EFFECT OF THE CALCIUM CHANNEL BLOCKER, NIFEDIPINE, ON HAEMOSTASIS, CLOTTING, AND THROMBOLYSIS EX VIVO.

1987 ◽  
Author(s):  
M Rademaker ◽  
R H Meyrick Thomas ◽  
J D Kirby ◽  
I B Kovaos
Keyword(s):  
Oral Dose ◽  
Calcium Channel ◽  
Ex Vivo ◽  
Peak Plasma ◽  
Peak Plasma Concentration ◽  
Plasma Concentrations ◽  
Channel Blockers ◽  
Clotting Time ◽  
Polyethylene Tubing

Nifedipine, as other calcium channel blockers, has been shown to inhibit platelet aggregation induced by various agonists in vitro. The therapeutic relevance of these findings are, however, questionable, as in vitro inhibition of platelet function occurs at plasma concentrations of nifedipine in excess of 50 uM, while the peak plasma concentration following a single 10 mg oral dose of nifedipine is only 0.2 uM. We have used the Haemostatometer, to assess the effect of nifedipine on haemostasis ex vivo. This instrument allows quantitative assessment of haemostasis by monitoring the pattern of haemostatic plug formation (HPF) in holes punched through polyethylene tubing through which non-anticoagulated blood flows under standard conditions (1,2). The pattern and speed of blood coagulation subsequent to HPF was measured as was the spontaneous thrombolysis time (STT) (taken as the time until expulsion of the haemostatic plug from heparinised blood). All values are for mean + SEM.Blood samples were taken from 10 healthy volunteers before and ninety minutes after a single 10 mg oral dose of nifedipine. Following nifedipine, the initial phase of the haemostatic reaction (HPF) was prolonged from 0.95 ± 0.12 min to 1.57 ± 0.14 min, (p< 0.01); clotting time was also increased from 13.1 ± 1.1 min to 20.7 ± 2.3 min, (p=0.013), and the STT fell from 48.0 ± 9.9 min to 27.5 ± 4.6 min (p=0.014).The increased bleeding time (HPF) provides evidence that a therapeutic dose of nifedipine evokes an anti-platelet effect. The prolongation of the clotting time seen in this study could be explained by,an effect of nifedipine on platelets and hence clotting. The mechanism of the enhanced spontaneous thrombolysis following nifedipine is not known.We suggest that the effect of nifedipine on haemostasis and thrombolysis may contribute to its therapeutic effect.(1) Gorog P and Kovacs I B. Haemostasis 16: 337-345, 1986.(2) Gorog P. Angiology 37: 99-105, 1986.

Inhibitory Effect of Piracetam on Platelet-rich Thrombus Formation in an Animal Model

1998 ◽  
Vol 79 (01) ◽  
pp. 222-227 ◽  
Author(s):  
F. Stockmans ◽  
W. Deberdt ◽  
Å. Nyström ◽  
E. Nyström ◽  
J. M. Stassen ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Peak Plasma ◽  
Thrombus Formation ◽  
Plasma Concentrations ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Cell Deformability

SummaryIntravenous administration of piracetam to hamsters reduced the formation of a platelet-rich venous thrombus induced by a standardised crush injury, in a dose-dependent fashion with an IC50 of 68 ± 8 mg/kg. 200 mg/kg piracetam also significantly reduced in vivo thrombus formation in rats. However, in vitro aggregation of rat platelets was only inhibited with piracetam-concentrations at least 10-fold higher than plasma concentrations (6.2 ± 1.1 mM) obtained in the treated animals. No effects were seen on clotting tests.In vitro human platelet aggregation, induced by a variety of agonists, was inhibited by piracetam, with IC50’s of 25-60 mM. The broad inhibition spectrum could be explained by the capacity of piracetam to prevent fibrinogen binding to activated human platelets. Ex vivo aggregations and bleeding times were only minimally affected after administration of 400 mg/kg piracetam i.v. to healthy male volunteers, resulting in peak plasma levels of 5.8 ± 0.3 mM.A possible antiplatelet effect of piracetam could be due to the documented beneficial effect on red blood cell deformability leading to a putative reduction of ADP release by damaged erythrocytes. However similarly high concentrations were needed to prevent stirring-induced “spontaneous” platelet aggregation in human whole blood.It is concluded that the observed antithrombotic action of piracetam cannot satisfactorily be explained by an isolated direct effect on platelets. An additional influence of piracetam on the rheology of the circulating blood and/or on the vessel wall itself must therefore be taken into consideration.

