Pepsin and Its Importance for Functional Dyspepsia: Relic, Regulator or Remedy?

BACKGROUND: Functional dyspepsia is a heterogeneous disorder lacking an established therapeutic strategy. Historical treatment attempts with pepsin products were shrugged off, as a simple calculation shows that quantitative substitution is pointless. However, such attempts might have been right for the wrong reason. SUMMARY: Today, the role of pepsins is primarily seen in the provision of signalling amino acids (especially phenylalanine and tryptophan) and peptides, which initiate processes promoting digestion. Proteolysis benefits from pepsin variants showing, contrary to common belief, activities of up to a pH value of 5.0. Non-clinical and clinical studies support the view that liberated amino acids produce a variety of direct and indirect effects. Signal chains stimulated by (mostly aromatic) amino acids lead to secretion of gastrin and cholecystokinin (CCK), mediated, respectively, by CCK2 (gastrin) and Ca2+-sensing receptors in the parietal cell, and Ca2+-sensing receptors in the antral and duodenal mucosa. Thus, CCK effects such as secretion of pancreatic enzymes and promotion of gastric accommodation are (also) consequential to peptic liberation of amino acids. Key Message: As functional dyspepsia represents a heterogeneous disorder, it may be intriguing to view pepsin as a potential (although still to be proven) treatment modality, distinguished by a diversity of pro-digestive effects.

Constipation in older people: A consensus statement.

BACKGROUND AND AIMS: Chronic constipation is a serious medical condition that affects 30%-40% of people over 60 years old. Although not normally life threatening, constipation reduces quality of life by the same extent as diabetes and osteoarthritis. There are currently no Europe-wide guidelines for treating constipation in older people, although there is some country-level guidance for the general population. We have evaluated the existing guidance and best clinical practice to improve the care of older people with constipation. METHOD: European healthcare professionals working in gastroenterology, geriatrics, nursing and pharmacology discussed the treatment of constipation in older people and reviewed existing guidance on the treatment of constipation in the general population. This manuscript represents the consensus of all authors. DISCUSSION: Most general guidance for constipation treatment recommends increased dietary fibre, fluid intake and exercise; however, this is not always possible in older patients. Although a common first-line treatment, bulk-forming laxatives are unsuitable for older people because of an associated need to increase fluid intake, osmotic laxatives are likely to be the most suitable laxative type for older patients. Treatment is often hampered by reluctance to talk about bowel problems so healthcare providers should proactively identify older constipated patients who are self-medicating or not receiving treatment. CONCLUSIONS: With certain modifications, general treatment guidelines can be applied to older people with constipation, although specific guidelines are still required for this age group. Awareness of constipation, its complications and treatment options need to be increased among healthcare providers, patients and carers.

[Options in the treatment of hepatic encephalopathy]. / Therapeutische Optionen bei der hepatischen Enzephalopathie.

Hepatic encephalopathy is a result of insufficient liver function, with grave consequences for the patients. It is primarily caused by disturbed hepatic elimination of the neurotoxin, ammonia (NH3). Aside from dietetic measures, treatment rests on drugs designed to reduce the NH3 burden. The primary options, lactulose and the practically unabsorbable antibiotic rifaximin are suitable to decrease the bacterial NH3 generation in the intestine. Other antibiotics like neomycin at best have a place in acute treatment. L-ornithine-L-aspartate (LOLA) and branched-chain amino acids (valine, leucine, isoleucine) aim at supporting the scavenge of NH3 in glutamine; however, the final balance of this pathway is unfavourable. In addition, the constituents of LOLA enhance the capacity of the urea cycle and, ultimately, the elimination of NH3. As the evidence from available studies--is not unequivocal in each case, the current place of LOLA in treatment is that of an option for patients, who do not respond to standard therapy.

Solulin increases clot stability in whole blood from humans and dogs with hemophilia.

