Midazolam 12 mg is moderately counteracted by 250 mg caffeine in man

OBJECTIVE: Caffeine (Caf) counteracts various effects of benzodiazepines (BZDs). Since the effects of zolpidem, a short-acting atypical GABA(A)-BZD agonist, were not antagonized by Caf, we studied an interaction between Caf and midazolam (Mid) in healthy volunteers. SUBJECTS, MATERIALS AND METHODS: In Study 1, 108 healthy students divided to 6 parallel groups were given Mid 12 mg (capsule) and Caf 125 and 250 mg (in decaffeinated coffee), alone and in combinations in the double-blind placebo-controlled manner. Objective and subjective tests were done before and at 45 and 90 min after intake. Ranked delta-values (changes from baseline) were analyzed by one-way contrast ANOVA and Scheffe's tests. In Study 2, six healthy subjects took Mid 15 mg (tablet) with and without Caf 300 mg. The dynamic effects were analyzed as in Study 1 and the plasma concentrations were assayed. RESULTS: In Study 1, learn effects after placebo (ad + 15%) were seen for letter cancellation and digit symbol substitution tests. Midazolam alone significantly (p < 0.05 vs. delta-placebo) reduced letter cancellation and digit symbol substitution, lowered flicker fusion, impaired digit learning and caused subjective calmness on VAS. Caffeine alone did not differ from placebo objectively, yet improved quick-wittedness and contentedness on VAS. In the combinations, Mid + Caf 125 mg differed from placebo objectively as Mid alone, whereas Mid + Caf 250 mg did not. Mid + Caf 250 mg differed from Mid on digit substitution, but did not differ from Mid+Caf 150 mg in impairing memory and causing subjective sedation. In Study 2, Mid 15 mg caused sedation and Caf 300 mg increased plasma Mid at 45 min. Mid + Caf did not differ from Mid alone objectively, but did so subjectively on VAS (p > 0.05). CONCLUSION: In conclusion, in a parallel group study, sedative effects of Mid 12 mg were only moderately antagonized by Caf 250 mg but not by Caf 125 mg. In a cross-over study, a weak interaction was found subjectively but not in objective measures.     

高效液相荧光色谱法测定人血浆中唑吡坦的浓度

目的：建立测定人血浆中唑吡坦浓度的高效液相荧光色谱法。方法：血浆样品经甲醇沉淀后,以甲醇-1％醋酸液（40：60）为流动相,流速为0．3ml·min^-1,色谱柱为Agilent Zorbax C18（150mm×3mm,3．5μm）,柱温为22℃,荧光检测波长：激发波长（λex）254nm,发射波长（λem）390nm。结果：血浆内源性杂质不干扰待测物测定,唑吡坦的线性范围为2～300μg·L^-1,定量下限为2μg·L^-1,日内、日间RSD均〈5％。样品经3次冻融及再沉淀后,4℃下6h内稳定性良好。结论：该法灵敏、快速、准确,操作简便,线性范围宽,可用于唑吡坦的临床药动学研究。     

高效液相色谱法测定人血浆中酒石酸唑吡坦的浓度

目的:建立HPLC法测定人血浆中酒石酸唑吡坦浓度。方法:采用Hypersil C_(18)色谱柱(200 mm×4.6 mm,5μm);流动相:0.02 mol·L~(-1)磷酸二氢钾(含0.5%三乙胺,pH=4.0)-甲醇(38:62);流速:1.2 ml·min~(-1);柱温:30℃;激发波长:300 nm,发射波长:385 nm。结果:血浆酒石酸唑吡坦在2～200 ng·ml~(-1)浓度范围内线性关系良好(r=0.999 9)。低、中、高3种浓度相对回收率分别为102.0%,102.1%,98.9%,日内、日间RSD均小于10%。结论:本法可用于血浆中酒石酸唑吡坦浓度的测定。     

高效液相色谱荧光法测定人血浆中唑吡坦浓度及生物等效性研究

目的：建立高效液相色谱荧光法（HPLC—FLU）测定人血浆中唑吡坦的血药浓度并对其口服制剂人体生物等效性进行研究,为临床用药提供参考依据。方法：采用随机自身对照双周期交叉实验设计,18名健康受试者口服受试制剂和参比制剂10mg,用HPLC—FLU法测定人血浆中的唑吡坦浓度,用非房室模型估算唑吡坦的药动学参数。结果：受试制剂和参比制剂的药动学参数如下：AUC0-t分别为（564．19±139．11）和（451．58±115．94）μg·h·L^-1;AUC0-∞分别为（588．49±139．40）和（474．56±119．43）μg·h·L^-1;Cmax分别为（155．48±39．43）和（125．11±33．33）μg·L^-1;tmax分别为（0．75±0．27）和（1．14±0．31）h;t1/2分别为（1．76±0．69）和（2．12±0．51）h。受试制剂的相对生物利用度为（126．0±12．0）％。结论：经统计学分析,两种国产唑吡坦片剂不具有生物等效性。     

