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  • 1
    ISSN: 1432-1041
    Keywords: Key words Repaglinide ; Insulin secretagogue ; Type-2 diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The present study was designed to assess the disposition of 14C-repaglinide in whole blood, plasma, urine and faeces, and to measure the total recovery of drug-related material in urine and faeces after a single 2-mg oral dose of 14C-repaglinide during multiple dosing. Methods: In this single-centre, open-label, phase-I trial, six healthy male volunteers received 2 mg of the prandial glucose regulator, repaglinide, four times daily for 13 days, 15 min before meals. On the morning of day 7, breakfast was omitted and the dose was given as an oral solution containing 2 mg of 14C-repaglinide. Results: After oral dosing, a mean peak plasma concentration of repaglinide of 27.74 ng · ml−1 (range: 16.84–36.65 ng · ml−1) was observed with a time to peak concentration of 0.5 h. Approximately 20% of repaglinide and its associated metabolites were distributed into red blood cells. No measurable 14C-radioactivity was present in whole blood samples 6 h after dosing. Within 96 h of dosing with 14C-repaglinide, 90% of the administered dose appeared in the faeces and 8% was excreted in urine. In the plasma, the major compound was repaglinide (61%). In the urine, the major metabolites were unidentified polar compounds, the aromatic amine (M1) (24%), and the dicarboxylic acid (M2) (22%). In the faeces, the major metabolite was M2 (66% of administered dose). Therefore, repaglinide was excreted predominantly as metabolites and the major in vivo metabolite of repaglinide in humans was M2. During regular dosing for 6 days, the morning plasma trough levels of repaglinide were, with very few exceptions, almost always too low to measure, indicating the absence of accumulation at this dose of 2 mg four times daily. Repaglinide was well tolerated, and there were no episodes of hypoglycaemia. Conclusion: After oral dosing with repaglinide, the mean peak plasma concentration was rapidly attained and, thereafter, plasma concentrations decreased promptly. The major route of excretion was via the faeces. These properties make repaglinide a suitable insulin secretagogue for all patients with type-2 diabetes who retain sufficient β-cell function.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 54 (1998), S. 355-357 
    ISSN: 1432-1041
    Keywords: Key words Tiagabine ; Digoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: To assess the possibility of any clinically relevant pharmacokinetic interactions between tiagabine, a novel antiepileptic drug, and digoxin. Methods: Potential pharmacokinetic interactions between tiagabine and digoxin were investigated in an open-label, two-period cross-over study in healthy male volunteers. Thirteen volunteers, aged between 18 and 43 years, were randomised to receive digoxin (0.5 mg twice a day for 1 day, then 0.25 mg once a day for 8 days) either alone or co-administered with tiagabine (4 mg three times daily for 9 days). Following a 7-day wash-out period, volunteers crossed over to the other dosing regimen. Peak serum concentration, time to maximum serum concentration, area under the serum concentration–time curve from zero to 24 h and steady state serum concentration were calculated for digoxin and compared between treatment groups. Results: No statistically significant differences between treatment groups were observed for any of the derived digoxin pharmacokinetic parameters. The most common adverse events reported during digoxin alone and in combination with tiagabine were somnolence and headache; an overall greater frequency of adverse events was reported during combined treatment. Adverse events were generally mild in nature; no serious adverse events were reported. Conclusions: At the doses administered, there is no evidence of a pharmacokinetic interaction between digoxin and tiagabine in healthy male volunteers.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 55 (1999), S. 101-104 
    ISSN: 1432-1041
    Keywords: Key words Troglitazone ; Erythropoietic ; parameters ; Plasma volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: Troglitazone is a new anti-diabetic agent for the treatment of type 2 diabetes. In placebo-controlled trials troglitazone improves glycaemic control, reduces hyperinsulinaemia and has beneficial effects on blood lipids. However, minor, reversible reductions in erythrocyte count, haemoglobin and haematocrit with no associated clinical symptoms have been observed in some troglitazone-treated patients. The primary objective of the present study was to determine if these changes could be explained by a decrease in red cell mass or change in plasma volume. Methods: Twenty-four healthy males were randomized in a double-blind manner to troglitazone (200 or 600 mg per day) or placebo for 6 weeks. Blood samples for the measurement of red cell mass and plasma volume were obtained in the 2 weeks prior to treatment and after 6 weeks of treatment. Reticulocyte and erythrocyte counts, haemoglobin and haematocrit were also measured. Results: At the end of the treatment period there were no statistically significant