Inconsistencies and ambiguities in liver-disease-related contraindications: a systematic analysis of SmPCs/PI of Major Drug Markets

Liver disease is a common condition worldwide that can cause alterations in drug disposition and susceptibility to drug toxicities, with increased risk of adverse drug reactions. European Summaries of Product Characteristics (SmPCs) and United States Prescribing Information (US PI) should therefore be comprehensible to prescribers regarding their liver-associated contraindications to ensure safe prescribing. This study aimed to evaluate the ambiguity of terminology used in communicating liver-associated absolute contraindications in SmPCs/PI of commonly prescribed drugs in four major drug markets (Germany, Switzerland, the United Kingdom, and the United States) by assigning wordings to different categories and analyzing their clinical comprehensibility. For US PI, 79% did not contain liver-related contraindications, compared to 2, 13, and 6% of German, Swiss, and British SmPCs, respectively. Study findings indicate that out of 228 examined SmPCs/PI containing liver-related contraindications, 77, 79, 76, and 52% contained unclear wording in the German, Swiss, British, and American drug market, respectively. Only 40% (German), 52% (Swiss), 39% (British), and 29% (American) of SmPCs/PI included terms with explicit wording. Including more precise statements in SmPCs/PI based on laboratory parameters (such as albumin) or scores (e.g., the Child–Pugh score) to objectify the severity of liver disease may improve the clarity of SmPCs/PI and the safety of drug prescription

The renal transport protein OATP4C1 mediates uptake of the uremic toxin asymmetric dimethylarginine (ADMA) and efflux of cardioprotective L-homoarginine

Elevated plasma concentrations of the uremic toxin asymmetrical dimethylarginine (ADMA) and low plasma concentrations of L-homoarginine are independently associated with cardiovascular events and total mortality. Enzymes degrading ADMA [dimethylaminohydrolase 1 (DDAH1)] and synthesizing L-homoarginine [L-arginine:glycine amidinotransferase (AGAT)] are expressed in human proximal tubule cells. So far, it is not known which transport protein in the basolateral membrane of proximal tubule cells is mediating the uptake of ADMA into the cells for subsequent degradation or the export of intracellularly synthesized L-homoarginine. One study suggested that the uptake transporter OATP4C1 (gene symbol SLCO4C1) may be involved in the transport of ADMA and other uremic toxins. OATP4C1 is a member of the SLCO/SLC21 family of solute carriers, localized in the basolateral membrane of human proximal tubule cells. By using stably-transfected HEK cells overexpressing human OATP4C1, we demonstrate that ADMA and L-homoarginine are substrates of OATP4C1 with Km values of 232.1 μM and 49.9 μM, respectively. ADMA and the structurally related uremic toxin SDMA (100 μM) inhibited OATP4C1-mediated L-homoarginine uptake (P < 0.01), whereas other tested uremic toxins such as urea and p-cresyl sulfate have no effect on OATP4C1-mediated transport. Preloading experiments (300 μM for 60 min) with subsequent efflux studies revealed that OATP4C1 also facilitates efflux e.g. of L-homoarginine. Both ADMA and L-homoarginine are substrates of human OATP4C1. Because proximal tubule cells are one site of ADMA metabolism and L-homoarginine synthesis, we postulate a protective role of OATP4C1 by mediating uptake of ADMA from and export of L-homoarginine into the systemic circulation

Asymmetric Dimethylarginine, L-Arginine, and Endothelial Dysfunction in Essential Hypertension

ObjectivesWe investigated the relationship between ADMA plasma levels and endothelium-dependent vasodilation in 36 never-treated essential hypertensives and in 8 normotensive healthy subjects.BackgroundIt has been demonstrated that endothelium-dependent vasodilatation is impaired in essential hypertension. The potential contribution of asymmetric dimethylarginine (ADMA) to endothelial dysfunction of hypertensive humans has received poor attention.MethodsEndothelial function was measured during intra-arterial infusion of acetylcholine (ACh), alone and during co-infusion of L-arginine, and sodium nitroprusside at increasing doses. Concentrations of ADMA and L-arginine in plasma were measured by high-performance liquid chromatography.ResultsHypertensive subjects had significantly higher ADMA and L-arginine plasma concentrations than normotensive healthy controls; ACh-stimulated forearm blood flow (FBF) was significantly reduced in hypertensive subjects in comparison to normotensive control subjects (p < 0.0001). Intra-arterial coinfusion of L-arginine induced a further significant enhancement in ACh-stimulated vasodilation in hypertensive patients. In these, ADMA was strongly and inversely associated with the peak increase in FBF. In a multivariate model, only ADMA and L-arginine were independent correlates, accounting for 33.9% and 8.9% of the variability in the peak FBF response to ACh (p < 0.0001), respectively.ConclusionsThe main finding in this study is that in essential hypertensives the L-arginine and endogenous inhibitor of nitric oxide synthase, ADMA, are inversely related to endothelial function