Comparison of amphetamine sulphate and caffeine citrate in man

Summary Ten male volunteer subjects were administered single doses of one of the following compounds on five successive weekly occasions using a fully balanced design: 5 mg and 10 mg of amphetamine sulphate, 300 mg and 600 mg of caffeine citrate and lactose placebo. Two hours after ingestion subjective estimations of several mood attributes were made using graphic rating scales. The palmar skin conductance (sweat gland activity) and pulse rate were recorded during the presentation of twenty identical auditory stimuli consisting of one sec 1 kHz tones of 100 dB intensity, the interval between the tones varying randomly from 45 to 80 sec.The rate of diminution of the skin conductance responses to the repeated stimuli (habituation rate) was slowed by both drugs. The number of spontaneous fluctuations in the skin conductance tracing was increased by both drugs. Sloperatio bioassays were computed for both these variables which were then combined in a discriminant-function analysis to increase the precision of the assay. Pulse rate was elevated by amphetamine but not by caffeine.The subjective effects of the drugs were complicated because one subject demonstrated a paradoxical response to amphetamine being relaxed, drowsy and slow while under its influence.Some problems in comparisons of psychopharmacological agents in normal humans are discussed in the light of the results obtained.     

Effect of a single dose (10 mg) of zolpidem on visual and spectral analysis of sleep in young poor sleepers

Four non-consecutive nights of sleep were recorded in eight young volunteers complaining of chronic poor sleep. The subjects received a placebo or a 10 mg zolpidem dose prior to bedtime according to a Latin square double-blind design. All-night spectral analyses of the Cz-Pz lead were associated to the standard polysomnography. According to the visual scoring performed with the Rechtschaffen and Kales criteria, zolpidem significantly increased the stage 4 amount and reduced waking. Compared to placebo no difference in sleep stages was observed when the scoring was based on the power in the 0.7 to 4-Hz band. In zolpidem nights power was significantly reduced in the 4 to 8-Hz band during NREM (stages 2, 3 and 4) and was increased in the 2 to 4-Hz band during REM sleep. A significant reduction of fast activities over 12 Hz was observed during the first 3 h of sleep. Concerning slow wave activity, the only change noted was a significant slowing of its build-up rate at the beginning of cycle 1.     

Puromycin's suppression of memory in mice as affected by caffeine.

It has previously been shown that expression of maze-learning in mice is blocked for long periods of time by puromycin injected intracerebrally one or more days after the training experience. Treatment with caffeine after training has now been found to reduce greatly the amnestic effects of puromycin. With a high dose of caffeine (200 mg/kg) this reduction is evident 6 days after treatment with puromycin. With a lower dose of caffeine (25 mg/kg) the effect becomes evident only after a more extended period of time. In view of control experiments, we suggest that caffeine modifies factors necessary for the expression of memory and that this alteration makes puromycin relatively ineffective in blocking memory.     

RP-HPLC同时测定血浆中对乙酰氨基酚和咖啡因的浓度

目的 采用RP-HPLC法同时测定血浆中对乙酰氨基酚和咖啡因的浓度。方法 以茶碱为内标，甲醇—2％醋酸(20：80)为流动相，检测波长260nm。结果 血浆中对乙酰氨基酚和咖啡因的平均回收率分别为10．6％和103．9％；对乙酰氨基酚日内RSD≤3．12％，日间RSD≤6．12％；咖啡因日内RSD≤3．94％，日间RSD≤5．13％6在室温条件下对乙酰氨基酚与咖啡因血浆样品至少能稳定4h，在冰冻条件下至少能稳定14d。结论 所用方法准确、简便、重复性好。     

HPLC法测定人血浆中咖啡因含量的不确定度评定

目的对高效液相色谱法测定血浆中咖啡因的不确定度进行分析,找出影响因素,对不确定度进行评估,如实反映测量的置信度和准确度。方法采用ACE 5 C18-AR柱(150 mm×4.6 mm,5μm),流动相:甲醇-0.2%醋酸溶液(17∶83),检测波长:273 nm,流速:1.0 mL/min,测定咖啡因含量后,建立数学模型,分析过程中各分量引起的不确定度,采用A类评定程序评价随机效应引起的不确定度,B类评定程序评价其他因素引起的不确定度。结果置信概率P为95%时,血浆中咖啡因可表示为:低浓度(1 058.08±29.24)ng/mL,中浓度(3 489.53±90.21)ng/mL,高浓度(8 453.32±115.92)ng/mL。结论该方法适用于HPLC法测定血浆中咖啡因浓度的不确定度评定,能为复杂生物样品分析过程的不确定度评定提供一定参考。     

