Identification of 2-Sulfonyl/Sulfonamide Pyrimidines as Covalent Inhibitors of WRN Using a Multiplexed High-Throughput Screening Assay.

Werner syndrome protein (WRN) is a multifunctional enzyme with helicase, ATPase, and exonuclease activities that are necessary for numerous DNA-related transactions in the human cell. Recent studies identified WRN as a synthetic lethal target in cancers characterized by genomic microsatellite instability resulting from defects in DNA mismatch repair pathways. WRN's helicase activity is essential for the viability of these high microsatellite instability (MSI-H) cancers and thus presents a therapeutic opportunity. To this end, we developed a multiplexed high-throughput screening assay that monitors exonuclease, ATPase, and helicase activities of full-length WRN. This screening campaign led to the discovery of 2-sulfonyl/sulfonamide pyrimidine derivatives as novel covalent inhibitors of WRN helicase activity. The compounds are specific for WRN versus other human RecQ family members and show competitive behavior with ATP. Examination of these novel chemical probes established the sulfonamide NH group as a key driver of compound potency. One of the leading compounds, H3B-960, showed consistent activities in a range of assays (IC50 = 22 nM, KD = 40 nM, KI = 32 nM), and the most potent compound identified, H3B-968, has inhibitory activity IC50 ∼ 10 nM. These kinetic properties trend toward other known covalent druglike molecules. Our work provides a new avenue for screening WRN for inhibitors that may be adaptable to different therapeutic modalities such as targeted protein degradation, as well as a proof of concept for the inhibition of WRN helicase activity by covalent molecules.

pH Dependence of a GPR4 Selective Antagonist Hampers Its Therapeutic Potential.

Inflammatory bowel disease (IBD) is characterized by chronic mucosal inflammation of the gastrointestinal tract and is associated with extracellular acidification of mucosal tissue. Several extracellular pH-sensing receptors, including G protein-coupled receptor 4 (GPR4), play an important role in the regulation of inflammatory and immune responses, and GPR4 deficiency has been shown to be protective in IBD animal models. To confirm the therapeutic potential of GPR4 antagonism in IBD, we tested Compound 13, a selective GPR4 antagonist, in the interleukin 10-/- mouse model of colitis. Despite good exposures and albeit there was a trend toward improvement for a few readouts, Compound 13 treatment did not improve colitis in this model, and there were no signs of target engagement. Interestingly, Compound 13 behaved as an "orthosteric" antagonist, i.e., its potency was pH dependent and mostly inactive at pH levels lower than 6.8 with preferential binding to the inactive conformation of GPR4. Mutagenesis studies confirmed Compound 13 likely binds to the conserved orthosteric binding site in G protein-coupled receptors, where a histidine sits in GPR4 likely preventing Compound 13 binding when protonated in acidic conditions. While the exact mucosal pH in the human disease and relevant IBD mice models is unknown, it is well established that the degree of acidosis is positively correlated with the degree of inflammation, suggesting Compound 13 is not an ideal tool to study the role of GPR4 in moderate to severe inflammatory conditions. SIGNIFICANCE STATEMENT: Compound 13, a reported selective GPR4 antagonist, has been widely used to assess the therapeutic potential of GPR4, a pH-sensing receptor, for numerous indications. Its pH dependence and mechanism of inhibition identified in this study clearly highlights the limitations of this chemotype for target validation.

The potent and selective RIPK2 inhibitor BI 706039 improves intestinal inflammation in the TRUC mouse model of inflammatory bowel disease.

Mouse and human data implicate the NOD1 and NOD2 sensors of the intestinal microbiome and the associated signal transduction via the receptor interacting protein kinase 2 (RIPK2) as a potential key signaling node for the development of inflammatory bowel disease (IBD) and an attractive target for pharmacological intervention. The TRUC mouse model of IBD was strongly indicated for evaluating RIPK2 antagonism for its effect on intestinal inflammation based on previous knockout studies with NOD1, NOD2, and RIPK2. We identified and profiled the BI 706039 molecule as a potent and specific functional inhibitor of both human and mouse RIPK2 and with favorable pharmacokinetic properties. We dosed BI 706039 in the spontaneous TRUC mouse model from age 28 to 56 days. Oral, daily administration of BI 706039 caused dose-responsive and significant improvement in colonic histopathological inflammation, colon weight, and terminal levels of protein-normalized fecal lipocalin (all P values <0.001). These observations correlated with dose responsively increasing systemic levels of the BI 706039 compound, splenic molecular target engagement of RIPK2, and modulation of inflammatory genes in the colon. This demonstrates that a relatively low oral dose of a potent and selective RIPK2 inhibitor can modulate signaling in the intestinal immune system and significantly improve disease associated intestinal inflammation.NEW & NOTEWORTHY The RIPK2 kinase at the apex of microbiome immunosensing is an attractive target for pharmacological intervention. A low oral dose of a RIPK2 inhibitor leads to significantly improved intestinal inflammation in the murine TRUC model of colitis. A selective and potent inhibitor of the RIPK2 kinase may represent a new class of therapeutics that target microbiome-driven signaling for the treatment of IBD.