scholarly journals Pharmacokinetic and Pharmacodynamic Evaluation of Marbofloxacin in Pig against Korean Local Isolates ofActinobacillus pleuropneumoniae

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Md. Akil Hossain ◽  
Hae-chul Park ◽  
Kyunghun Jeong ◽  
Yang ho Jang ◽  
Dae Gyun Kim ◽  
...  
Keyword(s):  
Body Weight ◽  
Ex Vivo ◽  
Peak Plasma ◽  
Plasma Concentrations ◽  
Antibacterial Activities ◽  
Time Intervals ◽  
Concentration Time ◽  
Elimination Half ◽  
The Mean

The pharmacokinetics of marbofloxacin in pigs after intravenous (i.v.), intramuscular (i.m.), and peroral (p.o.) administration and pharmacokinetic/pharmacodynamic indices of this drug against Korean local isolates ofActinobacillus pleuropneumoniaewere determined in this study. Marbofloxacin (2.50 mg/kg of body weight) was administered, and blood samples were collected with designated time intervals. Plasma-extracted marbofloxacin was injected into the LC-MS/MS system. The in vitro and ex vivo antibacterial activities of marbofloxacin were evaluated against 20 isolates ofA. pleuropneumoniae. The mean peak plasma concentrations (Cmax) after i.v., i.m., and p.o administration were2.60±0.10,2.59±0.12, and2.34±0.12 µg/mL at0.25±0.00,0.44±0.10, and1.58±0.40 h, respectively. The area under the plasma concentration-time curves (AUC0–24) and elimination half-lives were24.80±0.90,25.80±1.40, and23.40±5.00 h·μg/mL and8.60±0.30,12.80±1.10, and8.60±0.00 h, for i.v., i.m., and p.o. administration, correspondingly. The AUC0–24/MICs of marbofloxacin after i.v., i.m., and p.o. administration were253.86±179.91,264.1±187.16, and239.53±169.75 h, respectively. TheCmax/MIC values were26.58±18.84,26.48±18.77, and23.94±16.97, and T>MICs were42.80±1.01,36.40±1.24, and38.60±1.18 h, after i.v., i.m., and p.o. administration, respectively. Thus, marbofloxacin dosage of 2.50 mg/kg of body weight by i.v., i.m., and p.o. administration with 24 h dosing interval will provide effective treatment for the infection of pig byA. pleuropneumonia.

Inhibitory Effect of Citalopram on the Pharmacokinetics of Carvedilol in Rats and in vitro Models

Pharmacology ◽  
2017 ◽  
Vol 100 (5-6) ◽  
pp. 301-307
Author(s):  
Maria Bianca Abrudan ◽  
Dana Maria Muntean ◽  
Daniela Saveta Popa ◽  
Ana-Maria Gheldiu ◽  
Maria Adriana Neag ◽  
...  
Keyword(s):  
Drug Interaction ◽  
Plasma Concentration ◽  
Metabolic Rate ◽  
Liver Microsome ◽  
Peak Plasma ◽  
Peak Plasma Concentration ◽  
Femoral Vein ◽  
Plasma Concentrations ◽  
Drug Drug Interaction

Background/Aims: The aim of this study was to investigate the drug-drug interaction between carvedilol and citalopram based on carvedilol metabolism in vitro and his pharmacokinetics (PKs) in vivo after the oral administration of the single drug and both drugs, and reveal citalopram effects on the PKs of carvedilol. Methods: Each rat was cannulated on the femoral vein, prior to being connected to BASi Culex ABC®. Carvedilol was orally administrated in rats (3.57 mg/kg body weight [b.w.]) in the absence of citalopram or after a pre-treatment with multiple oral doses of citalopram (1.42 mg/kg b.w.). Plasma concentrations of carvedilol were determined using high-performance liquid chromatography-MS at the designated time points after drug administration, and the main PK parameters were calculated by noncompartmental analysis. In addition, effects of citalopram on the metabolic rate of carvedilol were investigated using rat-pooled liver microsome incubation systems. Results: During co-administration, significant increases of the area under the plasma concentration-time curve as well as of the peak plasma concentration were observed. The rat-pooled liver microsome incubation experiment indicated that citalopram could decrease the metabolic rate of carvedilol. Conclusion: Citalopram co-administration led to a significant alteration of carvedilol's PK profile in rats; it also demonstrated, in vitro, these effects could be explained by the existence of a drug-drug interaction mediated by CYP2D6 inhibition.

