Development of a radioimmunoassay for the anthrapyrazole chemotherapy agent CI-937 and the pharmacokinetics of CI-937 in rats.

The anthracyclines daunorubicin and doxorubicin are cancer chemotherapy agents that complex DNA and are widely utilized clinically. Cumulative cardiotoxicity, however, limits their prolonged use. The novel anthrapyrazole agent, CI-937, which has shown exceptional in vivo anticancer activity and reduced cardiotoxicity in preclinical models has been developed at the Parke-Davis Pharmaceutical Research Division, Warner-Lambert Co. Due to an inability to extract CI-937 reproducibly from biological fluids, high-performance liquid chromatography is not a feasible analytical method. We developed a radioimmunoassay by conjugating CI-937 to porcine thyroglobulin to elicit rabbit antibody which was used with a radioiodinated derivative. The assay was validated for rat plasma using 50 microliters of sample with a resulting limit of quantitation of 100 pg/ml. By dilution of samples the assay can quantitate CI-937 levels up to 16 micrograms/ml. The antiserum is very specific as evidenced by cross-reactivities of less than 0.4% for structural analogues and less than 0.004% for any of the commonly used cancer chemotherapy agents. Analysis of plasma samples from rats treated with a single 5 mg/kg i.v. dose indicated that CI-937 is rapidly cleared from plasma and is extensively bound to tissues.

Biological sample preparation and data reduction concepts in pharmaceutical analysis.

This paper describes strategies to rapidly develop sensitive and selective preparations using manual and robotic liquid-solid isolation (LSI) methods. LSI procedures offer selective isolation of drug or metabolites from complex matrices and are applicable to many pharmaceutical compounds. The beneficial effect of weighted linear regression is described, and several data reduction techniques are contrasted.

Recent analytical methods for cephalosporins in biological fluids.

Since 1980, RP chromatography has been the principal analytical technique used for cephalosporins. This technology offers selectivity, accuracy, and ease of use. Most of the methods rely on protein precipitation and, to a lesser extent, solid-phase isolation or extraction procedures. The proper selection of a method depends on the analytical constraints imposed by the overall objective of the study. For example, pharmacokinetic datum interpretation mandates that the method be validated and provide specific and accurate results. LC is the preferred technique, since it not only meets these specifications but may also distinguish between the drug and metabolites. Those chromatographic methods which quantify several different cephalosporins are not desirable for pharmacokinetic datum interpretation, since accuracy and precision are usually compromised in order that many different drugs may be quantified in a single analysis. The proper selection of sample preparation method is dependent on the presence of potential interferences and the acceptable lower limit of quantitation. Protein precipitation methods offer ease of sample preparation but may suffer from nonselectivity. Solid-phase isolation and extraction procedures may increase selectivity and improve the limit of quantitation. Although LC provides specific and accurate results, clinical laboratories may prefer to use the less specific methods for therapeutic drug monitoring. In this case, microbiological, enzymatic, and fluorimetric methods offer improved sample throughput but less specificity. However, these methods should not be used for drugs that may have a low margin of safety or if the patient is on multiple-antibiotic therapy. Future methods may involve incorporating solid-phase isolation columns to enhance the specificity of chromatographic, microbiological, enzymatic, and fluorescence methods. Advancements in microbore column technology may allow improvements in the selectivity and sensitivity of LC methods. Many investigators prefer to use simple protein precipitation procedures for sample preparation because of sample throughput constraints. However, advances in robotic sample preparation may allow the more cumbersome solid-phase isolation or extraction techniques to be used to improved sample throughput and specificity.

Analytical methods for measuring uric acid in biological samples and food products.

During the last 7 decades, uric acid methodology has kept pace with the introduction of state-of-the-art technology (e.g., spectroscopy, electrochemistry, chromatography) or the discovery of unique chemical processes (e.g., redox, enzymatic). We envision this practice will continue in the future. There never will be a single analytical method applicable for biofluids or foodstuffs. Therefore, it is imperative that the analyst not only understand the advantages and disadvantages of a procedure, but also thoroughly understand its underlying chemical and technological principles. Since many procedures available for analysis of biofluids and foodstuffs rely on identical chemical or technological principles, this report shall review both sample types and the available spectroscopic, electroanalytical, and chromatographic methods.

