The pharmacokinetics of intravenous and oral sulpiride in healthy human subjects

Summary The pharmacokinetics of sulpiride was studied in 6 healthy volunteers after intravenous and oral (tablets) administration of 100 mg. An open two- and in two subjects a three-compartment model was applied following intravenous administration. The average total distribution volume during the terminal slope was 2.72±0.66 l/kg and total systemic clearance was 415±84 ml/min. The serum half-life of the terminal slope following intravenous administration averaged 5.3 h (range 3.7–7.1 h) according to the two-compartment model. In two subjects the half-lives were 11.0 and 13.9 h when the three-compartment model was applied. Determination of urinary excretion rates of unchanged sulpiride indicated a half-life of 7.15 h. Following intravenous administration, 70±9% of the dose was recovered unchanged in urine within 36 h; the mean renal clearance was 310±91 ml/min. Sulpiride was absorbed slowly, with peak concentrations appearing between 3 and 6 h after oral administration. The recovery of unchanged drug in urine following oral administration was 15±5% of the dose, with a mean renal clearance of 223±47 ml/min. The bioavailability determined from combined plasma and urine data was only 27±9%. The low bioavailability was probably due to incomplete absorption.     

Steady state bioavailability of a new oral formulation of Hydergine® in geriatric patients

Summary The relative bioavailability of the newly developed formulation of co-dergocrine mesylate (Hydergine spezial, 1×4 mg) was determined in elderly patients under steady state conditions, with conventional Hydergine forte tablets (2×2 mg) as a reference. Both formulations were given once a day for 8 days in a randomised cross-over design. The areas under the curve showed that the bioavailability of the new tablet was about 30% higher (28±6.3%) than that of Hydergine forte. The peak plasma concentration was reached 3±0.9 h after administration. Because of its greater relative bioavailability higher plasma levels were found 2–24 hours after the Hydergine spezial formulation than after Hydergine forte tablets.     

Pharmacokinetics and bioavailability of diacetolol,the main metabolite of acebutolol

Summary The pharmacokinetics and bioavailability of diacetolol, the principal metabolite of acebutolol, were studied in 6 healthy subjects. Plasma concentrations were determined following a single intravenous injection of diacetolol 100 mg and three oral doses of diacetolol 100, 400 and 800 mg, in random order. The average oral bioavailability of diacetolol was F: 0.302±0.052 (100 mg), 0.363±0.052 (400 mg) and 0.426±0.068 (800 mg); the differences are not significant. The mean plasma half-life of the terminal phase, 7.94±0.26 h after intravenous administration, was significantly higher than after oral administration 12.27±1.00 h (100 mg), 12.82±1.59 h (400 mg) and 13.05±1.22 h (800 mg) (p<0.02 to 0.05); the mean urine half-lives of the terminal phase were not significantly different. Renal clearance of diacetolol 10.2±0.81·h^–1 represented about two-thirds of total body clearance 15.9±1.21·h^–1. The results suggest either a first-pass effect or incomplete absorption of diacetolol after oral administration.     

Clinical and chemical interactions between iron preparations and ciprofloxacin.

