Comparison of pharmacokinetic properties of alteplase and tenecteplase. The future of thrombolysis in acute ischemic stroke.

INTRODUCTION: The drug most frequently used for thrombolysis in cases of acute ischemic stroke (AIS) is alteplase. However, there is moderate-to-high-quality evidence that tenecteplase has similar or higher efficacy and safety. With improved pharmacokinetic properties over alteplase, tenecteplase could be a significant advantage in treating AIS. AREAS COVERED: After conducting an extensive search on Scopus and PubMed, this manuscript reviews and compares the pharmacokinetic properties of alteplase and tenecteplase. Additionally, it provides information on pharmacodynamics, clinical efficacy, safety, tolerability, and drug-drug interactions. EXPERT OPINION: The pharmacokinetic profile of alteplase and tenecteplase is derived from studies in patients with acute myocardial infarction. Thanks to its pharmacokinetic properties, tenecteplase is the drug closest to being the ideal fibrinolytic for AIS. Its longer half-life enables a single-bolus administration, which is particularly useful in emergencies. Tenecteplase has proven to have a good efficacy and safety profile in randomized clinical trials. Although we are awaiting the results of the ongoing phase 3 randomized clinical trials, we believe that tenecteplase has the potential to revolutionize the treatment of AIS through thrombolysis.

Tenecteplase for thrombolysis in stroke patients: Systematic review with meta-analysis.

INTRODUCTION: Alteplase is an approved treatment for acute ischemic stroke. Tenecteplase is a genetically modified form of alteplase, with lower cost and a more favourable pharmacokinetic profile allowing bolus injection. The aim of this study was to compare both drugs in adult patients with acute ischemic stroke undergoing thrombolysis. MATERIAL AND METHODS: PubMed and CENTRAL were searched for observational and experimental studies comparing both drugs in the population of interest. Additional studies were sought in clinical trial registries and by means of reference check. The efficacy outcomes of interest were functional status at 3 months, recanalization and early neurological improvement (ENI). The safety outcomes of interest were cerebral haemorrhage (ICH), symptomatic ICH and mortality. The effect measure of interest was the absolute risk difference (ARD). Effect measures for each outcome were pooled across studies using random effect models. RESULTS: Eight studies were included, involving 2031 patients. Overall, there were no differences in terms of good or excellent functional outcome (ARR = 0.07 and 0.03 respectively, p > 0.05 for both comparisons) but tenecteplase patients showed higher rates of recanalization (ARD = 0.11, 95% CI [0.01;0.20]) and ENI (ARD = 0.10, 95% CI [0.02;0.17]). There were no differences between groups in terms of ICH (ARD = -0.02, 95% CI [-0.06;0.01]), symptomatic ICH (ARD = 0.00, 95% CI [-0.01;0.02]) or death (ARD = 0.00, 95% CI [-0.03;0.03]). CONCLUSION: Tenecteplase is an alternative to alteplase for stroke thrombolysis, with lower cost and a more favourable pharmacokinetic profile.

Tenecteplase vs Alteplase Before Endovascular Therapy in Basilar Artery Occlusion.

