Pharmacokinetics of ibuprofen enantiomers after single and repeated doses in man.

The pharmacokinetic parameters of ibuprofen enantiomers after a single 600 mg dose and repeated 3 x 400 mg doses of Nurofen were determined in 12 healthy volunteers. Terminal half-lives were similar for both enantiomers, but plasma levels of S-ibuprofen were higher than those of R-ibuprofen, due to the chiral inversion and differences in distribution and metabolism. Comparison of maximal concentrations and areas under the concentration vs time curves between the first and last doses for each enantiomer indicated linear pharmacokinetics with no time-dependency. A large inter-individual variability in the ratio of S- to R-ibuprofen average concentrations at steady-state was observed (mean +/- SD 1.89 +/- 0.89) and probably accounts for the known lack of correlation between racemic ibuprofen concentrations and therapeutic efficacy.     

布洛芬混悬液与片剂的临床药理学比较

目的 :比较研究布洛芬混悬液和市售布洛芬片的生物利用度和药代动力学。方法 :选择20名健康男性志愿者 ,随机分为两组 ,进行单次混悬液或片剂交叉给药600mg后 ,利用HPLC法测定血浆中布洛芬浓度。结果 :两组血浆的布洛芬浓度分别在(1 12±0 23)和 (1 76±0 48)小时达到峰值 (14 46±1 85)和 (13 56±2 98)μg/ml。血药浓度曲线下面积 (AUC)分别达 (46 76±3 65)和 (44 13±5 01)μg/ml ,混悬液的相对生物利用度 (F)为 (104 3±10 7) %。结论 :布洛芬混悬液和市售布洛芬片两种制剂具有生物等效性。     

Pharmacokinetics,biodistribution and bioavailability of isoliquiritigenin after intravenous and oral administration

Context: Isoliquiritigenin (ISL) has been shown to exhibit a variety of biological activities. However, there is little research on the pharmacokinetic behavior and tissues distribution of ISL.

Objective: Pharmacokinetics, biodistribution and bioavailability of ISL after intravenous and oral administration were determined by systematic investigation in Sprague–Dawley rats.

Materials and methods: ISL was dissolved in medicinal ethanol-Tween 80–0.9% sodium chloride saline in a volume ratio of 10:15:75. The ISL solution was injected in rats via a tail vein at a single dose of 10, 20 and 50?mg/kg and administered orally in rats at a single dose of 20, 50 and 100?mg/kg, respectively. Blood samples were collected at time intervals of 0.08, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 6, 8 and 12?h after intravenous injection. Tissues of interests in mice were collected immediately at each determined time point (0.5, 1, 2, 3 and 6?h) after cervical dislocation.

Results: The dose-normalized AUC values were 7.3, 7.6 and 8.7?μg?×?h/ml (calculated based on the dose of 10?mg/kg) for intravenous doses of 10, 20 and 50?mg/kg, respectively. The elimination half-lifes (t_1/2λ) were 4.9, 4.6 and 4.8?h at 10, 20 and 50?mg/kg intravenous doses, respectively. The F values were 29.86, 22.70, 33.62% for oral doses of 20, 50 and 100?mg/kg, respectively. Liver, heart and kidney were major distribution tissues of ISL in mice. The plasma protein binding of ISL in rats was 43.72%.

Conclusion: The work may useful for further study of the bioactive mechanism of ISL.     

赖氨匹林胶囊药物动力学与相对生物利用度

目的:研究单剂量po赖氨匹林(LA)胶囊和来比林散(LA散)后,水杨酸在血浆中的药物动力学与相对生物利用度.方法:采用反相高效液相色谱法测定10名志愿受试者单剂量po1000mg LA胶囊和4000mgLA散后,血浆中水杨酸浓度变化情况;计算药物动力学参数与相对生物利用度,并以配对t检验与双单侧t检验进行统计分析.结果:LA胶囊和LA散以水杨酸计的AUC分别是(251.81±33.58)和(255.12±44.76)mg·h/L;达峰时间分别是(3.52±0.50)和(0.97±0.4)h,峰浓度分别是(39.69±3.58)和(48.14±3.99)mg/L.配对t检验与双单侧t检验结果均表明:po1000mg LA胶囊后,以水杨酸计药-时曲线下面积与po 4000mg LA散相比无显著性差异(P>0.05);峰浓度、达峰时间以水杨酸计有显著性差异(P<0.05).结论:以AUC_(0-∝)为指标,LA囊和LA散为生物等效制剂.以LA散为标准参比制剂,LA胶囊以水杨酸计的相对生物利用度为(99.97±9.84)%.但两种制剂的t_(max)与C_(max)差异提示临床应用时应予注意.     

