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  • 1
    Electronic Resource
    Electronic Resource
    Bioavailability and pharmacokinetics of theophylline in plain uncoated and sustained-release dosage forms in relation to smoking habit I. Single dose study (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 79-87 
    Details
    ISSN: 1432-1041
    Keywords: theophylline ; smoking habit ; absolute bioavailability ; pharmacokinetics ; sustained release preparation ; plain tablet preparation ; antipyrine pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability and pharmacokinetics of theophylline from a plain uncoated and 2 newly designed, sustained-release tablet formulations, as compared to intravenous aminophylline, were studied in 12 healthy adult male volunteers. The subjects were divided into two groups (n=6) with respect to smoking habit and on 4 separate occasions each received, on a randomized cross-over basis, a single dose of 400 mg equivalent of theophylline from every dosage form. The intravenous aminophylline study showed that habitual smoking had a significant (p〈0.05) effect on plasma theophylline clearance (0.051±0.006 vs 0.035±0.004 l/kg/h). Smoking significantly reduced the raw AUC from the 4 dosage forms (p〈0.05), but did not change the characteristics of absorption of each formulation. There was a non-significant trend towards reduced absolute bioavailability of theophylline from sustained-release formulations in smokers (percentage mean difference — 16% for one formulation and 13% for another). The trend was not observed for the plain uncoated tablet, which was rapidly absorbed (p〈0.01 to 0.05 in Ka, tmax and Cmax compared to sustained-release tablets). Similarity of the in vitro dissolution profiles of the two sustained-release formulations did not imply similarity of the in vivo absorption characteristics. Plasma clearances of theophylline and antipyrine were significantly correlated (p〈0.05,r=0.693,n=10). Thus, smoking enhanced the elimination of theophylline regardless of the dosage form administered. However, the extent to which habitual smoking may affect the hepatic first-pass effect on theophylline from sustained-release formulations requires further study. The results also suggest that theophylline and antipyrine may share a similar or common and presumably polycyclic hydrocarbon-inducible form(s) of microsomal drugmetabolizing enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613931
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  • 2
    Electronic Resource
    Electronic Resource
    Individualized aminophylline therapy in patients with obstructive airway disease: Oral dosage prediction from an intravenous test dose (1982)
    Springer
    European journal of clinical pharmacology 23 (1982), S. 111-121 
    Details
    ISSN: 1432-1041
    Keywords: aminophylline ; asthma ; individual aminophylline dose ; theophylline disposition ; intravenous test dose ; oral dosage prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Theophylline disposition after an intravenous test dose of aminophylline was determined in 83 subjects: 7 patients with and 58 without congestive heart failure (CHF), and 18 healthy controls. Based on the pharmacokinetics of theophylline in the individual, the oral dosage of aminophylline was scheduled to attain steady-state trough theophylline concentrations (Cpred) near the therapeutic margin. Significant differences in theophylline clearance with a relatively constant volume of distribution were observed between various groups divided by age, smoking habit and CHF; the significantly different (p〈0.001) mean clearance values were: 0.042±0.0161/h/kg (mean ± SD) in patients without CHF (n=58) as opposed to 0.016±0.001 l/h/kg in patients with CHF(n=7), 0.038±0.013 l/h/kg in non-smokers (n=59) versus 0.054±0.015 l/h/kg in smoking subjects (n=17), and 0.030±0.010 l/h/kg in elderly (〉60 years) non-smoking patients (n=7) versus 0.057±0.017 l/h/kg in smoking patients (n=5) aged 40 to 59 years. No gender-related difference was detected in theophylline disposition. For all subjects together (n=83), there was no significant correlation between age and clearance (r=-0.111, p〉0.1). The multivariate analysis indicated that the overall variability in theophylline clearance was affected first by the smoking habit (t=4.960; p〈0.001) and second by CHF (t=-3.052; p〈0.001), but not by age (t=1.140) or by sex (t=0.069). 78% of the patients who did not have CHF required a daily dose of aminophylline of 600 to 900 mg, whereas a dose of 300 to 450 mg was the rule in patients with CHF. The measured steady-state minimum concentration (Cmeas) ranged from 5.4 to 14.6 µg/ml (9.0±2.2 µg/ml: mean ± SD) which was in good agreement with the Cpred (5.6 to 13.6, 9.0±1.6 µg/ml) in all patients (n=60) who received the oral dose of aminophylline calculated from the test dose. The overall prediction error was -0.08±1.83 µg/ml (−1.42±19.90%); only 3 of 60 measurements were found to be outside±2 SD. It is concluded that using a test dose to individualize aminophylline therapy is likely to remain the most reliable means to assure the maximum therapeutic benefit in patients with airway obstruction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00545964
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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