注射用呋布西林钠与溶媒配伍后不溶性微粒的观察

目的:观察注射用呋布西林钠在葡萄糖注射液和氯化钠注射液中的不溶性微粒情况,为临床提供安全用药信息。方法:模拟临床用药,将注射用呋布西林钠分别加入10%葡萄糖注射液和0.9%氯化钠注射液中,利用GWJ-4型微粒检测仪计数配伍后的不溶性微粒数。结果:注射用呋布西林钠在两种溶媒中含≥10μm不溶性微粒数均有增加,含微粒数由多到少依次为0.9%氯化钠注射液50 ml>0.9%氯化钠注射液100 ml>0.9%氯化钠注射液250 ml>10%葡萄糖注射液50 ml>10%葡萄糖注射液100 ml>10%葡萄糖注射液250 ml,其中在0.9%氯化钠注射液50 ml中含≥10μm及≥25μm微粒明显增多。结论:呋布西林钠与葡萄糖注射液配伍使用比与氯化钠注射液配伍使用更为适宜,配伍后的微粒数不容忽视。     

Activities of Gemifloxacin and Five Other Antimicrobial Agents against Listeria monocytogenes and Coryneform Bacteria Isolated from Clinical Samples

The in vitro activities of gemifloxacin, ciprofloxacin, ampicillin, doxycycline, gentamicin, and vancomycin were evaluated against 15 Listeria monocytogenes strains and 205 coryneform bacteria isolated from clinical samples. The percentages of strains inhibited by gemifloxacin at 0.5 microg/ml were 100% (L. monocytogenes), 93.3% (Brevibacterium spp.), 90% (Corynebacterium minutissimum), 42.5% (Corynebacterium amycolatum), 20% (Corynebacterium striatum), 12.5% (Corynebacterium jeikeium), and 10% (Corynebacterium urealyticum). One hundred percent of the L. monocytogenes strains were inhibited by 0.25 microg of gemifloxacin per ml, whereas 0% of the strains were inhibited by 0.25 microg of ciprofloxacin per ml. Vancomycin at 2 microg/ml inhibited all strains. Doxycycline and gentamicin at 4 microg/ml inhibited 94 and 49% of the strains, respectively, while ampicillin at 0.5, 2, and 8 microg/ml inhibited 24, 61, and 66% of the strains, respectively. It is concluded that gemifloxacin shows good in vitro activity against L. monocytogenes and coryneform bacteria except C. jeikeium and C. urealyticum.     

Antimicrobial susceptibilities of anaerobic bacteria: recent clinical isolates

Minimal inhibitory concentrations of clindamycin, minocycline, metronidazole, penicillin, and carbenicillin were determined by agar dilution against 150 recent clinical isolates of anaerobic bacteria. Ninety-nine percent of Bacteroides fragilis and all B. melaninogenicus, Clostridium perfringens, and Fusobacterium were inhibited by clindamycin at 3.1 mug/ml. Only 58% of other clostridial species were inhibited by this concentration of clindamycin. Minocycline at 3.1 mug/ml inhibited 72% of C. perfringens, 81% of other Clostridium species, and 66, 75, and 100% of B. fragilis, B. melaninogenicus, and Fusobacterium, respectively. Metronidazole at 12.5 mug/ml inhibited all bacteria tested. B. fragilis was resistant to both penicillin and carbenicillin at 6.2 mug/ml. Concentrations of 25 mug/ml for penicillin and 100 mug/ml for carbenicillin were needed to inhibit more than 90% of B. fragilis. Organisms other than B. fragilis were moderately or extremely susceptible to the penicillins.     

Trends in frequency and in vitro susceptibilities to antifungal agents,including voriconazole and anidulafungin,of Candida bloodstream isolates. Results from a six-year study (1996-2001)

The frequency of isolation and antifungal susceptibility patterns to established and two new antifungal agents were determined for 218 Candida spp isolates causing bloodstream infection from 1996 to 2001. Overall, 41.7% of the candidemias were due to C. albicans, followed by C. parapsilosis (22%), C. tropicalis (16.1%), C. glabrata (11.9%), C. krusei (6%) and miscellaneous Candida spp (2.3%). Isolates of C. albicans C. parapsilosis and C. tropicalis (80% of isolates) were highly susceptible to fluconazole (94 to 100% at /= 32 microg/ml).     

