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  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    The Effect of Gastric pH on the Absorption of Controlled-Release Theophylline Dosage Forms in Humans (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1037-1045 
    Details
    ISSN: 1573-904X
    Keywords: controlled-release theophylline ; pH-dependent dissolution ; achlorhydric humans ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of three marketed controlled-release dosage forms and a reference solution of theophylline was studied in eight subjects with normal gastric fluid acidity and seven subjects who were achlorhydric. Gastric pH was monitored with a Heidelberg capsule. One of the controlled-release dosage forms dissolved more rapidly in vitro when exposed to acid conditions, one dissolved more rapidly in pH 7.5 media, and the third dissolved at a rate independent of pH. Using a crossover design, each subject received each dosage form twice. Blood was sampled for up to 47 hr after each dose, and serum was assayed for theophylline by HPLC. The product which dissolved more rapidly under acid conditions in vitro exhibited a 3 hr longer T max in the achlorhydrics compared to the normal subjects. The product which dissolved more rapidly in the pH 7.5 media exhibited a relatively higher AUC(0–∞) in the achlorhydric subjects than in normal subjects after the AUC data were normalized for clearance differences between the two subject groups. The in vivo bioavailability of these dosage forms could be related to the in vitro dissolution characteristics for some parameters. However, with the exception of the mean T max values, the mean bioavailability parameters differed by less than 20% between the two subject groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018923008579
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  • 4
    Electronic Resource
    Electronic Resource
    The Relative Bioavailability and In Vivo-In Vitro Correlations for Four Marketed Carbamazepine Tablets (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1787-1791 
    Details
    ISSN: 1573-904X
    Keywords: carbamazepine ; human ; bioavailability: gender, dissolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine if three marketed generic carbamazepine tablets were bioequivalent to the innovator formulation, as well as to each other. In addition, to examine in vivo-in vitro relationships among the four formulations. Methods. Each formulation was given as a single dose to 18 healthy male and female subjects using a crossover design. Blood samples were collected for 169 hr. Carbamazepine was assayed by HPLC with UV detection. Results.In vivo fraction absorbed plots indicated that the three generic formulations were absorbed more rapidly than the innovator product, and the mean time of maximum plasma concentration was 6−7 hr sooner for the generic formulations. The mean maximum plasma concentration ranged from 17−19 percent higher for the generic products compared to the innovator, and the 90% confidence limits for Cmax data ranged from 111% to 126%. The mean AUC(0−∞) for the generic products ranged from 101−104% compared to the innovator, and the confidence limits for AUC ranged from 97−108%. Conclusions. The generic products were all more rapidly absorbed than the innovator, but simulations of steady-state concentrations indicated that it would be unlikely that these differences would have any significant clinical effect. An excellent association was seen between the Cmax and the percent of drug dissolved in vitro. The correlation was used to accurately predict the Cmax of four other 200 mg tablets evaluated in an earlier study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011929300613
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  • 5
    Electronic Resource
    Electronic Resource
    Bioavailability of 11 phenytoin products (1977)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 5 (1977), S. 133-146 
    Details
    ISSN: 1573-8744
    Keywords: bioavailability ; phenytoin sodium capsules ; plasma levels ; human studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Eleven single lots of 100-mg phenytoin sodium capsules were evaluated for their relative bioavailability in 12 normal human volunteers. These products were manufactured by eight different companies and met all compendial specifications. The products were evaluated with respect to plasma levels at various times up to 96 hr following administration of single 100-mg doses, times of peak level, peak plasma concentrations, and areas under the plasma level—time curve. Several of the products exhibited statistically significant differences in the various parameters studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066217
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  • 6
    Electronic Resource
    Electronic Resource
    Bioavailability of microsize and ultramicrosize griseofulvin products in man (1980)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 8 (1980), S. 347-362 
    Details
    ISSN: 1573-8744
