Evaluation of cerebrospinal fluid concentration and plasma free concentration as a surrogate measurement for brain free concentration.

This study was designed to evaluate the use of cerebrospinal fluid (CSF) drug concentration and plasma unbound concentration (C(u,plasma)) to predict brain unbound concentration (C(u,brain)). The concentration-time profiles in CSF, plasma, and brain of seven model compounds were determined after subcutaneous administration in rats. The C(u,brain) was estimated from the product of total brain concentrations and unbound fractions, which were determined using brain tissue slice and brain homogenate methods. For theobromine, theophylline, caffeine, fluoxetine, and propranolol, which represent rapid brain penetration compounds with a simple diffusion mechanism, the ratios of the area under the curve of C(u,brain)/C(CSF) and C(u,brain)/C(u,plasma) were 0.27 to 1.5 and 0.29 to 2.1, respectively, using the brain slice method, and were 0.27 to 2.9 and 0.36 to 3.9, respectively, using the brain homogenate method. A P-glycoprotein substrate, CP-141938 (methoxy-3-[(2-phenyl-piperadinyl-3-amino)-methyl]-phenyl-N-methyl-methane-sulfonamide), had C(u,brain)/C(CSF) and C(u,brain)/C(u,plasma) ratios of 0.57 and 0.066, using the brain slice method, and 1.1 and 0.13, using the brain homogenate method, respectively. The slow brain-penetrating compound, N[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl-]sarcosine, had C(u,brain)/C(CSF) and C(u,brain)/C(u,plasma) ratios of 0.94 and 0.12 using the brain slice method and 0.15 and 0.018 using the brain homogenate method, respectively. Therefore, for quick brain penetration with simple diffusion mechanism compounds, C(CSF) and C(u,plasma) represent C(u,brain) equally well; for efflux substrates or slow brain penetration compounds, C(CSF) appears to be equivalent to or more accurate than C(u,plasma) to represent C(u,brain). Thus, we hypothesize that C(CSF) is equivalent to or better than C(u,plasma) to predict C(u,brain). This hypothesis is supported by the literature data.     

静脉注射利多卡因对丙泊酚全麻诱导浓度的影响

目的观察丙泊酚靶控输注(TCI)诱导时,静脉注射不同剂量利多卡因对丙泊酚TCI诱导浓度和气管内插管血流动力学的影响,探讨其全麻诱导期应用的最适剂量。方法选择80例拟在全麻下行甲状腺择期手术的患者,随机分为4组,每组20例。对照组静脉推注生理盐水3 m L(A组),实验组分别静脉推注利多卡因0.5 mg/kg(B组)、1 mg/kg(C组)、1.5 mg/kg(D组),1 min后开始丙泊酚TCI诱导,每30 s观察意识反应,初始血浆浓度设定为4μg/m L,5 min后意识仍未消失的每分钟增加0.5μg/m L,直至意识消失。之后给予舒芬太尼0.4μg/kg、罗库溴铵0.6 mg/kg,面罩辅助通气2 min后,完成气管插管。记录患者静脉注射利多卡因前(T0)、丙泊酚TCI开始(T1)、意识消失时(T2)、插管前(T3)、插管后(T4)各时点的心率(HR)、平均动脉压(MAP),效应室浓度(Ce)、脑电双频指数(BIS)值。询问患者丙泊酚TCI诱导开始后是否有注射痛。结果 T2时,B、C、D组的效应室浓度低于A组,而B、C、D组间差异无统计学意义。T2时,各组MAP、HR比较差异无统计学意义(P>0.05);B、C、D组气管插管前后MAP变化明显小于A组(P<0.05);T4时,C、D组HR明显低于A组(P<0.05)。静脉注射利多卡因1 min后,B、C、D组BIS值下降(P<0.05);T2时,各组BIS值比较差异无统计学意义(P>0.05);插管前后,B、C、D组的BIS值变化小于A组(P<0.05)。与A组比较,C、D组注射痛的发生率降低(P<0.05),C、D组间比较差异无统计学意义(P>0.05)。结论全麻诱导前静脉注射利多卡因有明显镇静作用,可显著降低丙泊酚诱导浓度,减轻气管插管的应激反应和丙泊酚的注射痛。诱导期静脉应用利多卡因的最适剂量为1 mg/kg。     