血液灌流吸附剂对百草枯吸附作用的实验研究

目的探讨血液灌流吸附剂对百草枯的吸附作用。方法采用0．5％百草枯溶液200ml、100ml、50ml及0．01％百草枯溶液200ml进行体外循环吸附2h，观察百草枯浓度的变化，以计算活性炭及大孔吸附树脂对百草枯的吸附率。结果百草枯的浓度为0．5％，循环容积为200ml，百草枯含量为1000mg时，活性炭和树脂的吸附率为46％、35％；百草枯的浓度为0．5％，循环容积为100ml，百草枯含量为500mg时，活性炭和树脂的吸附率为65％、47％；百草枯的浓度为0．5％，循环容积为50ml，百草枯含量为250mg时活性炭和树脂的吸附率为88％、57％；百草枯的浓度为0．01％，循环容积为200ml，百草枯含量为20mg时，活性炭和树脂的吸附率为95％、87％。结论在百草枯浓度较低0．01％、较低含量20mg时，活性炭及大孔吸咐树脂对百草枯的吸附率无明显差异；在百草枯浓度较高0．5％、较高含量时，活性炭清除百草枯的作用优于大孔吸附树脂；临床上清除百草枯可以根据患者情况选用炭肾或树脂吸附柱进行血液灌流治疗。     

Activities of beta-lactams against Acinetobacter genospecies as determined by agar dilution and E-test MIC methods.

The agar dilution MIC method was used to test activities of ticarcillin, ticarcillin-clavulanate, amoxicillin, amoxicillin-clavulanate, ampicillin, ampicillin-sulbactam, piperacillin, piperacillin-tazobactam, inhibitors alone, ceftazidime, and imipenem against 237 Acinetobacter genospecies. A total of 93.2% of strains were beta-lactamase positive by the chromogenic cephalosporin method. Overall, ampicillin-sulbactam was the most active combination against all strains (MIC at which 50% of the isolates are inhibited [MIC50] and MIC90, 4.0 and 32.0 microg/ml; 86.9% susceptible at < or = 16 microg/ml), followed by ticarcillin-clavulanate (16.0 and 128.0 microg/ml; 85.7% susceptible at < or = 64 microg/ml), piperacillin-tazobactam (16.0 and 128.0 microg/ml; 84.8% susceptible at < or = 64 microg/ml), and amoxicillin-clavulanate (16.0 and 64.0 microg/ml; 54.4% susceptible at < or =16 microg/ml). Ceftazidime and imipenem yielded MIC50s and MIC90s of 8.0 and 64.0 microg/ml (ceftazidime) and 0.5 and 1.0 microg/ml (imipenem), respectively; 71.3% of strains were susceptible to ceftazidime at < or = 16 microg/ml, and 99.2% were susceptible to imipenem at < or = 8 microg/ml. Sulbactam was the most active beta-lactamase inhibitor alone (MIC50 and MIC90, 2.0 and 16.0 microg/ml); clavulanate and tazobactam were less active (16.0 and 32.0 microg/ml for both compounds). Enhancement of beta-lactams by beta-lactamase inhibitors was not always seen in beta-lactamase-positive strains, and activity of combinations such as ampicillin-sulbactam was due to the inhibitor alone. Acinetobacter baumannii was the most resistant genospecies. By contrast, Acinetobacter haemolyticus, Acinetobacter calcoaceticus, Acinetobacter johnsonii, Acinetobacter junii, Acinetobacter radioresistens, and other non-Acinetobacter baumannii strains were more susceptible to all compounds tested. E-test MICs were within 1 dilution of agar dilution MICs in 38.4 to 89.6% of cases and within 2 dilutions in 61.6 to 98.6% of cases.     

化学发光免疫分析法检测低水平HBsAg与其他方法的比较在质膜上简

目的 比较并分析化学发光免疫分析法、ELISA法、胶体金法三种方法检测低水平HBsAg的结果.方法 以化学发光免疫分析仪Architect i2000检测结果作为参考,将100例＜50 IU/ml标本分为3组,分别为：＜1 IU/ml,1～5 IU/ml,＞5 IU/ml.采用ELISA、胶体金法对3组标本进行检测,对测定结果进行比较分析.结果 应用化学发光免疫分析仪Ar-chitect i2000与ELISA测定低水平（＜1 IU /ml） HBsAg的差异有统计学意义,在＜1 IU /ml组,两者符合率仅为3.8％（P＜0.05）,（1～5） IU/ml组和＞5 IU /ml组符合率分别为76.5％和100.0％.Architect i2000与胶体金法在测定低水平HB-sAg的差异有统计学意义（P＜0.05）,两种方法在＜1 IU/ml组符合率为0,（1～5） IU /ml组符合率为2.9％,＞5 IU /ml组符合率为100.0％.结论 化学发光免疫分析法检测低水平HBsAg （＜5IU /ml）灵敏度明显高于ELISA和胶体金法.     