Characteristics of non-smoking adult asthma patients with chronic airflow limitation.

OBJECTIVE: Chronic airflow limitation (CAL) can develop in a subgroup of patients with asthma. Characterising these patients is important because reduced lung function is a risk factor for adverse asthma outcomes. We hypothesised that heterogeneity in patients with CAL may be influenced by age at asthma onset. We first compared never-smoking asthma patients with and without CAL, and subsequently examined the differences between patients with late and early-onset asthma within the CAL cohort. METHODS: Patients seen in our hospital's respiratory clinic between 1 Jan 2015 and 31 December 2015 were recruited to the study. CAL was defined as post-bronchodilator forced expiratory volume in 1 second (FEV1)<80% predicted, in the presence of post-bronchodilator ratio <70%. Variables independently associated with CAL were determined using a multivariate logistic regression model. Comparisons between patients with late-onset asthma (age ≥18 years) and early-onset asthma were made within the CAL cohort. RESULTS: 247 patients were included in the study. Age was the only variable independently associated with CAL after regression analysis, with an increase in odds of 3.8% (95% CI 0.4-7.3%) for every 1 year increase in age, p = 0.027. 63.2% of patients with CAL had late-onset asthma. Compared to patients with early-onset asthma, those with late-onset asthma had higher fractional exhaled nitric oxide levels (43 ± 32 ppb vs 20 ± 8 pb, p = 0.008). CONCLUSIONS: An increase in age is associated with CAL in never-smoking asthma patients. In addition, age at asthma onset appears to influence airway inflammation in patients with CAL.

Modulation of P-glycoprotein at the Human Blood-Brain Barrier by Quinidine or Rifampin Treatment: A Positron Emission Tomography Imaging Study.

Permeability-glycoprotein (P-glycoprotein, P-gp), an efflux transporter at the human blood-brain barrier (BBB), is a significant obstacle to central nervous system (CNS) delivery of P-gp substrate drugs. Using positron emission tomography imaging, we investigated P-gp modulation at the human BBB by an approved P-gp inhibitor, quinidine, or the P-gp inducer, rifampin. Cerebral blood flow (CBF) and BBB P-gp activity were respectively measured by administration of (15)O-water followed by (11)C-verapamil. In a crossover design, healthy volunteers received quinidine and 11-29 days of rifampin treatment during different study periods. CBF and P-gp activity was measured in the absence (control; prior to quinidine treatment) and presence of P-gp modulation. At clinically relevant quinidine plasma concentrations, P-gp inhibition resulted in a 60% increase in (11)C-radioactivity distribution across the human BBB as measured by the brain extraction ratio (ER) of (11)C-radioactivity. Furthermore, the magnitude of BBB P-gp inhibition by quinidine was successfully predicted by a combination of in vitro and macaque data, but not by rat data. Although our findings demonstrated that quinidine did not completely inhibit P-gp at the human BBB, it has the potential to produce clinically significant CNS drug interactions with P-gp substrate drugs that exhibit a narrow therapeutic window and are significantly excluded from the brain by P-gp. Rifampin treatment induced systemic CYP3A metabolism of (11)C-verapamil; however, it reduced the ER by 6%. Therefore, we conclude that rifampin, at its usual clinical dose, cannot be used to induce P-gp at the human BBB to a clinically meaningful extent and is unlikely to cause inadvertent BBB-inductive drug interactions.

Outcome of microscopic excision of a subungual glomus tumor: a 12-year evaluation.