高效液相色谱法测定复方利多卡因乳膏中丙胺卡因与利多卡因的含量

目的：探讨复方利多卡因乳膏质量控制方法，为该药的质量控制提供依据。方法：采用高效液相色谱法。结果：丙胺卡因在133－240mg.L^-1，利多卡因在140－250mg.L^-1范围内呈现良好的线性关系，r均为0．9996，样品回收率高，丙胺卡因和利多卡因回收率分别为99．27％和99．05％，RSD分别为1．14％和0．67％，样品溶液稳定，3d内日间差异性试验结果：丙胺卡因RSD＝0．73％，利多卡因RSD＝0．65％，本实验方法重复性好，RSD分别为丙胺卡因1．30％，利多卡因0．91，对3批样品进行含量测定，结果分别为：丙胺卡因99．69％，100．53％，101．86％，利多卡因99．67％，98．30％，99．97％，结论：本方法准确，可靠，能同时测定复方利多卡因乳膏中利多卡因，丙胺卡因的含量，在本研究基础上制定的质量标准可以控制本品的质量，方法具有可行性。     

硬膜外舒芬太尼对利多卡因最低局麻药镇痛浓度的影响

目的 比较不同剂量舒芬太尼对成人腰段硬膜外利多卡因最低局麻药镇痛浓度（M LAC）的影响.方法 选择择期行泌尿科及肛肠科手术患者90例,ASA Ⅰ级或Ⅱ级,年龄32 ～ 63岁,随机分为3组（n=30）：L组（单纯利多卡因）、LSF1组（利多卡因＋10 μg舒芬太尼）、LSF2组（利多卡因＋20 μg舒芬太尼）.首例均用1％利多卡因20 ml,其后根据前一例患者的VAS评分,按照序贯增减法依次变动利多卡因的浓度,浓度变化梯度0.1％,观察30 min后痛觉阻滞的程度（VAS≤1为有效）,下肢运动阻滞的Bromage分级.根据Dixon和Massey法计算3组利多卡因的MLAC及95％可信区间（CI）.结果 LSF1组利多卡因用于成年人腰段硬膜外的MLAC为0.590％（95％CI为0.537％ ～0.660％）,LSF2组的MLAC为0.382％（95％CI为0.329％ ～0.446％）,均显著低于L组的MLAC 0.781％（95％ CI为0.728％～0.844％）（P＜0.01）.在镇痛有效的病例中,LSF2组Bromage分级显著低于L组和LSF1组.结论 硬膜外利多卡因复合10及20 μg舒芬太尼均能显著减少利多卡因的最低局麻药镇痛浓度,且无明显不良反应,硬膜外利多卡因复合20μg舒芬太尼在达到同等镇痛效果时,还能显著减轻下肢运动神经的阻滞.20μg舒芬太尼可能是最佳的复合剂量.     

利多卡因用于预防丙泊酚静脉注射痛的最佳浓度

目的观察不同剂量的利多卡因用于预防丙泊酚静脉注射痛的效果。方法选择200例人工流产患者,随机分成4组,L0组1％丙泊酚液中不加利多卡因、L1组总量为10ml的1％丙泊酚与利多卡因混合液中加2％利多卡因1ml、L2组总量为10ml的1％丙泊酚与利多卡因混合液中加2％利多卡因1．25ml、L组总量为10ml的1％丙泊酚与利多卡因混合液中加2％利多卡因1．5ml,每组各50例。所有患者均先静脉输注芬太尼1．0μg／kg后,再缓慢经脉注射1％丙泊酚或丙泊酚与利多卡因混合液,含丙泊酚1～2mg／kg。观察记录各组发生注射痛的情况。结果I_0组患者的静脉注射痛发生率最高,L1组仍有轻微静脉注射痛发生,L2组和L3组比较差异无统计学意义,基本消除了丙泊酚静脉注射痛。结论总量为10ml的1％丙泊酚与利多卡因混合液中加2％利多卡因1．25ml,即混合液中利多卡因的浓度为0．25％,是预防丙泊酚注射痛的最低满意浓度,即最佳浓度。     

Determination of free ceftriaxone concentration and its application in predicting lung tissue concentration

