Comparison of Two Spectrofluorometric Procedures for Quinidine Determination in Biological Fluids

Bioavailability of Three Commercial Sustained-Release Tablets of Quinidine in Maintenance Therapy

“…The highest level was obtained with Tablet B. The dose-corrected C,,,ax value of Tablet B was significantly different from that of A and C. Furthermore, the dose-corrected 4Cp values demonstrated that Tablets A and C presented similar fluctuation in blood levels and that this fluctuation was less pronounced than for B. Consequently, the statistical analysis of the data and the plasma level-time profiles shown in vestigation and previous dissolution data (6) suggest that Tablet B must have been reformulated.…”

“…The dissolution rate of some quinidine sustained-release tablets and its implication in bioavailability and therapeutic treatment were studied previously (6). The present study compared the bioavailability of three commercial dosage forms, considered as slow-release formulations, by measuring the plasma drug level and the degree of drug excretion during a regular dosing interval of a maintenance treatment.…”

“…There is a correlation between serum drug concentration and antiarrhythmic and toxic effects (2-4). The therapeutic drug level of unchanged quinidine and hydroquinidine is 0.8-2.5 mghiter of plasma (5). To maintain a sufficiently steady therapeutic plasma level with quinidine sulfate tablets USP, this dosage form must be administered at relatively frequent intervals because of rapid drug absorption and elimination.…”

“…The tubes were subsequently centrifuged, and the plasma was removed and frozen until assayed by the specific spectrofluorometric procedure5 of Armand and Badinand (5,7). Although the specificity of this method is limited, it was sufficiently sensitive, accurate, and precise for the measurement of concentrations as low as 0.1 p g h l (5).…”

“…Total quinidine-derived fluorescence also was monitored by the protein precipitation method of Brodie and Udenfriend (8). For each urine void, the volume was determined and an aliquot was frozen until just prior to drug analysis by the method of Armand and Badinand (5,7). Quinidine levels are reported in terms of quinidine base.…”