Neuroprotection and thrombolysis: combination therapy in acute ischaemic stroke

The administration of oral aspirin within 48 h and tissue plasminogen activator within 3 h of ischaemic stroke onset remain the only treatments that have been shown to have clinical benefit. There has been much excitement about neuroprotection over the last two decades, as it may minimise the harmful effects of ischaemic neuronal damage. Although each step along the ischaemic cascade offers a potential target for therapeutic intervention, and neuroprotection has shown benefit in animal studies, this has been difficult to translate to humans. Some hope has been offered by the recent finding that the free radical scavenger NXY-059 may improve outcomes in patients presenting within 6 h of onset of ischaemic stroke. There is logic to the idea that neuroprotection may be most effective when reperfusion has occurred with thrombolysis, as the neuroprotectant will have greater access to ischaemic tissue and the opportunity is presented to minimise free radical-mediated reperfusion injury. Numerous studies in animal models support this view, but the concept has not, as yet, been rigorously tested in humans.     

Studies on hydroxyethyl starch. Part II: Changes of the molecular weight distribution for hydroxyethyl starch types 450/0.7, 450/0.5, 450/0.3, 300/0.4, 200/0.7, 200/0.5, 200/0.3 and 200/0.1 after infusion in serum and urine of volunteers

32 volunteers, none of whom showed any symptoms for kidney, liver or pancreas disease, were given by infusion 500 ml of various type of hydroxyethyl starch (HES) at a concentration of 6% (450/0.7, 450/0.5, 450/0.3, 300/0.4) as well as of 10% (200/0.7, 200/0.5, 200/0.3, 200/0.1) over a period of 30 min. After infusion both the Mw and the Mn diminished. The rate of elimination of HES from serum entirely depended on molar substitution and not on Mw. The quotient Mw/Mn decreased considerably over the entire test period. The lower molecular weight limit in serum remained relatively the same at 60,000 Daltons. Maximum molecular weight limit of urine, too, was 60,000 Daltons.     

Plasma concentrations and haemodynamic effects of nitroglycerin during and after intravenous infusion in healthy volunteers

Summary The effects of nitroglycerin, infused intravenously at 3.4 and 7.5 µg/min over 30 min, on haemodynamic parameters were determined in the morning and the afternoon in a randomized, placebo-controlled study in 5 healthy volunteers. The mean steady-state concentrations of nitroglycerin reached in the plasma during the infusions of 3.4 and 7.5 µg/min were 0.35±0.06 ng/ml and 0.64±0.22 ng/ml, respectively. Wide inter-individual variation was noted. The nitroglycerin-induced increase in the orthostatic rise in heart rate and the change in digital-pulse-wave morphology roughly paralleled the plasma concentration, whereas the reduction in systolic blood pressure in the upright position was still evident 15 mins after the infusion, i.e. when nitroglycerin was no longer measurable in plasma. No significant diurnal variation in vascular sensitivity to the vasodilative action of nitroglycerin was demonstrable. The change in pulse-wave morphology resulting from the reduction in peripheral resistance (shift of the dicrotic wave in the descending limb towards the base-line) proved to be the most sensitive haemodynamic parameter.     

Relationship between arterial and peripheral venous catecholamine plasma catecholamine concentrations during infusion of noradrenaline and adrenaline in healthy volunteers

Summary Noradrenaline and adrenaline were infused IV at 5 different rates (0.01–0.2 μg · kg · min⁻ for 30 min to volunteers. The plasma catecholamine concentrations were determined by HPLC and electro-chemical detection. At the highest infusion rate, the arterial and venous plasma concentrations of noradrenaline increased from 1.18 to 44.1 nmol · l⁻¹and from 1.14 to 31.9 nmol · l⁻¹, respectively, and of adrenaline from 0.29 to 23.9 nmol · l⁻¹ and from 0.28 to 19.3 nmol · l⁻¹ respectively. The peripheral venous plasma concentration of noradrenaline averaged 76% of the arterial concentration, and of adrenaline it was 73%. There was a linear relationship between the peripheral venous and arterial plasma noradrenaline and adrenaline concentrations at therapeutic doses.     