Adrenergic-cholinergic imbalances: the physostigmine-syndrome is not antagonized by the MAO-A inhibitor brofaromine

The centrally active cholinesterase inhibitor physostigmine induces a behavioral syndrome which is thought to represent a model of spontaneous depression. In the present acute trial in 6 healthy volunteers, this model depression was accompanied by clearcut cardiovascular, metabolic and neuroendocrine phenomena of stress. The extent of the changes from baseline, however, scarcely correlated between the behavioral and physiologic phenomena. The behavioral and physiological phenomena could not be antagonized by brofaromine, a putative antidepressant reversibly and selectively inhibiting monoamine oxidase A (MAO-A), contrasting to the complete inhibition by the central cholinolytic scopolamine. This is further evidence that antidepressant efficacy depends on long-term adaptive changes secondary to the enhancement of aminergic neurotransmission rather than this enhancement itself.     

HPLC同时测定感冒灵冲剂中对乙酰氨基酚和咖啡因的含量

目的同时测定感冒宁冲剂中对乙酰氨基酚和咖啡因的含量。方法采用HPLC法,色谱柱为Hypersil C18(250 mm×4.6 mm,5μm),甲醇-水(15:85)为流动相,流速1.0 m l.m in-1,检测波长272 nm。结果对乙酰氨基酚在0.83~41.32μg范围内与峰面积呈良好的线性关系,平均加样回收率为99.54%;咖啡因在0.02~1.02μg范围内与峰面积呈良好的线性关系,平均加样回收率为96.27%。结论该方法简便、快速,重复性好,可用于感冒灵冲剂的质量控制。     

高效液相色谱法同时测定血清中咖啡因和氯唑沙宗的浓度

目的:建立同时测定血清中两种探针药物(咖啡因、氯唑沙宗)浓度的高效液相色谱法.方法:采用迪马C18色谱柱(250 mm×4.6 mm,5 μm);流动相:乙腈-0.02 mol·L-1 磷酸二氢钾溶液(1∶3,v/v),含0.01 mol·L-1三乙胺;流速:1.5 mL·min-1;紫外检测波长:280 nm;柱温:30℃.结果: 咖啡因在2.5～12.5 μg·mL-1、氯唑沙宗在2.5～12.5 μg·mL-1的浓度范围内线性关系良好,最低检测限分别为0.1 μg·mL-1、0.4 μg·mL-1,回收率分别为103.70%±4.36%、102.82%±4.39%.结论: 本法操作简便,灵敏度高,快速可靠,可用于血清中咖啡因和氯唑沙宗的浓度测定.     

Conditioned flavour preference negatively reinforced by caffeine in human volunteers

This study examined whether 100 mg caffeine could reinforce preference for the flavour of a novel drink in moderate caffeine users, both after overnight caffeine abstinence and 2 h after receiving 100 mg caffeine, using a two-stage between-groups procedure with 36 volunteers. In the first stage, liking for a test drink (fruit tea) was assessed at breakfast following overnight caffeine abstinence, with half the subjects receiving caffeine. Liking for the tea increased significantly over four trials for subjects receiving caffeine, and decreased significantly in those without caffeine. These effects were greatest in subjects who rated the drink as highly novel. In stage two, subjects evaluated a second drink (fruit-juice) 2 h after receiving the tea, and again half the subjects received caffeine Those subjects who received caffeine in stage two but not stage one showed a significant increase in liking for the fruit-juice over the 4 test days, whereas subjects who did not receive caffeine at either stage showed a progressive decrease in liking for this drink. In contrast, no significant change in liking for the fruit-juice was seen at stage two for subjects who had received caffeine in stage one, regardless of the presence or absence of caffeine at stage two. Caffeine at breakfast increased ratings of energetic and lively, and energetic ratings also increased following caffeine in the fruit-juice in subjects who had not had caffeine at breakfast. Overall, these data are consistent with a negative reinforcement model of caffeine reinforcement, and demonstrate further the utility of the conditioned flavour preference method for evaluating reinforcing effects of drugs in humans. Received: 30 September 1997/Final version: 17 November 1997     

Monkey liver cytochrome P450 2C9 is involved in caffeine 7-N-demethylation to form theophylline

Abstract

1. Caffeine (1,3,7-trimethylxanthine) is a phenotyping substrate for human cytochrome P450 1A2. 3-N-Demethylation of caffeine is the main human metabolic pathway, whereas monkeys extensively mediate the 7-N-demethylation of caffeine to form pharmacological active theophylline.