Solulin is a soluble form of thrombomodulin that is resistant to proteolysis and oxidation. It has been shown to increase the clot lysis time in factor VIII (fVIII)-deficient plasma by an activated thrombin-activatable fibrinolysis inhibitor (TAFIa)-dependent mechanism. In the present study, blood was drawn from humans and dogs with hemophilia, and thromboelastography was used to measure tissue factor-initiated fibrin formation and tissue-plasminogen activator-induced fibrinolysis. The kinetics of TAFI and protein C activation by the thrombin-Solulin complex were determined to describe the relative extent of anticoagulation and antifibrinolysis. In severe hemophilia A, clot stability increased by > 4-fold in the presence of Solulin while minimally affecting clot lysis time. Patients receiving fVIII/fIX prophylaxis showed a similar trend of increased clot stability in the presence of Solulin. The catalytic efficiencies of TAFI and protein C activation by the thrombin-Solulin complex were determined to be 1.53 and 0.02/µM/s, respectively, explaining its preference for antifibrinolysis over anticoagulation at low concentrations. Finally, hemophilic dogs given Solulin had improved clot strength in thromboelastography assays. In conclusion, the antifibrinolytic properties of Solulin are exhibited in hemophilic human (in vitro) and dog (in vivo/ex vivo) blood at low concentrations. Our findings suggest the therapeutic utility of Solulin at a range of very low doses.

Drug-Drug Interaction Potential of Remimazolam Mediated by CYP 450, Transporters, and Protein Binding.

BACKGROUND: The ultra-short-acting benzodiazepine, remimazolam, is a new treatment modality for procedural sedation and general anesthesia. Its activity is terminated by carboxylesterase 1 (CES1). OBJECTIVE: The objective of this study was to determine the drug-drug interaction (DDI) potential of remi-mazolam through mechanisms unrelated to its metabolizing enzyme, CES1. METHODS: Conventional in vitro co-exposure experiments were conducted to study possible interactions of remimazolam and its primary metabolite, CNS7054, mediated by competitive binding to plasma protein or competition for reactions with cytochrome P450 isoforms or drug transporters. RESULTS: No relevant interactions of remimazolam or its metabolite with cytochrome P450 (CYP) isoforms at clinically relevant concentrations were identified. Likewise, standard experiments revealed no clinically relevant interactions with drug transporters and plasma proteins. CONCLUSION: The present data and analyses suggest a very low potential of remimazolam for pharmacoki-netic DDIs mediated by CYP isoforms, drug transporters, and protein binding.

The Metabolism of the New Benzodiazepine Remimazolam.

BACKGROUND: Remimazolam (RMZ) is a novel ultrashort-acting benzodiazepine used for sedation by intravenous administration. The pharmacophore of RMZ includes a carboxyl ester group sensitive to esterase- mediated hydrolysis, which is the primary path of metabolic elimination. However, for the sake of drug safety, a deeper and broader knowledge of the involved metabolic pathways and the evolving metabolites is required. Information is needed on both humans and experimental animals to evaluate the possibility that humans form harmful metabolites not encountered in animal toxicity studies. OBJECTIVE: The current study aimed at identifying the mechanisms of remimazolam's metabolism and any potential clinically significant metabolites. METHOD: Using tissue homogenates from various animals and humans, the liver was identified as the tissue primarily responsible for the elimination of RMZ. CNS7054, the hydrolysis product of remimazolam, was identified as the only clinically relevant metabolite. Using bacterial or eukaryotic over-expression systems, carboxylesterase 1 (CES1) was identified as the iso-enzyme predominantly involved in RMZ metabolism, with no role for carboxylesterase 2. Using a variety of inhibitors of other esterases, the contribution to elimination mediated by esterases other than CES1 was excluded. RESULTS: Besides tissue carboxylesterases, rodents expressed an RMZ esterase in plasma, which was not present in this compartment in other laboratory animals and humans, hampering direct comparisons. Other pathways of metabolic elimination, such as oxidation and glucuronidation, also occurred, but their contribution to overall elimination was minimal. CONCLUSION: Besides the pharmacologically non-active metabolite CNS7054, no other clinically significant metabolite of remimazolam could be identified.

The case of drug causation of childhood asthma: antibiotics and paracetamol.

AIM: The rising prevalence of bronchial asthma has led to world-wide efforts to understand and stem this development. Cross-sectional studies appear to show that early childhood use of antibiotics may be an important contributory factor, with paracetamol as an additional suspected cause. However, mounting evidence, which is reviewed here, points to various confounding factors as the major reasons for these reported associations. METHODS: PubMed and EMBASE were systematically searched for studies on associations between antibiotics and/or paracetamol with asthma and/or wheezing, published up to November 2012. A total of 64 pertinent studies were identified, 35 focusing on antibiotics, 19 on paracetamol, and ten addressing both antibiotics and paracetamol, bringing the number of relevant datasets to 74. RESULTS: Numerous studies were cross-sectional and made no adjustment for the indication of antibiotics or paracetamol; consequently, they were unable to dismiss possible confounding by indication. Where such adjustments could be performed (mostly in longitudinal studies), they substantially weakened or entirely eliminated the association with asthma or asthma surrogates present in the unadjusted data. CONCLUSION: The weight of evidence of the collected studies in our review strongly suggests that the association of antibiotics with childhood asthma reflects various forms of bias, the most prominent of which is confounding by indication. Recent studies and meta-analyses support the same conclusion for paracetamol. Truly indicated antibiotics should not be withheld from infants or young children for fears they might develop asthma. Likewise, there is no sound reason to replace paracetamol as the preferred pain relief and fever medication in this age group.

