binding constant, intrinsic clearance, partition ratio of influx (k(in)) and efflux rate constant (k(out)), and k(in)/k(out) were related to physicochemical properties of drug (log P(app) or pK(a)) and liver histopathology (FI, MP, or P450). In addition, hepatocyte organelle ion trapping of cationic drugs was evident in all groups. It is concluded that fibrosis-inducing hepatic disease effects on cationic drug disposition in the liver may be predicted from drug properties and liver histopathology.

Expression of inositol 1,4,5-trisphosphate receptor isoforms in rat cirrhosis

Ca(2+) signals mediate the hepatic effects of numerous hormones and growth factors. Hepatic Ca(2+) signals are elicited by the inositol trisphosphate receptor, an intracellular Ca(2+) channel. Three isoforms of this receptor have been identified; they are expressed and regulated differently. We investigated the effect of liver fibrosis and cirrhosis on the hepatic expression of the inositol trisphosphate receptor isoforms. Two different rat models were used: bile duct ligation (fibrosis) and chronic exposure to CCl(4)/phenobarbital (cirrhosis). Messenger RNA levels were determined by ribonuclease protection assay (RPA), competitive polymerase chain reaction (PCR) followed by Southern blotting, and real-time quantitative PCR. Protein expression was assessed by Western blotting; tissue distribution was assessed by immunohistology. In control animals, isoform 2 was the predominant isoform, isoform 1 represented less than one third, and isoform 3 less than 1%. After bile duct ligation, expression of types 1 and 3 increased 1.9- and 5.7-fold, and expression of type 2 decreased 2. 5-fold at the protein level. After exposure to CCl(4)/phenobarbital, expression of types 1, 2, and 3 were 2.4-, 0.9-, and 4.2-fold their expression in control animals. Type 2 was localized to the apical domain of hepatocytes, consistent with a role for Ca(2+) signals in canalicular function. Type 3 was detectable in intrahepatic bile duct epithelial cells and not in hepatocytes, suggesting that Ca(2+) signals may be regulated differently in these cells. Signaling through inositol trisphosphate receptor participates in the pathogenesis of cirrhosis, because this process affects the expression of its isoforms.

Rat liver lysosomal and mitochondrial activities are modified by anabolic-androgenic steroids

PURPOSE

The aim of this study was to examine the separate and combined effects of an 8-wk treatment with high doses of 17alpha-alkylated anabolic-androgenic steroids (AAS) and exercise training on selected lysosomal and mitochondrial enzyme activities in rat liver.

METHODS

Sedentary and treadmill-trained (25 m x min(-1), 45 min x d(-1), 5 d x wk(-1)) male rats were treated with fluoxymesterone, methylandrostanolone, or stanozolol (2 mg x kg body weight(-1), 5 d x wk(-1)) for 8 wk.

RESULTS

Acid phosphatase, arylsulfatase, beta-glucuronidase, and beta-galactosidase activities were increased in liver homogenates of sedentary and trained AAS-treated rats. The mitochondrial respiratory chain activities rotenone-sensitive NADH-cytochrome c reductase (NCCR), succinate cytochrome c reductase (SCCR), and cytochrome oxidase (COX) showed a significant decrease in steroid-administered rats, whereas citrate synthase (CS), a matrix enzyme, exhibited no changes in activity, pointing to a selective effect of AAS on mitochondrial membrane complexes. In vitro studies in mitochondrial fractions isolated from the liver of control rats showed that COX and CS activities were insensitive to the AAS, whereas NCCR and SCCR activities were partly inhibited. On the other hand, the mean values of serum parameters related to hepatic function were within normal ranges in all the experimental groups of animals.

CONCLUSIONS

The present data show that 8-wk ingestion of three different anabolic-androgenic steroids, either with or without concurrent exercise training, affects lysosomal hydrolases and mitochondrial respiratory chain electron transport in rat liver without modifying classical serum indicators of hepatic function.