scholarly journals Influence of Bisphosphonates or Recombinant Human Parathyroid Hormone on in Vitro Chemotherapy Sensitivity in Acute Lymphoblastic Leukemia Cells

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4355-4355
Author(s):  
Demi T.C. de Winter ◽  
Jenneke E. van Atteveld ◽  
Jessica G.C.A.M. Buijs-Gladdines ◽  
Rob Pieters ◽  
Sebastian J.C.M.M. Neggers ◽  
...  
Keyword(s):  
Plasma Concentration ◽  
Peak Plasma ◽  
Lymphoblastic Leukemia ◽  
Peak Plasma Concentration ◽  
Plasma Concentrations ◽  
Leukemia Cell ◽  
Chemotherapeutic Agents ◽  
Mineral Density ◽  
All Treatment

Abstract BACKGROUND Osteonecrosis and low bone mineral density (BMD) are serious osteogenic side effects of acute lymphoblastic leukemia (ALL) treatment. Bisphosphonates and recombinant human parathyroid hormone (rPTH) tend to be used to ameliorate osteonecrosis-related symptoms as well as to enhance bone mineral density in children with ALL and severe bone fragility. Only one preclinical study on the safety of bisphosphonates during ALL treatment is available, which raises concerns about their impact on leukemic drug sensitivity. Here, we assessed the influence of various bone-modifying agents (zoledronate, pamidronate and rPTH) on in vitro cytotoxicity of chemotherapeutic agents (vincristine (VCR), daunorubicin (DNR), dexamethasone (DEXA), 6-mercaptopurine (6-MP), PEG-asparaginase (PEG-ASP)) and prednisone (PRED) that are commonly used in ALL treatment. METHODS Potential cytotoxic effects of the bone-modifying agents on leukemia cell viability and on in vitro cytotoxic responses of chemotherapeutic agents were tested in various T-cell and B-cell leukemia cell lines using methyl-thiazol-tetrazolium (MTT) assays. Bone-modifying agents were added at concentrations up to a five-fold of their physiological peak plasma concentration. For each assay, 50th percentile of maximal inhibitory concentration was determined. To quantify the combined effects of the bone-modifying agents on chemotherapeutic agent-induced cytotoxicity, median (interquartile range) combination indexes (CI) were calculated. We considered a median CI of &lt; 0.8 as synergism and &gt; 1.2 as antagonism (based on the method of Chou). RESULTS Zoledronate, pamidronate or rPTH in combination with DNR, 6-MP and PEG-ASP showed median CI values between 0.8 and 1.2. Variable inconclusive results were obtained in combination with VCR. Only the combination of a five-fold peak plasma concentration of zoledronate or pamidronate with DEXA resulted in median CI values of 1.15 (range, 1.08-1.48), and 1.34 (range, 1.07-1.62), respectively. Additional experiments using DEXA as well as PRED in combination with one-, three- or five-fold physiological peak plasma concentrations of zoledronate or pamidronate revealed that median CI values stay within 0.8 and 1.2, except for DEXA exposed leukemia cells in combination with a five-fold physiological peak plasma concentration of pamidronate which repeatedly showed a median CI value above 1.2 (1.34, range 1.04-1.86). CONCLUSIONS Zoledronate, pamidronate or rPTH do not seem to influence drug sensitivity of DNR, 6-MP or PEG-ASP, even at a five-fold physiological peak plasma concentration. Nevertheless, our findings suggest a minimal effect of pamidronate on DEXA-induced leukemia cell death. This suggests that even though zoledronate or pamidronate do not seem to negatively influence DEXA- or PRED- induced toxicity in expected physiological concentrations (one- to three-fold physiological peak plasma concentrations), these bone-modifying agents may only be considered with caution in individual cases, and preferably in clinical trial settings before being applied on a large scale in children with ALL. Disclosures No relevant conflicts of interest to declare.