changes in red cell mass. Similarly there were no changes in reticulocyte count, erythropoietin or soluble transferrin receptors. These data indicate that troglitazone does not affect erythropoiesis. In addition, troglitazone was not associated with increased red blood cell destruction or haemolysis. There was a trend towards increased plasma volume in the troglitazone groups: increases of 2.5 ml · kg−1 (5.7% increase) in the troglitazone 200 mg group and 3.4 ml · kg−1 (7.8% increase) in the troglitazone 600 mg group were observed compared with placebo. Conclusion: These data suggest that dilutional effects related to a modest increase in plasma volume may explain the haematological changes seen in other clinical trials with high doses of troglitazone, although this study has shown that the changes in plasma volume are not statistically significant.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1041
    Keywords: Key words CYP2D6 ; CYP2C19 ; Dutch population
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: We examined a large database containing results on CYP2D6 and CYP2C19 activity of 4301 Dutch volunteers phenotyped in the context of various clinical pharmacology studies. Methods: The subjects were given 22 mg dextromethorphan, 100 mg mephenytoin and 200 mg caffeine. For CYP2D6, the dextromethorphan/dextrorphan metabolic ratios in urine samples taken for a subsequent 8 h were used. Dextromethorphan and dextrorphan were quantified by reversed-phase high performance liquid chromatography. For CYP2C19 similarly obtained (R)-mephenytoin and (S)-mephenytoin ratios were used. (S)-mephenytoin and (R)-mephenytoin were analysed and quantified by enantioselective capillary gas chromatography. In addition, CYP2C19 poor metabolizer (PM) subjects were reanalysed after acidic pre-treatment of urine samples to confirm the PM status. Results: The investigated population mainly comprised Caucasian (98.9%) males (68%). The age ranged from 18 to 82 years. For CYP2D6, it was found that 8.0% of the subjects were PMs. The average metabolic ratio was 0.014 (0.033) for subjects who showed extensive metabolizing activity (EM) and 5.4 (7.6) for PM subjects. For CYP2C19, it was found that 1.8% of the subjects were PMs. The metabolic ratio was 0.162 (0.124) for EM subjects and 1.076 (0.040) for PM subjects. Within the EM group the metabolic ratio in females was significantly lower for CYP2D6 (−20%) and significantly higher for CYP2C19 (+40%) compared with males. For PMs there was no such difference for CYP2D6 (P = 0.79) or CYP2C19 (P = 0.20). Oral contraceptive (OC) use significantly decreased the CYP2C19 activity by 68% for mephenytoin as compared to non-OC using females. Conclusions: For CYP2D6, the PM incidence (8.0%) is in accordance with literature data. The CYP2C19, PM incidence (1.8%) is low compared to reports from other European countries. For mephenytoin, the acidification procedure has been shown to be very important for the confirmation of CYP2C19 PMs. In EM females compared to EM males, CYP2D6 activity is increased and CYP2C19 activity is reduced. For CYP2C19 in particular this reduction is substantial and most pronounced in the age range from 18 to 40 years. For CYP2C19, the reduced activity is associated with the use of oral contraceptives.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1041
    Keywords: Growth hormone ; Jet-injection ; pharmacokinetics ; pharmacodynamics ; Somatomedin C ; free fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The pharmacokinetics and pharmacodynamics of recombinant human growth hormone (rhGH) were studied after a single subcutaneous dose given by jet-injection, and have been compared with the results obtained after conventional needle-injection. Twelve healthy male volunteers completed an open label, randomised, two-way crossover study, with a 7-day washout period between the two single sc doses. Pharmacokinetic parameters were derived from rhGH concentrations in blood samples collected regularly over 24 h after dosing on Day 1 of each period. To investigate the pharmacodynamics, additional samples were taken for the analysis of somatomedin C (IGF-I) and free fatty acids (FFA). A higher and earlier Cmax was found after jet-injection (ratio (%) jet-injected/needle-injected 124; 90%-confidence interval 108 – 142). The AUC0−∞ for rhGH were similar (ratio (%) jet-injected/needle-injected 98; 90%-confidence interval 93 – 103). Both treatments were associated with a significant and similar rise in IGF-I. Both administrations of rhGH were associated with identical rhythmical changes in FFA. The study indicates that jet-injected and needle-injected rhGH are bioequivalent with respect to the amount absorbed. The criterion for bioequivalence is not met for the rate of absorption. It is unlikely that the latter finding will influence the pharmacodynamics of rhGH, since bioequipotency was established for the effect on IGF-I generation. Jet-injection was safe in use and was generally well tolerated.