1. The effect of ferrous sulphate (300 mg), ferrous gluconate (600 mg), and a combination tablet of iron (10 mg), magnesium (100 mg), zinc (15 mg), calcium (162 mg), copper (2 mg), and manganese (5 mg) (Centrum Forte) co-administration on ciprofloxacin bioavailability was tested in eight healthy subjects. 2. Peak serum ciprofloxacin concentrations and area under the curve (AUC) were significantly reduced when ciprofloxacin was administered with 300 mg ferrous sulphate (3.0 vs 2.0 mg l-1, P less than 0.05 and 12.3 vs 6.7 mg l-1 h, P less than 0.01, respectively). Reductions in peak ciprofloxacin concentrations and AUC also occurred when ciprofloxacin was ingested with 600 mg ferrous gluconate (1.3 mg l-1, P less than 0.01 and 4.1 mg l-1 h, P less than 0.01, respectively) and a Centrum Forte tablet (1.4 mg l-1, P less than 0.01 and 5.4 mg l-1 h, P less than 0.01, respectively). 3. When ferrous ion was mixed with ciprofloxacin, rapid spectral changes occurred (t1/2 = 1.9 min). Additional studies were consistent with oxidation of the ferrous form of iron to its ferric form, which is followed by rapid formation of a Fe(3+)-ciprofloxacin complex. Ciprofloxacin seems to bind to ferric ion in a ratio of 3:1 by interacting with the 4-keto and 3-carboxyl groups on ciprofloxacin. 4. The formation of a ferric ion-ciprofloxacin complex is probably the cause of the reduction in ciprofloxacin bioavailability in the presence of iron.     

The effect of ferrous sulphate on the absorption of norfloxacin, ciprofloxacin and ofloxacin.

The effect of ferrous sulphate on the absorption of norfloxacin, ciprofloxacin and ofloxacin was studied in three separate, two-period crossover trials, each involving eight healthy volunteers. After an overnight fast, a single dose of norfloxacin (400 mg), ciprofloxacin (500 mg) or ofloxacin (400 mg) was administered with and without ferrous sulphate (corresponding to 100 mg elemental iron). The absorption of all the fluoroquinolones studied was significantly reduced when they were co-administered with ferrous sulphate. The reduction in the area under the plasma drug concentration-time curve from 0 to 24 h was most marked in the case of norfloxacin, while ofloxacin was least affected by ferrous sulphate. The AUC of norfloxacin was reduced by 73% (P < 0.001) and its peak plasma concentration by 75% (P < 0.01) by concomitant ingestion of ferrous sulphate. The AUC and peak plasma concentration of ciprofloxacin were reduced by 57% (P < 0.001) and 54% (P < 0.01), respectively, by ferrous sulphate. Concomitant ingestion of ferrous sulphate reduced the AUC and peak plasma concentration of ofloxacin by 25% (P < 0.01) and 36% (P < 0.01), respectively. Similar results were obtained with respect to the urinary recoveries of each fluoroquinolone. We recommend that norfloxacin and ciprofloxacin should not be taken together with ferrous sulphate. It would also be advisable not to take ofloxacin with ferrous sulphate, especially if the organism causing infection is only moderately susceptible.     

Bioavailability and pharmacokinetics of ketanserin in elderly subjects

Summary The bioavailability of ketanserin has been examined in a cross-over experiment in 21 elderly subjects (aged 59–72 years) by administration of tablets (40 mg), solution (40 mg) and injectable solution (10 mg). After two weeks of treatment with 40 mg ketanserin tablets further 18 blood samples for analysis were collected under steady-state conditions. Plasma levels were measured by HPLC. The absolute bioavailability of ketanserin tablets was 52.7%; their relative bioavailability compared to a solution containing an equal quantity of active compound was 85.5%. Therefore, the low absolute bioavailability of ketanserin cannot be attributed to the formulation.The active compound was rapidly liberated from the tablet, reaching a peak of 103.8 ng/ml after 0.97 h. Individual plasma level-time curves were fitted to an open three compartment model and a half-life of 17.7±7.26 h was calculated for the terminal elimination phase. An average terminal elimination half-life of 15.4±4.2 ng/ml was found after administration of the ketanserin solution.Multiple dosing with 40 mg tablets b.d.s. resulted in an AUC over one dosing interval at steady-state of 666±201 ng × h/ml. The AUC extrapolated to infinity was 1200±405 ng × h/ml for the last tablet. This is 1.8-times the AUC in one dosing interval, and 2.3-times the AUC of a single dose. Under steady-state conditions, the mean peak plasma level was 155.1 ng/ml (1.08 h after dosing) and the terminal half-life was 19.1±5.1 h.For the metabolite ketanserinol terminal half-lives of 21.4 h after a single tablet and 31.0 h after discontinuation of multiple dosing were calculated. Compared to the parent compound there was much more marked accumulation of ketanserinol.Despite moderate accumulation and prolongation of the terminal half-life of ketanserin under steady-state conditions, dosage adjustment is not required in elderly people. First-pass metabolism and bioavailability remained in the range found in previous studies of ketanserin in young subjects.     