BACKGROUND: Glomus tumors are rare benign neurovascular tumors, up to 75% of which occur in the hand, mainly the subungual area. Local recurrence and nail deformity are commonly seen if tumor excision is not performed completely or properly. OBJECTIVE: This study was designed to assess the long-term efficacy of microscopic excision of subungual glomus tumors. MATERIALS AND METHODS: This retrospective analysis reviewed a total of 22 patients diagnosed with glomus tumors who underwent microscopic surgical excision at a single medical center over a 12-year period (2002-2014). Outcomes were analyzed based on symptom relief, recurrence rate, finger function, nail esthetics, and patient satisfaction. RESULTS: With a mean follow-up period of 48.4 months, neither recurrence nor postexcision nail deformity developed in any patient. Patient satisfaction was rated as "good" in 86.3% of patients (19/22). CONCLUSION: Microscopic surgical excision enables the surgeon to completely remove a glomus tumor while minimizing damage to the nail unit, thereby resulting in significantly decreased recurrence and nail deformity. In this study, an incision made according to the anatomic location provided an easy approach and the best visualization. Patients' finger function was successfully restored, nail esthetic outcome was good, and patient satisfaction was high.

Predicting the outer boundaries of P-glycoprotein (P-gp)-based drug interactions at the human blood-brain barrier based on rat studies.

Using positron emission tomography (PET), (11)C-verapamil as the P-gp substrate, and cyclosporine A (CsA) as the P-gp inhibitor, we showed that the magnitude of P-gp-based drug interactions at the human blood-brain barrier (BBB) is modest. However, such interactions at clinically relevant CsA blood concentrations may be greater for substrates where P-gp plays an even larger role (fractional contribution of P-gp, ft > 0.97) in preventing the CNS entry of the drug (e.g., nelfinavir). Since we have shown that the rat is an excellent predictor of the verapamil-CsA interaction at the human BBB, we determined the magnitude of drug interaction at the rat BBB between nelfinavir and CsA. Under isoflurane anesthesia, male Sprague-Dawley rats were coadministered IV infusions of nelfinavir and escalating doses of CsA to achieve pseudo steady-state plasma/blood and brain concentrations of both drugs (blood CsA ranged 0-264.9 µM, n = 3-6/group). The percent increase in the brain:blood nelfinavir concentration ratio (determined by LC/MS) was described by the Hill equation with Emax = 6481%, EC50 = 12.3 µM, and γ = 1.6. Then, using these data, as well as in vitro data in LLCPK1 cells expressing the human P-gp, we predicted that CsA (at clinically relevant blood concentration of 1.5 µM) will increase the distribution of nelfinavir into the human brain by 236%. Collectively, our data suggest that clinically significant P-gp based drug interactions at the human BBB are possible for P-gp substrates highly excluded from the brain (ft > 0.97) and should be investigated using noninvasive approaches (e.g., PET).

Quality Improvement Project to Develop a Pictorial Chronic Obstructive Pulmonary Disease (COPD) Action Plan.

Introduction Chronic obstructive pulmonary disease (COPD) is a global health concern and a leading cause of morbidity and mortality worldwide. COPD action plans help patients manage exacerbations by recognizing symptoms early and taking necessary steps. We found our COPD written action plan difficult to understand, potentially affecting the patient's ability to self-manage their COPD. Aims We aim to design a new COPD action plan to increase the knowledge scores of our patients during competency checks by 20%. Methods We employed the quality improvement methodology of needs analysis and root cause analysis and used a Pareto chart to identify the top four contributory factors to an ineffective COPD action plan. These include being too wordy, lacking pictorial illustrations, being only available in a single language (English), and too much medical jargon. Using the prioritization matrix to assess possible solutions, the team decided to implement a pictorial COPD action plan. After two cycles of Plan-Do-Study-Act, the final pictorial COPD plan was compared with the original written action plan. Results Ten English-speaking COPD patients from our outpatient respiratory clinics were surveyed with the original action plan while 11 more were surveyed after the introduction of the pictorial action plan. There was an improvement in mean knowledge scores by 92.8% (t(19) = 6.67, p < 0.01, at 95% CI). Patient satisfaction rates also increased from 44% to 100%. Sixty-three percent (63.6%) of patients surveyed said they referred back to the pictorial action plan 3 months after being introduced to it. Conclusion Pictorially enhanced COPD action plans have been shown to improve our patients' knowledge of COPD self-management.

