Correction: Li, P. et al. Mechanical Characteristics, In Vitro Degradation, Cytotoxicity, and Antibacterial Evaluation of Zn-4.0Ag Alloy as a Biodegradable Material. Int. J. Mol. Sci. 2018, 19, 755.

The authors wish to make the following corrections to this paper [...].

Mechanical Characteristics, In Vitro Degradation, Cytotoxicity, and Antibacterial Evaluation of Zn-4.0Ag Alloy as a Biodegradable Material.

Zn-based biodegradable metallic materials have been regarded as new potential biomaterials for use as biodegradable implants, mainly because of the ideal degradation rate compared with those of Mg-based alloys and Fe-based alloys. In this study, we developed and investigated a novel Zn-4 wt % Ag alloy as a potential biodegradable metal. A thermomechanical treatment was applied to refine the microstructure and, consequently, to improve the mechanical properties, compared to pure Zn. The yield strength (YS), ultimate tensile strength (UTS) and elongation of the Zn-4Ag alloy are 157 MPa, 261 MPa, and 37%, respectively. The corrosion rate of Zn-4Ag calculated from released Zn ions in DMEM extracts is approximately 10.75 ± 0.16 µg cm-2 day-1, which is higher than that of pure Zn [corrected]. In vitro cytotoxicity tests showed that the Zn-4Ag alloy exhibits acceptable toxicity to L929 and Saos-2 cells, and could effectively inhibit initial bacteria adhesion. This study shows that the Zn-4Ag exhibits excellent mechanical properties, predictable degradation behavior, acceptable biocompatibility, and effective antibacterial properties, which make it a candidate biodegradable material.

Population Pharmacokinetics as a Tool to Reevaluate the Complex Disposition of Ethanol in the Fed and Fasted States.

The pharmacokinetics (PK) of ethanol are important in pharmacology and therapeutics because of potential drug-alcohol interactions as well as in forensic science when alcohol-related crimes are investigated. The PK of ethanol have been extensively studied since the 1930s, although some issues remain unresolved, such as the significance of first-pass metabolism, whether zero-order kinetics apply, and the effects of food on bioavailability. We took advantage of nonlinear mixed-effects modeling to describe blood-alcohol concentration (BAC) profiles derived from 3 published clinical studies involving oral, intraduodenal, and intravenous administration of ethanol with and without food. The overall data set included 1510 BACs derived from 72 healthy subjects (60 men, 12 women) aged between 20 and 60 years. Two-compartment models with first-order absorption and Michaelis-Menten elimination kinetics adequately described the BAC profiles. Food intake had 2 separate effects: It reduced the absorption rate constant and accelerated the maximum elimination rate. Estimates of the maximum elimination rate (fasted) and the food effect (as a factor) were 6.31 g/h (95%CI, 6.04-6.59 g/h) and 1.39-fold (95%CI, 1.33-1.46-fold), respectively. Simulations showed that the area under the BAC-time curve (AUC) was smaller with lower input rate of ethanol, irrespective of any first-pass metabolism. The AUC from time 0 to 10 hours for a 75-kg subject was 2.34 g â€¢ h/L (fed) and 3.83 g â€¢ h/L (fasted) after an oral dose of 45 g ethanol. This difference was mainly attributable to the food effect on ethanol elimination and depended less on the absorption rate. Our new approach to explain the complex human PK of ethanol may help when BAC predictions are made in clinical pharmacology and forensic medicine.

Development, Processing and Aging of Novel Zn-Ag-Cu Based Biodegradable Alloys.

