国产去羟肌苷肠溶胶囊在中国健康男青年体内药物动力学研究

目的:研究国产去羟肌苷肠溶胶囊在中国健康男青年体内的药物动力学.方法:17名健康志愿者分别单剂量口服200 mg去羟肌苷肠溶胶囊后按试验方案采血,用液相色谱-串联质谱法测定血药浓度,DAS 2.0程序计算药物动力学参数.结果:健康受试者单剂量给药200 mg后去羟肌苷的体内过程符合二室模型,主要药物动力学参数分别为tmax(2.4±0.8)h,Cmax(432.0±278.6)μg/L,AUC0-t(1188.8±577.5)μg·h/L,AUC0-∞(1221.6±587.2)μg·h/L,t1/2(1.7±0.3)h,Vd(547.0±373.4)L,CL(218.3±139.1)L/h.结论:国产去羟肌苷肠溶胶囊吸收较片、分散片和散荆为慢,但主要药物动力学参数与其他剂型相近.     

马来酸曲美布汀缓释片在中国健康男青年体内药物动力学研究

目的:探讨马来酸曲美布汀缓释片在中国健康男青年体内的药物动力学。方法:10例健康志愿者分别单剂量口服300 mg马来酸曲美布汀缓释片后按试验方案采血,用高效液相色谱法测定血药浓度,DAS 2.0程序计算药物动力学参数。结果:健康志愿者单剂量给药300 mg后马来酸曲美布汀的体内过程符合一室模型,主要药物动力学参数分别为tmax(4.0±0.9)h,Cmax(545.0±232.9)μg/L,AUC0-t(2 987±1 185)μg.h/L,AUC0-∞(3 053±1 209)μg.h/L,t1/2(3.6±1.1)h,Vd(589.6±234.8)L,CL(121±68)L/h。结论:马来酸曲美布汀缓释片吸收明显滞后于普通片,显示出缓释特征,但主要药物动力学参数与其他剂型相近。     

埃索美拉唑肠溶胶囊人体生物等效性试验

目的采用高效液相色谱法测定受试者口服埃索美拉唑肠溶胶囊与埃索美拉唑镁肠溶片后血药浓度,评价埃索美拉唑肠溶胶囊的生物等效性。方法 2009年9月-10月,36例健康男性受试者单次交叉口服埃索美拉唑肠溶胶囊(试验制剂)和埃索美拉唑镁肠溶片(参比制剂),测定给药后不同时间点血浆中埃索美拉唑经时血药浓度,采用DAS 2.0软件进行药物代谢动力学参数计算和生物等效性评价。结果受试者单次口服试验制剂与参比制剂后,达峰时间分别为(2.19±0.96)、(2.43±0.92)h,峰浓度分别为(1 748.86±615.81)、(1 442.92±476.41)μg/L,药时曲线下面积(AUC)0-t分别为(3 927.14±1 839.10)、(3 878.79±1 734.84)μg/L.h,AUC0-∞分别为(3 998.36±1 866.22)、(3 918.31±1 773.44)μg/L.h。试验制剂与参比制剂的生物等效性为94.0%,其90%CI为(82.3%,107.2%)。结论埃索美拉唑肠溶胶囊与埃索美拉唑镁肠溶片生物等效。     

国产红霉素肠溶胶囊在健康志愿者的相对生物利用度

目的:研究国产红霉素肠溶胶囊与进口红霉素肠溶胶囊相对生物利用度。方法:20名健康男性志愿者双周期随机交叉口服单剂量(500 mg)国产和进口红霉素肠溶胶囊两种制剂,分别于服药前及服药后 1、2、2.5、3、3.5、4、4.5、5、6、8、10 h采集血样。用微生物法测定血清中红霉素的浓度,并对试验数据进行统计处理。结果:单次口服国产及进口红霉素肠溶胶囊的cmax分别为(2.14±0.75)和(2.11±0.77)mg/L;tmax分别为(3.10±0.58)和(3.30±0.64)h;AUC0~~10h分别为(6.63±2.08)和(6.64±2.18)mg·h/L;AUC0~∞分别为(7.38±2.34)和(7.46±2.41)mg·h/L;国产红霉素肠溶胶囊与进口品相比的相对生物利用度为(100.59± 19.47)%;用方差分析及双单侧t检验对国产和进口红霉素肠溶胶囊的生物等效性进行评价,两制剂间差异无显著性。结论:两种红霉素制剂具有生物等效性。     

