Effect of concomitant food intake on absorption kinetics of erythromycin in healthy volunteers

Summary The steady state absorption of erythromycin from enteric-coated pellets of erythromycin base was compared with that from enteric-coated tablets in a randomized, two-way cross-over study in 24 healthy adult volunteers. A higher mean individual peak concentration (p<0.01), and a greater mean area under the serum concentration-time (0–8 h) curve (AUC,p<0.01) was produced by the enteric-coated pellets, when the preparations were administered 1 hour before breakfast. No significant differences in the kinetic parameters between the two preparations were observed when they were taken during a non-standardized breakfast, as concomitant food intake was found to reduce both the peak levels and the AUC-values (p<0.01) produced by the pelleted preparation.     

The effect of food on the interaction of ofloxacin with sucralfate in healthy volunteers

We have studied the effect of food on the interaction of ofloxacin with sucralfate. Six healthy men took a single oral dose of ofloxacin (200 mg) on 4 occasions: alone after overnight fasting or after breakfast (non-fasting), and with sucralfate fasting or non-fasting.There were no significant differences in the plasma concentration-time profiles of ofloxacin after ofloxacin alone between fasting and non-fasting conditions. On the other hand, the peak plasma concentration and AUC of ofloxacin after co-administration with sucralfate while fasting fell by 70 and 61 % compared with ofloxacin alone; the changes non-fasting were 39 and 31 % respectively. The interaction of ofloxacin with sucralfate was markedly reduced by food, but still could not be disregarded.     

Zero-order absorption and linear disposition of oral colchicine in healthy volunteers

Summary The pharmacokinetics of colchicine has been studied in nine healthy male volunteers after oral doses of 0.5, 1, and 1.5 mg as tablets. Plasma and urine samples were collected over 48 h and analysed for colchicine by radioimmunoassay.Individual colchicine concentration profiles in plasma and urine were well described by a two-compartment open model with zero-order input. Considering the absorption variables as specific to each experiment, the lag time (0–0.35 h) and duration (0.39–2.38 h) of absorption were found to be independent of dose, while the zero-order rate constant of absorption (k₀) increased linearly with dose.Disposition variables were taken as common to the three experiments, except in six subjects in whom renal excretion varied significantly across experiments in a dose-independent manner. For seven subjects the terminal half-life was 19.4 h, the oral apparent volume of distribution at steady-state (V_ss/f) was 691 l, and the oral systemic clearance (CL/f) was 33.1 l·h^–1. In the two other subjects, the values were unreliable, but the estimated terminal half-life was greater than 48 h, V_ss/f ranged from 1690 to 3480 l, and CL/f was in the range of the other subjects in 1 subject, and it was about 15l·h^–1 in the other. In the latter subject, these estimates, together with the observation that plasma concentration reached a plateau at 2 to 5 h after ingestion, suggest enterohepatic cycling of colchicine.Overall, the disposition of colchicine was linear in the dose range 0.5–1.5 mg, with a long terminal half-life, and absorption obeyed zero-order kinetics, with k₀ proportional to dose.     

Erythromycin absorption in healthy volunteers from single and multiple doses of enteric-coated pellets and tablets

Summary The absorption of erythromycin from two different enteric-coated preparations was evaluated in three groups of healthy volunteers. After a single dose, taken after an overnight fast, absorption was significantly better from enteric-coated pellets than from tablets; both the mean peak serum concentration and the peak mean level were higher (p<0.01) in all three groups, and the mean area under the serum concentration-time curve (AUC) was at least 65% larger. Eight out of 23 subjects showed no or only a very low serum concentration after the enteric-coated tablets. In a follow-up study, 250 mg doses were given 6-hourly for 3 days, and again the mean maximum serum concentration was significantly higher (p<0.05) after the pellets. In conclusion, enteric-coated pellets led to more regular and predictable absorption of erythromycin than did coated tablets.     