OBJECTIVE: To investigate the efficacy of tenecteplase (TNK), a genetically modified variant of alteplase with greater fibrin specificity and longer half-life than alteplase, prior to endovascular thrombectomy (EVT) in patients with basilar artery occlusion (BAO). METHODS: To determine whether TNK is associated with better reperfusion rates than alteplase prior to EVT in BAO, clinical and procedural data of consecutive patients with BAO from the Basilar Artery Treatment and Management (BATMAN) registry and the Tenecteplase vs Alteplase before Endovascular Therapy for Ischemic Stroke (EXTEND-IA TNK) trial were retrospectively analyzed. Reperfusion >50% or absence of retrievable thrombus at the time of the initial angiogram was evaluated. RESULTS: We included 110 patients with BAO treated with IV thrombolysis prior to EVT (mean age 69 [SD 14] years; median NIH Stroke Scale score 16 [interquartile range (IQR) 7-32]). Nineteen patients were thrombolysed with TNK (0.25 mg/kg or 0.40 mg/kg) and 91 with alteplase (0.9 mg/kg). Reperfusion >50% occurred in 26% (n = 5/19) of patients thrombolysed with TNK vs 7% (n = 6/91) thrombolysed with alteplase (risk ratio 4.0, 95% confidence interval 1.3-12; p = 0.02), despite shorter thrombolysis to arterial puncture time in the TNK-treated patients (48 [IQR 40-71] minutes) vs alteplase-treated patients (110 [IQR 51-185] minutes; p = 0.004). No difference in symptomatic intracranial hemorrhage was observed (0/19 [0%] TNK, 1/91 [1%] alteplase; p = 0.9). CONCLUSIONS: TNK may be associated with an increased rate of reperfusion in comparison with alteplase before EVT in BAO. Randomized controlled trials to compare TNK with alteplase in patients with BAO are warranted. CLINICALTRIALSGOV IDENTIFIERS: NCT02388061 and NCT03340493. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that TNK leads to higher reperfusion rates in comparison with alteplase prior to EVT in patients with BAO.

Recombinant Tissue Plasminogen Activator-conjugated Nanoparticles Effectively Targets Thrombolysis in a Rat Model of Middle Cerebral Artery Occlusion.

The efficacy and safety of recombinant tissue plasminogen activator (rtPA) need to be improved due to its low bioavailability and requirement of large dose administration. The purpose of this study was to develop a fibrin-targeted nanoparticle (NP) drug delivery system for thrombosis combination therapy. We conjugated rtPA to poly(ethylene glycol)- poly(e-caprolactone) (PEG-PCL) nanoparticles (rtPA-NP) and investigated its physicochemical characteristics such as particle size, zeta potential, enzyme activity of conjugated rtPA and its storage stability at 4°C. The thrombolytic activity of rtPA-NP was evaluated in vitro and in vivo as well as the half-life of rtPA-NP, the properties to fibrin targeting and its influences on systemic hemostasis in vivo. The results showed that rtPA-NP equivalent to 10% of a typical dose of rtPA could dissolve fibrin clots and were demonstrated to have a neuroprotective effect after focal cerebral ischemia as evidenced by decreased infarct volume and improved neurological deficit (P<0.001). RtPA-NP did not influence the in vivo hemostasis or coagulation system. The half-life of conjugated rtPA was shown to be approximately 18 times longer than that of free rtPA. These experiments suggested that rtPA-conjugated PEG-PCL nanoparticles might be a promising fibrin-targeted delivery system for a combination treatment of thrombosis.

Retinal Penetration of Intravitreally Injected Tissue Plasminogen Activator: A Rat Model Study.

PURPOSE: To determine whether intravitreal unconjugated tissue plasminogen activator (tPA) (alteplase) can penetrate the intact neural retina and reach the subretinal space in an experimental model. METHODS: This study was performed in 24 Sprague-Dawley rats aged 12 weeks. Under general anesthesia, the right eye was injected with either 0.75 µg of 3 µL tPA (14 rats; study group) or saline (10 rats, control group) into the vitreous. Animals were euthanized at 3, 24, and 48 h. The eyes were enucleated, and cryosections were prepared for immunofluorescence staining. Goat anti-tPA antibody was used to detect tPA. RESULTS: In the study group, staining for tPA was detected in the deep retinal layers in all eyes. The staining was deeper and more intense at 3 and 24 h than at 48 h. There was no tPA staining in the retina of eyes injected with saline. CONCLUSIONS: This experimental study shows that unconjugated tPA administered into the vitreous is capable of penetrating the deep retinal layers and the subretinal space. These findings suggest that further clinical research is warranted on the benefits of intravitreal tPA in the treatment of submacular hemorrhage.

A Role for Low Density Lipoprotein Receptor-Related Protein 1 in the Cellular Uptake of Tissue Plasminogen Activator in the Lungs.