P-glycoprotein-based loperamide-cyclosporine drug interaction at the rat blood-brain barrier: prediction from in vitro studies and extrapolation to humans.

We have shown that the rat can quantitatively predict the verapamil-cyclopsorine A (CsA) drug-drug interaction (DDI) at the human blood-brain barrier (BBB). In addition, the potency (EC(50)) of CsA to inhibit rat BBB P-gp can be predicted from in vitro studies in MDRI-transfected cells. To assess if these excellent agreements extend to other substrates, we determined the magnitude of P-gp-based DDI at the rat BBB between loperamide (Lop) or its metabolite, N-desmethyl Lop (dLop), and escalating CsA blood concentrations. The percent increase in the brain:blood Lop concentration ratio was described by the Hill equation, E(max) = 2000%, EC(50) = 7.1 µM and γ = 3.7. The potency (EC(50)) of CsA to inhibit P-gp at the rat BBB was independent of the substrate used (verapamil, Lop, or dLop). Like the verapamil-CsA DDI, the potency (EC(50)) of CsA to inhibit rat BBB P-gp could be predicted from studies in MDRI-transfected cells. When (11)C-Lop was coadministered with a 10 mg/kg iv infusion of CsA (1) yielding ~5.6 uM CsA blood concentration to healthy volunteers, the brain distribution of (11)C-radioactivity was increased by 110%. (1) When corrected for diffusible Lop metabolite(s), this translates into an increase in (11)C-Lop brain distribution of 457%. Based on our rat data, we estimated a similar value at 5.6 µM blood CsA concentration, 588% increase in Lop brain distribution. These data support our conclusion that the rat is a promising model to predict P-gp based DDI at the human BBB.

In vitro-to-in vivo prediction of P-glycoprotein-based drug interactions at the human and rodent blood-brain barrier.

In vitro inhibition of P-glycoprotein (P-gp) expressed in cells is routinely used to predict the potential of in vivo P-gp drug interactions at the human blood-brain barrier (BBB). The accuracy of such predictions has not been confirmed because methods to quantify in vivo P-gp drug interactions at the human BBB have not been available. With the development of a noninvasive positron emission topography (PET) imaging method by our laboratory to determine P-gp-based drug interactions at the human BBB, an in vitro-in vivo comparison is now possible. Therefore, we developed a high throughput cell-based assay to determine the potential of putative P-gp inhibitors [including cyclosporine A (CsA)] to inhibit (EC(50)) the efflux of verapamil-bodipy, a model P-gp substrate. LLCPK1-MDR1 cells, expressing recombinant human P-gp, or control cells lacking P-gp (LLCPK1) were used in our assay. Using this assay, quinine, quinidine, CsA, and amprenavir were predicted to be the most potent P-gp inhibitors in vivo at their respective therapeutic maximal unbound plasma concentrations. The in vitro EC(50) of CsA (0.6 microM) for P-gp inhibition was virtually the same as our previously determined in vivo unbound EC(50) at the rat BBB (0.5 microM). Moreover, at 2.8 microM CsA (total blood concentration), our in vitro data predicted an increase of 129% in [(11)C]verapamil distribution into the human brain, a value similar to that observed by us (79%) using PET. These data suggest that our high throughput cell assay has the potential to accurately predict P-gp drug interactions at the human BBB.

Comparison of the Proportion and Healthcare Utilisation of Adult Patients with Uncontrolled Severe Asthma versus Non-Severe Asthma Seen in a Southeast Asian Hospital-Based Respiratory Specialist Clinic.

