Measurement of cyclosporine in plasma of cardiac allograft recipients by fluorescence polarization immunoassay.

The Abbott TDx fluorescence polarization immunoassay (FPIA) procedure for measuring cyclosporine A (CsA) was evaluated and compared with the Sandoz polyclonal radioimmunoassay (CsA RIA kit) method. This drug assay was evaluated for precision, calibration, stability, and accuracy. Within-run precision studies utilizing 25 replicate analyses of the three control preparations (containing CsA in the 60-800 ng/ml range) resulted in coefficients of variation (CV) ranging from 1.0 to 9.1%. The CVs of between-run precision determined by assaying the same control drug levels for five consecutive working days ranged from 3.9 to 4.6%. Calibration curve stability was assessed by examining the drift in control values over a 2-week period. Maximum plasma ranged from 82.6 to 108.2%. Four hundred plasma samples were obtained from 30 heart-transplant patients during the first 6 months of CsA therapy and each sample was analyzed simultaneously by TDx and RIA. Linear regression analysis of the results obtained for each patient (x = RIA, y = FPIA) revealed the following mean values: r = 0.87, (CV = 13.7%), slope = 1.47 (CV = 39.2%). Moreover, the concentration of CsA was determined in 35 patient samples both by TDx and high-performance liquid chromatography (HPLC). FPIA results up to 12 times higher than HPLC results have been noted.

Bioequivalency of three tableted gallopamil products.

A three cross-study was conducted in 12 healthy male volunteers to evaluate the relative bioavailability of three different gallopamil tablets: Product A-Galcan 25 mg, Product B-Galcan 50 mg and Product C-Procorum 50 mg. Each dose was administered as a single tablet after an overnight fast, and blood samples were obtained for 12 hours. There was no statistically significant differences among the three products for the mean area under the plasma concentration-time curves (when corrected for the different doses). The relative bioavailability of Product A and B to Product C was respectively 96.3% (ESM = 12.4%) and 103.1% (ESM = 10.2%). Statistically significant (p less than 0.05) differences were found in Tmax between Product C (1.0 hr) and both Product A (2.1 hr) and Product B (2.4 hr). A longer-lasting absorption should always diminish peak to trough fluctuations during multiple dosing and to this extent Product B has some advantage over Product C.