PURPOSE: To gain knowledge of lung clearance mechanisms of inhaled tissue plasminogen activator (tPA). METHODS: Using an in vivo mouse model and ex vivo murine whole organ cell suspensions, we examined the capability of the lungs to utilize LRP1 receptor-mediated endocytosis (RME) for the uptake of exogenous tPA with and without an LRP1 inhibitor, receptor associated protein (RAP), and quantitatively compared it to the liver. We also used a novel imaging technique to assess the amount LRP1 in sections of mouse liver and lung. RESULTS: Following intratracheal administration, tPA concentrations in the bronchoalveolar lavage fluid (BALF) declined over time following two-compartment pharmacokinetics suggestive of a RME clearance mechanism. Ex vivo studies showed that lung and liver cells are similarly capable of tPA uptake via LRP1 RME which was reduced by ~50% by RAP. The comparable lung and liver uptake of tPA is likely due to equivalent amounts of LRP1 of which there was an abundance in the alveolar epithelium. CONCLUSIONS: Our findings indicate that LRP1 RME is a candidate clearance mechanism for inhaled tPA which has implications for the development of safe and effective dosing regimens of inhaled tPA for the treatment of plastic bronchitis and other fibrin-inflammatory airway diseases in which inhaled tPA may have utility.

Towards a multi-physics modelling framework for thrombolysis under the influence of blood flow.

Thrombolytic therapy is an effective means of treating thromboembolic diseases but can also give rise to life-threatening side effects. The infusion of a high drug concentration can provoke internal bleeding while an insufficient dose can lead to artery reocclusion. It is hoped that mathematical modelling of the process of clot lysis can lead to a better understanding and improvement of thrombolytic therapy. To this end, a multi-physics continuum model has been developed to simulate the dissolution of clot over time upon the addition of tissue plasminogen activator (tPA). The transport of tPA and other lytic proteins is modelled by a set of reaction-diffusion-convection equations, while blood flow is described by volume-averaged continuity and momentum equations. The clot is modelled as a fibrous porous medium with its properties being determined as a function of the fibrin fibre radius and voidage of the clot. A unique feature of the model is that it is capable of simulating the entire lytic process from the initial phase of lysis of an occlusive thrombus (diffusion-limited transport), the process of recanalization, to post-canalization thrombolysis under the influence of convective blood flow. The model has been used to examine the dissolution of a fully occluding clot in a simplified artery at different pressure drops. Our predicted lytic front velocities during the initial stage of lysis agree well with experimental and computational results reported by others. Following canalization, clot lysis patterns are strongly influenced by local flow patterns, which are symmetric at low pressure drops, but asymmetric at higher pressure drops, which give rise to larger recirculation regions and extended areas of intense drug accumulation.

Therapeutic Potential of Tenecteplase in the Management of Acute Ischemic Stroke.

Given that alteplase has been the only approved thrombolytic agent for acute ischemic stroke for almost two decades, there has been intense interest in more potent and safer agents over the last few years. Tenecteplase is a bioengineered mutation of alteplase with advantageous pharmacodynamics and pharmacokinetics. The superiority of tenecteplase over alteplase has been proven by in vitro and animal studies, and it was approved for use in myocardial infarction more than a decade ago. In patients with acute ischemic stroke, tenecteplase has shown promise in randomized phase II trials and the drug is currently being tested in four phase III clinical trials that will start delivering definite results in the near future: NOR-TEST (NCT01949948), TASTE (ACTRN12613000243718), TEMPO-2 (NCT02398656), and TALISMAN (NCT02180204).

How to manage thrombolysis interruptions in acute stroke?