多潘立酮胶囊生物等效性临床研究

目的:评价多潘立酮胶囊(受试制剂)和多潘立酮片(参比制刺)的生物等效性.方法:血清样品采用高效液相色谱法测定.18名男性健康志愿者随机分为2组,自身交叉单剂量口服受试制剂和参比制剂,用DAS2.0程序进行生物等效性评价.结果:受试制剂和参比制剂的t1/2分别为(11.0±5.0)h和(10.8±3.9)h,tmax为(1.0±0.4)h和(0.9±0.3)h,Cmax为(43.8±17.2)μg/L和(40.1±15.6)μg/L,AUC0-1为(248.50±102.44)μg·h/L和(244.26±107.62)μg·h/L,AUC0-∞为(280.16±111.46)μg·h/L和(270.83±108.42)μg·h/L,相对生物利用度为(106.8±29.4)%.结论:2种制剂具有生物等效性.     

国产氢溴酸西酞普兰片的药物代谢动力学特征及相对生物利用度

目的:观察国产选择性5-羟色胺再摄取抑制剂氢溴酸西酞普兰片在正常人体内的药物代谢动力学行为,并与进口氢溴酸西酞普兰片进行生物等效性的对比。方法:选择经医院伦理委员会审议通过的健康男性志愿受试者20人。实验前签署知情同意书,受试期间停服任何药物,并禁烟和酒。采用随机交叉设计,口服国产氢溴酸西酞普兰片和进口氢溴酸西酞普兰片剂40mg,(国产氢溴酸西酞普兰片由北京万全药物技术开发有限公司和徐州恩华药业集团有限责任公司共同研发,20mg/片;进口氢溴酸西酞普兰片,商品名希普妙,丹麦灵北药厂,20mg/片)。服药后0.5～132h内间隔取血。血样加入内标盐酸普萘洛尔经预处理后用高效液相色谱测定。计算主要药物代谢动力学参数,并以进口片剂为参比制剂,估算国产氢溴酸西酞普兰片的生物利用度,判断其生物等效性。结果:志愿者1人缺席,1人在第一轮试验服药后1h发生呕吐,且132h的血药浓度为7.1μg/L,0.5h血药浓度为0,吸收和代谢均有影响,故舍去;其余18人进入结果分析。国产氢溴酸西酞普兰片和进口氢溴酸西酞普兰片的血药浓度-时间曲线均符合二房室模型,其血药浓度-时间曲线下面积AUC0-132分别为(1894.6±460.2)μg/(h·L)和(1876.9±398.3)μg/(h·L),差异无显著性(P>0.05);达峰浓度分别为(46.1±9.8)μg/L和(47.7±11.7)μg/L,差异无显著性(P>0.05);半衰期分别为(37.6±10.0)h和(38.8±9.8)h,差异无显著性(P>0.05);达峰时间分别(3.2±1.9)h和(3.2±1.5)h,差异无显著性(P>0.05)。以进口制剂为对照,用血药浓度-时间曲线下面积AUC0-132计算的国产氢溴酸西酞普兰片生物利用度为(100.3±11.7)%。结论:国产氢溴酸西酞普兰片与进口氢溴酸西酞普兰片具有生物等效性。     