Pharmacokinetics and Haemostatic Status During Consecutive Infusions of Recom binant Tissue-Type Plasminogen Activator in Patients with Acute Myocardial Infarction

1989 ◽  
Vol 61 (03) ◽  
pp. 497-501 ◽  
Author(s):  
E Seifried ◽  
P Tanswell ◽  
D Ellbrück ◽  
W Haerer ◽  
A Schmidt
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Plasminogen Activator ◽  
Peak Plasma ◽  
Peak Plasma Concentration ◽  
Tissue Type ◽  
Tissue Type Plasminogen Activator ◽  
Precise Control ◽  
Type Plasminogen Activator

SummaryPharmacokinetics and systemic effects of recombinant tissue type plasminogen activator (rt-PA) were determined during coronary thrombolysis in 12 acute myocardial infarction patients using a consecutive intravenous infusion regimen. Ten mg rt-PA were infused in 2 minutes resulting in a peak plasma concentration (mean ±SD) of 3310±950 ng/ml, followed by 50 mg in 1 h and 30 mg in 1.5 h yielding steady state plasma levels of. 2210±470 nglml and 930±200 ng/ml, respectively. All patients received intravenous heparin. Total clearance of rt-PA was 380±74 ml/min, t,½α was 3.6±0.9 min and t,½β was 16±5.4 min.After 90 min, in plasma samples containing anti-rt-PA-IgG to inhibit in vitro effects, fibrinogen was decreased to 54%, plasminogen to 52%, α2-antiplasmin to 25%, α2-macroglobulin to 90% and antithrombin III to 85% of initial values. Coagulation times were prolonged and fibrin D-dimer concentrations increased from 0.40 to 2.7 μg/ml. It is concluded that pharmacokinetics of rt-PA show low interpatient variability and that its short mean residence time in plasma allows precise control of therapy. Apart from its moderate effect on the haemostatic system, rt-PA appears to lyse a fibrin pool in addition to the coronary thrombus.

Monitoring of r-Hirudin Anticoagulation during Cardiopulmonary Bypass – Assessment of the Whole Blood Ecarin Clotting Time

1997 ◽  
Vol 77 (05) ◽  
pp. 0920-0925 ◽  
Author(s):  
Bernd Pötzsch ◽  
Katharina Madlener ◽  
Christoph Seelig ◽  
Christian F Riess ◽  
Andreas Greinacher ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Whole Blood ◽  
Heart Surgery ◽  
Ex Vivo ◽  
Open Heart Surgery ◽  
Clotting Time ◽  
Blood Samples ◽  
Alternative Approach ◽  
Ecarin Clotting Time

SummaryThe use of recombinant ® hirudin as an anticoagulant in performing extracorporeal circulation systems including cardiopulmonary bypass (CPB) devices requires a specific and easy to handle monitoring system. The usefulness of the celite-induced activated clotting time (ACT) and the activated partial thromboplastin time (APTT) for r-hirudin monitoring has been tested on ex vivo blood samples obtained from eight patients treated with r-hirudin during open heart surgery. The very poor relationship between the prolongation of the ACT and APTT values and the concentration of r-hirudin as measured using a chromogenic factor Ila assay indicates that both assays are not suitable to monitor r-hirudin anticoagulation. As an alternative approach a whole blood clotting assay based on the prothrombin-activating snake venom ecarin has been tested. In vitro experiments using r-hirudin- spiked whole blood samples showed a linear relationship between the concentration of hirudin added and the prolongation of the clotting times up to a concentration of r-hirudin of 4.0 µg/ml. Interassay coefficients (CV) of variation between 2.1% and 5.4% demonstrate the accuracy of the ecarin clotting time (ECT) assay. Differences in the interindividual responsiveness to r-hirudin were analyzed on r-hirudin- spiked blood samples obtained from 50 healthy blood donors. CV- values between 1.8% and 6% measured at r-hirudin concentrations between 0.5 and 4 µg/ml indicate remarkably slight differences in r-hirudin responsiveness. ECT assay results of the ex vivo blood samples linearily correlate (r = 0.79) to the concentration of r-hirudin. Moreover, assay results were not influenced by treatment with aprotinin or heparin. These findings together with the short measuring time with less than 120 seconds warrant the whole blood ECT to be a suitable assay for monitoring of r-hirudin anticoagulation in cardiac surgery.

scholarly journals Identification of Anti-Severe Acute Respiratory Syndrome-Related Coronavirus 2 (SARS-CoV-2) Oxysterol Derivatives In Vitro

2021 ◽  
Vol 22 (6) ◽  
pp. 3163
Author(s):  
Hirofumi Ohashi ◽  
Feng Wang ◽  
Frank Stappenbeck ◽  
Kana Tsuchimoto ◽  
Chisa Kobayashi ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Viral Replication ◽  
Cultured Cells ◽  
Peak Plasma ◽  
Plasma Concentrations ◽  
Membrane Vesicles ◽  
Drug Candidates ◽  
Increased Risk ◽  
Derivatives Of

