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  • Articles: DFG German National Licenses  (6)
  • bioavailability  (4)
  • first-pass metabolism  (2)
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  • Articles: DFG German National Licenses  (6)
Material
Years
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Superiority of stable isotope techniques in the assessment of the bioavailability of drugs undergoing extensive first pass elimination (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 127-131 
    Details
    ISSN: 1432-1041
    Keywords: verapamil ; tablets ; relative bioavailability ; intraindividual changes ; first-pass metabolism ; stable isotope technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Although the absorption of verapamil is almost complete after oral administration, its bioavailability is low due to extensive hepatic first-pass metabolism. Besides large interindividual differences in first-pass metabolism, pronounced day-to-day intraindividual variations in first-pass metabolism are observed, leading to erroneous results in relative bioavailability studies. Stable isotope techniques, which permit simultaneous administration of a solution and a tablet, can successfully be used to overcome these difficulties. The method has the advantage that two experiments can be carried out in a single test. Furthermore, the number of subjects required in bioavailability studies can be greatly reduced. Using this technique the bioavailability of verapamil tablets (Isoptin® 80) relative to a stable labelled solution of verapamil was found to be 108.1%, with a 95% confidence interval between 89.1 and 127.1%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568399
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Prediction of bioavailability for drugs with a high first-pass effect using oral clearance data (1982)
    Springer
    European journal of clinical pharmacology 22 (1982), S. 85-90 
    Details
    ISSN: 1432-1041
    Keywords: lignocaine ; verapamil ; propranolol ; bioavailability ; predictions ; first pass effect ; oral clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary For drugs with a high hepatic clearance, bioavailability is low due to the so-called “first pass effect”. Prediction of the bioavailability for these drugs has been only lossely tested. It is proposed that by plotting the reciprocal of bioavailability versus the oral clearance, a straight line with intercept of unity and slope of reciprocal of hepatic blood flow should ensue. For lignocaine and verapamil, this relationship was found to be strong and gave good predictability, whereas for propranolol this relationship was weak and gave poor predictability. The proposed method may be of value in determining whether the low bioavailability of a drug is due to hepatic first pass metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00606430
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Simultaneous determination of the intravenous and oral pharmacokinetic parameters of D,L-verapamil using stable isotope-labelled verapamil (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 133-137 
    Details
    ISSN: 1432-1041
    Keywords: verapamil ; pharmacokinetics ; bioavailability ; hepatic first-pass metabolism ; stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Following i. v. administration, the plasma concentration-time curve of verapamil could best be described by either a mono- or biexponential equation. Total plasma clearance (1.26 l/min) approached liver blood flow (1.5 l/min), so it can be concluded that its clearance is liver blood flow-dependent. Although absorption was almost complete after oral administration, absolute bioavailability (20%) was low, due to extensive hepatic first-pass metabolism. The approach using stable isotope-labelled and unlabelled drug permits simultaneous administration by the intravascular and extravascular routes, thus allowing determination of absolute bioavailability in a single experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00568400
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Influence of phenobarbital treatment on cimetidine kinetics (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 343-347 
    Details
    ISSN: 1432-1041
    Keywords: cimetidine ; phenobarbital ; gastro-intestinal absorption ; bioavailability ; renal clearance ; non-renal clearance ; enzyme induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of orally administered cimetidine was studied in 8 healthy subjects before and after 3 weeks of treatment with phenobarbital 100 mg daily, and in a separate study 4 subjects received cimetidine intravenously before and after the administration of phenobarbital. There was no change in the volume of distribution, but total plasma clearance was increased by a mean of 18%, mainly due to a 37% increase in nonrenal clearance. Renal clearance and half-life were not significantly altered. The area under the plasma concentration-time curve after oral administration was significantly (P≪0.05) reduced by a mean of 15% after phenobarbital treatment. The amount of cimetidine excreted in urine and its sulphoxide metabolite were significantly (P〈0.05) reduced, on average by 34% and 26%, respectively by phenobarbital treatment. The data indicate that an apparent 20% reduction in the absorption of cimetidine was due to induction of gastrointestinal metabolism of cimetidine, with some contribution also from hepatic metabolism. Reduced absorption per se could not be totally excluded. Although the magnitude of the change was small, the finding of an 11% decrease in the time to achieve an effective plasma level of cimetidine after phenobarbital treatment may contribute to the ineffectiveness of cimetidine in certain patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00544584
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Inter- and intra-subject variation in the first-pass elimination of highly cleared drugs during chronic dosing (1984)
    Springer
    European journal of clinical pharmacology 26 (1984), S. 47-53 
    Details
    ISSN: 1432-1041
    Keywords: verapamil ; first-pass metabolism ; pharmacokinetics ; interindividual variation ; intraindividual variation ; chronic administration ; deuterated verapamil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of verapamil in five healthy volunteers were investigated on 4 occasions during chronic administration of deuterated verapamil. There was no statistically significant difference in oral clearance, terminal half-life, bioavailability, morning trough level and peak concentration or in the time of their occurrence on the four occasions. The plasma clearance, however, exhibited considerable inter- and intra-individual variation, ranging between 26.3% and 85.4% and 12.0% and 48.0%, respectively. Comparison of these pharmacokinetic parameters with data from previous single dose studies in the same subjects revealed a significant (p〈0.05) decrease in the clearance and an increase in the apparent bioavailability of verapamil during chronic administration, although no difference in the half-life was found. Due to the considerable variation in the oral clearance of verapamil during chronic dosing, steady-state conditions in a strict pharmacokinetic sense may never be attained, and pharmacokinetic data obtained in single dose studies will be of limited value in predicting steady-state plasma concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00546708
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    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Impaired cimetidine absorption due to antacids and metoclopramide (1981)
    Springer
    European journal of clinical pharmacology 20 (1981), S. 225-228 
    Details
    ISSN: 1432-1041
    Keywords: cimetidine ; antacids ; metoclopramide ; absorption ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In 8 healthy subjects the absorption of cimetidine was investigated when given alone, together with 60 ml aluminium/magnesium hyroxyde containing antacid (neutralising capacity 26 mmol HCl/10 ml), and together with liquid metoclopramide 14 mg. The antacid significantly (P〈0.01) reduced the bioavailability (area under the plasma level-time curve) of cimetidine, on average by one third. Metoclopramide also reduced the bioavailability by an average of 22%. The reductions were associated with significantly reduced excretion of cimetidine in urine. There was no change in the half-life or renal clearance of cimetidine, supporting the hypothesis of reduced gastrointestinal absorption. The results indicate that cimetidine and antacids should not be given together, and that the dose of cimetidine may have to be increased if it is administered concomitantly with metoclopramide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00544602
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    Paper (German National Licenses)
    Fulltext
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