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  • 1
    Electronic Resource
    Electronic Resource
    Drug Marker Absorption in Relation to Pellet Size, Gastric Motility and Viscous Meals in Humans (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 233-238 
    Details
    ISSN: 1573-904X
    Keywords: gastric emptying ; oral absorption ; gastric motility ; enteric coated ; caffeine ; acetaminophen ; viscous meal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The objective of this study was to evaluate drug marker absorption in relation to the gastric emptying (GE) of 0.7 mm and 3.6 mm enteric coated pellets as a function of viscosity and the underlying gastric motility. Methods. Twelve subjects were evaluated in a 3-way crossover study. 0.7 mm caffeine and 3.6 mm acetaminophen enteric coated pellets were concurrently administered with a viscous caloric meal at the levels of 4000, 6000 and 8000 cP. Gastric motility was simultaneously measured with antral manometry and compared to time events in the plasma profiles of the drug markers. Results. Caffeine, from the 0.7 mm pellets, was observed significantly earlier in the plasma than acetaminophen, from the 3.6 mm pellets, at all levels of viscosity. Motility related size differentiated GE was consistently observed at all viscosity levels, however, less variability was observed with the 4000 cP meal. Specifically, the onset of absorption from the of 3.6 mm pellets correlated with the onset of Phase II fasted state contractions (r = 0.929, p 〈 0.01). Conclusions. The timeframe of drug marker absorption and the onset of motility events were not altered within the range of viscosities evaluated. Rather, the differences in drug marker profiles from the non-digestible solids were most likely the result of the interaction between viscosity and motility influencing antral flow dynamics. The administration of the two sizes of pellets and a viscous caloric meal with subsequent monitoring of drug marker profiles is useful as a reference to assess the influence of motility patterns on the absorption profile of orally administered agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011962501270
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  • 2
    Electronic Resource
    Electronic Resource
    Gastric pH Influences the Appearance of Double Peaks in the Plasma Concentration-Time Profiles of Cimetidine After Oral Administration in Dogs (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 780-786 
    Details
    ISSN: 1573-904X
    Keywords: cimetidine ; double peaks ; bioavailability ; absorption rate constant ; gastric pH ; intestinal pH ; gastric emptying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The plasma concentration-time profiles of cimetidine often exhibit two peaks following oral administration of a single dose in the fasted state, while the concurrent administration of some antacids results in a lower extent as well as rate of absorption. In the present work, absorption of cimetidine after a single dose in the fasted state was studied as a function of gastric pH in male beagle dogs to determine whether gastric pH plays a role in the double peak phenomenon and/or can account for the decrease in bioavailability when antacids are coadministered. The extent of absorption of cimetidine was not influenced significantly by gastric pH, indicating that elevation of gastric pH is not the cause of decreases in the bioavailability of cimietidine when it is administered with antacids. Distinct double peaks or plateaux were noted in 8 of 10 plasma profiles when the gastric pH was 3 or below. Irregular absorption behavior was observed in 2 of 6 profiles in the pH range of 3 to 5, while single peaks were observed in all 10 profiles when the gastric pH was maintained at pH ≥ 5. It was concluded that gastric pH is a major factor in the generation of cimetidine double peaks. Changes in gastric pH also resulted in changes in the apparent kinetics of absorption. Below pH 5, absorption mostly followed zero-order kinetics (9 of 16 profiles) or a more complex kinetic process involving at least two components to the absorption phase (5 of 16 profiles). At gastric pH ≥ 5, however, absorption followed first order kinetics in 7 of 10 profiles. These differences in kinetics of absorption are postulated to arise from variations in gastric emptying as a function of pH and/or carryover effects of gastric pH into the upper intestine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016284214708
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  • 3
    Electronic Resource
    Electronic Resource
    Celiprolol double-peak occurrence and gastric motility: Nonlinear mixed effects modeling of bioavailability data obtained in dogs (1995)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 23 (1995), S. 267-286 
    Details
    ISSN: 1573-8744
    Keywords: gastric motility ; celiprolol ; NONMEM ; double-peak phenomenon ; variable oral pharmacokinetics ; nonlinear oral bioavailability ; gastric emptying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Investigation of the underlying mechanism leading to inter- and intrasubject variations in the plasma concentration-time profiles of drugs (1) can considerably benefit rational drug therapy. The significant effect of gastric emptying on the rate and extent of celiprolol absorption and its role with respect to double-peak formation was demonstrated in the present study. In four dogs racemic celiprolol was dosed perorally in a crossover design during four different phases of the fasted-state gastric cycle and gastric motility was recorded simultaneously using a manometric measurement system. Intravenous doses were also given to obtain disposition and bioavailability parameters. The blood samples were assayed by a stereoselective HPLC method (2). The time to onset of the active phase of the gastric cycle showed an excellent correlation with the time to celiprolol peak concentration. Furthermore, bioavailability was increased when celiprolol was administered during the active phase. Double peaks were observed when the first active phase was relatively short, suggesting that a portion of the drug remained in the stomach until the next active phase. Population pharmacokinetic modeling of the data with a two-compartment open model with two lag times incorporating the motility data confirmed the effect of time to gastric empyting on the variability of the oral pharmacokinetics of celiprolol. The fasted-state motility phases determine the rate and extent of celiprolol absorption and influence the occurrence of double peaks. Peak plasma levels of celiprolol exhibit less variability if lag times, and therefore gastric emptying times, are taken into consideration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02354285
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of variable gastric emptying and intestinal transit rates on the plasma level curve of cimetidine; an explanation for the double peak phenomenon (1987)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 15 (1987), S. 529-544 
    Details
    ISSN: 1573-8744
    Keywords: cimetidine ; oral absorption ; double peaks ; gastric emptying ; fasted motility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A physiological flow model is presented to account for plasma level double peaks based on cyclical gastric emptying and intestinal motility in the fasted state. Central to the model is the assumption that gastric emptying and intestinal transit rates will vary directly with the strength of the contractile activity characteristic of the fasted state motility cycle. Simulated curves clearly indicate that variable gastric emptying rates can result in variable absorption rates from the gastrointestinal tract and double peaks in the plasma level curves of cimetidine. Vital to the occurrence of double peaks are (i) dosing time relative to phasic activity, (ii) variability in flow out of the stomach, and (iii) a small emptying rate constant Qs/Vs, for a period of time within the first hour after administration. Variability in intestinal flow rates alone does not cause a double peak in the plasma level curve. Results of the simulations, as well as experimental results, can be categorized according to the shapes of the plasma level curves into four types: type A, Cpmax(1) 〈Cpmax(2); type B, single peak; type C, Cpmax(1)〉Cpmax(2); type D, Cpmax(1)=Cpmax(2). Assuming that the experimental results were obtained from fasted subjects, with the time of dose administration being a random variable, the frequency of the experimental curves having shape A, B, C, or D correlates extremely well with theoretical predictions. It is concluded that variable gastric emptying rates due to the motility cycle can account for plasma level double peaks. Furthermore, variable gastric emptying rates combined with the short plasma elimination half-life and poor gastric absorption of cimetidine can be the cause of the frequently observed plasma level double peaks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061761
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