Pharmacokinetics and relative bioavailability of cyclobarbital calcium in man after oral administration

Summary The pharmacokinetics and relative bioavailability of cyclobarbital calcium have been studied after oral administration of Phanodorm, of tablets according to the Formularium Nederlandse Apothekers (1968; FNA), and an aqueous solution. Six healthy volunteers participated in the investigation on three occasions and each received the three preparations. The dose administered was 300 mg cyclobarbital calcium. Plasma concentrations of cyclobarbital were determined at regular intervals. Absorption from the three preparations was rapid and was faster from the solution. Peak concentrations were usually attained within 1 h. The elimination of cyclobarbital could be described by a single first-order process with an average half-life of 11.6 h (range 8 – 17 h). There was little intra-subject variation of the half-life. Relative bioavailability for each volunteer was estimated by comparing the areas under the plasma concentration curves. The FNA-tablets and Phanodorm exhibited similar bioavailability, whereas the average bioavailability of the solution was 78% of that of FNA-tablets; the reason for this unexpected finding is unknown. It was concluded that cyclobarbital cannot be regarded as a uniformly suitable drug for the treatment of insomnia. The long half-life that was apparent in some of the volunteers (15 – 17 h) creates a substantial risk of residual effects on the following morning. In principle, however, the calcium salt of cyclobarbital may be used for induction of sleep, because of its rapid absorption.     

Pharmacokinetics and bioavailability of theophylline following enema and suppository administration in man

The pharmacokinetics and bioavailability of theophylline from a commercial oral elixir of theophylline, a rectal suppository of aminophylline, and a rectal enema of theophylline monoethanolamine was compared in six normal subjects. Using a complete crossover design, the fasted subjects received a single dose of each dosage form. Blood and saliva samples were collected at frequent time intervals for 24 h, and the plasma assayed for theophylline by a specific thin-layer chromatography densitometric method. No statistically significant differences existed among the three dosage forms with respect to Cmax and AUC corrected for the elimination rate constant and the dose (mg kg-1). However, tmax was significantly larger for the suppository. While the rate of absorption was significantly slower for the suppository, no differences in the extent of absorption existed among the three dosage forms. A one-compartment open model with apparent first-order absorption adequately described the plasma concentration-time data for the elixir and enema, whereas the suppository data were best fitted by a one-compartment open model with apparent zero-order absorption and a lag time. A rate-limiting, concentration-independent release of drug from the base most likely accounts for the slow absorption of theophylline from the suppository. While the saliva:plasma ratio remained fairly constant for most of the study period, the large variability found during the absorption phase following drug administration limits the usefulness of this parameter as a monitor of theophylline plasma concentrations.     

艾普拉唑肠溶片在中国健康人体中药代动力学及绝对生物利用度研究

目的 采用液相色谱串联质谱(UPLC-MS/MS)分析方法研究艾普拉唑肠溶片在中国健康人体中的吸收特性. 方法 采用随机交叉自身对照试验设计,16名健康受试者随机等分成4组,先后口服艾普拉唑肠溶片或静脉注射艾普拉唑钠,采用UPLC-MS/MS测定血浆药物浓度.利用WinNonlin(V6.1)软件标准非房室模型方法进行药代动力学参数的计算. 结果 注射用艾普拉唑钠(10mg)的主要药代动力学参数:最大血药浓度(Cmax)为(834.3±101.2)ng/mL,消除半衰期(t1/2)为(3.4±0.9)h,表观分布容积(Vz)为(14.0±2.2)L, 0到t时间药时曲线下面积(AUC0_t)为(3520.9±915.3)ng·h/mL,血浆清除率(CL)为(3.0±0.9)L/h.艾普拉唑肠溶片(10mg)的主要药代动力学参数:Cmax为(347.9±176.3)ng/mL,t1/2为(3.5±0.8)h,Vz为(29.1±12.2)L,AUC0_t为(1970.2±834.7)ng·h/mL,CL为(5.9±2.5)L/h.与静脉给药相比,口服艾普拉唑肠溶片的绝对生物利用度为(55.2±13.9)%. 结论 艾普拉唑肠溶片生物利用度良好,适于开发.     