2. Roles of monkey P450 enzymes in theophylline formation from caffeine were investigated using individual monkey liver microsomes and 14 recombinantly expressed monkey P450 enzymes, and the results were compared with those for human P450 enzymes.

3. Caffeine 7-N-demethylation activity in microsomes from 20 monkey livers was not strongly inhibited by α-naphthoflavone, quinidine or ketoconazole, and was roughly correlated with diclofenac 4′-hydroxylation activities. Monkey P450 2C9 had the highest activity for caffeine 7-N-demethylation. Kinetic analysis revealed that monkey P450 2C9 had a high V_max/K_m value for caffeine 7-N-demethylation, comparable to low K_m value for monkey liver microsomes. Caffeine could dock favorably with monkey P450 2C9 modeled for 7-N-demethylation and with human P450 1A2 for 3-N-demethylation.

4. The primary metabolite theophylline was oxidized to 8-hydroxytheophylline in similar ways by liver microsomes and by recombinant P450s in both humans and monkeys.

5. These results collectively suggest a high activity for monkey liver P450 2C9 toward caffeine 7-N-demethylation, whereas, in humans, P450 1A2-mediated caffeine 3-N-demethylation is dominant.     

Self-injurious behavior produced in rats by daily caffeine and continuous amphetamine

Self-biting (SB) is an unusual behavioral effect of high doses of certain amphetamine-like drugs in rats. This bizarre behavior has received little attention, perhaps because the high doses of drug required and the dramatic disturbance of the animals' behavioral repertoire have raised the possibility that SB is a high dose phenomenon. However, we have found that continuous administration of very low amounts of amphetamine reliably produces SB in rats, and that this behavioral change can be very selective. We compared SB produced by continuous amphetamine to SB produced by daily caffeine; the latter has been proposed as an animal model for self-injurious behavior (SIB) in the Lesch-Nyhan syndrome. Subcutaneous silicone pellets containing amphetamine base were implanted for 4.5 days; caffeine was administered daily for 10 days. The amphetamine pellets produced the highest rate of SB (75% vs 40%) with the least toxic effects (no deaths vs three deaths). Neither drug produced stereotypy. The dopamine antagonist haloperidol was only marginally effective in controlling SB produced by daily caffeine but the dopamine antagonist pimozide (which has a longer duration of action) prevented SB by amphetamine pellet rats. Continuous release amphetamine pellets may provide an alternative to the caffeine model of SIB in humans, particularly for the Lesch-Nyhan syndrome.     

HPLC法测定复方通感片中对乙酰氨基酚、咖啡医含量研究

目的：建立复方通感片中对乙酰氨基酚、咖啡因测定方法。方法：高效液相色谱法,色谱柱为Hypersil BDS C18柱,流动相甲醇-水-冰醋酸（28∶69∶3）,检测波长为275nm。结果：对乙酰氨基酚在0.5048～1.5144μg间呈良好线性关系,r=0.999307,平均回收率为99.30%,RSD为0.55%（n=6）;咖啡因在0.0640～0.1920μg呈良好线性关系,r=0.963275,平均回收率=98.24%,RSD为1.03%（n=6）。结论：本法专属性强,重显性好,能够控制该产品的质量。     

反相高效液相色谱法测定人血清中茶碱,咖啡因浓度

本文采用反相高效液相色谱法测定了人血清中茶碱、咖啡因浓度。色谱柱：Ｈｙｐｏｒｓｌｌ－ＯＤＳ（２００×２．１），流动相：醋酸—醋酸钠缓冲液（ｐＨ４．５）：甲醇（７０∶３０ｖ／ｖ），检测波长２７０ｎｍ。本文方法简便、快速，结果令人满意。     

反相高效液相色谱法同时测定微量血中茶碱和咖啡因的浓度

建立了在同一血样中测定茶碱和咖啡因的高效液相色谱法。具有简便、快速、准确、可靠、灵敏度高、专一性好等优点。二药的检测下限均为0.02μg。平均回收率均为100.9%。在4～32μg/ml的线性范围内,茶碱和咖啡因的相关系数为γ=0.9999和γ=0.9983。血清用量只需25μl,尤适用于临床哮喘病人和早产儿、新生儿支气管发育不良的常规监测和临床药理的研究。