Disposition and clinical pharmacokinetics of theophylline after administration of a new sustained release tablet

Summary The systemic disposition of theophylline after taking a new, sustained release tablet (Theolair Retard^® 250 mg, Theolair S. R.^®, Riker Laboratories) has been studied in 8 hospitalized patients. Absolute bioavailability was determined from the ratios of the areas under the serum concentration-time curves after intake of the tablet and after intravenous infusion of aminophylline in the same patient. The absolute bioavailability of Theolair Retard^® 250 mg was 110.9±20.8% (mean ± SD). Maximal serum concentrations were reached after 7.3±3.5 h, the large intersubject variation being due to differences in gastric emptying time. The tablets appear to release theophylline slowly in acid conditions, but more rapidly in an alkaline medium. Invasion was found to be either monophasic with a rate constant of about 0.8 h^–1 (intestine), or biphasic with rate constants of 0.2 h^–1 (stomach) and 0.8 h^–1 (intestine). The peak levels accounted for 7.9±2.2 mg · 1^–1. The profiles of the serum concentration-time curves were such that the concentrations remained above 80% of c^max for 6.5±3.3 h. The relevant pharmacokinetic parameters (half-life of elimination, total body clearance and volume of distribution) were determined and were used to calculate the individual dosage regimens required to obtain therapeutic serum concentrations. The optimal dosing interval to obtain an average steady state serum concentration of 12.5 mg · l^–1 was 9.8±3.1 h.     

Pharmacokinetic Evaluation of Aconiazide,A Potentially Less Toxic Isoniazid Prodrug

Study Objective . To determine the bioavailability and renal elimination of isoniazid, acetylisoniazid, monoacetylhydrazine, diacetylhydrazine, aconiazide, and 2-formylphenoxyacetic acid. Study Design . Randomized, double-blind, two-period, crossover phase I study. Setting . Pharmacokinetics unit at a referral hospital that specializes in the treatment of mycobacterial infections. Subjects . Twelve healthy volunteers selected from the hospital staff. Interventions . Subjects received aconiazide tablets 650 mg (containing isoniazid 300 mg) and isoniazid tablets 300 mg. Blood and urine samples were collected over 24 hours after the dose. Measurements and Main Results . Intact aconiazide and 2-formylphenoxyacetic acid were not detected in the serum. Compared with isoniazid tablets, aconiazide's relative bioavailability (based on the area under the serum concentration-time curve) was 50.7%; its relative maximum serum concentration was 13.4%. Conclusions . Isoniazid is less bioavailable after aconiazide tablets than after isoniazid tablets. The optimum dose of aconiazide remains to be determined.     

Pharmacokinetics of epidural morphine in man

Summary Cerebrospinal fluid (CSF) and plasma morphine concentrations were determined in 5 patients after epidural administration of 6 mg morphine; plasma samples were collected frequently during the initial 6 h and 6–7 CSF samples were obtained from each patient over a 24 h period. Morphine was analysed using gas chromatography and electron capture detection. Individual morphine concentration-time curves were plotted for plasma and CSF and various pharmacokinetic variables were calculated. Plasma morphine concentrations after epidural injection were similar to those found after intramuscular administration; C_max (66±8 mg/ml: mean±SEM) appeared within 12±3 min, and the terminal elimination half-life in plasma was 213±24 min. In CSF, morphine reached a peak (1575±359 ng/ml) after 135±40 min. The terminal elimination half-life for morphine in CSF was 239±10 min. The CSF bioavailability of morphine after epidural administration was calculated to be 1.9±0.5%.The study showed that epidural administration of morphine resulted in CSF concentrations many times higher than those in plasma, but still only 2% of the dose administered was available to the CSF compartment. Morphine was eliminated with similar speed from CSF and plasma.     