The pharmacokinetics of ofloxacin in healthy adult male volunteers

Conclusion In healthy subjects ofloxacin pharmacokinetics were found to be linear in the dose range studied (100–400 mg). The terminal half-time was 7.5–8 h and plasma ofloxacin concentrations were still detectable at 16 and 24 h after administration. The ratio of renal ofloxacin clerance: creatinine clearance was 1.35–1.82 and was not significantly different for the three doses. The non-renal clearance of ofloxacin was 40–60 ml·min^–1, i.e. 20–30% of the total body clearance.Food intake delayed the absorption of ofloxacin but did not significantly modify its elimination.     

来氟米特在中国健康人群中的群体药动学研究

目的：建立来氟米特口服给药在中国健康受试者体内的群体药动学模型,探讨其药动学特征及可能的影响因素。方法：21名健康男性受试者参与本次研究,应用Phoenix NLME（Vision 8.0）软件中的群体模块分析来氟米特口服给药后其代谢产物的血药浓度数据,估算相关药动学参数及其变异情况。结果：来氟米特活性代谢产物特立氟胺在健康志愿者中符合一级吸收的一室模型。吸收速率常数K_a、分布容积V、药物清除率CL的群体典型值分别为0.691 h^-1、12.843 L和0.031 L·h^-1。协变量筛选结果显示,BMI对分布容积V有显著影响（P<0.01）。结论：本研究成功建立了来氟米特在中国健康人群中的群体药动学模型,最终模型可对个体药代参数做出精确的估计,BMI对分布容积V有显著影响。     

Pharmacokinetics of nicardipine enantiomers in healthy young volunteers

Objectives: The present study was conducted to compare pharmacokinetic behaviors of nicardipine enantiomers given in different doses with different formulations of racemic nicardipine in healthy volunteers. Methods: One or two 20-mg racemic nicardipine tablets, and a 40-mg sustained-release capsule of nicardipine were administered to eight healthy volunteers in a cross-over fashion and pharmacokinetic parameters were evaluated. Enantiomer concentrations were determined by GC-MS combined with chiral stationary phase HPLC. Results and conclusions: Serum concentration of (+)-nicardipine was approximately 2–3 times higher than that of (−)-nicardipine in 20- and 40-mg doses of conventional formulations and a non-linear increase in bioavailability with dose was demonstrated. The value for AUC of (+)-nicardipine was approximately 2.3–2.8 times greater than that of the (−)-nicardipine (P < 0.05) when 20 and 40 mg racemic nicardipine were administered in a conventional preparation. Relative bioavailability of the sustained-release preparation vs the conventional preparation was 28% and 44% for (+)- and (−)-nicardipine, respectively, for the 40-mg dose. Received: 23 September 1996 / Accepted in revised form: 23 February 1997     

Pharmacokinetics of (+)-rolipram and (−)-rolipram in healthy volunteers

Summary Plasma levels of S-(+)-rolipram and R-(–)-rolipram in six healthy male volunteers were measured by radioimmunoassay after intravenous injection of 0.1 mg and oral administration of 1.0 mg of the pure enantionmers. Following i.v. treatment, plasma levels of both isomers declined in three phases, with half-lives of 0.2 h, 0.6–0.9 h and 6–8 h. Total clearance was 6 ml · min^–1 · kg^–1. Oral administration of 1.0 mg gave a peak concentration of 16 ng · ml^–1 after 0.5 h. Bioavailability of (+)-rolipram was 77% and of the (–) enantiomer it was 74%. There was no significant difference in C_max, half-life, total clearance or bioavailability between the two enantiomers.     