国产头孢拉定临床药代动力学及其胶囊剂的生物等效性

目的 :研究口服国产头孢拉定胶囊在 18名健康志愿者中的药代动力学和相对生物利用度。方法 :18名健康志愿者分别双交叉口服单剂量国产头孢拉定胶囊和进口头孢拉定胶囊各 0 .5 g ,用反相高效液相 (RP HPLC)法测定血浆中头孢拉定浓度。采用双向单侧t检验进行生物等效性评价。结果 :国产品和进口品t1/ 2 分别为 (1.0 9± 0 .2 6 )和 (1.0 8± 0 .30 )h ,tmax分别为 (0 .86± 0 .15 )和 (0 .85± 0 .13)h ,cmax分别为 (18.5 9± 3.6 9)和 (17.35± 3.81)mg/L ,AUC0 5分别为 (30 .4 0± 4 .2 8)和(2 9.92± 3.2 6 )mg·h/L。国产品的相对生物利用度为 10 1.5 3%± 8.4 6 % ,ln(AUC0 5)、ln(AUC0 ∞)、ln(cmax)经双向单侧t检验 :接受生物等效的假设。结论 :国产品与进口品具有生物等效性。     

乳酸左氧氟沙星片剂的健康人体药代动力学和相对生物利用度研究

目的:研究乳酸左旋氧氟沙星片剂的健康人体药代动力学和相对生物利用度。方法:18名健康受试者单次,交叉口服乳酸左旋氧氟沙星片200 mg后,用HPLC-荧光法测定血浆中左氧氟沙星浓度,用BAPP2.0软件进行数据处理,计算药代动力学参数。结果:供试与参比制剂的药时曲线可用二室模型拟合,两者主要药代动力学参数Cmax分别为(2.92±0.60)μg/mL(、3.22±0.53)μg/mL;Tmax分别为(0.9±0.3)h(、0.9±0.3)h;t1/2分别为(7.27±1.02)h、(6.83±0.80)h;AUC0~24分别为(17.18±2.46)μg/(mL.h)(、17.19±2.55)μg/(mL.h),乳酸左氧氟沙星片供试制剂的相对生物利用度为(100.3±9.4)%。结论:供试与参比制剂具有生物等效性。     

塞克硝唑胶囊健康人体生物等效性研究

目的研究塞克硝唑胶囊在健康志愿者中的生物等效性。方法21名男性健康志愿者随机交叉单次空腹服用试验制剂塞克硝唑胶囊和参比制剂塞克硝唑片剂。用高效液相色谱法测定血清中塞克硝唑的药物浓度。结果受试者单剂口服1000mg塞克硝唑试验药和对照药后,主要药动学参数Cmax分别为(22.69±3.60)和(23.29±3.62)mg/L;Tmax分别为(1.18±0.49)和(1.15±0.65)h;t1/2β分别为(26.43±5.77)和(27.08±5.46)h;AUC0-t分别为(701.12±123.89)和(709.93±89.06)mg·h/L;AUC0-∞分别为(761.14±147.96)和(773.71±108.23)mg·h/L。试验制剂对于参比制剂的平均相对生物利用度AUC0-∞为(98.38±12.83)%。结论受试者单剂空腹给药后塞克硝唑在体内的过程符合二室模型,AUC0-t、AUC0-∞及Cmax经统计学处理,表明试验制剂塞克硝唑胶囊和参比制剂塞克硝唑片具有生物等效性。     

氧氟沙星片在中国健康男青年体内的生物等效性

目的:研究2种氧氟沙星片在健康人体内的生物等效性。方法:18例男性健康志愿者随机交叉口服国产氧氟沙星片0.3 g,HPLC法测血药浓度,用DAS 2.0程序计算药物动力学参数。结果:受试和参比氧氟沙星片tmax分别为(1.19±0.85)和(0.89±0.42)h,cmax分别为(3.28±1.22)和(3.67±1.03)mg/L,t1/2分别为(5.80±1.02)和(5.54±0.84)h,AUC0-t分别为(20.24±3.84)和(20.86±3.42)mg.h/L,AUC0-∞分别为(21.56±4.14)和(21.98±3.80)mg.h/L。2种国产氧氟沙星片的相对生物利用度F0-t为(97.1±9.2)%,方差分析和双单侧t检验表明2种制剂主要参数间差异无统计学意义,受试制剂AUC0-t和Cmax的90%可信限分别为参比制剂的93.0%~100.4%和73.7%~101.7%。结论:2种氧氟沙星片生物等效。     

