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  • 1
    Electronic Resource
    Electronic Resource
    Influence of Tablet Dissolution on Furosemide Bioavailability: A Bioequivalence Study (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 150-153 
    Details
    ISSN: 1573-904X
    Keywords: furosemide ; bioavailability/bioequivalence ; dissolution ; intersubject variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to evaluate the in vitro dissolution and in vivo bioavailability relationship for furosemide, a bioequivalence study was carried out. Furosemide (40 mg) was administered orally to 12 normal volunteers in a 6 × 6 crossover design using six products (five tablets and one solution) obtained from three pharmaceutical companies. Plasma and urine concentrations of furosemide were quantitated by high-performance liquid chromatography (HPLC). Plasma furosemide profiles were analyzed by non-compartmental methods. Compared to the oral solution, all of the formulations exhibited lower peak furosemide concentrations, longer mean residence times, and, in some cases, diminished bioavailability (range, 66–96%). Similar results were obtained when the reference product (a rapidly dissolving tablet) was used as the standard. All of the products failed the 75/75 rule when compared to either reference standard, apparently because of large intersubject variability. The total amount of furosemide excreted in urine could be associated with the percentage drug dissolved (in vitro) at 30 min. The pH 5.6 dissolution medium (compared to pH 4.6) appears to be an appropriate test medium for assuring batch uniformity and bioequivalence of furosemide products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016427321532
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of in Vitro Dissolution of Whole vs. Half Controlled-Release Theophylline Tablets (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 416-419 
    Details
    ISSN: 1573-904X
    Keywords: controlled-release theophylline ; dissolution ; whole vs. half tablets ; statistical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Controlled-release (CR) drug products dissolve more slowly than conventional-release products, reflecting their quality of sustaining a prolonged therapeutic effect. A frequent practice with scored tablets when only half the dosage is desired is to divide the tablet at the score mark and administer only half of the product. The dissolution characteristics of the divided tablets are unknown. It is only an assumption that the halved tablet behaves similarly to the whole tablet both in vitro and in vivo. A series of in vitro dissolution analyses was performed on whole and half CR theophylline tablets from different manufacturers. Statistical tests were carried out between the dissolution results of whole and those of halved tablets to determine whether the mean overall percentages dissolution (averaged over sampling times) were similar and whether the patterns of percentage dissolution over time were similar. The dissolution of halved tablets was slightly faster compared to that of intact (whole) tablets. However, these small differences were not large enough to cause concern or to require bioavailability studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016442514205
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  • 3
    Electronic Resource
    Electronic Resource
    The Effect of Gelatin Cross-Linking on the Bioequivalence of Hard and Soft Gelatin Acetaminophen Capsules (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 962-966 
    Details
    ISSN: 1573-904X
    Keywords: Gelatin capsules ; acetaminophen ; crosslinking ; dissolution ; human bioequivalence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine if changes in the in vitrodissolution of hard and soft gelatin acetaminophen capsules, which resultfrom gelatin crosslinking, are predictive of changes in the bioavailabilityof the capsules in humans. Methods. Both hard and soft gelatin capsules were“stressed” by a controlled exposure to formaldehyde, resultingin unstressed, moderately stressed and highly stressed capsules. invitro dissolution studies were conducted using water or SGF with andwithout pepsin as the media. Separate 24-subject, 3-way crossover humanbioequivalence studies were performed on the unstressed and stressedacetaminophen capsules. Plasma acetaminophen was determined by highperformance liquid chromatography (HPLC) for 12 hr after each dose. Results. The in vitro rate of dissolution of hardand soft gelatin capsules was decreased by crosslinking. The bioequivalencestudies showed that both hard and soft gelatin capsules, which failed tomeet the USP dissolution specification in water, but complied when tested inSGF containing pepsin, were bioequivalent to the unstressed controlcapsules. The capsules that were cross-linked to the greatest extent werenot bioequivalent to the unstressed control capsules, based on Cmax. Atrend toward an increase in Cmax with increased level of cross-linking wasobserved, but this was only significant for the severely stressedcapsules. Conclusions. On the basis of this study a two-tier invitro dissolution test was developed using enzymes to distinguishbetween bioequivalent and bioinequivalent gelatin capsules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007579221726