The purpose of this study was to establish a method for determining the free concentration of ceftriaxone based on hollow fiber centrifugal ultrafiltration (HFCF-UF) technology in combination with high-performance liquid chromatography (HPLC) for free pharmacokinetic studies and the prediction of ceftriaxone concentrations in lung tissue. This method only required centrifugation for a short time, and the filtrate could be injected directly for HPLC analysis without further treatment. The specificity, linearity, precision and stability of this method were validated for quantification of free ceftriaxone. Under the optimized conditions, the absolute recoveries were more than 92.5%. The intraday and interday precision RSDs were less than 3.6%. Additionally, nonspecific adsorption (NSB) between the analyte and the ultrafiltration membrane was considered. This method was successfully applied to the analysis of the free ceftriaxone concentration in rat plasma and lung tissue. The free ceftriaxone concentration of lung tissue could be predicted by using the linear formula C_fl = C_fp (0.342x – 0.0129) (x: time). This method also provides a reliable alternative for accurate monitoring of the free ceftriaxone concentration in therapeutic drug monitoring (TDM).     

高效液相色谱法测定猫血浆利多卡因浓度

目的应用高效液相色谱法测定猫血浆中利多卡因浓度,探索试验方法及精确度,以便进一步应用于利多卡因对心血管系统影响的药理学试验。方法应用高效液相色谱法分别测定对照溶液和猫血浆中利多卡因浓度。结果猫血浆中内源性物质对测定无干扰;浓度在0．43—427．00μmol／L范围内与峰面积线性关系良好;峰面积的日内相对标准偏差（RSD）分别为2．16％、1．48％和0．65％;峰面积的日间RSD分别为3．38％、1．78％和0．76％;绝对回收率分别为（84．25±3．54）％、（82．33±3．87）％和（86．38±1．75）％;方法回收率分别为（99．58±5．43）％、（100．88±4．65）％和（99．54±3．65）％。结论高效液相色谱法稳定、回收率高,并且检测方法简单,适用于大多数的实验室,可应用于药物代谢动力学的研究。     

Effect of ultrafiltrate volume on determination of free phenytoin concentration

Monitoring free phenytoin concentration is clinically useful for patients with uremia, hepatic disease, hypoalbuminemia, and related conditions. Free phenytoin is commonly measured by immunoassay in the protein-free ultrafiltrate prepared by centrifuging serum for 20-30 minutes, using an appropriate ultrafiltration device. We studied the effect of centrifugation time (15-40 minutes) and protein concentrations on ultrafiltration volume, and the related effects on measured free phenytoin concentrations. Temperature was ambient for all studies. The ultrafiltration volumes were directly proportional to centrifugation time and were inversely proportional to the protein concentrations. Although ultrafiltration volume significantly increased with longer centrifugation time, the measured free phenytoin concentrations did not increase proportionately. The concentration of phenytoin in the residual serum retained in the ultrafiltration device did not change proportionally either. Therefore, equilibrium of phenytoin concentrations between the ultrafiltrate and retentate was maintained, regardless of centrifugation time or protein concentration.     

Should we routinely measure free plasma phenytoin concentration?

The plasma protein binding of phenytoin was investigated in 56 epileptic patients attending the outpatient clinic. The free phenytoin fraction was measured by equilibrium dialysis at 37 degrees C and the total concentration by a homogenous enzyme immunoassay technique. The free fraction ranged from 0.123 to 0.177 (median 0.144, mean +/- s.d. = 0.145 +/- 0.12). Distribution was consistent with normality. Four of the patients were also taking sodium valproate. The median free fraction of phenytoin in these patients was 0.174, 21% higher than that of the total group (P less than 0.05). The total concentration of phenytoin varied from 0.3 to 29.4 micrograms/ml (median 12 micrograms/ml, mean +/- s.d. = 13.31 +/- 6.13 micrograms/ml) and the free fraction was not related to the total drug concentration. There was a highly significant relationship between free phenytoin concentration and total phenytoin concentration (r = 0.986, P less than 0.001). There appears to be very little variability in protein binding of phenytoin in epileptic patients and thus total plasma phenytoin concentration closely reflects the free (unbound) drug concentration. Routine estimation of free plasma phenytoin concentration is therefore unnecessary and should be reserved for those patients where alteration in binding is likely, e.g. renal or hepatic disease or where adverse effects occur at unexpectedly low total phenytoin concentrations.     

高效液相色谱法测定地西泮的血药浓度

地西泮为临床常用的苯二氮(艹)/(卓)类镇静催眠药之一,但滥用或误用会引起急性中毒.在药物急性中毒抢救中,除了常规的抢救措施及对症处理外,监测其血药浓度,可迅速判明药物的性质、中毒程度,为临床及时掌握病情、评价疗效提供依据.该药物的定性、定量方法国内外文献[1～3]有不同的报道.作者结合本室的实验条件,建立了相应的提取方法和色谱条件,结果方法简便、快速、重现性好,适合于临床检测.     