Effect of tenofovir on didanosine absorption in patients with HIV

OBJECTIVE: To evaluate the pharmacokinetic interaction between tenofovir and didanosine when used in combination as a highly active antiretroviral therapy regimen. DATA SOURCES: Literature retrieval was accessed through MEDLINE (1966-January 2003) using the terms tenofovir and didanosine. Abstracts from recent meetings, including the International AIDS Society, Interscience Conference on Antimicrobial Agents and Chemotherapy, and the Infectious Diseases Society of America, were reviewed for relevant abstracts and poster presentations. DATA SYNTHESIS: Pharmacokinetic studies evaluating the concurrent use of tenofovir and didanosine have been performed in healthy volunteers. Tenofovir 300 mg administered concurrently with 400 mg didanosine results in a 48-64% increase in the didanosine maximum plasma concentration and AUC with no significant alterations in the tenofovir pharmacokinetic parameters. Tenofovir 300 mg and didanosine 250 mg has been compared with didanosine 400 mg alone. The results demonstrated equivalent didanosine AUCs. CONCLUSIONS: When used concurrently, tenofovir significantly increases the maximum plasma concentration and the AUC of didanosine. Additional data in HIV-infected patients are needed to determine the long-term toxicities of this combination therapy. Didanosine dose reduction should be considered when these 2 agents are used concurrently.     

Time–Action Profile of an Oral Enteric Insulin Formulation in Healthy Chinese Volunteers

BackgroundInsulin is an essential treatment for both type 1 and 2 diabetes. Among the available routes of insulin administration, oral delivery is the most appealing option.ObjectiveThe purpose of this study was to evaluate the pharmacodynamic and pharmacokinetic profiles of orally administered enteric insulin and compare the time–action of these oral insulin capsules with neutral protamine Hagedorn (NPH) insulin.MethodsThis was a single-center, randomized, 4-period, crossover study. Twelve healthy volunteers (3 per group) received 1 of 3 doses of oral enteric insulin (50, 100, or 200 U) or 1 subcutaneous injection of NPH insulin (6 U) on 4 separate days. After administration, glucose infusion rates and serum insulin concentrations were monitored for 10 hours.ResultsGlucose infusion rates increased after administration of either NPH or oral enteric insulin. The mean times for maximal metabolic effects for 50, 100, and 200 U of oral enteric insulin were 250 (118), 170 (58), and 236 (132) minutes, respectively, compared with 243 (79) minutes for NPH insulin. The onset of action was slower for oral enteric insulin at 50 U (38 [10] minutes), 100 U (41 [18] minutes), and 200 U (65 [58] minutes) compared with NPH insulin (35 [8] minutes). The maximum glucose infusion rates for oral enteric insulin treatment (1.66 [0.50], 1.61 [1.00], and 1.80 [0.60] mg/kg/min for 50, 100, and 200 U, respectively) were lower compared with NPH insulin (2.06 [0.82] mg/kg/min), although these differences were not statistically significant.ConclusionsOral enteric insulin capsules induced significant glucodynamic effects and exhibited a time–action profile similar to that of NPH insulin in these healthy volunteers. No detectable increases in serum insulin concentration were observed in any treatment group. Trial registry number: ChiCTR-TRC-12001872.     

泮托拉唑肠溶胶囊的人体生物等效性研究

目的评价2种泮托拉唑肠溶胶囊的生物等效性。方法18名健康男性受试者,随机分组,自身交叉口服泮托拉唑肠溶胶囊实验制剂和参比制剂40 mg,采用高效液相色谱法-质谱法测定用药后不同时间的经时血药浓度,以方差分析方法对主要药动学参数AUC0→13、Cmax进行均数的差别检验,以双单侧t检验进行生物等效性判断;对Tmax以非参数检验(符号秩检验)进行生物等效性判断。结果2种泮托拉唑肠溶胶囊实验制剂和参比制剂的药代动力学参数AUC0→13、AUC0→∞、Tmax、Cmax、t1/2分别为7 670.1±2509.6和7 549.6±2 149.9、7 724.4±2 535.1和7 591.2±2 161.2[ng/(h.mL)]、3.0±0.2和3.0±0.2 h、3 107.2±567.0和3 267.2±717.3(ng/mL)、1.1±0.3和1.0±0.2(h)。实验制剂的相对生物利用度为(100.8±10.3)%。方差分析结果表明两种制剂的主要药动学参数AUC0→13、Cmax之间无明显差异。结论2种制剂为生物等效制剂。     

Lack of effect of simultaneously administered didanosine encapsulated enteric bead formulation (Videx EC) on oral absorption of indinavir, ketoconazole, or ciprofloxacin.