INTRODUCTION: Understanding the burden of uncontrolled severe asthma is essential for disease-targeted healthcare planning. There is a scarcity of data regarding the proportion, healthcare utilisation and costs of patients with uncontrolled severe asthma in Asia. This study aimed to plug the knowledge gap in this area. MATERIALS AND METHODS: Consecutive patients with asthma managed in our respiratory specialist clinic were evaluated prospectively. Healthcare utilisation comprising unscheduled asthma-related primary care visits, emergency department (ED) visits and hospital admissions were obtained from the national health records system. We defined uncontrolled severe asthma as poor symptom control (Asthma Control Test score <20); 2 or more asthma exacerbations requiring ≥3 days of systemic corticosteroids in the previous year; 1 or more serious asthma exacerbation requiring hospitalisation in the previous year; or airflow limitation with pre-bronchodilator forced expiratory volume in 1 second (FEV1) <80% predicted despite high dose inhaled corticosteroids and another controller medication. RESULTS: Of the 423 study participants, 49 (11.6%) had uncontrolled severe asthma. Compared to non-severe asthma, patients with uncontrolled severe asthma were older and more likely to be female and obese. They had a median of 2 (interquartile range: 0 to 3) exacerbations a year, with 51% having ≥2 exacerbations in the past 12 months. They were responsible for 43.9% of the hospital admissions experienced by the whole study cohort. Mean annual direct asthma costs per patient was S$2952 ± S$4225 in uncontrolled severe asthma vs S$841 ± S$815 in non-severe asthma. CONCLUSION: Approximately 12% of patients with asthma managed in a hospital-based respiratory specialist clinic in Singapore have uncontrolled severe asthma. They account for a disproportionate amount of healthcare utilisation and costs. Healthcare strategies targeting these patients are urgently needed.

The role of transporters in drug interactions.

Transport proteins play an important role in the adsorption, distribution and elimination of a wide variety of drugs. Therefore, it is not surprising that transporter-based drug interactions can occur in the clinic. These interactions can lead to changes in toxicity and/or efficacy of the affected drug. Here, we review such interactions and ask if these interactions could have been predicted from in vitro data. Conducting such in vitro-in vivo correlation is important for predicting future transporter-based drug interactions.

Risk factors and incidence of repeat osteoporotic fractures among the elderly in Taiwan: a population-based cohort study.

The incidence of osteoporotic fracture (OF), a condition that leads to higher morbidity and mortality in the elderly, is increasing yearly worldwide. However, most studies of OF have focused on the epidemiology of initial fractures, mainly in female and white populations. This study aimed to explore the incidence and the risk factors for repeat osteoporotic fracture (ROF) in Taiwan.We performed a retrospective cohort study using the Taiwan National Health Insurance Database (NHIRD) from 1995 through 2011. Individuals aged 65 years or older who experienced an initial OF were included. The patients were followed until death, the end of registration in the NHIRD, ROF occurrence, or the end of the study period (December 31, 2011), whichever occurred first. The incidence of ROF over ≥ 5 years after the initial fracture was analyzed, and the risk factors for ROF were assessed using Cox proportional hazards models. The incidence rates of ROF were 950.5, 321.4, 158.7, 92.8, and 70.2 per 1000 person-years among subjects in their first, second, third, fourth, and fifth years after the initial OF, respectively. Nearly 45% of the subjects sustained a ROF in the first year after OF. ROF risk increased with age and Charlson Comorbidity Index (CCI) score. Greater risk for ROF was observed among female subjects and those who had suffered from hip and vertebral fracture at the first OF, had undergone OF-related surgery, and had received bone-related medications. The incidence of ROF in the Taiwanese elderly is higher during the first year after the initial OF, and ROF risk increases with age, female sex, high CCI score, and in those who have undergone OF-related surgery, sustained hip or vertebral fracture, and used bone-related medications.

[A concept analysis of stress].

Stress formation, which depends on an individual's perception of a situation, can lead to changes in physiology, emotions, or behavior, and cause damage to one's physical and/or mental health. Nurses can help their patients reduce the impact of stress by teaching some essential stress attributes. Applying concept analysis, the authors provide information on definition, critical attributes, antecedents, and consequences, and presents both references for empirical research and construct demonstration examples. The article concludes with a discussion of potential applications to nursing practices.

Beyond the ITC White Paper: emerging sciences in drug transporters and opportunities for drug development.