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  • 4
    Electronic Resource
    Electronic Resource
    In Vitro Dissolution Profile Comparison—Statistics and Analysis of the Similarity Factor, f2 (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 889-896 
    Details
    ISSN: 1573-904X
    Keywords: dissolution ; similarity factor ; estimation bias ; bootstrap confidence interval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To describe the properties of the similarity factor (f2) as a measure for assessing the similarity of two dissolution profiles. Discuss the statistical properties of the estimate based on sample means. Methods. The f2 metrics and the decision rule is evaluated using examples of dissolution profiles. The confidence interval is calculated using bootstrapping method. The bias of the estimate using sample mean dissolution is evaluated. Results. 1. f2 values were found to be sensitive to number of sample points, after the dissolution plateau has been reached. 2. The statistical evaluation of f2 could be made using 90% confidence interval approach. 3. The statistical distribution of f2 metrics could be simulated using 'Bootstrap' method. A relatively robust distribution could be obtained after more than 500 'Bootstraps'. 4. A statistical 'bias correction' was found to reduce the bias. Conclusions. The similarity factor f2 is a simple measure for the comparison of two dissolution profiles. But the commonly used similarity factor estimate ^f2 is a biased and conservative estimate of f2. The bootstrap approach is a useful tool to simulate the confidence interval.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011976615750
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  • 5
    Electronic Resource
    Electronic Resource
    Lack of In Vivo/In Vitro Correlations for 50 mg and 250 mg Primidone Tablets (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1085-1089 
    Details
    ISSN: 1573-904X
    Keywords: primidone ; bioavailability ; human ; pharmacokinetics ; in vitro dissolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine if large differences in the in vitro dissolution profiles for primidone tablets would result in significant bioavailability differences. Methods. Two separate bioavailability studies were conducted. The first study used 18 healthy subjects and compared the bioavailability of an old 50 mg tablet formulation, a new 50 mg tablet formulation, and a suspension containing 50 mg/ml of primidone. The second study enrolled 24 subjects who were to receive a new 250 mg tablet formulation, two lots of an old 250 mg tablet formulation and a 250 mg tablet from a second manufacturer. In vitro dissolution was conducted over 90 minutes, using USP 23 Apparatus 2 at 50 rpm, with 900 ml of water. Results. Dissolution at 90 minutes for the old and new 50 mg tablets was approximately 20% and 100%, respectively. The dissolution of the four 250 mg tablets ranged from approximately 30% to 100%. The 50 mg tablet that dissolved slower had a longer Tmax and a 14% lower Cmax than the more rapidly dissolving tablet, but the AUC(0−∞) values differed by only 3%. Only nine subjects completed the 250 mg study because of side effects. The differences in Cmax and AUC(0−∞) among the four 250 mg tablets were less than 7%. Conclusions. Even though there were large differences in the in vitro dissolution of the 50 mg and the 250 mg primidone tablets, the two 50 mg tablets were shown to be bioequivalent, as were the four 250 mg tablets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011942530288
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  • 6
    Electronic Resource
    Electronic Resource
    The Bioinequivalence of Carbamazepine Tablets with a History of Clinical Failures (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1612-1616 
    Details
    ISSN: 1573-904X
    Keywords: carbamazepine ; human ; bioavailability ; pharmacokinetics ; dissolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of three lots of a generic 200-mg carbamazepine tablet, which had been withdrawn from the market, was compared to the bioavailability of one lot of the innovator product in 24 healthy volunteers. Fifty-three lots of the generic product had been recalled by the manufacturer because of concerns over reports of clinical failures for several of the lots. The three generic lots tested in this study exhibited a wide range of bioavailability, as well as large differences in the in vitro dissolution rates. The mean maximum carbamazepine plasma concentrations for two of the generic lots were only 61-74% that of the innovator product, while the third lot was 142% of the innovator. The mean areas under the plasma concentration-time curve for the three generic lots ranged from 60 to 113% that of the innovator product. The results clearly indicate a significant difference in the rate and extent of absorption of the generic products compared to the innovator, as well as among the generic lots. A good relationship was found between the in vivo parameters and the in vitro dissolution results for the four dosage forms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015872626887