Didanosine formulation that contains a buffer to prevent it from acid-mediated degradation can result in a significant decrease in the oral absorption of certain drugs because of interactions with antacids. An enteric formulation of didanosine is unlikely to cause such drug interactions because it lacks antacids. This study was undertaken to determine whether the enteric bead formulation of didanosine (Videx EC) influences the bioavailability of indinavir, ketoconazole, and ciprofloxacin, three drugs that are representative of a broader class of drugs affected by interaction with antacids. Healthy subjects of either gender were enrolled in three separate open-label, single-dose, two-way crossover studies. Subjects were randomized to treatment A (800 mg of indinavir, 200 mg of ketoconazole, or 750 mg of ciprofloxacin) or treatment B (same dose of indinavir, ketoconazole, or ciprofloxacin, but with 400 mg of didanosine as an encapsulated enteric bead formulation). A lack of interaction was concluded if the 90% confidence interval (CI) of the ratio of the geometric means of log-transformed C(max) and AUC(0-infinity) values (i.e., values for the area under the concentration-time curve from time zero to infinity) of indinavir, ketoconazole, and ciprofloxacin were contained entirely between 0.75 and 1.33. For indinavir (n = 23), the point estimate (90% CI; minimum, maximum) of the ratios of C(max) and AUC(0-infinity) values were 0.99 (0.91, 1.06) and 0.96 (0.91, 1.02), respectively. In the ketoconazole study, 3 of 24 subjects showed anomalous absorption of ketoconazole (i.e., an approximately 8-fold-lower AUC compared to historical data), which was the reference treatment. A post hoc analysis performed after these three subjects were excluded indicated that the point estimates (90% CI) of the ratios of C(max) and AUC(0-infinity) values were 0.99 (0.86, 1.14) and 0.97 (0.85, 1.10), respectively. For ciprofloxacin (n = 16), the point estimate (90% CI) of the ratios of C(max) and AUC(0-infinity) values were 0.92 (0.79, 1.07) and 0.91 (0.76, 1.08), respectively. All three studies clearly indicated a lack of interaction. The T(max) and t(1/2) for indinavir, ketoconazole, and ciprofloxacin were similar between treatments. Our results showed that the lack of interaction of didanosine encapsulated enteric bead formulation with indinavir, ketoconazole, and ciprofloxacin indicates that this enteric formulation of didanosine can be concomitantly administered with drugs whose bioavailability is known to be reduced by interaction with antacids.     

Pharmacokinetic-interaction study of didanosine and ranitidine in patients seropositive for human immunodeficiency virus.

The potential pharmacokinetic interactions between didanosine, an acid-labile antiretroviral agent, and ranitidine, an H2-receptor antagonist, were evaluated by a crossover study of 12 male patients seropositive for the human immunodeficiency virus. Single oral doses of 375 mg of didanosine, formulated as a citrate-phosphate-buffered sachet, or of 150 mg of ranitidine were administered alone or in combination (ranitidine was given 2 h prior to didanosine). Serial blood samples and total urinary output were collected after each treatment and analyzed for didanosine and/or ranitidine by validated high-performance liquid chromatography-UV assay methods. Pharmacokinetic parameters were calculated by noncompartmental methods. There were significant increases in mean area under the curve from time zero to infinity and mean urinary recovery for didanosine given in combination with ranitidine compared with those for didanosine alone. There were no significant differences between didanosine coadministered with ranitidine and didanosine alone in the respective mean peak concentrations in plasma, times to peak, elimination half-lives, or renal clearances. The mean area under the curve for ranitidine given with didanosine was significantly less than that for ranitidine given alone. There were no significant differences between the mean peak concentrations in plasma, times to peak, elimination half-lives, renal clearances, or urinary recovery values for ranitidine coadministered with didanosine and values for ranitidine given alone. These data demonstrate that administration of didanosine 2 h after ranitidine will result in a minor increase in the bioavailability of didanosine. A modification in the dose of didanosine or ranitidine is not necessary if the dose of ranitidine precedes that of didanosine by 2 h.     

