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  • bioavailability  (2)
  • indomethacin  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 15 (1979), S. 269-274 
    ISSN: 1432-1041
    Keywords: phenytoin ; food-intake ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of food intake on the absorption of phenytoin was examined in eight healthy volunteers, by study of single-dose kinetics following ingestion of phenytoin 300 mg either with a standardized breakfast or on an empty stomach. Blood samples were collected at regular intervals from 0 to 48 h, and serum concentrations of unmetabolized phenytoin were determined by gas chromatography. Serum concentrations of the major metabolite of phenytoin, 4-hydroxyphenytoin, were measured by mass fragmentography. Concurrent intake of food and phenytoin appeared to accelerate absorption of the drug from the formulation used, and the peak concentrations were significantly higher (mean increase 40%) in the postprandial than in the preprandial state. As reflected by the AUC (area under the curve), the amount of drug absorbed was increased during postprandial conditions, although the difference only reached borderline significance. It is suggested that phenytoin should always be taken in a defined relation to meals.
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  • 2
    ISSN: 1432-1041
    Keywords: indomethacin ; diflunisal ; pharmacokinetics ; drug interaction ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The single-dose pharmacokinetics of indomethacin following 100 mg rectally was measured in two groups of 8 healthy subjects before and after diflunisal 500 mg p.o. once daily, or 500 mg in the morning and 1000 mg in the evening, until steady state conditions were reached. A further group of 8 healthy subjects was given 50 mg indomethacin rectally before and after diflunisal 500 mg p.o. twice daily. High dose diflunisal (1500 mg/day) decreased the renal clearance of indomethacin from 21.9 to 1.8 ml/min (92%) and reduced the renal excretion of both unchanged (63%) and conjugated (82%) indomethacin. The apparent total body clearance (0.12 l/h/kg), apparent volume of distribution (0.98 l/kg), and volume of distribution at steady state (0.80 l/kg) were decreased by 47%, 35% and 30%. The maximum plasma concentration (2.4 µg/ml) and total area under the curve (13.0 µg × h/ml) were increased by 40% and 119%, respectively. The terminal elimination half-life (5.7 h) and mean residence time (6.7 h) were slightly prolonged (7.0 h and 8.8 h) in the presence of diflunisal. The contribution of metabolism to the overall elimination of indomethacin was increased by only 2%. Similar results were obtained when the subjects were challenged with the low dose of diflunisal (500 mg/day), although the magnitude of the changes were smaller. The interaction between indomethacin and diflunisal may be due to competition both at the metabolic (conjugation) and the excretory (tubular secretion) levels. When the subjects were given 50 mg indomethacin and diflunisal 1000 mg/day simultaneously, the achieved maximum plasma concentration of indomethacin (2.53 µg/ml) was comparable to that seen after 100 mg in the absence of diflunisal (3.1 µg/ml), but the AUC was greater (21.7 µg × h/ml vs 13.0 µg × h/ml). Adverse central nervous reactions were more frequent and more pronounced at higher plasma indomethacin concentrations.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 22 (1982), S. 309-314 
    ISSN: 1432-1041
    Keywords: acetylsalicylic acid ; salicylic acid ; dipyridamol ; bioavailability ; kinetics ; rapid- and slow-release formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Acetylsalicylic acid (ASA) is a strong, irreversible inhibitor of platelet aggregation, but loses this activity following first-pass deacetylation to salicylic acid (SA). In order to compare the bioavailability of unchanged ASA from rapid- and slow-release formulations, the single-dose concentration profiles of ASA and SA were studied in healthy volunteers following intake of two different rapid-release (conventional and effervescent tablets) and three different slow-release (microencapsulated ASA in tablets and in capsules, and enteric-coated tablets) formulations of ASA, and of one slow-release formulation of sodium salicylate. Since anti-platelet therapy with ASA is often combined with dipyridamol, the influence of this drug was also examined. The concentrations of ASA and SA were measured by high-pressure liquid chromatography. While the bioavailability of SA from the 5 ASA formulations was essentially equal and similar to that of the salicylate formulation, the bioavailability and peak concentrations of ASA appeared to be the much greater after rapid-release than after slow-release formulations. Indeed, ASA was only rarely detected in systemic blood following intake of slow-release ASA. Co-administered dipyridamol did not significantly influence the kinetics of ASA or SA. It appears that rapid-release formulations of ASA should be prefered in anti-platelet therapy, either alone or in combination with dipyridamol.
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  • 4
    ISSN: 1432-1041
    Keywords: acetylsalicylic acid ; diflunisal ; indomethacin ; salicylic acid ; indoprofen ; indobufen ; high-pressure liquid chromatography ; plasma level
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A high-pressure liquid chromatographic technique was developed which allowed concurrent measurement of acetylsalicylic acid (ASA) and salicylic acid (SA) in plasma. ASA was extensively deacetylated to SA not only in vivo but also in vitro, even in frozen plasma. The in vitro conversion could be prevented by physostigmine. In vivo, ASA was eliminated within few hours, whereas SA was continuously present following daily administration of conventional doses of ASA. A slight modification of a similar method, originally developed for naproxen determination [9], was found appropriate for measurement of the SA derivative diflunisal, of two non-SA antiinflammatory agents, indomethacin and indoprofen, and of a related anti-platelet agent, indobufen.
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