Antibiotic susceptibility survey of Neisseria gonorrhoeae in Thailand.

The antibiotic susceptibilities of Neisseria gonorrhoeae isolates obtained from patients attending sexually transmitted disease clinics in Cholburi and Bangkok, Thailand, were determined by agar dilution. Some 28.2% of isolates produced beta-lactamase. A total of 97.9% of beta-lactamase-positive and 51% of beta-lactamase-negative isolates tested were resistant to penicillin (MICs, greater than or equal to 2 micrograms/ml), 70% of isolates tested were resistant to tetracycline (MICs, greater than or equal to 2 micrograms/ml), and 91% of isolates tested were susceptible to spectinomycin (MICs, less than or equal to 64 micrograms/ml). The MICs for 90% of isolates for the other drugs tested were 2 micrograms/ml for erythromycin, 2 micrograms/ml for cefoxitin, 1 micrograms/ml for cefuroxime, 0.125 micrograms/ml for cefpodoxime, 0.06 micrograms/ml for cefotaxime, 0.25 micrograms/ml for ceftazidime, 0.03 micrograms/ml for ceftizoxime, 0.03 micrograms/ml for ceftriaxone, 0.03 micrograms/ml for cefixime, 0.06 micrograms/ml for aztreonam, 0.008 micrograms/ml for ciprofloxacin, 0.125 micrograms/ml for norfloxacin, and 0.075 micrograms/ml for ofloxacin. Fewer than 1.5% of isolates were resistant to the extended-spectrum cephalosporins tested. Some 0.3% or fewer isolates were resistant to broad-spectrum cephalosporins, fluoroquinolones, or the monobactam aztreonam. Antibiotic resistance among N. gonorrhoeae isolates from Cholburi and Bangkok in May 1990 appeared to be primarily limited to penicillin and tetracycline, which are no longer used to control gonorrhea. Spectinomycin, which has been in general use against gonorrhea in Thailand since 1983, has dwindling utility, with resistance at a level of 8.9%.     

In vitro susceptibility of anaerobic bacteria to ciprofloxacin (Bay o 9867).

About 80% of 70 clinical isolates of Bacteroides fragilis were inhibited by 4 micrograms of ciprofloxacin (Bay o 9867) per ml. The 90% MIC of ciprofloxacin was 8 micrograms/ml for other Bacteroides species, 2 micrograms/ml for Peptococcus species, 8 micrograms/ml for Peptostreptococcus species, and 16 micrograms/ml for Clostridium and Eubacterium species.     

微量MIC检测判断结核分枝杆菌药敏的方法学研究

目的 建立用微量MIC值判断结核分枝杆菌药物敏感性的方法 ,并进行初步临床应用评价.方法 采用液体培养基MIC测定技术,在96孔U型板中进行检测,以60株已知药敏结果 的本院菌株库保存菌株作为试验菌株, 根据Bactec MGIT结果采用ROC曲线分析建立微量MIC药敏判断界值,最后用80株连续时间段内收集的结核分枝杆菌临床分离株对微量MIC药敏判断界值进行验证和修正.结果 微量MIC药敏法的最佳接种菌量为10~(-3)mg/ml数量级,7～10 d即可报告结果 ,链霉素、异烟肼、利福平、乙胺丁醇、氧氟沙星、阿米卡星和卷曲霉素的最佳判断界值分别为2、0.25、1、2、1、4和4 μg/ml,其敏感度分别为93.5%、97.7%、93.5%、84.4%、95.8%、91.7%和88.9%, 特异度分别为95.6%、94.6%、100.0%、93.8%、92.9%、95.6%和91.5%.其准确性分别达95.0%、96.3%、97.5%、90.0%、93.8%、95.0%和91.3%. 结论 微量MIC药敏检测方法 具有快速、准确、低成本和操作简单的优点,具有良好的推广应用前景,适合在我国各级结核病专业收治机构使用.     

Synergistic effect of amoxicillin and cefotaxime against Enterococcus faecalis.