The impact of zidovudine compared with didanosine on health status and functioning in persons with advanced HIV infection and a varying duration of prior zidovudine therapy. AIDS Clinical Trials Group 116/117 Study Group

The objective of this study was to compare the effects of zidovudine and didanosine on health-related quality of life in persons with advanced HIV infection and varying duration of prior zidovudine exposure. It was designed as a substudy nested in two similar placebo-controlled active-control-arm randomized trials, using sites of the AIDS Clinical Trials Group participating in the randomized trials of zidovudine versus didanosine (ACTG 116 and 117). The patients comprised 356 participants enrolled in ACTG 116 and 117. All had HIV infection and either a CD4 count of <200 cells/mm3, or a CD4 count of <300 cells/mm3 plus symptoms of HIV disease. Participants were randomized equally within strata defined by duration of prior zidovudine therapy, to receive didanosine sachets at a dose of 500 mg daily (334 mg in subjects weighing <60 kg) or 750 mg daily (500 mg in subjects weighting <60 kg) plus inactive capsules resembling zidovudine, or to receive zidovudine capsules at a dose of 600 mg daily plus inactive sachets resembling didanosine. The main outcome measures were self-reported health-related quality of life, healthcare utilization, disability, work and symptom impact. The results showed no differences in reported symptom impact or healthcare utilization, and most measures of disability were similar. In the group with more than 8 weeks of prior zidovudine therapy, several of the health status scale scores for ongoing participants were significantly better for didanosine recipients, but average differences were small. Use of several different approaches to combining health status and survival showed no differences in the overall quality-time experiences between the treatment groups. Individuals taking zidovudine, low-dose didanosine and high-dose didanosine experienced 33, 34 and 35 weeks, respectively, in at least the typical health state if they had fewer than 8 weeks of previous zidovudine therapy, and had 23, 23 and 26 weeks, respectively, if they had more than 8 weeks previous use of zidovudine. Results did not differ when data were analysed within strata ofpatients who had any versus no prior exposure to zidovudine, or AIDS versus non-AIDS status. In conclusion, functional status and health-related quality of life were substantially similar among persons receiving either zidovudine or didanosine, regardless of the duration of prior zidovudine treatment.     

Pharmacokinetics of didanosine in patients with acquired immunodeficiency syndrome or acquired immunodeficiency syndrome-related complex

The pharmacokinetics of didanosine (2',3'-dideoxyinosine) after intravenous and oral administration were evaluated in an open, escalating-dose phase I study in patients with acquired immunodeficiency syndrome (AIDS) or severe AIDS-related complex. Didanosine was administered twice a day for 2 weeks as an intravenous infusion of 60 minutes duration at doses ranging from 0.4 to 16.5 mg/kg, followed by 4 weeks of oral treatment at twice the intravenous dose. Serial blood and urine samples were obtained on the first and final day of intravenous administration and after the first oral dose, as well as at steady state. Didanosine demonstrated linear pharmacokinetic behavior over the dose ranges of 0.4 to 16.5 mg/kg intravenously and 0.8 to 10.2 mg/kg orally. There was no indication of significant changes in pharmacokinetic parameters with repeated administration. The apparent elimination half-life after oral administration was approximately 1.4 hour. Renal clearance values exceeded the glomerular filtration rate, indicating that active tubular secretion of didanosine occurs. Bioavailability of didanosine when administered as a solution with an antacid was approximately 43% for doses from 0.8 to 10.2 mg/kg in patients with AIDS and advanced AIDS-related complex. Bioavailability of didanosine from the citrate-phosphate-buffered solution, the formulation currently used in phase II and expanded access studies, was comparable to the formulation used in the phase I trials.     