Influence of input rates on (±)-isradipine haemodynamics and concentration-effect relationship in healthy volunteers

Summary Since the magnitude of the response to a drug may depend upon the drug input rate, the concentration-effect relationship of the new dihydropyridine (±)-isradipine was investigated using different administration modalities.Ten normotensive healthy volunteers were given, double-blind and in a crossover fashion, isradipine as a 1 mg iv infusion, 5 mg oral solution, 5 mg standard tablet, 10 mg slow release formulation, and a placebo. Blood pressure, heart rate, and plasma isradipine concentrations were recorded for 24 h.The maximal fall in diastolic blood pressure was similar after the infusion (-11.40 mmHg), the oral solution (-15.20 mmHg), and the standard tablet (-12.50 mmHg). In healthy volunteers the slow release form had no significant effect on blood pressure. The concentration-effect plots showed an increasing slope in the order infusion, solution, and tablet, and anticlockwise hysteresis. This was partly due to marked heart rate counter-regulation, the corresponding mean maximal heart rate increases being 24, 19, and 17 beats·min^–1.The pronounced counter-regulation of the heart rate implies that a slow isradipine input rate would be more effective in decreasing blood pressure.     

Metabolism and disposition of intravenously administered acetyl-L-carnitine in healthy volunteers

Summary The pharmacokinetics of acetyl-L-carnitine hydrochloride were investigated in 6 healthy volunteers of both sexes after i.v. injection of 500 mg of the drug, expressed as inner salt.Plasma concentrations and urinary excretion of acetyl-L-carnitine (A), L-carnitine (B) and total acid soluble L-carnitine fraction were evaluated over a period lasting from 24 h before to 48 h after the administration. Plasma concentrations of A increased quickly after administration and then declined reaching base values within 12 h.Conversely, plasma concentrations of B rose more slowly, reaching a peak in 30–60 min, and then declined to base values within 24 h. Most of the injected dose of acetyl-L-carnitine was recovered in the urine during the first 24 h after administration as B and A.Mean renal clearance of both A and B during the first 12 h after injection was higher than the base values, suggesting the presence of a saturable tubular reabsorption process which may counterbalance major changes occurring in plasma concentrations of L-carnitine pattern. Present address: Institute of Pharmacology, University of Siena, Italy     

Effect of fenoldopam prodrug,SK&F R-105058, on renal function in rats

Recent development of and studies on fenoldopam prodrugs have shown their prolonged hemodynamic effects. This study was carried out in order to examine the effect of a fenoldopam prodrug on renal function in rats. In the present study we administered SK&F R-105058, the 4′,7,8-tris-N-ethyl carbamate ester of R-fenoldopam, at a dose of 30 μg/kg/min intravenously to the anesthetized rats. This prodrug produced long-lasting increases in water and sodium excretion after termination of the 30-min drug infusion with minimum changes in hemodynamic parameters. The diuresis and natriuresis were attenuated in the presence of a selective DA₁ receptor antagonist SCH 23390. Therefore, it is suggested that production of fenoldopam from its precursor drug SK&F R-105058 caused these prolonged renal effects, which were mediated via the activation of DA₁ receptors located on renal tubules. © 1992 Wiley-Liss, Inc.     

The pharmacokinetics and pharmacodynamics of lisuride in healthy volunteers after intravenous,intramuscular, and subcutaneous injection

Summary The plasma concentration of lisuride and prolactin have been measured in twelve healthy male volunteers after IV, IM or SC injection of 25 g lisuride hydrogen maleate as an aqueous solution.After IV administration the plasma lisuride fell in two phases with half-lives of 14 min and 1.5 h. Total clearance was 13 ml·min^–1·kg^–1. After IM and SC injection the plasma concentrations peaked at 12 to 15 min and the profiles were similar to that found after IV administration. The systemic availabilities were 90% and 94%, respectively. Prolactin concentrations were reduced by a maximum of 60% relative to the normal circadian rhythm after all three routes of administration.The treatments were well tolerated, the only adverse reactions reported by some of the volunteers being mild, transient dizziness, tiredness, and nausea.     