The use of biodegradable materials for implants is a promising strategy to overcome known long-term clinical complications related to permanent implants. Ideally, biodegradable implants support the damaged tissue for a certain period and then degrade, while the physiological function of the surrounding tissue is restored. Although Mg-based alloys nearly ideally lend themselves to biodegradable implants, a few critical shortcomings promoted the development of alternative alloy systems. Due to their reasonably good biocompatibility, moderate corrosion rate without hydrogen evolution and adequate mechanical properties, increasing attention has been paid to Zn alloys. In this work, precipitation-hardening alloys in the system Zn-Ag-Cu were developed relying on thermodynamic calculations. After casting the alloys, their microstructures were refined by thermomechanical treatment. The processing was tracked and directed, respectively, by routine investigations of the microstructure, associated with hardness assessments. Although microstructure refinement increased the hardness, the material proved to be susceptible to aging as the homologous temperature of zinc is at 0.43 Tm. Besides mechanical performance and corrosion rate, long-term mechanical stability is another crucial factor that must be taken into consideration to ensure the safety of the implant and thus requires a profound understanding of the aging process.

Role of organic anion-transporting polypeptides for cellular mesalazine (5-aminosalicylic acid) uptake.

The therapeutic effects and metabolism of mesalazine (5-aminosalicylic acid) in patients with inflammatory bowel disease require intracellular accumulation of the drug in intestinal epithelial cells and hepatocytes. The molecular mechanisms of mesalazine uptake into cells have not been characterized so far. Using human embryonic kidney cells stably expressing uptake transporters of the organic anion-transporting polypeptide (OATP) family, which are expressed in human intestine and/or liver, we found that mesalazine uptake is mediated by OATP1B1, OATP1B3, and OATP2B1 but not by OATP1A2 and OATP4A1. Moreover, genetic variations (*1b, *5, *15) in the SLCO1B1 gene encoding OATP1B1 reduced the K(m) value for mesalazine uptake from 55.1 to 16.3, 24.3, and 32.4 µM, respectively, and the respective V(max) values. Finally, budesonide, cyclosporine, and rifampin were identified as inhibitors of OATP1B1-, OATP1B3-, and OATP2B1-meditated mesalazine uptake. These in vitro data indicate that OATP-mediated uptake and its modification by genetic factors and comedications may play a role for mesalazine effects.

Response of human periosteal cells to degradation products of zinc and its alloy.

Zinc (Zn) and its alloys are proposed as promising resorbable materials for osteosynthesis implants. Detailed studies should be undertaken to clarify their properties in terms of degradability, biocompatibility and osteoinductivity. Degradation products of Zn alloys might affect directly adjacent cellular and tissue responses. Periosteal stem cells are responsible for participating in intramembranous ossification during fracture healing. The present study aims at examining possible effects emanating from Zn or Zn-4Ag (wt%) alloy degradation products on cell viability and osteogenic differentiation of a human immortalized cranial periosteal cell line (TAg cells). Therefore, a modified extraction method was used to investigate the degradation behavior of Zn and Zn-4Ag alloys under cell culture conditions. Compared with pure Zn, Zn-4Ag alloy showed almost fourfold higher degradation rates under cell culture conditions, while the associated degradation products had no adverse effects on cell viability. Osteogenic induction of TAg cells revealed that high concentration extracts significantly reduced calcium deposition of TAg cells, while low concentration extracts enhanced calcium deposition, indicating a dose-dependent effect of Zn ions. Our results give evidence that the observed cytotoxicity effects were determined by the released degradation products of Zn and Zn-4Ag alloys, rather than by degradation rates calculated by weight loss. Extracellular Zn ion concentration was found to modulate osteogenic differentiation of TAg cells. These findings provide significant implications and guidance for the development of Zn-based alloys with an optimized degradation behavior for Zn-based osteosynthesis implants.

Pharmacokinetics and drug metabolism in the elderly.

Aging involves progressive impairments in the functional reserve of multiple organs, which might also affect drug metabolism and pharmacokinetics. In addition, the elderly population will develop multiple diseases and, consequently, often has to take several drugs. As the hepatic first-pass effect of highly cleared drugs could be reduced (due to decreases in liver mass and perfusion), the bioavailability of some drugs can be increased in the elderly. Significant changes in body composition occur with advancing age. Lipophilic drugs may have an increased volume of distribution (Vd) with a prolonged half-life, and water-soluble drugs tend to have a smaller Vd. In the elderly, hepatic drug clearance of some drugs can be reduced by up to 30% and CYP-mediated phase I reactions are more likely to be impaired than phase II metabolism, which is relatively preserved in the elderly. Concerning the most important CYP3A4 studies with human liver microsomes and clinical studies with the validated probe, midazolam, it is indicated that there are no significant differences in CYP3A4 activity between young and old populations. Finally, renal excretion is decreased (up to 50%) in about two thirds of elderly subjects, but confounding factors such as hypertension and coronary heart disease account also for a decline in kidney function. In conclusion, age-related physiological and pharmacokinetic changes as well as the presence of comorbidity and polypharmacy will complicate drug therapy in the elderly.