Studies on hydralazine

Summary The bioavailability of orally administered hydralazine was assessed in 4 healthy subjects after separate administration of a single oral or intravenous dose (0.3 mg·kg^–1). Comparison of the areas under the serum concentration-time curves showed that 26 – 55 % of the oral dose was available to the systemic circulation as unchanged drug. The O - 24 h excretion of the drug in urine was rapid: 11.4 – 14.1 % of the dose after intravenous administration, and 2.0 – 3.6 % after an oral dose. Acetylation of hydralazine leads to formation of 3-methyl-s-triazolo-3,4,a-phthalazine (MTP) and a gas-liquid-chromatographic method for its measurement in urine was developed. After oral and intravenous administration, 0.8 – 1.2 % and 1.4 – 2.3 % of the dose, respectively, were recovered within 24 hours from urine as MTP. After oral administration there was a relative increase in the amount of MTP in every subject, which indicates route-dependent metabolism. The lower bioavailability of oral hydralazine could be explained in terms of first-pass metabolism.     

Pharmacokinetics of fluoride absorbed from dried seafoods by healthy adults

Summary Dried seafoods are a rich source of fluoride (F). The systemic availability of F from seafoods was studied in 3 healthy adults. The plasma concentration and urinary excretion of F for 24 h following the ingestion of 3.87±0.32 mg F (mean ± SD) in seafoods were compared with plasma and urine data following oral administration of 3 mg F in aqueous solution.There was a marked reduction and delay in the absorption of F from seafoods. The relative bioavailability of F from seafoods was 40.8±5.1%.These findings should be taken into consideration when determining the optimum level of daily F intake.This work was performed at the Prince Philip Dental Hospital, University of Hong Kong, Hong Kong     

富马酸亚铁叶酸片中铁的人体生物等效性研究

目的:研究富马酸亚铁叶酸片中铁在健康志愿者体内的生物利用度及生物等效性。方法:24例健康志愿者分别随机交叉口服受试制剂(富马酸亚铁叶酸片:一次2片,含富马酸亚铁304 mg×2,叶酸0.35 mg×2),参比制剂1(富马酸亚铁片:一次3片,200 mg×3)和参比制剂2(叶酸片:一次2片,0.4 mg×2),采用原子吸光分光光度法测定血中铁的浓度。结果:健康志愿者口服受试制剂和参比制剂后,铁的Cmax分别为(1.70±0.53)μg·mL-1和(1.61±0.62)μg·mL-1;Tmax分别为(4.0±1.0)h和(4.3±1.5)h;AUC0-24 h分别为(14.4±8.5)μg·h·mL-1和(14.3±8.1)μg·h·mL-1;t1/2分别为(3.3±2.9)h和(3.2±2.3)h。Cmax、AUC0-24 h和AUC0-∞剂量校正后经双向单侧t检验和(1-2α)置信区间生物等效性评价,Tmax经非参数检验(Wilcoxon符号秩法)均无显著性差异(P>0.05)。结论:根据铁的结果判定,富马酸亚铁叶酸片和富马酸亚铁片生物等效。     