OBJECTIVES: Tissue plasminogen activator (t-PA) is the only approved thrombolytic therapy for the treatment of stroke patients. Its effectiveness is highly time dependent because of the sensitivity of brain tissue to ischemia. Because of the short half-life of t-PA, it should be administered as a bolus followed by an immediate infusion. However, in clinical practice, there are sometimes delays between the application of the bolus and the start of the infusion; in addition, interruptions of the infusion may occur. There are no recommendations regarding how to handle such situations. METHODS: We simulate the effects on serum t-PA concentrations of different delays in administering t-PA using its known pharmacokinetic parameters in a 2-compartment model. RESULTS: Our results demonstrate that even short delays of only 1 minute between bolus and infusion severely affect serum t-PA concentrations. In addition, interruptions to the infusion that are over 1 minute in duration affect serum t-PA concentrations. CONCLUSIONS: These results strongly suggest avoiding bolus-infusion delays by giving the bolus only when the infusion is ready. In case of a delayed start of the infusion, the possibilities are restricted to do nothing or to give a second bolus. We have estimated the dosing of the second bolus depending on the duration of the delay/interruption to allow for the achievement of appropriate serum t-PA concentrations. However, clinical safety data are needed to recommend the application of a second bolus.

Impact of alcohol consumption on the outcome of ischemic stroke and thrombolysis: role of the hepatic clearance of tissue-type plasminogen activator.

BACKGROUND AND PURPOSE: Tissue-type plasminogen activator (tPA) is the only acute treatment for ischemic stroke. Unfortunately, the benefit of tPA-driven thrombolysis is not systematic, and understanding the reasons for this is mandatory. The balance between beneficial and detrimental effects of tPA might explain the limited overall efficiency of thrombolysis. Here, we investigated whether this balance could be influenced by excessive alcohol intake. METHODS: We used a murine model of thromboembolic stroke, coupled to an array of biochemical assays, near-infrared or magnetic resonance imaging scans, 2-photon microscopy, hydrodynamic transfections, and immunohistological techniques. RESULTS: We found that 6 weeks of alcohol consumption (10% in drinking water) worsens ischemic lesions and cancels the beneficial effects of tPA-induced thrombolysis. We accumulate in vivo and in vitro evidence showing that this aggravation is correlated with a decrease in lipoprotein receptor-related protein 1-mediated hepatic clearance of tPA in alcohol-exposed mice. CONCLUSIONS: An efficient liver-driven clearance of tPA might influence the safety of thrombolysis after stroke.

Pharmacokinetics and Pharmacodynamics of Tissue Plasminogen Activator Administered Through an External Ventricular Drain.

BACKGROUND: Intraventricular hemorrhage (IVH) frequently complicates spontaneous intracerebral or subarachnoid hemorrhage (SAH). Administration of intraventricular tissue plasminogen activator (TPA) accelerates blood clearance, but optimal dosing has not been clarified. Using a standardized TPA dose, we assessed peak cerebrospinal fluid (CSF) TPA concentrations, the rate at which TPA clears, and the relationship between TPA concentration and biological activity. METHODS: Twelve patients with aneurysmal SAH and IVH, treated with endovascular coiling and ventricular drainage, were randomized to receive either 2 mg intraventricular TPA or placebo every 12 h (five doses). CT scans were performed 12, 48, and 72 h after initial administration, and blood was quantified using the SAH Sum and IVH Scores. CSF TPA and fibrin degradation product (D-dimer) concentrations were measured at baseline and 1, 6, and 12 h after the first dose using ELISA assays. RESULTS: Median CSF TPA concentrations in seven TPA-treated patients were 525 (IQR 352-2129), 323 (233-413), and 47 (29-283) ng/ml, respectively, at 1, 6, and 12 h after drug administration. Peak concentrations varied markedly (401-8398 ng/ml). Two patients still had slightly elevated levels (283-285 ng/ml) when the second dose was due after 12 h. There was no significant correlation between the magnitude of CSF TPA elevation and the rate of blood clearance or degree of D-dimer elevation. D-dimer peaked at 6 h, had declined by 12 h, and correlated strongly with radiographic IVH clearance (r = 0.82, p = 0.02). CONCLUSIONS: The pharmacokinetics of intraventricular TPA administration varies between individual patients. TPA dose does not need to exceed 2 mg. The optimal administration interval is every 8-12 h.

The influence of bolus to infusion delays on plasma Tissue Plasminogen Activator levels.