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  • 7
    Electronic Resource
    Electronic Resource
    Feasibility of Measuring the Bioavailability of Topical Betamethasone Dipropionate in Commercial Formulations Using Drug Content in Skin and a Skin Blanching Bioassay (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 45-51 
    Details
    ISSN: 1573-904X
    Keywords: bioavailability ; skin blanching ; vasoconstriction ; topical corticosteroids ; betamethasone dipropionate ; tape-stripping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An in vivo technique has been developed which simultaneously compares a skin blanching bioassay with drug content in human stratum corneum following topical application of four 0.05% beta-methasone dipropionate formulations. Bioavailability of drug from commercial cream and ointment formulations was assessed by quantification of drug content in tape-stripped stratum corneum and skin blanching in the treated skin site under occluded conditions. Tape-stripping removed stratum corneum to a varying degree between individuals but was consistent (35%) within an individual with all formulations, day to day. A correlation (r = 0.9935) between the amount of drug in the treated stratum corneum normalized for surface area and the corresponding skin blanching score was observed with four 0.05% betamethasone dipropionate formulations. Increasing the amount of drug in the tape-stripped stratum corneum correlated with an increased skin blanching score. Ointment formulations delivered more drug to the skin and produced greater blanching scores than the cream formulations. Topical corticosteroid content in the treated skin site can therefore be quantified and correlates well with the resulting pharmacodynamic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018975626210
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  • 8
    Electronic Resource
    Electronic Resource
    A Theoretical Basis for a Biopharmaceutic Drug Classification: The Correlation of in Vitro Drug Product Dissolution and in Vivo Bioavailability (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 413-420 
    Details
    ISSN: 1573-904X
    Keywords: bioavailability ; drug absorption ; mathematical modeling ; in vitro–in vivo correlation ; intestinal permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A biopharmaceutics drug classification scheme for correlating in vitro drug product dissolution and in vivo bioavailability is proposed based on recognizing that drug dissolution and gastrointestinal permeability are the fundamental parameters controlling rate and extent of drug absorption. This analysis uses a transport model and human permeability results for estimating in vivo drug absorption to illustrate the primary importance of solubility and permeability on drug absorption. The fundamental parameters which define oral drug absorption in humans resulting from this analysis are discussed and used as a basis for this classification scheme. These Biopharmaceutic Drug Classes are defined as: Case 1. High solubility-high permeability drugs, Case 2. Low solubility-high permeability drugs, Case 3. High solubility-low permeability drugs, and Case 4. Low solubility-low permeability drugs. Based on this classification scheme, suggestions are made for setting standards for in vitro drug dissolution testing methodology which will correlate with the in vivo process. This methodology must be based on the physiological and physical chemical properties controlling drug absorption. This analysis points out conditions under which no in vitro-in vivo correlation may be expected e.g. rapidly dissolving low permeability drugs. Furthermore, it is suggested for example that for very rapidly dissolving high solubility drugs, e.g. 85% dissolution in less than 15 minutes, a simple one point dissolution test, is all that may be needed to insure bioavailability. For slowly dissolving drugs a dissolution profile is required with multiple time points in systems which would include low pH, physiological pH, and surfactants and the in vitro conditions should mimic the in vivo processes. This classification scheme provides a basis for establishing in vitro-in vivo correlations and for estimating the absorption of drugs based on the fundamental dissolution and permeability properties of physiologic importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016212804288
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