The antibacterial efficacy of the combination of amoxicillin and cefotaxime was assessed against 50 clinical strains of Enterococcus faecalis. For 48 of 50 strains, the MIC of amoxicillin that inhibited 50% of isolates tested decreased from 0.5 microgram/ml (range, 0.25 to 1 microgram/ml) to 0.06 microgram/ml (range, 0.01 to 0.25 microgram/ml) in the presence of only 4 micrograms of cefotaxime per ml. Alternatively, the MIC of cefotaxime that inhibited 50% of isolates tested decreased from 256 micrograms/ml (range, 8 to 512 micrograms/ml) to 1 micrograms/ml (range, 0.5 to 16 micrograms/ml) in the presence of only 0.06 microgram of amoxicillin per ml. For JH2-2, a reference strain of E. faecalis, the MICs of amoxicillin, cefotaxime, and amoxicillin in the presence of cefotaxime (4 micrograms/ml) were 0.5, 512, and 0.06 microgram/ml, respectively. By using a penicillin-binding protein (PBP) competition assay, it was shown that with cefotaxime, 50% saturation of PBPs 2 and 3 was obtained at very low concentrations (< 1 microgram/ml), while 50% saturation of PBPs 1, 4, and 5 was obtained with > or = 128 micrograms/ml. With amoxicillin, 50% saturation of PBPs 4 and 5 was obtained at 0.12 and 0.5 microgram/ml, respectively. Therefore, the partial saturation of PBPs 4 and 5 by amoxicillin combined with the total saturation of PBPs 2 and 3 by cefotaxime could be responsible for the observed synergy between these two compounds.     

Antileishmanial activity of a linalool-rich essential oil from Croton cajucara

The in vitro leishmanicidal effects of a linalool-rich essential oil from the leaves of Croton cajucara against Leishmania amazonensis were investigated. Morphological changes in L. amazonensis promastigotes treated with 15 ng of essential oil per ml were observed by transmission electron microscopy; leishmanial nuclear and kinetoplast chromatin destruction, followed by cell lysis, was observed within 1 h. Pretreatment of mouse peritoneal macrophages with 15 ng of essential oil per ml reduced by 50% the interaction between these macrophages and L. amazonensis, with a concomitant increase by 220% in the level of nitric oxide production by the infected macrophages. Treatment of preinfected macrophages with 15 ng of essential oil per ml reduced by 50% the interaction between these cells and the parasites, which led to a 60% increase in the amount of nitric oxide produced by the preinfected macrophages. These results provide new perspectives on the development of drugs with activities against Leishmania, as linalool-rich essential oil is a strikingly potent leishmanicidal plant extract (50% lethal doses, 8.3 ng/ml for promastigotes and 8.7 ng/ml for amastigotes) which inhibited the growth of L. amazonensis promastigotes at very low concentrations (MIC, 85.0 pg/ml) and which presented no cytotoxic effects against mammalian cells.     

Relationship between steady-state plasma nizatidine concentrations and inhibition of basal and stimulated gastric acid secretion

Steady-state plasma nizatidine concentrations were related in a linear fashion to nizatidine infusion rate. Infusion rates of 2.5, 10, and 20 mg/hr resulted in mean plasma nizatidine concentrations of 69, 247, and 575 ng/ml. Basal acid secretion was inhibited by 50% and 90% at mean plasma nizatidine concentrations of 60 and 430 ng/ml. Protein-stimulated acid secretion was inhibited by 50% and 90% at mean plasma nizatidine concentrations of 75 and 490 ng/ml. The mean pH of basal gastric secretions was 1.6 during placebo infusion and 4.6 when the mean plasma nizatidine concentration was 575 ng/ml.     

刺五加注射液与脑复素联合治疗脑梗死疗效观察

目的:探讨刺五加注射液与脑复素联合治疗脑梗死的临床疗效。方法:治疗组采用刺五加注射液60mL、脑复素20mL分别加入生理盐水500mL、10％葡萄糖500mL中静脉滴注,每天1次,15d为1个疗程。对照组用丹参注射液40mL、胞二磷胆碱1.0分别加入生理盐水500mL、10％葡萄糖500mL中静脉滴注,每天1次,15d为1个疗程。结果:治疗第3周后,治疗组总有效率(91.6％)较对照组(63.3％)明显增高;2组治疗后神经功能缺损积分值比较有显著性差异,治疗组优于对照组(P<0.05)。结论:刺五加注射液与脑复素联合应用是治疗脑梗死较有效的方法。     

In vitro activities of 5-fluorocytosine against 8,803 clinical isolates of Candida spp.: global assessment of primary resistance using National Committee for Clinical Laboratory Standards susceptibility testing methods