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Aims: To compare the effects on intragastric acidity of a single evening dose of either standard or effervescent formulations of ranitidine (300 mg) or cimetidine (800 mg). Methods: Twelve healthy subjects were studied, using a four-period randomized cross-over design and an ambulatory intragastric pH monitoring technique. The subjects received a standard evening meal at 17.00 hours and one of the H2-receptor antagonist formulations was given at 23.00 hours. Results: Both effervescent formulations caused a transient rapid increase in intragastric pH, reaching a maximum at about 3 min after ingestion. After both effervescent formulations a significantly higher pH was measured during the first 45 min after ingestion (P 〈 0.05), compared to the regular formulations. The onset of action of the H2 receptor antagonists was similar for both formulations of ranitidine and the effervescent cimetidine, but tended to be slower for the regular cimetidine (P= 0.06). Nocturnal intragastric pH was significantly increased by all four formulations, but more effectively so by the two ranitidine formulations. The duration of action (taken as time with pH 〉 4) of both ranitidine formulations was longer than that of both cimetidine formulations (P 〈 0.002). Conclusions: A single evening dose of 300 mg ranitidine produces a stronger decrease of nocturnal gastric acid secretion than 800 mg cimetidine. The effervescent formulations of both drugs offer the advantage of a rapid decrease (within minutes) of intragastric acidity, with preservation of the sustained systemic effect.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Metformin analysis ; Stationary phase variability ; Validation of methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two assay methods for the antidiabetic metformin, one developed and validated in 1990 and one developed and validated in 1996, are compared. The first method, using an octadecyl phase and an ion pairing agent in the eluent, could not be reproduced some five years later, but another method, using a phenyl phase and no ion pairing agent, could be successfully applied. This paper shows that the retention mechanism of the positively charged analyte is not due to ion-pair formation, as originally assumed, but to interaction with free silanol groups in the LC phase. It is suggested that the number of free silanol groups in octadecyl phases was strongly reduced between 1990 and 1996, whereas for phenyl phases this was not the case. For the second method, validation results on linearity, specificity, accuracy, precision, recovery and stability as well as application of the method to samples from a clinical trial are shown. The validated calibration range is from 20.0 to 2000 ng.mL−1, with accuracy (bias) and precision (coefficient of variation) being below 15% at all levels. Using automated solid-phase extraction for sample preparation, a sample throughput of typically 100 per day can be achieved.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1041
    Keywords: Key words Tiludronate; healthy volunteers ; bisphosphonates ; pharmacokinetics ; calcium metabolism ; bone resorption ; adverse events
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objectives: A double-blind, placebo-controlled study was conducted to assess the pharmacokinetics and pharmacodynamics of the bisphosphonate tiludronic acid, administered once daily as sodium tiludronate 200, 400, 600 and 800 mg for 12 days. Four groups of ten subjects participated in the study, with a drug to placebo ratio of 4:1. Methods: Pre-dose blood samples were taken on alternate days, starting on Day 1 and additional samples were collected over 144 h following the final dose on Day 12. Urine was collected over 24 h after the final dose. Indices of calcium homeostasis and biochemical markers of bone turnover were assessed during the study as pharmacodynamic parameters. Tolerability was evaluated with special emphasis on renal function and gastrointestinal irritation. Adverse experiences were assessed at regular time intervals. Results and conclusions: Steady state was attained from Day 4 (200 mg) or from Day 6 (400, 600 and 800 mg). Following the final dose on Day 12, minimal plasma concentrations (Cmin) ranged between 0.19 and 1.5 mg ⋅ l−1, and maximal plasma concentrations (Cmax) between 1.1 and 7.8 mg⋅l−1 for the lowest and highest doses, respectively. A supra-proportional increase in Cmax, AUC24 and Ae 24 with dose was observed. There was a linear relationship between the plasma tiludronic acid and its urinary excretion rate, so, the disproportional rise in Cmax and AUC24 with increasing dose could not be attributed to saturation of renal excretion. Certain indices of calcium homeostasis changed significantly during the study, but generally, became only prominent at the highest dose level of 800 mg. Total serum calcium and the urinary calcium/creatinine clearance ratio fell, indicating depression of osteoclastic bone resorption, which was not revealed by serum osteocalcin levels probably because of the brevity of the treatment (12 days). In response to the decline in serum calcium, serum 1,25-dihydroxyvitamin D3 and intact PTH (1–84) levels increased. None of the safety parameters raised any concerns about the safety of sodium tiludronate administered in this way.
    Type of Medium: Electronic Resource
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