Statistical survey of "saturation analysis" calibration curve data for prednisolone, prednisone and digoxin

An extensive survey of radioimmunoassay calibration data for prednisolone, prednisone and digoxin indicated that the common practice of preparing calibration curves with individual subject's pre-dose plasma or serum, and using this to estimate unknown concentrations for the same subject, is not supported by statistical considerations. Preparation of calibration plots from pooled data is better because this introduces less bias in estimated concentrations. Such a method also saves a great deal of time, since it is not necessary to repeat the calibration procedure each time "unknowns" are being assayed. The data suggest that there is no optimum calibration plot for all radioimmunoassays. Rather, each antibody-drug combination should be investigated thoroughly to determine the best calibration plot for the particular combination. We found that the best calibration plots are; the logistic-logarithmic plot for prednisolone; nonlinear least squares fit to a polyexponential equation for prednisone; and a weighted least squares regression of normalized % bound concentration for digoxin. The error in the radioimmunoassay is usually concentration-dependent, and, in certain regions of the standard curve, is larger than the literature indicates, since, frequently, the error has been gauged from % bound values, but should be gauged from inversely-estimated concentrations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21684/1/0000074.pd

Bioavailability of prednisolone tablets

Two fourtreatment crossover studies were performed using 12 adult male volunteers in each with seven different commercially available prednisolone tablets. Plasma samples were assayed for prednisolone by a radioimmunoassay method. Statisacal analyses of the data, by analysis of variance for crossover design (ANOVA), showed no significant differences among the treatment averages at any of the sampling times except at 0.25 and 4 hr in one of the studies. There were also no significant differences among the treatment averages for peak plasma level, time of peak plasma level, area 0–12 hr, area 0–24 hr, and the halflife of elimination of prednisolone. We conclude that the average plasma concentrations of prednisolone are superimposable in a statistical sense and that the tablets tested are bioequivalent. Results of dissolution studies of six tablets of each of the seven lots of prednisolone tablets, using deaerated water in the spin filter apparatus, are presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45072/1/10928_2005_Article_BF01065399.pd

Plasma prednisolone concentrations: Comparison of radioimmunoassay and competitive protein binding assay

A comparison was made between plasma concentrations of prednisolone measured by both competitive protein binding radioassay (CPB) and radioimmunoassay (RIA) and, with each assay, using a calibration curve generated from individual subject data and from pooling the individual calibration curve data. The plasma samples were obtained from six normal adult male volunteers who were pretreated with dexamethasone to suppress endogenous hydrocortisone and who then ingested 10 mg of prednisolone. Both the standard curve data and the plasma concentrations were evaluated statistically. It was shown that the CPB method has considerably greater precision than the RIA method and could be employed in bioavailability and pharmacokinetic studies of both prednisolone and prednisone. It was also shown that corticosteroid binding globulin cross-reacts considerably less with the major metabolite of prednisolone, 20[beta]-dihydroprednisolone, than the particular antiserum used in the RIA.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22936/3/0000502.pd