BACKGROUND: Estimates of neuronal loss in acute ischemic stroke show that the typical patient may lose 1·9 million neurons each minute that treatment is delayed. Consequently, significant emphasis has been placed on early evaluation and thrombolysis with tissue plasminogen activator (TPA), the only approved thrombolytic therapy. TPA should be administered as a bolus followed by an immediate infusion because of its short half life. However, in the real life clinical situation, delays in starting the infusion after the bolus can occur. Similarly, once infusion has started, interruptions in the infusion of TPA can also occur. These scenarios may result in lower serum concentrations which could decrease the effectiveness of thrombolysis. We sought to simulate, the influence of bolus infusion delays and also the influence of different intervals of interruptions in the infusion of TPA on serum TPA concentrations. METHODS: We simulated the effect of multiple intervals of delay after the bolus on serum TPA concentrations using known pharmacokinetics parameters of TPA. The effect of different intervals of interruptions in the infusion of TPA was also determined. The effect of rebolusing with TPA on serum concentrations in the event of significant bolus to infusion delays or significant infusion interruption was also simulated. RESULTS: Our data show that delays in starting the infusion may have significant effects on serum TPA concentrations. After the initial bolus, there is a rapid decrease in serum TPA concentrations unless the infusion is started immediately. Greater than 5 min delays in starting the infusion results in a slow gradual increase in serum TPA levels and levels stay well below the target concentrations for significant periods of time. Similarly, interruptions in the infusion of TPA lasting longer than 5 min can also significantly influence TPA levels. Rebolusing with TPA in these scenarios rapidly restores TPA levels to target concentrations. CONCLUSION: Because of its short half life, TPA should be administered as a bolus followed by an immediate infusion. Bolus to infusion delays or interruptions in the infusion of TPA after the bolus may significantly impact serum TPA levels and may reduce the efficacy of thrombolysis. Protocols or administration regimens should be employed to prevent delays or interruptions in the infusion. When delays do occur, rebolusing of TPA may be needed to rapidly restore TPA to target levels.

Pharmacokinetics and thrombolytic effects of the recombinant tissue-type plasminogen activator in horses.

BACKGROUND: To test the efficacy of the recombinant tissue-type plasminogen activator (rt-PA) alteplase in horses, the thrombolytic effect was tested in in vitro generated equine thrombi. The extent of lysis was determined by measuring the decrease in thrombi weight over a period of 4 hours. In vivo pharmacokinetics of alteplase were determined in 6 healthy horses. A single dose (1 mg/kg) was applied via intravenous infusion over a period of 30 minutes Coagulation-related variables, blood count and clinical parameters were taken before the treatment and until 48 h after treatment. In addition, plasma rt-PA concentration was measured until 300 min after commencing the infusion. RESULTS: In vitro, a dose dependent decrease of thrombus weight ranging from a 56 (± 6.5) % decrease for 0.5 µg/ml to 92 (± 2.1) % decrease for 5 µg/ml rt-PA was noted. The D-dimer concentration in the lysis medium correspondingly increased from 0.10 up to 10.8 mg/l. In vivo, none of the horses showed an adverse reaction to the alteplase infusion. In some horses blood parameters were slightly altered. The 1 mg/kg dose yielded the following pharmacokinetic parameters: Cmax = 1.25 ± 0.27 µg/ml; CL = 21.46 ± 5.67 ml/min/kg; dominant half life (t1/2α) = 6.81 ± 1.48 minutes; median elimination half life (t1/2ß) = 171 min (range: 85­1061); AUC = 50.33 ± 17.62 µg · min /ml. CONCLUSION: These findings indicate that a single dose of 1 mg/kg alteplase results in rt-PA plasma concentrations comparable to those in humans and might be sufficient for a thrombolytic therapy in horses. Further studies must be performed to determine the alteplase effectiveness in horses with jugular vein thrombosis.

Serendipitous recanalization of basilar artery occlusion.