Pharmacokinetics and oral bioavailability of carbimide in man

A pharmacokinetic study of carbimide, an inhibitor of aldehyde dehydrogenase, used as an adjuvant in the aversive therapy of chronic alcoholism, has been carried out in male human volunteers for intravenous and oral administration. Carbimide plasma concentrations were determined by a sensitive and specific high performance liquid chromatographic method. The intravenous doses administered were 0.1, 0.3, 0.6, and 1 mg kg-1 and linear pharmacokinetics were observed for this dose range. Elimination half-life and total plasma clearance values ranged from 42 to 52 min and from 14.4 to 20.5 ml kg-1 min-1, respectively. After oral administration of 1 and 1.5 mg kg-1 of carbimide, elimination half-life values were 75 and 61 min, respectively, being higher than the corresponding value obtained after 0.3 mg kg-1 doses, i.e. 39 min. In all cases, rapid absorption was indicated by tmax values ranging from 10.5 to 15.5 min. Absorption was not complete, the oral bioavailability being 53 per cent and 70 per cent for the 0.3 and 1 mg kg-1 carbimide dose, respectively. The data indicate that there is a first-pass effect for carbimide.     

Pharmacokinetics and relative bioavailability of heptabarbital and heptabarbital sodium after oral administration to man

Summary A method has been developed for the quantitative determination of heptabarbital [5-(1-cyclohepten-1-yl)-5-ethylbarbituric acid] in human plasma after administration of single therapeutic doses of the drug. It involves a single extraction step followed by gas chromatography with alkali flame ionization detection, and the results were linear in the concentration range 0.125 – 5.0 µg/ml plasma. The pharmacokinetics and relative bioavailability of heptabarbital and heptabarbital sodium were studied in a crossover design in 7 healthy volunteers after oral administration of 20 tablets containing 200 mg heptabarbital and hard gelatine capsules containing an equivalent amount of its sodium salt. Heptabarbital concentrations in plasma were determined at regular intervals. The absorption of heptabarbital from the tablets was quite slow and peak level times varied from 1.5 to 4 h. The sodium salt was absorbed more rapidly and peak concentrations occurred between 1/3 and 2 h. In all cases the elimination of heptabarbital could be described by a single first-order process with an average half-life of 7.6 h (range 6.1 – 11.2 h). The half-life of the drug in each individual was about the same in the two trials. The relative bioavailability in each volunteer was estimated by comparing the areas under the plasma concentration curves. The sodium salt had an average bioavailability of 83% relative to the free acid. In some volunteers urinary excretion of unchanged heptabarbital was measured; cumulative excretion amounted to 0.16 – 0.30% of the administered dose. Four volunteers received one tablet each night for eight or ten days, but no accumulation was found. In three volunteers the half-life of the drug prior to and after these experiments did not change, whereas in the other volunteer the half-life decreased from 7.1 to 4.6 h. The possibility of enzyme induction should be considered when heptabarbital is taken regularly. It was concluded that heptabarbital was a suitable drug for the treatment of insomnia, since its half-life was rather short. Heptabarbital sodium may be used for induction of sleep, whereas Medomin^® tablets, i.e. heptabarbital free acid, may be prescribed when the maintenance of sleep is the primary reason for treatment with a hypnotic drug.     

Absorption kinetics of rectally and orally administered ibuprofen

The bioavailability of rectally administered sodium ibuprofen solution and aluminum ibuprofen suspension was determined in eight normal subjects relative to the same treatments administered orally. The results indicate that the suspension was less bioavailable than the solution irrespective of the route of administration. Although not bioequivalent, rectally administered ibuprofen solution compared favourably with orally administered ibuprofen solution. The mean AUC and Cmax from rectal administration were 87 per cent and 62 per cent of the corresponding values achieved after oral administration. Mean residence times and peak times were 1-3 h longer with the rectal solution, indicating a slower rate of absorption. Absorption after rectal administration was zero order in some subjects while absorption after oral administration was first order. This may be due to the large differences in surface area between absorption sites. Since sodium ibuprofen solution is absorbed when given rectally, this route of administration could be used in patients unable to take oral ibuprofen.     