We determined the in vitro activity of flucytosine (5-fluorocytosine [5FC]) against 8,803 clinical isolates of Candida spp. (18 species) obtained from more than 200 medical centers worldwide between 1992 and 2001. The MICs were determined by broth microdilution tests performed according to NCCLS guidelines by using RPMI 1640 as the test medium and the following interpretive breakpoints: susceptible (S), < or =4 micro g/ml; intermediate (I), 8 to 16 micro g/ml; resistant (R), > or =32 micro g/ml. 5FC was very active against the 8,803 Candida isolates (MIC(90), 1 micro g/ml), 95% S. A total of 99 to 100% of C. glabrata (MIC(90), 0.12 micro g/ml), C. parapsilosis (MIC(90), 0.25 micro g/ml), C. dubliniensis (MIC(90), 0.12 micro g/ml), C. guilliermondii (MIC(90), 0.5 micro g/ml), and C. kefyr (MIC(90), 1 micro g/ml) were susceptible to 5FC at the NCCLS breakpoint. C. albicans (MIC(90), 1 micro g/ml; 97% S) and C. tropicalis (MIC(90), 1 micro g/ml; 92% S) were only slightly less susceptible. In contrast, C. krusei was the least susceptible species: 5% S; MIC(90), 32 micro g/ml. Primary resistance to 5FC is very uncommon among Candida spp. (95% S, 2% I, and 3% R), with the exception of C. krusei (5% S, 67% I, and 28% R). The in vitro activity of 5FC, combined with previous data demonstrating a prolonged post-antifungal effect (2.5 to 4 h) and concentration-independent activity (optimized at 4x MIC), suggest that 5FC could be used in lower doses to reduce host toxicity while maintaining antifungal efficacy.     

Piperacillin, a new penicillin active against many bacteria resistant to other penicillins.

The in vitro activity of piperacillin, a new semisynthetic piperazine penicillin derivative, was evaluated against 626 clinical isolates and compared with the activity of other beta-lactam antibiotics. At a concentration of 0.1 microgram/ml, piperacillin inhibited all streptococci except enterococci. Non-beta-lactamase-producing staphylococci were inhibited by 1.6 microgram or less per ml. Both beta-lactamase- and non-beta-lactamase-producing Haemophilus were inhibited by 0.1 microgram/ml. Piperacillin inhibited non-beta-lactamase-producing Escherichia coli, Salmonella, and Shigella at a concentration of 6.3 micrograms/ml, but 20% of strains of these species containing type III beta-lactamase were not inhibited by 100 micrograms/ml. Piperacillin at 25 micrograms/ml, inhibited 83% of Citrobacter, 58% of Klebsiella, 88% of Enterobacter, and 50% of indole-positive Proteus, Acinetobacter, and Providencia. At 25 micrograms/ml, piperacillin inhibited 95% of Pseudomonas aeruginosa and 78% of Bacteroides fragilis. The minimal inhibitory concentration of piperacillin against Pseudomonas was affected by increasing the inoculum size and by pH. Minimum bactericidal concentrations against Pseudomonas and Serratia often were eightfold greater than the minimum inhibitory concentrations. Piperacillin was equal in activity to ampicillin against enterococci. It was more active than carbenicillin against E. coli, Klebsiella, Enterobacter, and Bacteroides. It was the most active penicillin against Pseudomonas and inhibited many strains of Pseudomonas for which the MICs of carbenicillin were above 200 micrograms/ml. Piperacillin was hydrolyzed by many different beta-lactamases. Synergistic activity of piperacillin was demonstrated when it was combined with amikacin, gentamicin, and cefazolin against P. aeruginosa and members of the Enterobacteriaceae. No antagonism was observed when piperacillin was combined with aminoglycosides; however, antagonism was observed rarely against E. coli when piperacillin was combined with cefazolin.     

硫酸镁静滴治疗先兆早产49例的临床疗效观察

目的观察25%的硫酸镁治疗先兆早产的疗效。方法对我院收治的49例先兆早产孕妇首先给予冲击量为25%硫酸镁10 ml加入5%葡萄糖100 ml 30 min内缓慢静脉滴注,然后再以25%硫酸镁20-40 ml加入5%葡萄糖500 ml中,以1-2 g/h速度静脉滴注,1次/d,给药8-12 h。结果 49例患者中,42例宫缩得到有效抑制,早产症状消失,总有效率为85.7%。无效者7例。结论硫酸镁静滴来治疗先兆早产效果满意,但用药过程中一定要防止镁离子中毒现象发生。     