OBJECTIVE: To describe a case of recanalization of a basilar artery occlusion with intravenous (IV) tenecteplase. CASE: A 74-year-old man with a history of cardiomyopathy presented to an outside hospital with acute vertigo, dysarthria, gaze deviation, and ataxia. Computerized tomography arteriography demonstrated occlusion of the proximal basilar artery. IV tissue plasminogen activator was ordered; however, the patient received a cardiac dose of IV tenecteplase. The patient was transferred to our facility, whereby symptoms resolved, and repeat computerized tomography arteriography displayed recanalization of the basilar artery. CONCLUSIONS: Tenecteplase has enhanced biochemical and pharmacokinetic properties that may be ideal for treatment of basilar artery occlusion and should be further investigated in a randomized clinical trial.

Intravitreal tenecteplase (metalyse) for acute management of retinal vein occlusions.

PURPOSE: To determine the ability of an intravitreal injection of tenecteplase (TNK) to penetrate an intraretinal venous thrombus and its effectiveness in thrombolysis in a porcine model of branch retinal vein occlusion (BRVO). METHODS: Six pigs (group 1) were anesthetized, and a BRVO was induced photothrombotically in the left eye; immediately afterward, fluorescence-conjugated TNK (100 µg) was injected into both eyes, with enucleation at 24 hours. Retinal penetration was assessed on frozen sections by epifluorescence microscopy. A further six pigs (group 2) were anesthetized; BRVO was induced in both eyes, and TNK was injected into the vitreous in the left eye. Both eyes were harvested a week later. The area of the lasered site and an area away from the burn were dissected and processed in epoxy resin and stained for light or transmission electron microscopy. The percentage blockage, clot volume, cytostructure, and extent of thrombolysis by TNK were assessed. RESULTS: TNK penetrated the veins in both eyes of group 1 pigs, with more intense staining in the eyes with the occlusion. In group 2 eyes, thrombolysis was significant in the eyes injected with TNK (P = 0.03); blockage was seen in all six untreated eyes and one treated eye. Clot volume was significantly higher in untreated eyes (P = 0.028). Percentage blockage varied from 8.5% to 83.9%. Damage by TNK to the neural retina was not seen. There was no significant difference in cytostructure between treated and untreated eyes (P = 0.357). CONCLUSIONS: TNK was able to penetrate the retinal veins with and without an occlusion and effect lysis of BRVO, and did not cause damage to the retinal tissue. Intravitreal TNK may be useful as an acute treatment for RVOs of recent onset.

Evolución y respuesta al tratamiento intravenoso con activador del plasminógeno tisular en relación con el hospital de derivación. Experiencia de una unidad de ictus de referencia / Development and response to intravenous treatment with tissue plasminogen activator with regard to referral hospitals. The experience of a stroke referral unit

Introducción. La administración del activador del plasminógeno tisular por vía intravenosa constituye un tratamiento seguro y eficaz en pacientes con un ictus isquémico agudo. El pronóstico depende de múltiples factores, siendo el intervalode tiempo desde el inicio del ictus hasta su administración uno de los de mayor impacto. Pacientes y métodos. Estudio prospectivo observacional de los pacientes que recibieron fibrinólisis intravenosa en nuestra unidad de ictus entre junio de 2007 y diciembre de 2010. Los pacientes se dividieron en dos grupos: los que acudieron directamente a urgencias de nuestro hospital y los que fueron derivados desde otros centros hospitalarios de Extremadura. Se compararon las características basales, la respuesta al tratamiento y la evolución entre ambos grupos. Resultados. Los pacientes que procedían de fuera de nuestra área de salud se caracterizaban por ser mayoritariamente varones, con ictus tipo TACI, y presentaban una mayor puntuación en la National Institutes of Health Stroke Scale (NIHSS).El tiempo hasta la administración de la fibrinólisis fue menor en los pacientes de nuestra área de salud. La NIHSS al alta fue mayor en pacientes que venían de otra área de salud, pero no hubo diferencias en la escala Rankin a los tres mesesni en la mortalidad. Conclusiones. Los pacientes sometidos a fibrinólisis que provienen de otro centro hospitalario obtienen al alta una puntuaciónen la NIHSS mayor. Esto probablemente se debe a un sesgo en la selección de los pacientes, derivando mayoritariamentevarones, con una peor situación clínica al ingreso y que reciben el tratamiento en un período significativamente mayor desde el inicio de los síntomas (AU)