Pharmacokinetics and oral bioavailability of pyridostigmine in man

Summary The pharmacokinetics of pyridostigmine was evaluated after intravenous injection in two healthy male volunteers and after oral administration to five subjects. Plasma concentrations of pyridostigmine were determined after ion pair extraction from plasma and analysis by gas chromatography — mass spectrometry with chemical ionization, using d₆-pyridostigmine as internal standard. Degradation of pyridostigmine in vitro was compensated for by use of the deuterated internal standard and by rapid cooling and separation of plasma after blood sampling. After intravenous administration of pyridostigmine 2.5 mg the plasma elimination half-life was 1.52 h, the volume of distribution was 1.43 l/kg and the plasma clearance 0.65 l/kg × h. The pharmacokinetic constants were very similar after oral administration of pyridostigmine 120 mg; the elimination half-life was 1.78±0.24 h, the volume of distribution 1.64±0.29 l/kg and the plasma clearance was 0.66±0.22 l/kg × h. The bioavailability was calculated to be 7.6±2.4%. When pyridostigmine was taken together with food, the time to reach the peak plasma concentration was prolonged from 1.7 to 3.2 h. Bioavailability, however, was not influenced by concomitant food intake. Steady-state plasma concentrations of pyridostigmine were measured in myasthenic patients on their ordinary dose schedule of cholinesterase inhibitor drugs. More than a seven-fold difference in steady-state plasma concentration was found between patients taking approximately the same daily dose of pyridostigmine.     

灵仙新苷在Beagle犬体内的药动学及其绝对生物利用度研究

目的：研究灵仙新苷在Beagle犬体内的药动学和绝对生物利用度。方法：采用四周期交叉设计,即Beagle犬8只,雌雄各半,随机等分为4组,分别采取单剂量静脉注射（0．75mg／kg）及灌胃（7．5、15和30mg／kg）两种给药方式,交叉给药,间隔1周。并于给药后不同时间点取血,采用LC—MS／MS测定血浆中灵仙新苷的浓度,利用DAS2．0软件估算灵仙新苷在Beagle犬体内的药动学参数,并计算绝对生物利用度。结果：Beagle犬i．g．7．5、15和30mg／kg灵仙新苷后,估算的tl／2分别为（14．3±2．7）、（13．3±1．3）和（13．7±2．4）h,AUC0—36分别为（1．9±1．2）、（4．5±1．9）和（8．0±3．3）μg·h·mL-1,Cmax分别为（0．14±0．08）、（0．27±0．10）和（0．52±0．28）μg／mL。i．v．0．75mg／kg灵仙新苷后,估算的t1／2为（13．3±3．0）h,AUC0-36为（66．2±12．8）μg·h·mL-1。灌胃灵仙新苷在Beagle犬体内的绝对生物利用度分别为0．32％、0．35％和0．30％。结论：口服灵仙新苷后在Beagle犬体内绝对生物利用度很低,其药动学过程在研究剂量范围内是线性的。     

Pharmacokinetics of furosemide after three different single oral doses

Furosemide solution was orally administered to 21 healthy adult males to determine dose proportionality over the dose range used and the reproducibility of disposition following a repeated dose. Furosemide solution was given in doses of 20, 40, and 80 mg, with the 40 mg dose repeated once. Blood was collected for 12 hours post-dose and urine for 24 hours. The maximum plasma concentrations resulting from 20, 40, and 80 mg doses were significantly different (p less than 0.05). Dose normalized maximum concentrations for the 20 and 80 mg doses were significantly different (p less than 0.05). Mean time to Cpmax was 50 minutes, with no differences observed among doses. Plasma AUCs were significantly different (p less than 0.05) for 20, 40, and 80 mg. Dose normalized AUCs were not significantly different. Mean amounts of furosemide in urine (Xu) were 9.62, 16.7, and 32.0 mg for the 20, 40, and 80 mg doses, respectively. These amounts were significantly different (p less than 0.05); dose normalized amounts were not significantly different. Renal clearances of furosemide following the three doses were not significantly different. Regressions of Cpmax, AUC and Xu on dose were significant. There were no significant differences in Cpmax, tmax, AUC or Xu for 40 mg given on two separate days. Renal clearance of furosemide was statistically different for 40 mg given on two separate days, but the difference was not clinically significant. The pharmacokinetics of furosemide are linear over the dosage range studied. Furosemide 40 mg given on two separate days results in similar disposition parameters.     