头孢吡肟注射液在汉族健康人体的药物代谢动力学

目的研究汉族健康志愿者单剂量静脉滴注盐酸头孢吡肟后的药物代谢动力学。方法汉族健康志愿者10名,男女各半,单剂量静脉滴注盐酸头孢吡肟1.0 g,采用HPLC法测定血浆中头孢吡肟的含量,用DAS软件进行数据处理。结果健康志愿者单剂量静脉滴注1.0 g盐酸头孢吡肟后的药物动力学参数:mρax为(68.75±10.41)mg.L-1、t1/2β为(1.97±0.20)h、AUC0-10.5 h为(136.89±23.02)mg.h.L-1、AUC0-∞为(139.69±23.78)mg.h.L-1。结论汉族健康志愿者单剂量静脉滴注盐酸头孢吡肟的体内药物动力学过程符合二室模型,不同性别受试者药物动力学参数的差异无统计学意义。     

Effects of Schisandra sphenanthera extract on the pharmacokinetics of tacrolimus in healthy volunteers

AIM: To assess the effect of Schisandra sphenanthera extract (SchE) on the pharmacokinetics of tacrolimus in healthy volunteers. METHODS: Twelve healthy male volunteers were orally treated with SchE, three capsules twice daily for 13 days. Pharmacokinetic investigations of oral tacrolimus administration at 2 mg were performed both before and at the end of the SchE treatment period. Whole blood tacrolimus concentrations were determined by enzyme-linked immunosorbent assay. Estimated pharmacokinetic parameters before and with SchE were calculated with noncompartmental techniques. RESULTS: Following administration of SchE, the average percentage increases of individual increases in AUC, AUMC and C(max) of tacrolimus were 164.2% [95% confidence interval (CI) 70.1, 258.4], 133.1% (95% CI 49.5, 261.3) and 227.1% (95% CI 155.8, 298.4), respectively (P < 0.01 or 0.05). On average, there was a 36.8% (95% CI 13.4, 60.2) increase in tacrolimus t(max) (P < 0.01). The average percentage decreases in CL/F and V/F were 49.0% (95% CI 31.1, 66.9) and 53.7% (95% CI 40.1, 67.4), respectively (P < 0.01). CONCLUSIONS: SchE can increase the oral bioavailability of tacrolimus. The results of this study will add important information to the interaction area between drugs and herbal products.     

Influence of fluconazole on the pharmacokinetics of omeprazole in healthy volunteers

Influence of fluconazole on the pharmacokinetics of omeprazole was evaluated by single oral administration of omeprazole capsule 20 mg (control group), or single oral administration of fluconazole capsule, 100 mg, and omeprazole, 20 mg, after 4 days of daily oral administration of fluconazole, 100 mg (treated group), to 18 healthy male volunteers. Omeprazole is extensively metabolized in the liver through 5-hydroxylation and sulfoxidation reactions catalyzed predominantly by CYP2C19 and CYP3A4, respectively. Fluconazole is a potent competitive inhibitor of CYP2C19 and a weak inhibitor of CYP3A4. In treated group, the area under the plasma concentration-time curve of omeprazole from time zero to time infinity (AUC) was significantly greater (3090 vs 491 ng h/ml), terminal half-life of omeprazole was significantly longer (2.59 vs 0.85 h), and peak plasma concentration of omeprazole (C(max)) was significantly higher (746 vs 311 ng/ml) than that in control group. The greater AUC and higher C(max) in treated group could be due to inhibition of omeprazole metabolism by fluconazole.     

Pharmacokinetics and absolute bioavailability of salbutamol in healthy adult volunteers

Summary Salbutamol was administered to sixteen healthy male volunteers intravenously and by mouth in liquid, tablet, and capsule form using a Latin-Squares design. Pharmacokinetic parameters from intravenous data were similar to previously reported values obtained with oral administration, with a mean terminal half-life of 3.8 h and a mean clearance of 439 ml·min⁻¹·1.73 m⁻². Peak plasma concentrations of 10–20 ng·ml⁻¹ were obtained 1–3 h following oral administration. The absolute bioavailability of each of the oral preparations was 44%. While statistically significant differences in lag time and time to peak concentration were noted among the various oral preparations, the drug is rapidly absorbed in all three dosage forms and the observed differences are unlikely to be of clinical significance.     