The clinical impact of pharmacogenetics on the treatment of epilepsy.

Drug treatment of epilepsy is characterized by unpredictability of efficacy, adverse drug reactions, and optimal doses in individual patients, which, at least in part, is a consequence of genetic variation. Since genetic variability in drug metabolism was reported to affect the treatment with phenytoin more than 25 years ago, the ultimate goal of pharmacogenetics is to use the genetic makeup of an individual to predict drug response and efficacy, as well as potential adverse drug events. However, determining the practical relevance of pharmacogenetic variants remains difficult, in part because of problems with study design and replication. This article reviews the published work with particular emphasis on pharmacogenetic alterations that may affect efficacy, tolerability, and safety of antiepileptic drugs (AEDs), including variation in genes encoding drug target (SCN1A), drug transport (ABCB1), drug metabolizing (CYP2C9, CYP2C19), and human leucocyte antigen (HLA) proteins. Although the current studies associating particular genes and their variants with seizure control or adverse events have inherent weaknesses and have not provided unifying conclusions, several results, for example that Asian patients with a particular HLA allele, HLA-B*1502, are at a higher risk for Stevens-Johnson syndrome when using carbamazepine, are helpful to increase our knowledge how genetic variation affects the treatment of epilepsy. Although genetic testing raises ethical and social issues, a better understanding of the genetic influences on epilepsy outcome is key to developing the much needed new therapeutic strategies for individuals with epilepsy.

Relative potency of proton-pump inhibitors-comparison of effects on intragastric pH.

AIM: Comparative potency of proton-pump inhibitors (PPIs) is an important clinical issue. Most available trials have compared the different PPIs at one or a few selected specific dosages, making it difficult to derive quantitative equivalence dosages. Here we derived PPI dose equivalents based on a comprehensive assessment of dose-dependent effects on intragastric pH. METHODS: All available clinical studies reporting the effects of PPIs on mean 24-h intragastric pH were sought from electronic databases including Medline. Studies included were restricted to those targeting the Caucasian population, and healthy volunteers or gastroesophageal reflux disease (GERD) patients. The dose-effect relationships for mean 24-h intragastric pH and for percentage of time with pH > 4 in 24 h were analyzed for each PPI using pharmacodynamic modeling with NONMEM and a model integrating all available data. RESULTS: Fifty-seven studies fulfilled the inclusion criteria. Based on the mean 24-h gastric pH, the relative potencies of the five PPIs compared to omeprazole were 0.23, 0.90, 1.00, 1.60, and 1.82 for pantoprazole, lansoprazole, omeprazole, esomeprazole, and rabeprazole, respectively. Compared with healthy volunteers, patients with GERD needed a 1.9-fold higher dose and Helicobacter pylori-positive individuals needed only about 20% of the dose to achieve a given increase in mean 24-h intragastric pH. CONCLUSION: The present meta-analysis provides quantitative estimates on clinical potency of individual PPIs that may be helpful when switching between PPIs and for assessing the cost-effectiveness of specific PPIs. However, our estimates must be viewed with caution because only a limited dose range has been tested and not exactly the same study conditions were applied for the different substances.

Evaluation of a Zn-2Ag-1.8Au-0.2V Alloy for Absorbable Biocompatible Materials.