Pharmacokinetics and absolute bioavailability of lansoprazole

Objective: In a crossover study 12 healthy volunteers received lansoprazole 15 mg or 30 mg orally, or 15 mg intravenously in randomized order as a single dose. Blood samples were taken and plasma levels of lansoprazole were determined using an HPLC method. The volunteers were phenotyped for the debrisoquine/sparteine and mephenytoin polymorphisms. Results: The total clearance was 517 ml⋅min⁻¹, and the absolute bioavailability was 91% for the 30-mg and 81% for the 15-mg enteric-coated formulation. The elimination half-life was about 1 h. No correlation of the plasma levels to the sparteine metabolic ratio was found, and no correlation to the mephenytoin type could be established, since all volunteers of the mephenytoin type were extensive metabolizers. Although considerable variation, inter- and intraindividually, was observed, the increase in c_max and AUC did not deviate from dose proportionality. The present galenic formulation ensures a high bioavailability after a single dose. Received: 24 March 1995/Accepted in revised form: 11 July 1995     

The absolute bioavailability of caffeine in man

Summary The absolute bioavailability of orally administered caffeine was investigated in 10 healthy adult male volunteers, aged 18.8 to 30.0 years. The subjects were administered a 5 mg/kg dose of caffeine as either an aqueous oral solution or an intravenous infusion, on separate occasions about 1 week apart, in a randomized crossover fashion. Plasma samples were collected over the 24-h period following each dose and assayed for their caffeine content using a high-performance liquid chromatographic technique. The oral absorption was very rapid, reaching a peak (T_p) plasma concentration after 29.8±8.1 min (mean±SEM). In addition, the variation in the maximum plasma concentration (C_max) was low, 10.0±1.0 µg/ml. The absolute bioavailability was assessed by comparing the areas under the plasma concentration vs. time curves for the intravenous and oral doses of caffeine. The rapid absorption resulted in essentially complete bioavailability of the oral caffeine, F(%)=108.3±3.6%. The caffeine plasma half-lives varied from 2.7 to 9.9 h, indicating substantial inter-subject variability in its elimination.     

Cocaine pharmacodynamics after intravenous and oral administration in rats: relation to pharmacokinetics

  Rationale: To design optimal dose regimes for oral cocaine, it is essential to characterize pharmacokinetics (PK) of cocaine after IV and PO administration. Objectives: To investigate the absolute bioavailability of oral cocaine, its effectiveness and the relation between PK and PD in a within-subject design. Methods: We used the effects of IV and PO cocaine on a contingency-controlled timing behavior, the differential reinforcement of low rate schedule (DRL 45-s) in 3-h sessions, as the PD measures [i.e., the shorter-response rate (srr) and the reinforcement rate (rr)]. Cocaine PK parameters were determined by simultaneous modeling of the concentration-time profiles (CTPs) after IV 2 mg/kg and PO 20 mg/kg cocaine administration. The absolute oral cocaine bioavailability was determined pharmacokinetically (F) and pharmacodynamically (F_srr and F_rr). Results: IV and PO cocaine increased the shorter response rate and decreased the reinforcement rate in a dose- and time-related fashion, which mirrored the respective prototypical serum cocaine CTPs. After the absorption phase, the serum cocaine CTP of PO cocaine paralleled that of IV cocaine. The duration of action for PO cocaine was longer than that for IV cocaine owing to its larger mean residence time. The active metabolite, norcocaine, was not detected after IV but after PO cocaine administration. The value of F was 4.66% which was significantly lower than the values of F_srr (13.67%) and F_rr (32.63%). Furthermore, the concentration-effect relations for the reinforcement rate revealed that PO cocaine was more potent than IV cocaine. Conclusions: Oral cocaine is more effective behaviorally than from predictions made in terms of its PK. The differences in active metabolite profiles as well as the rate and extent of acute tolerance for IV versus PO cocaine may account for the greater potency observed for oral cocaine. Received: 23 July 1998 / Final version: 2 February 1999     