Antibodies preventing the interaction of tissue-type plasminogen activator with N-methyl-D-aspartate receptors reduce stroke damages and extend the therapeutic window of thrombolysis.

BACKGROUND AND PURPOSE: Tissue-type plasminogen activator (tPA) is the only drug approved for the acute treatment of ischemic stroke but with two faces in the disease: beneficial fibrinolysis in the vasculature and damaging effects on the neurovascular unit and brain parenchyma. To improve this profile, we developed a novel strategy, relying on antibodies targeting the proneurotoxic effects of tPA. METHODS: After production and characterization of antibodies (αATD-NR1) that specifically prevent the interaction of tPA with the ATD-NR1 of N-methyl-d-aspartate receptors, we have evaluated their efficacy in a model of murine thromboembolic stroke with or without recombinant tPA-induced reperfusion, coupled to MRI, near-infrared fluorescence imaging, and behavior assessments. RESULTS: In vitro, αATD-NR1 prevented the proexcitotoxic effect of tPA without altering N-methyl-d-aspartate-induced neurotransmission. In vivo, after a single administration alone or with late recombinant tPA-induced thrombolysis, antibodies dramatically reduced brain injuries and blood-brain barrier leakage, thus improving long-term neurological outcome. CONCLUSIONS: Our strategy limits ischemic damages and extends the therapeutic window of tPA-driven thrombolysis. Thus, the prospect of this immunotherapy is an extension of the range of treatable patients.

Solulin reduces infarct volume and regulates gene-expression in transient middle cerebral artery occlusion in rats.

BACKGROUND: Thrombolysis after acute ischemic stroke has only proven to be beneficial in a subset of patients. The soluble recombinant analogue of human thrombomodulin, Solulin, was studied in an in vivo rat model of acute ischemic stroke. METHODS: Male SD rats were subjected to 2 hrs of transient middle cerebral artery occlusion (tMCAO). Rats treated with Solulin intravenously shortly before reperfusion were compared to rats receiving normal saline i.v. with respect to infarct volumes, neurological deficits and mortality. Gene expression of IL-6, IL-1ß, TNF-α, MMP-9, CD11B and GFAP were semiquantitatively analyzed by rtPCR of the penumbra. RESULTS: 24 hrs after reperfusion, rats were neurologically tested, euthanized and infarct volumes determined. Solulin significantly reduced mean total (p=0.001), cortical (p=0.002), and basal ganglia (p=0.036) infarct volumes. Hippocampal infarct volumes (p=0.191) were not significantly affected. Solulin significantly downregulated the expression of IL-1ß (79%; p<0.001), TNF-α (59%; p=0.001), IL-6 (47%; p=0.04), and CD11B (49%; p=0.001) in the infarcted cortex compared to controls. CONCLUSIONS: Solulin reduced mean total, cortical and basal ganglia infarct volumes and regulated a subset of cytokines and proteases after tMCAO suggesting the potency of this compound for therapeutic interventions.

[Evaluation of pharmacokinetic drug-drug-interactions. Critical considerations of the relevance of pharmacokinetic drug-drug interactions of proton pump inhibitors in self medication]. / Pharmakokinetische Interaktionen und ihre Beurteilung. Kritische Betrachtungen zur Relevanz von Interaktionen der Protonenpumpenhemmer Omeprazol und Pantoprazol in der Selbstmedikation.