Dose proportionality of iopromide pharmacokinetics and tolerability after IV injection in healthy volunteers

Twelve healthy male volunteers participated in a single-blind, randomised, placebo-controlled cross-over study of IV iopromide in doses of 15 g iodine or 80 g iodine infused over a period of 15 min. The volunteers were observed for three days during which time blood samples, urine and faeces were collected.The terminal disposition phase half-life of iopromide was 2 h and 1.9 h, and the total clearance was 110 and 103 ml·min^-1 at the lower and at the higher dose levels, respectively. The steady state volume of distribution was 16 and 17 l, indicating predominantly extracellular distribution of iopromide.Statistical analysis (one-sided t-test) showed that all the target parameters (AUC, half-life and urinary excretion) were equivalent at both dose levels, indicating dose proportionate, first order kinetics of iopromide over the large dose range tested. Iopromide was well tolerated after both doses.     

Pharmacological activity and safety of trandolapril (RU 44570) in healthy volunteers

Summary The pharmacological activity and safety of the new angiotensin converting enzyme (ACE) inhibitor trandolapril (RU 44570) has been evaluated in ten healthy male volunteers given 2 mg once daily for seven days. Assessment criteria included evaluation of plasma ACE and renin activity and aldosterone levels in the supine and standing positions, monitoring of blood pressure, heart rate and electrocardiogram, routine blood and urine laboratory tests, and evaluation of adverse effects.Plasma ACE activity (both in the supine and standing positions) was significantly lower after the first dose and was almost completely suppressed after 7 days of treatment. Plasma renin activity with the subjects in both positions was significantly increased at the end of treatment. Plasma aldosterone did not vary significantly, except for an increase in the standing position after 7 days of washout. No significant changes occurred in blood pressure, heart rate, electrocardiogram, blood or urine laboratory tests. No adverse effects were reported, in particular, no orthostatic hypotension, cough or episodes of bronchospasm occurred.It is concluded that oral trandolapril 2 mg o.d. is an effective and long-lasting ACE inhibitor with a good safety profile on repeated dosing. Further studies are warranted to investigate its therapeutic application as well as its safety profile after long-term administration.     

The pharmacokinetics of tiopronin and its principal metabolite (2-mercaptopropionic acid) after oral administration to healthy volunteers

Summary We have studied the pharmacokinetics of tiopronin and its principal metabolite, 2-mercaptopropionic acid (2-MPA) in healthy volunteers after the oral administration of 500 mg (2 Acadione® tablets), followed by simultaneous assay of the two compounds in plasma over a period of 48 h using a new method (emission of fluorescence after HPLC and post-column derivatization by pyrene-maleimide). The absorption of tiopronin was slow (t_max between 4 and 6 h) and the plasma concentrations subsequently fell biexponentially. The principal metabolite 2-MPA appeared later in the plasma (t_max between 10 and 12 h after a lag-time of 3 h) then disappeared monoexponentially. About 15% of the tiopronin was metabolized to 2-MPA.     

Gastrointestinal absorption of hydrochlorothiazide enhanced by concomitant intake of food

Summary Hydrochlorothiazide (hct) 75 mg was administered orally to eight healthy volunteers without (Study I) or together with a standardized meal (Study II), and plasma and urine concentrations of hct were analyzed by GLC. The plasma levels of hct were higher initially when the tablets were taken on an empty stomach, but after 5 h they were higher in Study II. There was no difference between the two studies in the area under plasma concentration time curves. The urinary recovery of hct totalled 55.6±4.9 mg when the drug was given with food and 47.4±6.0 when it was taken on an empty stomach. The difference is significant (p<0.01). As the urinary recovery represents the uptake of hct, it appears that the gastrointestinal absorption of hct is enhanced when the drug is given with food.Supported by the Swedish Medical Research Council (Grant No. B 78-19X-00227-14)