Chromatographic determination of free lidocaine and its active metabolites in plasma from patients under epidural anesthesia

OBJECTIVE: We developed a simple and selective assay method for simultaneous determination of free lidocaine (LDC) and its active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX) in plasma, by using high-performance liquid chromatography (HPLC). The method was applied to the plasma concentration monitoring in continuous epidural anesthesia with LDC. MATERIALS AND METHODS: Free fraction was separated from plasma by using an ultrafiltration technique. Free and total LDC, MEGX and GX in plasma were analyzed by HPLC equipped with ordinary octadecylsilyl silica (ODS) column and ultraviolet (UV) detector. PATIENTS: Five male patients with cancer who received epidural injection of 1.5% LDC for 5 hours in elective thoracic surgery, were enrolled to determine the plasma levels of total and free LDC, MEGX and GX. RESULTS AND DISCUSSION: The calibration curve for free LDC, MEGX and GX were linear at the concentration of 25 to 1,000 ng ml(-1) (r = 0.9998 - 0.9999). The recoveries for LDC, MEGX and GX from plasma water were ranged 73.2-89.1%. The coefficient variations for intra- and inter-day assay for LDC, MEGX and GX were less than 4.1%. The detection limit ofeach drug was 20 ng ml(-1). Plasma-free MEGX after 180 min epidural injection was higher than free LDC, even though the total concentration of MEGX was 4 times lower than that of LDC. The percentages of free fraction for LDC, MEGX and GX were 11.7, 48.5 and 78.3% after 5-hour epidural administration of LDC. Since the free fraction of MEGX and GX increases and exceeds the concentration of free LDC during continuous epidural anesthesia, accumulation of these toxic metabolites should be carefully monitored as well as LDC. CONCLUSION: The present method is a reliable technique and can be applied to monitoring free LDC, MEGX and GX, which provide us beneficial information as to the LDC metabolism and toxicity.     

Monitoring of the free concentration of cyclosporine in plasma in man

Summary The free fraction of cyclosporine A (CsA) and its total plasma concentration as determined by HPLC(CsA_T) were prospectively monitored in 66 recipients of renal transplants. The free CsA levels (CsA_u) were calculated.The variability in free CsA levels was no less than for total CsA_T levels. The correlation between CsA_u and CsA_T was high (r=0.90). Both CsA_T and CsA_u covaried with serum triglycerides and apolipoprotein A1.Fourty-four of the 66 patients suffered acute rejection episodes on 69 occasions. CsA_T and CSA_u both decreased and to a similar extent at the occurrence of acute rejection (42% and 59% decrease, respectively; significant vs baseline. Notsignificant difference in decrease in CsA_TvsCsA_u).Acute nephrotoxicity occurred on 11 occasions in 10 patients. Both CsA_T and CSA_u were approximately twice as high at the time of acute nephrotoxicity as compared to one week previously. Both CsA_T and CsA_u were higher during the first month after transplantation in patients with than in patients without systemic infection.Thus, plasma CsA_u gave no additional clinical information or guidance compared to CsA_T in renal transplant recipients. Due to the complexity of its assay, which requires two consecutive analyses, there does not appear to be any need for routine monitoring of CsA_u in renal transplant recipients.     

游离药物浓度监测及其应用研究进展

血浆中游离药物浓度与受体部位药物平衡,因而其与药效或药物不良反应密切相关。在特定病理生理情况下,对游离药物进行监测(TDM)更有意义。本文介绍了常用的游离药物浓度监测的样品处理和检测方法,及其在抗癫痫药、心血管药物、免疫抑制剂、蛋白酶抑制剂等游离药物浓度监测的应用。     