Over the recent years there has been a greater appreciation in the important roles drug transporters play in drug-drug interactions (DDI), safety and effectiveness of drugs. Notable consequence of this recognition includes the white paper published by the International Transporter Consortium (ITC) and the guidance documents drafted by regulatory agencies for investigating transporter-mediated DDIs during drug development. While DDIs as a result of transporter-mediated alterations in drug absorption, disposition, or excretion are typically undesirable, there are exceptions. When specific transporters selectively regulate the exposure of a drug at the site of action and/or toxicity, the use of these transporters as molecular targets has been proposed as a promising strategy for tissue-selective drug delivery to enhance efficacy or mitigate toxicity. Furthermore, membrane transporters play a pivotal role in the transport of nutrients and endogenous compounds into or out of cells to sustain cell survival. Genetic polymorphism of drug transporters as well as transporter-inhibiting drugs can alter the transporter functional activity and/or protein expression, causing transporter-specific diseases. Therefore, investigating drug-transporter interactions is a critical aspect in candidate drug selection, in order to enhance the pharmacological effects and/or prevent the unintended off-target toxicity. The goal of this review is to provide the drug discovery scientists with a cadre of concepts beyond the ITC White Paper that facilitate rational drug design for optimal safety and efficacy. To that end, this review focuses on the following aspects: 1) regulatory landscape on drug transporter-mediated DDIs, 2) transporter related organ toxicity, 3) utility of drug transporters for target organ delivery, and 4) to highlight the diseases known thus far that are associated with variants of transporter genes.

Differences in COPD patient care by primary family caregivers: an age-based study.

BACKGROUND: Because Taiwan has the fastest aging rate among developed countries, care for the elderly is becoming more prominent in the country. Primary family caregivers play an important role in patient health and health promotion behavior. Chronic obstructive pulmonary disease (COPD), an age-related disease, is a major public health problem with high morbidity and mortality and can be a long-term burden for family members; however, little attention has been given to the differences in COPD care between elder caregivers and other caregivers. This study aimed to investigate the differences between elder family caregivers and non-elder family caregivers caring for COPD patients in Taiwan, including caring behavior, caregiver response, and caring knowledge. METHODS: This cross-sectional study was conducted between March 2007 and January 2008; 406 primary family caregivers of COPD patients from the thoracic outpatient departments of 6 hospitals in north-central Taiwan were recruited to answer questionnaires measuring COPD characteristics, care behavior, caregiver response, and COPD knowledge. All questionnaires, which addressed caregiver knowledge, care behaviors, and care reactions, were shown to have acceptable validity and reliability, and the data were analyzed using univariate and generalized linear model techniques. RESULTS: The elder caregivers group had 79 participants, and the non-elder caregivers comprised 327 participants. The COPD-related knowledge scale results were positively correlated with the family caregiver caring behavior scale, suggesting that better COPD-related knowledge among family caregivers may result in improved caring behavior. After adjusting for all possible confounding factors, the elder caregivers had significantly lower COPD-related knowledge than the non-elder caregivers (P<0.001). However, there were no significant differences in the family caregiver caring behavior scale or the caregiver reaction assessment scale between the two groups. CONCLUSIONS: Elder family caregivers require increased education regarding medications and preventive care in COPD patient care.

Activity of P-Glycoprotein, a ß-Amyloid Transporter at the Blood-Brain Barrier, Is Compromised in Patients with Mild Alzheimer Disease.

UNLABELLED: Studies in animals and postmortem human brain tissue support a role for P-glycoprotein in clearance of cerebral ß-amyloid across the blood-brain barrier (BBB). We tested the hypothesis that BBB P-glycoprotein activity is diminished in Alzheimer disease (AD) by accounting for an AD-related reduction in regional cerebral blood flow (rCBF). METHODS: We compared P-glycoprotein activity in mild-AD patients (n = 9) and cognitively normal, age-matched controls (n = 9) using PET with a labeled P-glycoprotein substrate, (11)C-verapamil, and (15)O-water to measure rCBF. BBB P-glycoprotein activity was expressed as the (11)C-verapamil radioactivity extraction ratio ((11)C-verapamil brain distributional clearance, K1/rCBF). RESULTS: Compared with controls, BBB P-glycoprotein activity was significantly lower in the parietotemporal, frontal, and posterior cingulate cortices and hippocampus of mild AD subjects. CONCLUSION: BBB P-glycoprotein activity in brain regions affected by AD is reduced and is independent of rCBF. This study improves on prior work by eliminating the confounding effect that reduced rCBF has on assessment of BBB P-glycoprotein activity and suggests that impaired P-glycoprotein activity may contribute to cerebral ß-amyloid accumulation in AD. P-glycoprotein induction or activation to increase cerebral ß-amyloid clearance could constitute a novel preventive or therapeutic strategy for AD.

Drug interactions at the blood-brain barrier: fact or fantasy?