环丙沙星的临床药物动力学研究

研究健康志愿者口眼和静脉滴注环丙沙星的药物动力学，并比较不同剂量、空腹与进餐、单剂与多剂给药的体内过程。单剂空腹口服环丙沙星５００ｍｇ后，Ｃｍａｘ为３．４８ｍｇ·Ｌ－１、为３．０１ｈ、ＡＵＣ为１４．１４ｈ．ｍｇ·Ｌ－１，静脉滴注环丙沙星２００ｍｇ后Ｃｍａｘ为６．５６ｍｇ·Ｌ－１、为３．７３ｈ，口服环丙沙星绝对生物利用度为６８．８９％。单剂空腹口服２５０、５００和１０００ｍｇ环丙沙星后，Ｃｍａｘ为１．８２～７．７２ｍｇ·Ｌ－１，为２．４７～３．１５ｎ，ＡＵＣ与剂量呈比例增加，进餐与空腹口服环丙沙星５００ｍｇ后的体内过程显示进食可使该药的吸收轻度减少。与单剂口服５００ｍｇ相比，５００ｍｇ日２次×７ｄ多剂给药后的Ｃｍａｘ和ＡＵＣ均较单剂者略增高，草剂口服２５０、５００、１０００和５００ｍｇ多剂量后２４ｈ尿排出率为给药量的４７％～５５％，静滴２００ｍｇ者为７１．０６％，基于上述药动学资料，拟订了环丙沙星对各种感染的治疗方案。     

Evaluation of the Intestinal Absorption of Erythromycin in Man: Absolute Bioavailability and Comparison with Enteric Coated Erythromycin

To determine the role of acid hydrolysis on the gastrointestinal absorption of erythromycin, six healthy subjects received erythromycin as a 240 mg intravenous dose, a 250 mg oral solution administered via endoscope directly into the duodenum and bypassing the stomach, and an enteric-coated 250 mg capsule. Blood samples were collected for 6 hours and serum erythromycin quantified by a microbiological method. The time to achieve maximum serum concentrations for the solution was 0.25 ± 0.08 (mean ± SD) hours and for the capsule was 2.92 ± 0.55 hours. The absolute bioavailability of erythromycin from the capsule was 32 ± 7% and for the duodenal solution 43 ± 14%. The ratio of the areas under the serum erythromycin concentration-time curve of capsule to solution was 80 ± 28% (range 38 to 110%). There is substantial loss of erythromycin apart from gastric acid hydrolysis, which cannot be accounted for by hepatic first-pass metabolism. Attempts to further improve the oral bioavailability of erythromycin beyond 50% by manipulation of formulation are likely to be futile.     

Effect of oral ferrous sulphate on the half-life of doxycycline in man

Summary In a double-blind cross-over study in seven patients, oral ferrous sulphate (80 mg Fe⁺⁺) given 3, 7 and 11 h after a daily oral dose of doxycycline, lowered the serum concentration of doxycycline by 20–45%. The half-life of intravenous doxycycline was shortened from 16.6±0.7 h to 11.0±0.4 h by concomitant oral iron therapy. These results are an indirect indication of significant intestinal secretion and reabsorption of doxycycline. The interaction between doxycycline and iron cannot be avoided completely by leaving an interval of 3 h between doses of the two drugs.     

Rectal administration of nicomorphine in patients improves biological availability of morphine and its glucuronide conjugates

The pharmacokinetics of 30 mg nicomorphine after rectal administration with a suppository are described in 8 patients under combined general and epidural anaesthesia. No nicomorphine or 6-mononicotinoylmorphine could be detected in the serum. Morphine appeared almost instantaneously with a lag-time of 8 min and had a final elimination half-life of 1.48±0.48 h. Morphine was metabolized to morphine-3-glucuronide and morphine-6-glucuronide. These glucuronide conjugates appeared after a lag-time of 12 min and the half-life of these two glucuronide conjugates was similar: about 2.8 h (P>0.8). The glucuronide conjugate of 6-mononicotinoylmorphine was not detected. In the urine only morphine and its glucuronides were found. The renal clearance value for morphine was 162 m·min^–1 and for the glucuronides 81 ml·min^–1. This study shows that administration of a suppository with 30 mg nicomorphine gives an excellent absolute bioavailability of morphine and its metabolites of 88%. The lipid-soluble prodrug nicomorphine is quickly absorbed and immediately hydrolysed to morphine.     