Platelet aggregation and plasma levels of acetylsalicylic acid in stroke patients on long-term treatment with an enteric-coated aspirin formulation

Summary Enteric-coated formulations of acetylsalicylic acid (ASA) should be advantageous in prophylaxis after stroke because they cause fewer gastrointestinal side effects. However, the absorption of unchanged ASA and the effectiveness of these formulations have been questioned, which prompted the present investigation. Fourteen elderly stroke patients on long-term medication with enteric-coated ASA 1.5 g daily and four patients on placebo were studied. When tested with arachidonic acid platelet aggregation was completely inhibited in all ASA subjects whereas it was normal in the controls. Plasma samples, drawn every 1/2 h for 6 h after tablet intake, were analyzed by HPLC. The presence of ASA was short lasting with a mean peak concentration of 55 µmol/l reached after 2–3.5 h. Salicylic acid (SA) appeared later, having a mean peak value of 591 µmol/l after 2.5–6 h. Thus, absorption of ASA as well as inhibition of platelet aggregation were confirmed during long-term medication with enteric-coated ASA.     

Relationships among duration of infusion,dose, dosing interval,and steady-state plasma concentrations during intermittent intravenous infusions: Studies with metronidazole

Relationships among duration of infusion (T), dose, dosing interval (), maximum and minimum plasma drug concentrations at steady state (C_max,ssand C_min,ss, respectively), and the duration of effective plasma concentrations (t_D) during multidose intermittent infusion regimens were studied by computer simulation using metronidazoie as a model drug. Pharmacokinetic parameter values for metronidazole were obtained from the literature and the minimum effective plasma concentration (MEC) was taken as 6.0 g/ ml. Increasing the infusion period of the dose reduces C_max,ss, but increases C_min,ss. If intermittent bolus injection of a given dose of drug results in effective plasma concentrations for the entire dosage interval (i.e., C_min,ss,bolus> MEC), then infusion of that dose over any period (T) will also result in effective concentrations for the entire dosage interval. However, if the dosage is such that C_min,ss,bolus < MEC, the relationships among duration of infusion, dose, dosage interval, and duration of effective plasma concentrations are complex. Therefore a nomogram was developed to allow selection of dose, dosing interval, and infusion period such that C_max,ss and C_min,ss could be maintained within a desired range.     

LC-MS/MS测定人血浆中对乙酰氨基酚及其人体药动学和生物等效性研究

目的 建立一种快速、灵敏的高效液相色谱-串联质谱（HPLC-MS/MS）方法以测定人血浆中对乙酰氨基酚浓度,并应用于两种对乙酰氨基酚制剂的人体药代动力学和生物等效性研究。方法 以替硝唑为内标,200μL血浆样品经5倍于其体积的乙酸乙酯液液萃取,再经Waters XBridge? C18柱等度洗脱分离后导入串联质谱,以正离子多反应监测模式进行定量分析,对乙酰氨基酚和内标的选择性反应离子对分别是m/z 152→110和248→121。方法经验证后应用于19名健康受试者单剂量空腹口服两种对乙酰氨基酚制剂500mg后药代动力学和生物等效性的研究。结果 血浆中对乙酰氨基酚在0.1～8.0 μg·mL-1范围内线性良好（r2 > 0.99）,最低检测限为 0.1 μg·mL-1,提取回收率为91.0%～98.7%,日内和日间准确度分别为98.8%～111.3% （精密度：CV ? 9.03%）和94.9%～102.6% （精密度：CV ? 10.68%）。生物等效性试验中,受试制剂与参比制剂的主要药代动力学参数Cmax、AUC0-t和AUC0-∞ 几何均值比的90%置信区间分别为83.50%～105.79%,94.25%～101.54%和93.24%～101.02%,均落在生物等效可接受标准80.00%～125.00%范围内。结论 所建立测定人血浆中对乙酰氨基酚浓度的HPLC-MS/MS法具有快速灵敏、回收率高、选择性好的特点,适用于对乙酰氨基酚片人体药代动力学和生物等效性研究。受试制剂与参比制剂在人体内吸收速度和程度相似,两种制剂生物等效。     