Mechanisms and evaluation of pharmacokinetic drug interactions are discussed in general, including mechanisms beyond the hepatic phase-I reactions, and especially for the example of proton pump inhibitors (PPI), preferentially omeprazole. Particular attention is paid to the use of PPI as self-prescribed drugs. The sequelae of pharmacokinetic drug interactions can be serious. However, only the evidence of clinical consequences will convert such an interaction from a laboratory finding into a possible adverse effect. Without this, interacting drugs can still be co-administered if the specific characteristics of the concerned drugs, quantitative aspects of the interaction, and especially severity and frequency of possible clinical correlates are taken into consideration. It is encouraging that the laboratory findings reported for the PPI--in vitro or ex vivo from volunteer studies--have hardly found equivalents in clinical consequences. As of today, this is also true of the widely discussed interaction with clopidogrel. Regarding the safety of use of PPI as self-prescribed drugs, it also needs to be emphasized that a sizable number of interactions reported for omeprazole and/or pantoprazole were observed at higher dose levels than the 20 mg licensed for self medication. In conjunction with the temporal limitation of PPI self-prescription (14 days), it can be expected that pharmacokinetic drug interactions will generally be no critical factor in the usage of PPI in self-medication. However clinically relevant interactions can occur, e.g. when PPI are combined with extracts from St. John's wort, methotrexat or some inhibitors of HIV-protease with pH-dependent absorption.

The Role of Sphere Size in the Context of Pancreatin Therapy for Exocrine Pancreatic Insufficiency: A Systematic Review.

While lipase content and appropriate acid protection of pancreatin preparations (PP) are well defined determinants of an effective therapy of exocrine pancreatic insufficiency, the optimal sphere size of PP has remained a matter of discussion. We performed a systematic review to assess the optimal sphere size of enteric coated pancreatin products that may best guarantee coordinated delivery of PP and food to the duodenum. PubMed was searched for studies on gastric emptying of indigestible spheres in the digestive phase, using overlapping search algorithms; identified sources were searched for further leads, extending the investigation to Google Scholar. Of 739 screened publications, 26 were included in the final assessment. Contrary to current guideline recommendations, no scientific evidence was found to support a 2 mm diameter threshold for gastric emptying of indigestible particles. There is no documented advantage of ≤2 mm spheres regarding duodenal delivery and restoring maldigestion. The evolving picture is that of a gradation of sizes, over which gastric emptying becomes slower and more variable as particle size increases. Even 7 mm particles may be emptied from the stomach in conjunction with nutrient uptake. In conclusion sphere size of PP is not the essential parameter for selecting an effective PP fitting all patients. A variety of brands offer different lipase contents and sphere sizes that allow the physician to tailor treatment to the individual patient`s needs.

A miniature pig model of pharmacological tolerance to long-term sedation with the intravenous benzodiazepines; midazolam and remimazolam.

As a new and ultra fast-acting IV benzodiazepine, pharmacological tolerance may be anticipated during long-term treatment with remimazolam e.g. in intensive care. In this context, tolerance is particularly relevant for withdrawal syndrome. However, apart from primates, existing models of sedative tolerance are unsuitable for remimazolam due to its excessive metabolic clearance (i.e. in rodents) or paradoxical responses (in dogs). Pigs are a well-established model species, especially for in-vivo drug safety studies, and appear a well suited as model for evaluation of remimazolam. In a series of experiments from dose-range-finding bolus and infusion studies through to 28-day continuous level sedation, we established a viable model of intravenous benzodiazepine sedation in NIBS micropigs to compare tolerance development during 28 days sedation with either midazolam or remimazolam. Dose increases after 28 days were lower for remimazolam (0 to 3-fold) than for midazolam (2 to 4-fold) and recovery times were approximately 40% faster for remimazolam vs midazolam. Tolerance to remimazolam is therefore likely in long-term human sedation and may be less than that seen for midazolam.

Impact of concurrent remifentanil on the sedative effects of remimazolam, midazolam and propofol in cynomolgus monkeys.

Drug-drug interactions can substantially change pharmacological effects of the individual substances involved. For the use of sedatives or anaesthetics, having knowledge of the extent and characteristics of such interactions is crucial for ensuring the proper protection of patients undergoing any kind of sedation. Remimazolam is a new ultra-short acting benzodiazepine that is currently under development for intravenous use in procedural sedation and general anaesthesia. It exhibits a fast onset and fast offset which enables a more rapid recovery than currently available drugs in that class, such as midazolam. The purpose of this study was to more closely investigate the sedative properties and pharmacodynamic drug-drug interaction potential of remimazolam with the opioid analgesic remifentanil and compare it with other commonly used sedatives - midazolam and propofol. For this purpose, six Cynomolgus monkeys received escalating doses of remimazolam, propofol, and midazolam intravenously without or with concurrent remifentanil. Sedation was evaluated using a general sedation scale that included monitoring exploratory and avoidance behaviour, responses to sensory stimuli, posture and gait, and eyelid position as endpoints. Based on the results, sedative doses were calculated to allow evaluation of pharmacological drug-drug interaction with remifentanil. Remimazolam induced dose-dependent and consistent sedative effects in each endpoint tested and showed a high degree of synergism with remifentanil. Midazolam showed a comparable synergism while the interaction between propofol and remifentanil was less pronounced.