There is considerable interest in the therapeutic and adverse outcomes of drug interactions at the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). These include altered efficacy of drugs used in the treatment of CNS disorders, such as AIDS dementia and malignant tumors, and enhanced neurotoxicity of drugs that normally penetrate poorly into the brain. BBB- and BCSFB-mediated interactions are possible because these interfaces are not only passive anatomical barriers, but are also dynamic in that they express a variety of influx and efflux transporters and drug metabolizing enzymes. Based on studies in rodents, it has been widely postulated that efflux transporters play an important role at the human BBB in terms of drug delivery. Furthermore, it is assumed that chemical inhibition of transporters or their genetic ablation in rodents is predictive of the magnitude of interaction to be expected at the human BBB. However, studies in humans challenge this well-established paradigm and claim that such drug interactions will be lesser in magnitude but yet may be clinically significant. This review focuses on current known mechanisms of drug interactions at the blood-brain and blood-CSF barriers and the potential impact of such interactions in humans. We also explore whether such drug interactions can be predicted from preclinical studies. Defining the mechanisms and the impact of drug-drug interactions at the BBB is important for improving efficacy of drugs used in the treatment of CNS disorders while minimizing their toxicity as well as minimizing neurotoxicity of non-CNS drugs.

Verapamil P-glycoprotein transport across the rat blood-brain barrier: cyclosporine, a concentration inhibition analysis, and comparison with human data.

To predict the magnitude of P-glycoprotein (P-gp)-based drug interactions at the human blood-brain barrier (BBB), rodent studies are routinely conducted where P-gp is chemically inhibited. For such studies to be predictive of interactions at the human BBB, the plasma concentration of the P-gp inhibitor must be comparable with that observed in the clinic. Therefore, we determined the in vivo EC(50) of P-gp inhibition at the rat BBB using verapamil as a model P-gp substrate and cyclosporine A (CsA) as the model P-gp inhibitor. Under isoflurane anesthesia, male Sprague-Dawley rats were administered i.v. CsA to achieve pseudo steady-state CsA blood concentrations ranging from 0 to approximately 12 microM. Then, an i.v. tracer dose of [(3)H]verapamil was administered, and 20 min after verapamil administration, the animals were sacrificed for determination of blood, plasma, and brain (3)H radioactivity by scintillation counting. The percentage increase in the brain/blood (3)H radioactivity (relative to 0 microM CsA) was described by the Hill equation with E(max), 1290%; EC(50), 7.2 microM; and gamma, 3.8. Previously, using [(11)C]verapamil, we have shown that the human brain/blood (11)C radioactivity was increased by 79% at 2.8 microM CsA blood concentration. At an equivalent CsA blood concentration, the rat brain/blood (3)H radioactivity was increased by a remarkably similar extent of 75%. This is the first time that an in vivo CsA EC(50) of P-gp inhibition at the rat BBB has been determined and the magnitude of such inhibition was compared between the rat and the human BBB at the same blood CsA concentration.

Postoperative sedation after major surgery with midazolam or propofol in the ICU: effects on amnesia and anxiety.

BACKGROUND: Propofol and midazolam are commonly used in the ICU to alleviate physical and psychological disturbances in consequence of anxiety. This study was conducted to assess and compare the impact of postoperative sedation after major surgery with midazolam or propofol on amnesia and anxiety in conscious patients under intensive care. METHODS: One hundred and two adult patients irrespective of sex and age, receiving thoracic, abdominal or other major truncal surgery necessitating close care at the ICU, were randomly allocated into midazolam or propofol group. Prior to surgery, all patients were subjected to evaluation of the levels of anxiety and amnesia, which was repeated on the following morning with the level of anxiety and the level of amnesia assessed just before and 30 min after cessation of midazolam or propofol medication, respectively. RESULTS: There were no significant differences between the two groups regarding gender, age, types of analgesics used, and anxiety. In both groups, the levels of anxiety (P < 0.001) and amnesia (P < 0.001) were improved significantly over the following day. Midazolam had more pronounced effects on amnesia than propofol (P < 0.001). There were no significant differences between the two groups in the pre- or post-drug anxiety (P = 0.189). CONCLUSIONS: Both midazolam and propofol are effective amnesic and anxiolytic drugs. Midazolam tends to have more favorable effects on amnesia. It is speculated that combination of propofol and midazolam may give better results for treating critically ill ICU patients, the confirmation of which necessitates further study.