Zinc (Zn) and Zn-based alloys have been proposed as a new generation of absorbable metals mainly owing to the moderate degradation behavior of zinc between magnesium and iron. Nonetheless, mechanical strength of pure Zn is relatively poor, making it insufficient for the majority of clinical applications. In this study, a novel Zn-2Ag-1.8Au-0.2V (wt.%) alloy (Zn-Ag-Au-V) was fabricated and investigated for use as a potential absorbable biocompatible material. Microstructural characterization indicated an effective grain-refining effect on the Zn alloy after a thermomechanical treatment. Compared to pure Zn, the Zn-Ag-Au-V alloy showed significantly enhanced mechanical properties, with a yield strength of 168 MPa, an ultimate tensile strength of 233 MPa, and an elongation of 17%. Immersion test indicated that the degradation rate of the Zn-Ag-Au-V alloy in Dulbecco's phosphate buffered saline was approximately 7.34 ± 0.64 µm/year, thus being slightly lower than that of pure Zn. Biocompatibility tests with L929 and Saos-2 cells showed a moderate cytotoxicity, alloy extracts at 16.7%, and 10% concentration did not affect metabolic activity and cell proliferation. Plaque formation in vitro was reduced, the Zn-Ag-Au-V surface inhibited adhesion and biofilm formation by the early oral colonizer Streptococcus gordonii, indicating antibacterial properties of the alloy.

Selection of extraction medium influences cytotoxicity of zinc and its alloys.

Zinc (Zn) alloys have been considered as promising absorbable metals, mainly due to their moderate degradation rates ranging between magnesium alloys and iron alloys. The degradation behavior depends on the specific physiological environment. Released metallic ions and corrosion products directly influence biocompatibility. The initial contact of orthopedic implants or vascular stents after implantation will be with blood. In this study, fetal bovine serum (FBS) was used as a model system of blood components. We investigated the influence of FBS on in vitro degradation behavior and cytotoxicity of pure Zn, and Zn-4Ag and Zn-2Ag-1.8Au-0.2 V (wt%) alloys. The initial degradation rates in FBS were assessed and compared with the degradation and toxicity in four other common physiological model systems: DMEM cell culture medium ±â€¯FBS and McCoy's 5A medium ±â€¯FBS. Test samples in pure FBS showed the highest initial degradation rates, and accordingly, FBS supplemented media accelerated the degradation process as well. Moreover, an extract test according to ISO 10993-5 and -12 with L929 and Saos-2 cells was performed to investigate the role of FBS in the extraction medium. The cytotoxic effects observed in the tests were correlated with FBS-mediated Zn2+ release. These findings have significant implications regarding the selection of appropriate media for in vitro degradation and cytotoxicity evaluation of Zn and its alloys. STATEMENT OF SIGNIFICANCE: Metallic zinc and its alloys have been considered as promising biodegradable metals, mainly due to their moderate degradation rates. However, in vitro cytotoxicity tests according to the current ISO 10993 standard series are not suitable to predict biocompatibility of Zn alloys due to the inconsistent correlation between in vitro and in vitro biocompatibility. In this study, we show that the outcomes of standardized in vitro cytotoxicity tests of Zn and Zn alloys are influenced by fetal bovine serum in the extraction vehicle because FBS promotes Zn2+ release during the extraction process. The results of the study provide significant information for selection of appropriate model systems to evaluate in vitro degradation behavior and cytotoxicity.

Improved estimation of glomerular filtration rate by serum cystatin C in preventing contrast induced nephropathy by N-acetylcysteine or zinc--preliminary results.

