The purpose of the study was to examine the bioequivalence of five commercially available oral prednisone products. The in vivo study utilized 18 healthy males, each of whom was administered 20 mg of prednisone as a reference solution or as a tablet in a 6-week, six-way crossover design. Blood was collected and serum was assayed, using an HPLC procedure specific for prednisone and prednisolone. Mean pharmacokinetic parameters (t 1/2, ke, Cmax, tmax, and AUC) were determined. ANOVA was performed on the prednisone and prednisolone data (F-test, p less than 0.05) as well as Duncan's multiple range analysis. Dissolution tests were also performed on each of the five products in order to test the relationship between dissolution and bioequivalence among prednisone products. The in vitro study consisted of a standard USP dissolution test which included tablets from the same lots as the tablets used in the in vivo study. The data showed no statistical difference in any of the pharmacokinetic parameters among tableted products, subjects, or dosing periods in the study. There was also no statistical difference in the dissolution study among the five commercial tablet forms.
Promethazine in doses of 50 mg has demonstrated detrimental effects upon the performance of visual tasks. The purpose of the study was to examine the relationship between the blood concentration levels of promethazine and two human performance tasks. Fifteen paid healthy male volunteers completed a randomized five-way crossover design which included a 25 mg and 50 mg dose of the innovator dosage form, a 50 mg dose of a generic dosage form, a 50 mg solution dosage form, and a placebo. Serial blood samples were obtained in addition to performance measures of rotary pursuit and a simple force choice reaction time. Analysis of the forced choice reaction depicted a mild relationship with the blood concentration levels of promethazine. However, the measures of rotary pursuit, a more sensitive determinant of human motor performance, proved to be more related to both the promethazine blood concentration and the inherent learning which was confounded in the experiment. The degree of impaired pursuit performance and reaction time differences could be defined in terms of a linear relationship to the promethazine concentration.
Data from a five-way crossover study in human subjects using four talented promethazine products and a promethazine solution are presented. All products were administered as a single oral dose. The five objectives of the study were to investigate bioequivalency, to estimate dose proportionality at two dose levels, to establish validity of a reference production solution for future bioequivalency studies, to estimate intersubject variation, and to compare bioavailability/tablet dissolution data. Blood samples were collected at given intervals over a 24-hour period and analysed for promethazine using an HPLC technique. Pharmacokinetic parameters were calculated using standard procedures and a two-way analysis of variance (ANOVAR) was used to assess whether the differences were statistically significant. The AUC0----infinity data from the ANOVAR analysis showed that the 50 mg innovator and generic products and the 50 mg solution were not significantly different. However, the innovator product had a significantly lower Cmax and longer tmax than the solution. The generic product did not differ significantly from the solution. Promethazine was found to exhibit linear dose proportionality in the range and product studied. Intersubject variation was high for all parameters (23 to 63 per cent) and the in vivo and in vitro data showed a positive relationship.
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