Comparative pharmacokinetic analysis of a novel sustained-release dosage form of theophylline in humans

Summary The pharmacokinetics and relative bioavailability of theophylline from a new sustained-release formulation (Theotard^®) and from a standard sustained-release formulation (Theo-Dur^®) were compared in 6 healthy, adult, male volunteers. After a single oral dose of 300 mg Theotard, a mean maximal plasma concentration (Cb_max of 3.49±1.05 mg/l was obtained after 8 h (t_max). After an identical dose of Theo-Dur, a peak plasma concentration of 4.68±1.33 mg/l was obtained after 6.33 h. The mean relative bioavailability of theophylline from Theotard was 1.02±0.16 relative to that of Theo-Dur. In 5 of the volunteers the Theotard formulation exhibited a more prolonged and uniform absorption rate and yielded more sustained plasma levels.     

Polymorphic acetylation of sulphadimidine in normal and uraemic man

Summary After oral administration of sulphadimidine (mean dose 3.33 g) to 21 volunteers it was possible to distinguish fast and slow acetylators by calculating the acetylated fraction (%acSDD) in a single serum sample obtained at any time between 1/2–24 h. There was a close correlation between %acSDD in serum and in urine collected from 0–8 h. Two groups of patients with chronic renal failure were studied. Four of the first 8 patients studied would have been designated as slow acetylators from their low %acSDD in 0–8 h urine, but as fast acetylators from their %acSDD in serum 6 h after drug administration. The next 18 patients were given a smaller dose of SDD (2 g) and they showed complete intra-individual correlation between %acSDD in 0–24 h urine and in a serum sample obtained at 24 h. The patients could be divided into 2 sub-groups on the basis of %acSDD in serum and urine, thus demonstrating the ability of this procedure to distinguish fast and slow acetylators, even in advanced chronic renal failure.     

Pharmacokinetics of intraarticular indomethacin in patients with osteoarthritis

Summary The pharmacokinetics of intraarticular indomethacin was evaluated in 10 patients with osteoarthritis in an open labelled, randomized, cross-over study. Each patient received a single dose of 10 mg indomethacin by the intraarticular and the intravenous routes with a seven-day interval between the injections. Blood was repeatedly collected and urine was collected for 24 h after dosing.Indomethacin was rapidly absorbed from the joint, giving a maximum serum concentration (C_max) of 0.60 g · ml^–1 approximately 1 h after dosing. The systemic bioavailability (f) was 80% and the mean absorption time (MAT) was about 2 h. The apparent terminal half-life and mean residence time (MRT) were 2.8 h and 4 h, respectively. The urinary recovery of total indomethacin (unchanged + glucuronides) was 24% of the dose and renal clearance (CL_R) was estimated to be about 21 ml · min^–1. The disposition of indomethacin after intravenous and intraarticular administration appeared to be similar.The results suggest that the intraarticular administration of indomethacin would not exclude the risk of developing untoward, systemic, concentration-dependent effects.     

Dose dependent methotrexate elimination following bolus intravenous injection

Summary The pharmacokinetics of methotrexate have been assessed at two dose levels in six patients recciving the drug for treatment of malignant disease. Each patient received bolus intravenous doses of 25 mg and 100 mg given at least one week apart, the order of administration being random. Blood and urine were collected until 48 h for methotrexate analysis by radioimmunoassay and data analysed by a model-independent pharmacokinetic approach. In each patient area under the methotrexate serum concentration-time curve (o to ) increased out of proportion to the increase in methotrexate dose. This was reflected in a mean clearance value after the 100 mg dose of 31±16 (SD) ml · min^–1 compared with a mean clearance of 62±19 ml · min^–1 following injection of 25 mg methotrexate. Renal clearance of methotrexate was markedly lower following the 100 mg dose (18±6 ml · min^–1) than after 25 mg (53±19 ml · min^–1). Saturation of the proximal tubular organic acid transport system is the likely cause of methotrexate's capacity limited elimination.