BACKGROUND: Prevention of contrast media (CM) induced nephropathy (CIN) by prophylaxis (e.g. N-acetylcysteine; NAC) is controversially discussed. Up to now, assessment of kidney function has been based on measurements of serum creatinine, although this biomarker has several limitations. We investigated NAC and zinc (Zn) for the prevention of CIN by monitoring creatinine and cystatin C. METHODS: In a prospective, placebo-controlled, double blind trial, patients with moderately impaired kidney function receiving low-osmolar, non-ionic CM were randomly assigned to an oral treatment for 2 days with 1.2 g/day of NAC (n = 19), for 1 day with 60 mg/day of Zn (n = 18) or placebo (n = 17). All patients received peri-procedurally 1 ml/kg/h of 0.45% saline for 24 h. At baseline, prior to exposure of CM, 2 and 6 days after CM, creatinine and cystatin C were measured. RESULTS: There was no difference in the incidence of CIN, but a significant drop in creatinine (P < 0.05) was observed in all patients during volume expansion. Creatinine showed no increase after CM and it was normalized to the baseline values in all groups at the study end. In contrast, 2 days after CM there was a significant rise in cystatin C in the Zn (P = 0.012) and the placebo (P = 0.041) group, whereas NAC prevented this deterioration of kidney function. CONCLUSIONS: Cystatin C seems to reflect CM-induced changes in kidney function better than creatinine. NAC and Zn have no effect in preventing CIN by the standard definition, but based on cystatin C we can confirm a preventive effect of NAC. It appears mandatory to assess kidney function by cystatin C in CIN intervention trials, because relying on creatinine can be misleading.

Proton pump inhibitors: an update of their clinical use and pharmacokinetics.

BACKGROUND: Proton pump inhibitors (PPIs) represent drugs of first choice for treating peptic ulcer, Helicobacter pylori infection, gastrooesophageal reflux disease, nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal lesions (complications), and Zollinger-Ellison syndrome. RESULTS: The available agents (omeprazole/esomeprazole, lansoprazole, pantoprazole, and rabeprazole) differ somewhat in their pharmacokinetic properties (e.g., time-/dose-dependent bioavailability, metabolic pattern, interaction potential, genetic variability). For all PPIs, there is a clear relationship between drug exposure (area under the plasma concentration/time curve) and the pharmacodynamic response (inhibition of acid secretion). Furthermore, clinical outcome (e.g., healing and eradication rates) depends on maintaining intragastric pH values above certain threshold levels. Thus, any changes in drug disposition will subsequently be translated directly into clinical efficiency so that extensive metabolizers of CYP2C19 will demonstrate a higher rate of therapeutic nonresponse. CONCLUSIONS: This update of pharmacokinetic, pharmacodynamic, and clinical data will provide the necessary guide by which to select between the various PPIs that differ-based on pharmacodynamic assessments-in their relative potencies (e.g., higher doses are needed for pantoprazole and lansoprazole compared with rabeprazole). Despite their well-documented clinical efficacy and safety, there is still a certain number of patients who are refractory to treatment with PPIs (nonresponder), which will leave sufficient space for future drug development and clinical research.

Antiarrhythmics: elimination and dosage considerations in hepatic impairment.

Many drugs, including most antiarrhythmics (some of which are now of limited clinical use) are eliminated by the hepatic route. If liver function is impaired, it can be anticipated that hepatic clearance will be delayed, which can lead to more pronounced drug accumulation with multiple dosing. Consequently, the potential risks of adverse events could be increased, especially as antiarrhythmics have a narrow therapeutic index. The present review summarises the available pharmacokinetic data on the most popular antiarrhythmic drugs to identify the enzymes involved in the metabolism of the various agents and confirm whether liver disease affects their elimination. Despite long usage of some of these drugs (e.g. amiodarone, diltiazem, disopyramide, procainamide and quinidine), surprisingly few data are available in patients with liver disease, making it difficult to give recommendations for dosage adjustment. In contrast, for carvedilol, lidocaine (lignocaine), propafenone and verapamil, sufficient clinical studies have been performed. For these drugs, a marked decrease in systemic and/or oral clearance and significant prolongation of the elimination half-life have been documented, which should be counteracted by a 2- to 3-fold reduction of the dosage in patients with moderate to severe liver cirrhosis. For sotalol, disopyramide and procainamide, renal clearance contributes considerably to overall elimination, suggesting that dosage reductions are probably unnecessary in patients with liver disease as long as renal function is normal. The hepatically eliminated antiarrhythmics are metabolised mainly by different cytochrome P450 (CYP) isoenzymes (e.g. CYP3A4, CYP1A2, CYP2C9, CYP2D6) and partly also by conjugations. As the extent of impairment in clearance is in the same range for all of these agents, it could be assumed that they have a common vulnerability and that, consequently, hepatic dysfunction will affect CYP-mediated phase I pathways in a similar fashion. The severity of liver disease has been estimated clinically by the validated Pugh score, and functionally by calculation of the clearance of probe drugs (e.g. antipyrine). Both approaches can be helpful in estimating/predicting impairments in drug metabolism, including antiarrhythmics. In conclusion, hepatic impairment decreases the elimination of many antiarrhythmics to such an extent that dosage reductions are highly recommended in such populations, especially in patients with cirrhosis.