Time-to-Event Modeling for Remimazolam for the Indication of Induction and Maintenance of General Anesthesia.

Remimazolam is an ultra-short-acting benzodiazepine being investigated for induction and maintenance of general anesthesia and for procedural sedation. This dose-response analysis of 4 phase 2-3 studies evaluated covariates that may impact the pharmacodynamic profile (based on theoretical pharmacokinetic principles) and require dose adjustments in subpopulations, particularly elderly, and if remimazolam has cumulative properties. Covariates affecting the time to loss of consciousness and time to extubation were evaluated using Cox proportional hazards models. Factors affecting steady-state infusion rate required to produce adequate sedation were evaluated using linear regression. Variability in time to loss of consciousness was explained by induction dose, age, body mass index, and time from initiation of opioids to initiation of remimazolam. The steady-state infusion rate producing adequate sedation was higher in European than Japanese subjects due to differences in study design. American Society of Anesthesiologists physical status class 3 subjects had a 28% lower maintenance infusion rate than class 1 subjects. Other statistically significant covariates (American Society of Anesthesiologists class 2, estimated glomerular filtration rate, and sex) resulted in small (≤14%), non-clinically relevant differences. Factors affecting time to extubation included the last infusion rate (ie, tapering), the bispectral index score at the end of infusion, and sex. The time to extubation after remimazolam did not increase with increased cumulative dose of remimazolam or duration of surgery. This evaluation of remimazolam's pharmacodynamic profile, in the absence of pharmacokinetic data, informed dosing recommendations and showed that remimazolam does not have cumulative properties in the general anesthesia setting.

Population pharmacokinetic/pharmacodynamic modeling for remimazolam in the induction and maintenance of general anesthesia in healthy subjects and in surgical subjects.

STUDY OBJECTIVE: To evaluate factors affecting variability in response to remimazolam in general anesthesia. DESIGN: Plasma concentration-time data from 11 Phase 1-3 clinical trials were pooled for the population pharmacokinetic (popPK) analysis and concentration-bispectral index (BIS) data were pooled from 8 trials for popPK-PD analysis. A 3-compartment model with allometric exponents on clearance and volume described remimazolam concentrations over time. An effect compartment model with an inhibitory sigmoid Emax model was fit to the concentration-BIS data. Simulations were performed to assess sedation in general anesthesia and post-surgical sedation in healthy and sensitive populations. SETTING: General anesthesia and post-surgical sedation. PATIENTS: 689 subjects included in popPK and 604 subjects included in popPK-PD. Most subjects (>85%) were ASA Class 1 or 2, with the remaining subjects being ASA Class 3. INTERVENTIONS: Serial plasma concentrations and BIS scores. MEASUREMENTS: Standard intra-operative monitoring. MAIN RESULTS: PopPK model included an effect of extracorporeal circulation, ASA class, and sex on PK and a time-dependent clearance (~30% lower at 24 h) that was not related to cumulative dose. Co-administered remifentanil had a synergistic decrease in BIS with remimazolam. Remimazolam IC50 increased with cumulative dose. Onset was faster in overweight subjects and slower in Asian subjects. If using a weight-based regimen, simulations showed that remimazolam 6 mg/kg/h until loss of consciousness followed by 1 mg/kg/h during general anesthesia and 0.25 mg/kg/h for post-surgical sedation for up to 24 h is optimal, regardless of ASA class or sensitivity of subjects. CONCLUSIONS: If using a weight-based regimen, results illustrated an appropriate regimen of remimazolam for general anesthesia and post-surgical sedation in general and sensitive populations, although lower doses can be considered in elderly patients with a significant disease burden or in ASA Class 3 patients. The time-dependent change in clearance is not clinically relevant for up to 24 h.

Metabolism of remimazolam in primary human hepatocytes during continuous long-term infusion in a 3-D bioreactor system.