单剂量口服布洛芬控释片的药物动力学与相对生物利用度

研究单剂量ｐｏ布洛芬控释片与缓释胶囊后，血清中的药物动力学与相对生物利用度。结论两种制剂单剂量给药６００ｍｇ时为生物等效；以Ｂ为标准参比制剂，单剂量给药时Ａ相对生物利用度为     

Comparison of the bioavailability of dexibuprofen administered alone or as part of racemic ibuprofen

Two bioavailability studies of S(+)-ibuprofen (dexibuprofen) were conducted in healthy volunteers to define the relationship between the bioavailability of the drug after administration of dexibuprofen alone or as part of ibuprofen racemate. Enantioselective plasma drug analysis was used throughout. In the first study, the bioavailability of dexibuprofen from a 400 mg tablet formulation was compared with that from 400 mg in aqueous solution.The tablet formulation did not influence the bioavailability of the drug and dexibuprofen was well absorbed from the gastro-intestinal tract.The second study was divided into three identical parts. Bioavailability of dexibuprofen 200, 400 and 600 mg was compared with its bioavailability from ibuprofen racemate 400, 800 and 1200 mg.The second study showed that the mean relative bioavailability of dexibuprofen to ibuprofen racemate was 0.66, thus enabling the estimation of clinically useful dexibuprofen doses from the usual doses of the racemate. The 95% confidence interval limits did not include 0.5, leading to the conclusion that administering half of the racemate dose would not provide patients with an adequate amount of therapeutically active drug.     

Pilot toxicokinetic study and absolute oral bioavailability of the Fusarium mycotoxin enniatin B1 in pigs

The aim of present study was to reveal the toxicokinetic properties and absolute oral bioavailability of enniatin B1 in pigs. Five pigs were administered this Fusarium mycotoxin per os and intravenously in a two-way cross-over design. The toxicokinetic profile fitted a two-compartmental model. Enniatin B1 is rapidly absorbed after oral administration (T_1/2a = 0.15 h, T_max = 0.24 h) and rapidly distributed and eliminated as well (T_1/2elα = 0.15 h; T_1/2elβ = 1.57 h). The absolute oral bioavailability is high (90.9%), indicating a clear systemic exposure. After intravenous administration, the mycotoxin is distributed and eliminated rapidly (T_1/2elα = 0.15 h; T_1/2elβ = 1.13 h), in accordance with oral administration.     

Absolute bioavailability of chlorthalidone in man: A cross-over study after intravenous and oral administration

Summary Seven normal human volunteers each received a constant-rate infusion of chlorthalidone for 2 h, and the same (commonly 50 mg) single oral dose on separate occasions. The concentration of unchanged chlorthalidone was analyzed over a 100 to 220 h period in plasma, red blood cells, urine and faeces after both dosage forms. A three compartment model was required to describe the intravenous plasma concentrations in five of the subjects. A two compartment model sufficed to account for the decay of the oral plasma concentrations in all seven subjects. The mean plasma t_1/2 after i.v. dosing was 36.5 h (±10.5 SD), and the mean plasma t_1/2 after oral doses was 44.1 h (±9.6 SD). The mean red blood cell concentration t_1/2 after i.v. doses was 46.4 h (±9.9 SD), and the mean red blood cell t_1/2 after the oral doses was 52.7 h (±9.0 SD). The shorter i.v. half-live was not equally manifest in all subjects, being mainly apparent in three of them. In all cases the urinary excretion rate plots were parallel to the plasma concentration curves. As the faster decay after i.v. administration was not accompanied by increased renal clearance, the difference must have been due to non-renal mechanism. The mean total of 65.4 (±8.6 SD) % of the intravenous dose was excreted in urine over infinite time, whereas the mean total excretion after the oral dose was 43.8 (±8.5 SD) %. Faecal excretion ranged from 1.3–8.5% of dose in the i.v. study to 17.5–31.2% of dose in the oral study. The sum of the amounts present in urine plus faeces pointed strongly to an important metabolic route of elimination of chlorthalidone. Bioavailability estimates (F) from three sets of data were — a mean F of 0.61 from plasma concentrations, 0.67 from urinary excretion measurements and 0.72 from the erythrocyte concentrations. Simulations with a non-linear model indicated lesser validity of the estimate from erythrocyte concentrations. It was concluded that the average of plasma and urine data, F=0.64, yielded the best estimate of the oral availability of chlorthalidone 50 mg in man.