    Keywords: griseofulvin ; bioavailability ; HPLC assay ; plasma levels ; human study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The relative bioavailability of ten marketed dosage forms of griseofulvin was evaluated in two separate crossover studies. Each study utilized 12 healthy subjects, with eight of the subjects being common to both studies. Plasma griseofulvin concentrations were determined 1, 2, 3, 4, 6, 8, 10, 25, 34, 49, and 73 hr after dosing, using a high-pressure liquid chromatographic method. The “high-dose” study compared four microsize dosage forms administered as 500-mg doses and two ultramicrosize formulations given as 250-mg doses. The “low-dose” study employed four 250-mg microsize products and two 125-mg ultramicrosize products. The individual plasma level-time profiles for the majority of doses suggested prolonged absorption of microsize griseofulvin. The ultramicrosize dosage forms exhibited peak concentrations which were not significantly different (p〉0.05) from those of the microsize products administered as twice the dose. In the high-dose study, the two 250-mg ultramicrosize dosage forms exhibited areas under the plasma level-time curve (AUC) which were significantly (p〈0.05) less than the AUCs for all but one of the 500-mg microsize products. In the low-dose study the AUCs for the ultramicrosize products were significantly lower than the AUCs for all of the microsize dosage forms. Significant differences were also noted among the AUCs for the microsize products, although the maximum difference was less than 20% in both studies. A comparison of the AUCs observed in the high- and low-dose studies revealed that the AUCs for two of the 500-mg microsize dosage forms were only approximately 75% the AUC predicted from the 250-mg dose for the eight subjects common to both studies. All other formulations exhibited a dose proportionality for AUC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059383
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  • 7
    Electronic Resource
    Electronic Resource
    The Effect of Raising Gastric pH with Ranitidine on the Absorption and Elimination of Theophylline from a Sustained-Release Theophylline Tablet (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 1516-1519 
    Details
    ISSN: 1573-904X
    Keywords: theophylline ; ranitidine ; Heidelberg capsule ; gastric pH ; pharmacokinetics ; absorption ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Prior to evaluating the effect of ranitidine on theophylline absorption from a sustained-release theophylline tablet, the effect of ranitidine on the time course of gastric pH in 12 healthy subjects was evaluated with an encapsulated radio-telemetry device (Heidelberg capsule). Gastric pH was measured hourly from 7 AM to 1 PM prior to beginning ranitidine treatment at 2 PM (150 mg every 4 hr for eight doses). The next day, pH was again measured hourly from 7 AM to 7 PM. Subjects fasted overnight and remained fasted until lunch at 11 AM. Prior to ranitidine treatment, the mean morning gastric pH remained between 1.5 and 2.2. After lunch, the pH increased to 2.2–2.3. During ranitidine treatment the mean morning gastric pH measurements were 5.5 to 5.8, decreasing after lunch to 3.1 by 4 PM and increasing to 3.9 at 7 PM. One week later the subjects participated in a three-way crossover theophylline bioavailability study receiving at weekly intervals, single doses at 7 AM of (a) 5 × 100-mg immediate-release tablets, (b) 2 × 300-mg sustained-release theophylline tablets, and (c) 2 × 300-mg sustained-release theophylline tablets after ranitidine pretreatment of 150 mg every 4 hr beginning at 2 PM the previous day. The increase in gastric pH with ranitidine had no effect (P 〉 0.05) on the rate and extent of absorption or on the elimination rate of theophylline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015846417085
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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Bioequivalence of Methylphenidate Immediate-Release Tablets Using a Replicated Study Design to Characterize Intrasubject Variability (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 381-384 
    Details
    ISSN: 1573-904X
    Keywords: methylphenidate ; average bioequivalence ; individual bioequivalence ; human ; pharmacokinetics ; replicated design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine the relative bioavailability of two marketed,immediate-release methylphenidate tablets. The study used a replicatedstudy design to characterize intrasubject variability, and determinebioequivalence using both average and individual bioequivalencecriteria. Methods. A replicated crossover design was employed using 20subjects. Each subject received a single 20 mg dose of the reference tableton two occasions and two doses of the test tablet on two occasions.Blood samples were obtained for 10 hr after dosing, and plasma wasassayed for methylphenidate by GC/MS. Results. The test product was more rapidly dissolved in vitro and morerapidly absorbed in vivo than the reference product. The mean Cmaxand AUC(0 − ∞) differed by 11% and 9%, respectively. Using anaverage bioequivalence criterion, the 90% confidence limits for theLn-transformed Cmax and AUC(0 − ∞), comparing the two replicatesof the test to the reference product, fell within the acceptable range of80–125%. Using an individual bioequivalence criterion the test productfailed to demonstrate equivalence in Cmax to the reference product. Conclusions. The test and reference tablets were bioequivalent usingan average bioequivalence criterion. The intrasubject variability of thegeneric product was greater and the subject-by-formulation interactionvariance was borderline high. For these reasons, the test tablets werenot individually bioequivalent to the reference tablets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007560500301
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