The effect of long-term microcrystalline chitosan therapy on plasma lipids and glucose concentrations in subjects with increased plasma total cholesterol: a randomised placebo-controlled double-blind crossover trial in healthy men and women

Objective To evaluate the long-term effect of microcrystalline chitosan (MCC) on plasma lipids, especially the concentration of low-density lipoprotein (LDL) cholesterol, in subjects with a moderately increased concentration of plasma total cholesterol.Methods A total of 130 middle-aged men and women without severe disease and with a total cholesterol of 4.8–6.8 mmol/l and triglycerides below 3.0 mmol/l were randomised into two treatment groups. At the beginning of the 10-month trial, all participants received placebo 1.2 g twice daily during a 1-month run-in period. Subsequently, group 1 first received 1.2 g placebo twice daily for 3 months and then 1.2 g MCC twice daily for 3 months. Correspondingly, group 2 received 1.2 g MCC twice daily during the first and 1.2 g placebo twice daily during the second 3-month period. During the final 3-month follow-up period, both groups received MCC. Altogether, 83 participants completed the study.Results No difference was detected in the change in the LDL-cholesterol concentration between the treatments during the crossover trial (P=0.98 for interaction between time period and treatment group, repeated-measures analysis of variance for crossover design). In an otherwise similar analysis, no differences were detected between the treatments in the concentrations of total cholesterol, high-density lipoprotein cholesterol, triglycerides and glucose.Conclusions Treatment with MCC had no effect on the concentrations of plasma lipids or glucose in healthy middle-aged men and women with moderately increased plasma cholesterol concentrations.     

A validated,sensitive HPLC‐MS/MS method for quantification of cis‐para‐methyl‐4‐methylaminorex (cis‐4,4'‐DMAR) in rat and human plasma: application to pharmacokinetic studies in rats

4,4′‐DMAR is an analogue of the known psychostimulants 4‐methylaminorex and aminorex. In the light of reports of deaths associated with its abuse, and the easy access from Internet vendors, the EU Council recently decided on control measures across member states. Here we describe a validated method for measuring plasma levels of cis ‐4,4′‐DMAR, crucial for preclinical studies and analysis in human plasma. Chromatographic separation was done by gradient elution on a Kinetex C18 column with 0.1% formic acid in water and 0.1% formic acid in acetonitrile at 0.2 mL/min. Detection was by positive electrospray ionization (ESI+) in multiple reaction monitoring mode monitoring the quantifier transitions m /z 191.4 → m /z 148.3 for cis ‐4,4'‐DMAR and m /z 259.3 → m /z 194.2 for carbamazepine (internal standard). Protein precipitation with 1% of formic acid in acetonitrile was used in cis ‐4,4'‐DMAR extraction from plasma; recovery was high (>93%) with a negligible matrix effect. This method provides an accurate, precise, and sensitive method for cis ‐4,4’‐DMAR quantification in human and rat plasma, following European Medicine Agency guidelines for bioanalytical method validation. Pharmacokinetic studies were conducted in rats. After an intravenous dose of 1 mg/kg, plasma levels declined rapidly (≥80% in 4 h), followed by a slow elimination phase (t_1/2 of 5.14 ± 0.65 h). Absorption was rapid after intraperitoneal injection (t_max = 15 min) with a rapid decline thereafter; C_max and AUC_0‐240min showed dose‐proportionality over the dose range 1–10 mg/kg. This method was successfully applied to investigate pharmacokinetic properties in rats and could be used to quantify cis ‐4,4’‐DMAR levels in human plasma. Copyright © 2016 John Wiley & Sons, Ltd.