Accuracy and Completeness of Drug Information in Wikipedia: A Comparison with Standard Textbooks of Pharmacology

The online resource Wikipedia is increasingly used by students for knowledge acquisition and learning. However, the lack of a formal editorial review and the heterogeneous expertise of contributors often results in skepticism by educators whether Wikipedia should be recommended to students as an information source. In this study we systematically analyzed the accuracy and completeness of drug information in the German and English language versions of Wikipedia in comparison to standard textbooks of pharmacology. In addition, references, revision history and readability were evaluated. Analysis of readability was performed using the Amstad readability index and the Erste Wiener Sachtextformel. The data on indication, mechanism of action, pharmacokinetics, adverse effects and contraindications for 100 curricular drugs were retrieved from standard German textbooks of general pharmacology and compared with the corresponding articles in the German language version of Wikipedia. Quantitative analysis revealed that accuracy of drug information in Wikipedia was 99.7%+/- 0.2% when compared to the textbook data. The overall completeness of drug information in Wikipedia was 83.8 +/- 1.5% (p<0.001). Completeness varied in-between categories, and was lowest in the category "pharmacokinetics'' (68.0% +/- 4.2%;p<0.001) and highest in the category "indication'' (91.3%+/- 2.0%) when compared to the textbook data overlap. Similar results were obtained for the English language version of Wikipedia. Of the drug information missing in Wikipedia, 62.5% was rated as didactically non-relevant in a qualitative re-evaluation study. Drug articles in Wikipedia had an average of 14.6 +/- 1.6 references and 262.8 +/- 37.4 edits performed by 142.7 +/- 17.6 editors. Both Wikipedia and textbooks samples had comparable, low readability. Our study suggests that Wikipedia is an accurate and comprehensive source of drug-related information for undergraduate medical education

Mobilization of putative high-proliferative-potential endothelial colony-forming cells during antihypertensive treatment in patients with essential hypertension

Recent studies have shown that in response to vascular damage or ischemia, bone marrow-derived endothelial progenitor cells (EPCs) are recruited into the circulation. To investigate whether antihypertensive treatment has an influence on the number of circulating EPCs, patients with essential hypertension were treated either with the angiotensin receptor antagonist telmisartan, the calcium channel blocker nisoldipine, or their combination for 6 weeks. At baseline and after 3 and 6 weeks of treatment, EPCs were identified and quantified by fluorescence-activated cell sorting (FACS) analysis and by their capacity to generate colony-forming units of the endothelial lineage (CFU-EC) in a methylcellulose-based assay. During treatment, patients in the nisoldipine groups, but not in the telmisartan group, showed a significant mobilization of EPCs, which in part had the capacity to generate large-sized colonies comprising more than 1,000 cells. Moreover, a remarkable correlation between the number of CFU-EC and the number of circulating CD133(+)/CD34(+)/CD146(+) cells was observed, thereby providing strong evidence that cells with this phenotype represent functional EPCs. No correlation was found between the numbers of CFU-EC and the blood pressure levels at any time point during the treatment. Hence, nisoldipine-induced mobilization of EPCs might represent a novel mechanism by which this antihypertensive compound independently of its blood pressure-lowering effect contributes to vasoprotection in patients with essential hypertension

Asymmetric Dimethylarginine Determines the Improvement of Endothelium-Dependent Vasodilation by Simvastatin Effect of Combination With Oral L-Arginine