BACKGROUND: Remimazolam is an ultra-short acting benzodiazepine under development for procedural sedation and general anesthesia. It is hydrolyzed by CES1 to an inactive metabolite (CNS7054). PURPOSE: In this study, the effect of continuous remimazolam exposure on its metabolism and on CES1 expression was investigated in a dynamic 3-D bioreactor culture model inoculated with primary human hepatocytes. METHODS: Remimazolam was continuously infused into bioreactors for 5 days at a final concentration of 3,000 ng/ml (6.8 µM). In parallel, 2-D cultures were run with cells from the same donors, but with discontinuous exposure to remimazolam. RESULTS: Daily measurement of clinical chemistry parameters (glucose, lactate, urea, ammonia, and liver enzymes) in culture supernatants indicated no noxious effect of remimazolam on hepatocyte integrity as compared to untreated controls. Concentrations of remimazolam reached steady-state values of around 250 ng/ml within 8 hours in 3-D bioreactors whereas in 2-D cultures remimazolam concentrations declined to almost zero within the same time frame. Levels of CNS7054 showed an inverse time-course reaching average values of 1,350 ng/ml in perfused 3-D bioreactors resp. 2,800 ng/ml in static 2-D cultures. Analysis of mRNA expression levels of CES1 indicated no changes in gene expression over the culture period. CONCLUSION: The results indicated a stable metabolism of remimazolam during 5 days of continuous exposure to clinically relevant concentrations of the drug. Moreover, there was no evidence for a harmful effect of remimazolam exposure on the integrity and metabolic activity of in vitro cultivated primary human hepatocytes.

Toward safer thrombolytic agents in stroke: molecular requirements for NMDA receptor-mediated neurotoxicity.

Current thrombolytic therapy for acute ischemic stroke with tissue-type plasminogen activator (tPA) has clear global benefits. Nevertheless, evidences argue that in addition to its prohemorrhagic effect, tPA might enhance excitotoxic necrosis. In the brain parenchyma, tPA, by binding to and then cleaving the amino-terminal domain (ATD) of the NR1 subunit of N-methyl-D-aspartate (NMDA) glutamate receptors, increases calcium influx to toxic levels. We show here that tPA binds the ATD of the NR1 subunit by a two-sites system (K(D)=24 nmol/L). Although tenecteplase (TNK) and reteplase also display two-sites binding profiles, the catalytically inactive mutant TNKS478A displays a one-site binding profile and desmoteplase (DSPA), a kringle 2 (K2) domain-free plasminogen activator derived from vampire bat, does not interact with NR1. Moreover, we show that in contrast to tPA, DSPA does not promote excitotoxicity. These findings, together with three-dimensional (3D) modeling, show that a critical step for interaction of tPA with NR1 is the binding of its K2 domain, followed by the binding of its catalytic domain, which in turn cleaves the NR1 subunit at its ATD, leading to a subsequent potentiation of NMDA-induced calcium influx and neurotoxicity. This could help design safer new generation thrombolytic agents for stroke treatment.

Recombinant Desmodus rotundus salivary plasminogen activator crosses the blood-brain barrier through a low-density lipoprotein receptor-related protein-dependent mechanism without exerting neurotoxic effects.

BACKGROUND AND PURPOSE: Desmoteplase, a recombinant form of the plasminogen activator DSPAalpha1 from Desmodus rotundus, may offer improved clinical benefits for acute ischemic stroke treatment over the current therapy, recombinant tissue plasminogen activator (rtPA). Accumulating evidence suggests that clinical use of rtPA could be limited by unfavorable properties, including its ability to cross the blood-brain barrier (BBB), thus potentially adding to the pro-excitotoxic effect of endogenous tPA in cerebral parenchyma. Here, to investigate whether desmoteplase may display a safer profile than the structurally-related tPA, both agents were compared for their ability to cross the BBB and promote neurotoxicity. METHODS: First, the passage of vascular DSPA and rtPA was investigated in vitro in a model of BBB, subjected or not to oxygen and glucose deprivation. Second, we studied DSPA- and rtPA-mediated effects in an in vivo paradigm of excitotoxic necrosis. RESULTS: The rtPA and desmoteplase cross the intact BBB by LRP-mediated transcytosis. Under conditions of oxygen and glucose deprivation, translocation rates of both compounds increased; however, unlike rtPA, desmoteplase transport remained LRP-dependent. Additionally, neither intracerebral nor intravenous desmoteplase administration enhanced NMDA-induced excitotoxic striatal damage in vivo. Interestingly, intravenous but not intrastriatal coadministration of desmoteplase and rtPA reduced the pro-excitotoxic effect of rtPA. CONCLUSIONS: We show that desmoteplase crosses the BBB but does not promote neuronal death. Moreover, intravenous administration of desmoteplase antagonizes the neurotoxicity induced by vascular rtPA. This action may be caused by competition of desmoteplase with rtPA for LRP binding at the BBB, thus effectively blocking rtPA access to the brain parenchyma.