Introduction. The intravenous administration of tissue plasminogen inhibitor is a safe and effective treatment for patients with an acute ischaemic stroke. The prognosis depends on a number of factors, the time that elapses between the onsetof the stroke and its administration being one of those with the greatest impact. Patients and methods. This is a prospective observational study of the patients who received intravenous fibrinolysis in our stroke unit between June 2007 and December 2010. The patients were divided into two groups, a distinction being made between those who went directly to A&E at our hospital and those who were referred from other hospitals in Extremadura. The baseline characteristics, response to treatment and development in each group were compared. Results. The patients who came from outside our health district were mainly males, with a TACI-type stroke and theypresented higher scores on the National Institutes of Health Stroke Scale (NIHSS). The time elapsed prior to administration of the fibrinolysis was shorter in the patients from our health district. The NIHSS score on discharge was higher in patientswho came from another health district, but there were no differences in the Rankin scale at three months or in themortality rate. Conclusions. Patients submitted to fibrinolysis who come from another hospital score higher on the NIHSS on discharge.This is probably due to a bias in the selection of the patients, since those referred are mainly males, who have a poorer clinical situation on admission and receive treatment in a significantly longer time interval following the onset of symptoms (AU)

Pharmacokinetics of alteplase in the treatment of ischaemic stroke.

INTRODUCTION: Alteplase is the only approved drug for thrombolysis in acute ischaemic stroke (AIS) after its initial use in acute myocardial infarction (AMI). Its role in functional recovery is time-dependent while its major adverse effect, intracranial haemorrhage, is dose-dependent. These underline the importance of the pharmacokinetics of alteplase to its clinical use. AREAS COVERED: The authors discuss the pharmacology of alteplase with a major focus on its pharmacokinetics based on literature obtained from the OVID electronic database and other institutional resources. EXPERT OPINION: The pharmacokinetic profile of alteplase is almost entirely derived from studies in AMI. Differences in the pathophysiology of AMI and AIS mean it cannot be assumed that the pharmacokinetics of alteplase is similar in these two populations. During AMI, cardiac function and, hence, hepatic perfusion and clearance of alteplase may be impaired. The relatively older population in AIS may have impaired metabolic clearance which may increase plasma concentrations. The concurrent use of medications such as nitrates in the management of elevated blood pressure during AIS thrombolysis is also associated with reduced plasma concentrations of alteplase. Again, differences in clot size and type between AMI and AIS and between subtypes of AIS may influence response to alteplase. There is an inherently higher risk of intracranial haemorrhage in AIS compared to AMI emanating from cerebral infarction and BBB disruption. Accordingly, stroke-specific pharmacokinetics of alteplase and its relationship to efficacy and safety outcomes are required.

Ultrasound-responsive thrombus treatment with zinc-stabilized gelatin nano-complexes of tissue-type plasminogen activator.

This study is undertaken to design zinc-stabilized gelatin nano-complexes of tissue-type plasminogen activator (t-PA) for thrombolytic therapy where the t-PA activity can be recovered in the blood circulation upon ultrasound irradiation. Various molecular weights of gelatin were complexed with t-PA by their simply mixing in aqueous solution. Then, zinc acetate, calcium acetate or magnesium acetate was added to form nano-sized gelatin-t-PA complexes. The complexes had the apparent molecular size of about 100 nm. When zinc ions were added to the gelatin-t-PA complexes, the t-PA activity was suppressed most strongly to 57% of the original, free t-PA activity. Upon ultrasound exposure in vitro, the t-PA activity was fully recovered. A cell culture experiment with L929 fibroblasts demonstrated no cytotoxicity of complexes at the concentration used for the in vivo experiment. The half-life of t-PA in the blood circulation prolonged by the complexation with gelatin and zinc ions. The zinc-stabilized t-PA-gelatin complex is a promising t-PA delivery system which can manipulate the thrombolytic activity by the local ultrasound irradiation.