ObjectivesWe hypothesized that the level of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of endothelial nitric oxide (NO) synthase (eNOS), might determine the endothelial effects of statins.BackgroundEndothelial NO synthase is up-regulated by statins. However, statins failed to improve endothelial function in some studies. Asymmetric dimethylarginine inhibits eNOS by a mechanism that is reversible by L-arginine.MethodsNinety-eight clinically asymptomatic elderly subjects had their plasma ADMA levels screened. Those in the highest (high ADMA, n = 15) and lowest quartiles of the ADMA distribution (low ADMA, n = 13) were eligible to receive, in a randomized order, simvastatin (40 mg/day), L-arginine (3 g/day), or a combination of both, each for 3 weeks. Endothelium-dependent vasodilation (EDD) was assessed by brachial artery ultrasound.ResultsSimvastatin had no effect on EDD in subjects with high ADMA (6.2 ± 1.2% vs. 6.1 ± 0.9%), whereas simvastatin plus L-arginine significantly improved EDD (9.8 ± 1.5% vs. 5.3 ± 0.8%; p < 0.01). In subjects with low ADMA, simvastatin improved endothelial function when given alone (9.5 ± 3.2% vs. 6.1 ± 3.8%; p < 0.001) or in combination with L-arginine (9.0 ± 3.1% vs. 6.3 ± 3.3%; p = 0.001). L-arginine alone improved endothelial function in both groups. Endothelium-independent vasodilation was not affected.ConclusionsSimvastatin does not enhance endothelial function in subjects with elevated ADMA, whereas it does so in patients with low ADMA. Combination of simvastatin with oral L-arginine improves endothelial function in subjects with high ADMA, but has no additional effect in subjects with low ADMA. As NO-mediated effects may play a major role in the therapeutic effects of statins, ADMA concentration is an important factor that influences the “pleiotropic” effects of simvastatin

Associations of Circulating Dimethylarginines with the Metabolic Syndrome in the Framingham Offspring Study

BACKGROUND: Circulating levels of the endogenous inhibitor of nitric oxide synthase, asymmetric dimethylarginine (ADMA), are positively associated with the prevalence of metabolic syndrome (MetS) in cross-sectional investigations. It is unclear if circulating ADMA and other methylarginines are associated with incident MetS prospectively. METHODS: We related circulating ADMA, symmetric dimethylarginine (SDMA), L-arginine (ARG) concentrations (measured with a validated tandem mass spectrometry assay) and the ARG/ADMA ratio to MetS and its components in 2914 (cross-sectional analysis, logistic regression; mean age 58 years, 55% women) and 1656 (prospective analysis, Cox regression; mean age 56 years, 59% women) individuals from the Framingham Offspring Study who attended a routine examination. RESULTS: Adjusting for age, sex, smoking, and eGFR, we observed significant associations of ADMA (direct) and ARG/ADMA (inverse) with odds of MetS (N = 1461 prevalent cases; Odds Ratio [OR] per SD increment 1.13, 95%CI 1.04-1.22; and 0.89, 95%CI 0.82-0.97 for ADMA and ARG/ADMA, respectively). Upon further adjustment for waist circumference, systolic and diastolic blood pressure, glucose, high-density lipoprotein cholesterol, and triglycerides, we observed a positive relation between SDMA and MetS (OR per SD increment 1.15, 95% CI 1.01-1.30) but the other associations were rendered statistically non-significant. We did not observe statistically significant associations between any of the methylarginines and the risk of new-onset MetS (752 incident events) over a median follow-up of 11 years. CONCLUSION: It is unclear whether dimethylarginines play an important role in the incidence of cardiometabolic risk in the community, notwithstanding cross-sectional associations. Further studies of larger samples are needed to replicate our findings

Extended Pharmacist Assessment of Medication Safety for Nursing Home Residents—A Cross-Sectional and Prospective Study

In the routine pharmacist’s medication review in ambulatory care and nursing homes in Germany, clinical diagnoses are often insufficiently considered as they are frequently not accessible to pharmacists and their electronic support tools. This may leave a significant proportion of medication-related problems (MRP) undetected and unresolved. Moreover, limited and incomplete data may promote spurious alerts of low clinical relevance. In order to assess the impact of improved data availability, we conducted a study (German Clinical Trials Register DRKS00025346) to evaluate the impact of an extended pharmacist’s medication review, made possible by diagnosis data being routinely available to the pharmacist. At six nursing homes in the Nuremberg metropolitan area, 338 patients treated by 32 physicians were enrolled. A pharmacist’s medication review, considering only the medication data, identified 114 potential MRPs, and additional consideration of diagnoses further identified 69 potential MRPs. The physicians adapted the therapy in response to 69.9% of alerts. The observed gain in MRP identified indicates that efforts should be intensified to facilitate and improve consideration of drug–diagnosis-related MRP by improving data sharing and communication between pharmacists and physicians caring for nursing home residents