The role of pharmacogenetics in the metabolism of antiepileptic drugs: pharmacokinetic and therapeutic implications.

Several different factors, including pharmacogenetics, contribute to interindividual variability in drug response. Like most other agents, many antiepileptic drugs (AEDs) are metabolised by a variety of enzymatic reactions, and the cytochrome P450 (CYP) superfamily has attracted considerable attention. Some of those CYPs exist in the form of genetic (allelic) variants, which may also affect the plasma concentrations or drug exposure (area under the plasma concentration-time curve [AUC]) of AEDs. With regard to the metabolism of AEDs, the polymorphic CYP2C9 and CYP2C19 are of interest. This review summarises the evidence as to whether such polymorphisms affect the clinical action of AEDs. In the case of mephenytoin, defects in its metabolism may be attributable to >10 mutated alleles (designated as *2, *3 and others) of the gene expressing CYP2C19. Consequently, poor metabolisers (PMs) and extensive metabolisers (EMs) could be differentiated, whose frequencies vary among ethnic populations. CYP2C19 contributes to the metabolism of diazepam and phenytoin, the latter drug also representing a substrate of CYP2C9, with its predominant variants being defined as *2 and *3. For both AEDs, there is maximally a 2-fold difference in the hepatic elimination rate (e.g. clearance) or the AUC between the extremes of EMs and PMs which, in the case of phenytoin (an AED with a narrow 'therapeutic window'), would suggest a dosage reduction only for patients who are carriers of mutated alleles of both CYP2C19 and CYP2C9, a subgroup that is very rare among Caucasians (about 1% of the population) but more frequent in Asians (about 10%). The minor contribution of CYP2C19 to the metabolism of phenobarbital (phenobarbitone) can be overlooked. In rare cases, valproic acid can be metabolised to the reactive (hepatotoxic) metabolite, 4-ene-valproic acid. It is not yet clear whether genetic variants of the involved enzyme (CYP2C9) are responsible for this problem. Likewise, the active metabolite of carbamazepine, carbamazepine-10,11-epoxide, is transformed by the microsomal epoxide hydrolase, an enzyme that is also highly polymorphic, but the pharmacokinetic and clinical consequences still need to be evaluated. Pharmacogenetic investigations have increased our general knowledge of drug disposition and action. As for old and especially new AEDs the pharmacogenetic influence on their metabolism is not very striking, it is not surprising that there are no treatment guidelines taking pharmacogenetic data into account. Therefore, the traditional and validated therapeutic drug monitoring approach, representing a direct 'phenotype' assessment, still remains the method of choice when an individualised dosing regimen is anticipated. Nevertheless, pharmacogenetics and pharmacogenomics can offer some novel contributions when attempts are made to maximise drug efficacy and enhance drug safety.

Clinical pharmacokinetics and use of infliximab.