磷酯酶C对人血小板细胞质游离钙离子浓度的影响

目的　测定磷酯酶C(phospholipaseC ,简称PLC ,下同 )对静息状态和激活状态下人血小板胞质游离钙离子浓度的影响 ,从而进一步阐明PLC抗血小板聚集作用的机制。方法　将健康成人的洗涤血小板用荧光指示剂Fura 2 /AM进行负载 ,分别用生理盐水、ASA和不同剂量的PLC处理荧光负载后的血小板 ,采用双波长荧光分光光度法分别测定经过不同处理后的血小板在静息状态和以ADP为诱导剂时的激活状态下的胞质游离钙离子浓度 [Ca2 + ]i。结果　以健康成人血为样品时 ,经生理盐水、ASA 334μmol·L-1、2 5、3 75、5、10和 2 0UPLC·ml-1处理后的血小板 ,在静息状态下测得的胞质游离 [Ca2 + ]i 浓度 (nmol·L-1)分别为15 2 5 5± 15 0 7,131 6 3± 15 5 8,14 0 2 7± 12 0 3,139 4 8± 1 73,12 1 11± 9 5 8,116 6 2± 15 96和 10 7 2 0± 17 0 7,而以ADP为诱导剂激活血小板后测得的胞质游离 [Ca2 + ]i(nmol·L-1)分别为 90 2 6 2± 94 74 ,6 87 99± 6 2 86 ,810 99± 72 37,70 1 73± 2 1 37,4 2 9 6 7± 71 5 9,342 82± 4 4 86和 2 6 3 2 7± 2 5 4 6。以生理盐水作为对照 ,ASA 334μmol·L-1、2 5、3 75、5、10和 2 0UPLC·ml-1剂量组对激活状态下血小板胞质 [Ca2 + ]i 的抑制率I(% )分别为 2 5 8     

糖尿病对游离地高辛浓度的影响及其测定

目的比较在同一地高辛血药浓度水平下,单纯心力衰竭患者及心力衰竭伴糖尿病患者的游离地高辛浓度的差异,为临床制定合理的地高辛用药方案提供可靠的实验室数据。方法18例地高辛适应证患者按是否有糖尿病分为A、B两组。A组为单纯心力衰竭患者,B组为心力衰竭伴糖尿病患者,分别用荧光偏振免疫测定法(FPIA法)测定其地高辛血药浓度,用超滤-FPIA法测定其血清中游离地高辛浓度。采用成组t检验对两组数据进行统计分析,对两组间地高辛总浓度及游离地高辛进行比较。结果A组地高辛总浓度(1.29±0.29)ng/ml(0.81～1.63ng/ml);B组地高辛总浓度(1.45±0.42)ng/ml(0.88～1.98ng/ml)。A组游离地高辛浓度(0.63±0.11)ng/ml(0.42～0.74ng/ml);B组游离地高辛浓度为(0.87±0.19)ng/ml(0.59~1.07ng/ml)。结论在地高辛总浓度处于同一水平情况下,心力衰竭伴糖尿病患者的游离地高辛浓度与单纯心力衰竭患者的游离地高辛浓度具有统计学差异,前者浓度和游离百分率均明显高于后者(P<0.05)。     

Sensitive methods for determination of free digitoxin concentration using digitoxin immunoassays: demonstration of elevated free digitoxin concentration caused by digitoxin-phenytoin interaction by applying these new techniques

Digitoxin is very strongly bound to serum albumin. Although free digitoxin is pharmacologically active, it is not monitored because of the lack of a sufficiently sensitive technique. The concentration of free digitoxin in the protein-free ultrafiltrate is usually below the detection limit of digitoxin immunoassays. A modified technique is described by which free digitoxin can be routinely monitored using commercially available immunoassays. The fluorescence polarization immunoassay for determining total digitoxin concentration requires that 100 microL of serum be treated with 300 microL of methanol to precipitate proteins. It is demonstrated that free digitoxin can easily be measured by adding 100 microL of methanol to 300 microL of ultrafiltrate, thus improving the sensitivity of the assay three-fold. The free digitoxin concentration can easily be calculated by dividing the observed value by 3. An attempt to use only ultrafiltrate (no methanol added) caused significant bias in the result, probably as a result of a matrix problem. The chemiluminescent assay for digitoxin does not require any specimen pretreatment and requires only 10 microL of serum. The program was modified and used 50 microL of ultrafiltrate to improve the sensitivity of the free digitoxin assay. If the chemiluminescent assay is used to measure free digitoxin, the true free digitoxin concentration can be calculated by dividing the observed value by 4.3. The free digitoxin concentrations were comparable in eight patients receiving digitoxin as measured by both methods. To show an application of this technique, two serum pools were prepared from patients receiving digitoxin and supplemented with various concentrations of phenytoin. A significant increase in free digitoxin concentration was observed because of the displacement of digitoxin from protein binding sites by phenytoin.