Single-dose pharmacokinetics of enteric-coated didanosine in HIV-infected children

Didanosine remains a cornerstone nucleoside analogue for the treatment of HIV infection. A potential problem with the buffered formulations of didanosine is the likelihood of interactions with other drugs that require an acidic pH for absorption or can be chelated by cations in the buffer. An encapsulated enteric-coated (EC) bead formulation of didanosine has been approved and is routinely used as an alternative to the chewable/dispersible buffered tablet formulation. The objective of this study was to evaluate the single-dose pharmacokinetics of didanosine EC at 240 mg/m2 in 10 HIV-infected children. Didanosine EC was administered at time 0 on an empty stomach with no other concomitant medications. Blood samples were collected at pre-dose, 0.5, 1, 2, 4, 8 and 12 h post-dose. Didanosine was measured in plasma using radioimmunoassay. Ten subjects completed the intensive pharmacokinetic evaluation; data are available for eight participants. Plasma concentrations of didanosine following EC administration were analysed using non-compartmental methods. Median (range) AUCinfinity, Cmax, Tmax and CL/F for didanosine following EC administration were 2385 (1291, 3966) ng x h/ml, 854 (300, 1799) ng/ml, 3.0 (1.0, 8.1) h and 3.3 (2.7-6.4) l/h/kg, respectively. Results from this study indicate that the didanosine Cmax is decreased and Tmax is prolonged, but total exposure of didanosine in plasma following didanosine EC administration appears similar to previous data collected in HIV-infected children following buffered didanosine administration.     

Penetration of didanosine in semen of HIV-1-infected men

OBJECTIVES: The disposition of antiretroviral agents into genital tissue and fluids is one of the factors implicated in the control of viral replication within the male genital tract and should be an objective of highly active antiretroviral therapy. We have investigated didanosine penetration in seminal plasma of 16 HIV-infected patients. PATIENTS AND METHODS: A total of 16 patients on didanosine (200 mg every 12 h or 400 mg once daily) participated in the pharmacokinetic study. After the didanosine morning dose, peripheral blood plasma and semen plasma were collected within the intervals 0-4, 4-8 and 8-12 h in the twice-daily regimen and 0-4, 4-12 and 12-24 h in the once-daily regimen. RESULTS: Within each sampling time interval didanosine concentrations in seminal plasma were higher than in blood. The interquartile range of concentrations in seminal plasma was 292-1217 ng/mL, compared with 50-150 ng/mL in blood plasma. Didanosine could be detected in 14 of the 16 semen samples analysed and in 8 of the 16 blood samples. CONCLUSIONS: We have demonstrated that didanosine penetrates into the seminal plasma in higher concentrations than in blood plasma.     

Relationship between Didanosine Exposure and Surrogate Marker Response in Human Immunodeficiency Virus-Infected Outpatients

We used information available from routine clinic visits to characterize the pharmacokinetics of didanosine in 82 human immunodeficiency virus-infected patients. A total of 271 blood samples were collected for the measurement of didanosine concentrations in plasma (mean ± standard deviation [SD], 3.30 ± 2.21 samples/patient). Bayesian estimates of didanosine oral clearance (CL_oral) were obtained for these patients by the POSTHOC option within the NONMEM software package. Population priors from a previous NONMEM analysis of didanosine pharmacokinetics were used. The mean ± SD CL_oral was 132 ± 27.7 liters/h, which agrees reasonably well with estimates obtained from previous pharmacokinetic studies of didanosine. Estimates of individual didanosine exposure were then used to consider potential relationships between drug exposure and surrogate marker response over a 6-month period. No correlations were found between the didanosine area under the concentration-time curve from 0 to 6 months and the absolute CD4 cell count (r = 0.305; 0.1 < P < 0.2), weight response (r = 0.0857; P > 0.4), or percentage of CD4 lymphocytes (r = 0.0559; P > 0.4). Future efforts to characterize didanosine exposure in outpatients by random sampling methods should involve more directed efforts to limit residual variability in the data.