The development of effective antiviral drugs targeting the severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) is urgently needed to combat the coronavirus disease 2019 (COVID-19). We have previously studied the use of semi-synthetic derivatives of oxysterols, oxidized derivatives of cholesterol as drug candidates for the inhibition of cancer, fibrosis, and bone regeneration. In this study, we screened a panel of naturally occurring and semi-synthetic oxysterols for anti-SARS-CoV-2 activity using a cell culture infection assay. We show that the natural oxysterols, 7-ketocholesterol, 22(R)-hydroxycholesterol, 24(S)-hydroxycholesterol, and 27-hydroxycholesterol, substantially inhibited SARS-CoV-2 propagation in cultured cells. Among semi-synthetic oxysterols, Oxy210 and Oxy232 displayed more robust anti-SARS-CoV-2 activities, reducing viral replication more than 90% at 10 μM and 99% at 15 μM, respectively. When orally administered in mice, peak plasma concentrations of Oxy210 fell into a therapeutically relevant range (19 μM), based on the dose-dependent curve for antiviral activity in our cell-based assay. Mechanistic studies suggest that Oxy210 reduced replication of SARS-CoV-2 by disrupting the formation of double-membrane vesicles (DMVs); intracellular membrane compartments associated with viral replication. Our study warrants further evaluation of Oxy210 and Oxy232 as a safe and reliable oral medication, which could help protect vulnerable populations with increased risk of developing COVID-19.

Clopidogrel

2006 ◽  
Author(s):  
Richard C. Becker ◽  
Frederick A. Spencer
Keyword(s):  
Steady State ◽  
Oral Dose ◽  
Oral Administration ◽  
Randomized Clinical Trials ◽  
Peak Plasma ◽  
Parent Compound ◽  
Plasma Concentrations ◽  
Significant Inhibition ◽  
Inhibiting Effect ◽  
Dependent Inhibition

Clopidogrel, a thienopyridine derivative, is a novel platelet antagonist that is several times more potent than ticlopidine but associated with fewer adverse effects. After repeated 75-mg oral doses of clopidogrel, plasma concentrations of the parent compound, which has no platelet-inhibiting effect, are very low. Clopidogrel is extensively metabolized in the liver. The main circulating metabolite is a carboxylic acid derivative with a plasma elimination half-life of 7.7 ± 2.3 hours. Approximately 50% of an oral dose is excreted in the urine and the remaining 50% in feces over the following 5 days. Dose-dependent inhibition of platelet aggregation is observed 2 hours after a single oral dose of clopidogrel, with a more significant inhibition achieved with loading doses (≥300 mg) by approximately 6 hours. Repeated doses of 75 mg of clopidogrel per day inhibit adenosine diphosphate (ADP)-mediated aggregation, with steady state being reached between day 3 and day 7. At steady state, the average inhibition to ADP is between 40% and 60%. Based on ex vivo studies, clopidogrel is approximately 100-fold more potent than ticlopidine. There are no cumulative antiplatelet effects with prolonged oral administration. The combined administration of clopidogrel (300 mg loading dose) and aspirin yields a readily discernible platelet-inhibiting effect within 90 to 120 minutes. Clopidogrel selectively inhibits the binding of ADP to its platelet receptor (P2Y12) and the subsequent G-protein–linked mobilization of intracellular calcium and activation of the glycoprotein (GP)IIb/IIIa complex (Gachet et al., 1992). The specific receptor has been cloned and is abundantly present on the platelet surface (Hollopter et al., 2001). Clopidogrel has no direct effect on cyclooxygenase, phosphodiesterase, or adenosine uptake. Clopidogrel is rapidly absorbed following oral administration with peak plasma levels of the predominant circulating metabolite occurring approximately 60 minutes later. Administration with meals does not significantly modify the bioavailability of clopidogrel. The available information suggests that clopidogrel offers safety advantages over ticlopidine, particularly with regard to bone marrow suppression and other hematologic abnormalities. Although thrombotic thrombocytopenic purpura (TTP) has been reported with clopidogrel (Bennett et al., 2000), its occurrence (11 cases per 3 million patients treated) is rare, and has not been reported in randomized clinical trials performed to date.

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