常规定量杀菌试验方法的缺陷及其改进

采用悬液与载体试验方法，对定量杀菌试验中的接种量对结果的影响，进行了试验观察。结果，以本试验所用消毒剂及其浓度，作用至规定时间，按常规取０．５０ ｍｌ菌药混合液加 ４．５０ ｍｌ中和剂中和后，取 ０．５０ ｍｌ接种（相当菌药混合液 ０．０５ｍｌ），培养结果无菌，杀灭率为１００％；将０．５０ ｍｌ菌药混合液与４．５０ ｍｌ中和剂混匀后全量接种，或将菌药混合液全部（５．１０ ｍｌ）接种，则消毒后残留菌数为 ６～２３ｃｆｕ／ｍｌ，杀灭率为９９．９９７％～９９．９９９％。在载体定量杀菌试验中，经消毒液作用后的菌片用 ５．０ ｍｌ中和剂洗下菌片上菌，按常规取０．５ ｍｌ洗脱液接种，杀灭率均为１００％；将洗脱液全量接种，则消毒后残留菌数为９０～１００ｃｆｕ／片，杀灭率为９９．９９６％～９９．９９８％。因此，在定量杀菌试验报告杀灭率为 １００％时，宜根据增量接种所得结果。     

Microdilution Technique for Antimicrobial Susceptibility Testing of Anaerobic Bacteria

A microdilution technique using commercially available media and materials was developed and used to determine the minimal inhibitory concentrations (MICs) of clindamycin, chloramphenicol, tetracycline, minocycline, ampicillin, carbenicillin, cephalothin, and gentamicin for 101 anaerobic isolates. Representative strains of Bacteroides, Clostridium, Fusobacterium, Peptococcus, and Peptostreptococcus were tested. The use of Schaedler broth at pH 7.2, an inoculum of 10(5) to 10(7) colony-forming units per ml, and incubation at 35 C in an anaerobic glove box with an atmosphere of 80% nitrogen, 10% hydrogen, and 10% carbon dioxide resulted in good growth and easily interpretable results. After 48 h of incubation, 97% of strains tested were inhibited by 3.1 mug or less of clindamycin per ml and 98% were inhibited by 12.5 mug or less of chloramphenicol per ml. Tetracycline and minocycline inhibited 81 and 88% of strains tested in concentrations of 1.6 mug or less per ml and 1.6 mug or less per ml, respectively. Ampicillin inhibited all strains other than B. fragilis in concentrations of 3.1 mug or less per ml. Excluding certain strains of Bacteroides and Clostridium, carbenicillin in concentrations of 12.5 mug or less per ml and cephalothin in concentrations of 6.2 mug or less per ml inhibited all strains tested. Gentamicin was inactive although some strains of anaerobic cocci and Bacteroides were inhibited by 3.1 mug or less per ml. After 18 to 24 h of incubation, eight of the 101 strains had not grown sufficiently for MICs to be determined; for the 93 strains which had grown sufficiently, 93% of 744 MICs were the same or one concentration lower than the 48-h MICs.     

Caffeine and theophylline attenuate adenosine-induced vasodilation in humans

In this study the local vasoactive effects of adenosine were explored in the human forearm. Adenosine (15 micrograms/100 ml forearm/min) infused into the brachial artery (n = 6) increased forearm blood flow by 572% +/- 140%, versus - 0.5% +/- 5.8% during placebo infusion (p less than 0.01). Lower adenosine infusion rates (5 micrograms/100 ml forearm/min, three times) induced forearm blood flow increments to 330% +/- 94%, 339% +/- 67% and 330% +/- 79%, respectively (n = 8). These forearm blood flow responses were reduced (p = 0.02) during concomitant intra-arterial infusion of two doses of caffeine (30 and 90 micrograms/100 ml forearm/min) to 150% +/- 45% and 98% +/- 28%, respectively. Theophylline (30 micrograms/100 ml forearm/min; n = 6) also significantly attenuated the adenosine-induced increase in forearm blood flow. Enprofylline (30 micrograms/100 ml forearm/min), a related xanthine with a low affinity to adenosine receptors in vitro, did not change the response to adenosine. Nonspecific vasodilation by sodium nitroprusside infusion (50 ng/100 ml forearm/min) was not inhibited by caffeine compared with placebo (forearm blood flow responses were 202% +/- 21% versus 216% +/- 40%; n = 6). This study demonstrated that caffeine and theophylline specifically reduce adenosine-induced vasodilation in humans, supporting the existence of functional human vascular adenosine receptors.