Tumor necrosis factor-alpha (TNFalpha) is a key proinflammatory cytokine involved in chronic inflammatory diseases. Infliximab, a chimeric (human-murine) monoclonal IgG1 anti-TNFalpha antibody, is used in the treatment of Crohn's disease (including fistulising disease) and rheumatoid arthritis (in combination with methotrexate) if standard treatments have failed. The indications for infliximab have recently been expanded to include ankylosing spondylitis, psoriatic arthritis, psoriasis and ulcerative colitis. The biological agent infliximab is given by multiple intravenous infusions in a dosage of 3-5 mg/kg (initially at weeks 0, 2 and 6; subsequently in intervals of 4-8 weeks). In controlled trials, clinical response rates of 20-40% have been achieved with such regimens in Crohn's disease and rheumatoid arthritis. However, the therapeutic benefits must be balanced against the risks of a variety of severe adverse events (e.g. severe infections including tuberculosis, hepatotoxicity, infusion reactions, serum sickness-like disease and lymphoma). Following single and multiple infusions of infliximab, no relevant differences in median concentration-time profiles have been observed between patients with Crohn's disease, patients with rheumatoid arthritis and patients with psoriasis. The apparent volume of distribution of the high-molecular-weight infliximab (149.1 kDa) is low (3-6L) and represents the intravascular space. The long persistence in this compartment (elimination half-life 7-12 days, mean residence time 12-17 days) is due to the very low systemic clearance of about 11-15 mL/hour (0.18-0.25 mL/minute). Elimination of infliximab is most probably accomplished through degradation by unspecific proteases. During multiple infusions (every 4-8 weeks), no accumulation was observed, and serum concentrations and the area under the plasma concentration-time curve of infliximab increased in proportion to the infused dose, indicating linear pharmacokinetics. Co-medication with methotrexate delayed the decline in the serum concentrations of infliximab. When relating serum concentrations to the clinical response in patients with rheumatoid arthritis and patients with Crohn's disease, it can be assumed that trough concentrations above 1 microg/mL could be used as a kind of therapeutic target. In the future, identification of biomarkers for (non-)response and risk factors for adverse drug reactions would be very helpful. Furthermore, combined biological, pharmacokinetic, pharmacogenomic and clinical studies have not yet been performed and are needed to optimise the therapeutic potential of infliximab, which is currently established as a rescue treatment in refractory patients.

Thiopurine treatment in inflammatory bowel disease: clinical pharmacology and implication of pharmacogenetically guided dosing.

This review summarises clinical pharmacological aspects of thiopurines in the treatment of chronic inflammatory bowel disease (IBD). Current knowledge of pharmacogenetically guided dosing is discussed for individualisation of thiopurine therapy, particularly to avoid severe adverse effects. Both azathioprine and mercaptopurine are pro-drugs that undergo extensive metabolism. The catabolic enzyme thiopurine S-methyltransferase (TPMT) is polymorphically expressed, and currently 23 genetic variants have been described. On the basis of an excellent phenotype-genotype correlation for TPMT, genotyping has become a safe and reliable tool for determination of a patient's individual phenotype. Thiopurine-related adverse drug reactions are frequent, ranging from 5% up to 40%, in both a dose-dependent and -independent manner. IBD patients with low TPMT activity are at high risk of developing severe haematotoxicity if pharmacogenetically guided dosing is not performed. Based on several cost-benefit analyses, assessment of TPMT activity is recommended prior to thiopurine therapy in patients with IBD. The underlying mechanisms of azathioprine/mercaptopurine-related hepatotoxicity, pancreatitis and azathioprine intolerance are still unknown. Although the therapeutic response appears to be related to 6-thioguanine nucleotide (6-TGN) concentrations above a threshold of 230-260 pmol per 8 x 10(8) red blood cells, at present therapeutic drug monitoring of 6-TGN can be recommended only to estimate patients' compliance.Drug-drug interactions between azathioprine/mercaptopurine and aminosalicylates, diuretics, NSAIDs, warfarin and infliximab are discussed. The concomitant use of allopurinol without dosage adjustment of azathioprine/mercaptopurine leads to clinically relevant severe haematotoxicity due to elevated thiopurine levels. Several studies indicate that thiopurine therapy in IBD during pregnancy is safe. Thus, azathioprine/mercaptopurine should not be withdrawn in strictly indicated cases of pregnant IBD patients. However, breastfeeding is contraindicated during azathioprine/mercaptopurine therapy. Use of azathioprine/mercaptopurine for induction and maintenance of remission in corticosteroid-dependent or corticosteroid-refractory IBD, particularly Crohn's disease, is evidence based. To improve response rates in thiopurine therapy of IBD, comprehensive analyses including metabolic patterns and genome-wide profiling in patients with azathioprine/mercaptopurine treatment are required to identify novel candidate genes.

Unchanged serum levels of advanced glycation endproducts in patients with liver disease.

Advanced glycation end products (AGEs), e.g., carboxymethyllysine (CML) or imidazolone are involved in several age-related disorders. Concerning their accumulation, the importance of hepatic and renal function is controversially discussed. To test whether impairment of hepatic or renal function will affect their accumulation, both AGEs have been measured in various populations, such as 52 patients with liver disease [viral hepatitis C without (n = 19) and with (n = 10) fatty liver; nonalcoholic fatty liver (n = 13), nonalcoholic steatohepatitis (n = 10)]. Serum concentrations of both AGEs have been compared to those in 20 healthy controls and 24 patients with moderate renal impairment (creatinine clearance 23-55 ml/min). Concerning CML (95% C.I. 803-1200 ng/ml), no differences between the various groups could be observed. Likewise, serum levels of imidazolone (95% C.I. 1.3-5.6 units) were similar in all populations. In conclusion, moderate impairment in hepatic or in renal function did not affect serum levels of CML and imidazolone. Apparently, any increase observed in severe cirrhosis or renal failure seems to be rather a consequence than a cause of both disorders.

Screening of telomerase inhibitors.

Shortening of telomeres prevents cells from uncontrolled proliferation. Progressive telomere shortening occurs at each cell division until a critical telomeric length is reached. Telomerase expression is switched off after embryonic differentiation in most normal cells, but it is expressed in a very high percentage of tumors of different origin. Thus, telomerase is regarded as the best tumor marker and a promising novel molecular target for cancer treatment. Therefore, different strategies to inhibit telomerase have been developed. However, systematic screening of telomerase inhibitors has not been performed to compare their therapeutic potential. We propose a suitable strategy for estimation of the therapeutic potential of telomerase inhibitors, which is based on a systematic screening of different inhibitors in the same cell system. From the long list of compounds discussed in the literature, we have selected four telomerase inhibitors of different structure and mode of action: BRACO19 (G-quadruplex-interactive compound), BIBR1532 (non-nucleosidic reverse transcriptase inhibitor), 2'-O-methyl RNA, and peptide nucleic acids (PNAs; hTR antisense oligonucleotides). To determine minimal effective concentrations for telomerase inhibition, telomerase activity was measured using the cell-free telomerase repeat amplification protocol (TRAP) assay. We also tested inhibitors in long-term cell-culture experiments by exposing A-549 cells to non-cytotoxic concentrations of inhibitors for a period of 99 days. Subsequently, telomerase activity of A-549 cells was investigated using the TRAP assay, and telomere length of samples was assessed by telomere restriction fragment (TRF) Southern blot analysis.

Sensitive quantification of omeprazole and its metabolites in human plasma by liquid chromatography-mass spectrometry.

A sensitive method was developed for the simultaneous determination of omeprazole and its major metabolites 5-hydroxyomeprazole and omeprazole sulfone in human plasma by HPLC-electrospray mass spectrometry. Following liquid-liquid extraction HPLC separation was achieved on a ProntoSil AQ, C18 column using a gradient with 10 mM ammonium acetate in water (pH 7.25) and acetonitrile. The mass spectrometer was operated in the selected ion monitoring mode using the respective MH(+) ions, m/z 346 for omeprazole, m/z 362 for 5-hydroxy-omeprazole and omeprazol-sulfone and m/z 300 for the internal standard (2-{[(3,5-dimethylpyridine-2-yl)methyl]thio}-1H-benzimidazole-5-yl)methanol. The limit of quantification (LOQ) achieved with this method was 5 ng/ml for 5-hydroxyomeprazole and 10 ng/ml for omeprazole and omeprazole-sulfone using 0.25 ml of plasma. Intra- and inter-assay variability was below 11% over the whole concentration range from 5 to 250 ng/ml for 5-hydroxyomeprazol and from 10 to 750 ng/ml for omeprazole and omeprazole-sulfone. The method was successfully applied to the determination of pharmacokinetic parameters of esomeprazole and the two major metabolites after a single dose and under steady state conditions.