Robotic analysis of 3,7-dimethoxy-4-phenyl-N-1H-tetrazol-5-yl-4H-furo [3,2-b]indole-2-carboxamide in human plasma.

An automated liquid chromatographic assay using unattended robotic sample preparation has been developed and validated to quantitate 3,7-dimethoxy-4-phenyl-N-1H-tetrazol-5-yl-4H-furo(3,2-b)indole-2- carboxamide (CI-922) in human plasma. The drug and internal standard 2 were isolated from plasma by solid-phase extraction onto Bond-Elut C-18 cartridges. Plasma interferences were selectively removed, and the compounds were eluted from the cartridge. Separation was achieved at ambient temperature using a C-18 column (5 microns, 4.0 X 150 mm) with an isocratic eluant consisting of acetonitrile:water:glacial acetic acid (45:55:1). The column effluent was monitored spectrophotometrically at 340 nm. Peak-height ratios were proportional to plasma concentrations of 1 over the range 0.025-5.0 micrograms/mL, and the recovery of 1 from plasma was 63.5%. Calibration curve precision was +/- 6.7%, based on relative standard deviations (RSD) of 1.9 to 6.7% for calibration standards. The accuracy of calibration curves was +/- 7.2%, with relative errors ranging from -7.2 to 3.6%. Assay precision was +/- 4.8%, based on RSD values of 3.9, 4.8, and 3.4% for spiked control samples of pooled human plasma containing 0.20, 1.50, and 2.50 micrograms/mL of 1, respectively. Assay accuracy was -0.7 to 2.0%. This method has been used to analyze 1 in clinical plasma samples.

Bioanalytic considerations for pharmacokinetic and biopharmaceutic studies.

The correct evaluation of pharmacokinetic and biopharmaceutic data can only be achieved if accurate analytic data are obtained. The accuracy of analytic data depends on the criteria used to validate the method. Consequently, careful scrutiny of drug stability, assay sensitivity, selectivity, recovery, linearity, precision, and accuracy is necessary for the proper interpretation of data. The importance of method validation and its influence on pharmacokinetic and biopharmaceutic data evaluation and interpretation will be discussed.

A validated liquid chromatographic method for the antiallergy agent CI-922 in dog and rat plasma.

A sensitive, specific and rapid liquid chromatographic procedure to selectively monitor CI-922 in dog and rat plasma was developed and validated. Plasma samples were acidified and extracted with ethyl ether. The organic layer was evaporated to dryness, reconstituted with mobile phase, and the analytes were separated and quantified on an octadecylsilane stationary phase (lambda = 340 nm). The procedure was linear from 0.05 to 3.0 mug ml(-1) with a detection limit of 0.02 mug ml(-1). The accuracy of the method had relative errors of 7.6, 4.2 and 5.4% for dog plasma controls containing 0.5, 1.50 and 2.5 mug CI-922 ml(-1), respectively. The corresponding precision was 5.0, 4.0 and 4.8% (RSD). Similarly, relative standard deviations less than 4.6% and relative errors of less than 1.4% were obtained for rat plasma controls. The method is suitable for pharmacology, toxicology and pharmacokinetic studies of CI-922.

Analysis of 3-(2-(ethylamino)propyl)-1,2,3,4-tetrahydro-5H(1)benzopyrano (3,4-c)pyridin-5-one in plasma by liquid chromatographic column switching after derivatizing the secondary amine with fluorescein-6-isothiocyanate.

A high-performance liquid chromatographic (HPLC) assay has been developed to quantify the bronchodilator 3-(2-ethylamino)propyl)-1,2,3,4-tetrahydro-5H(1)benzopyrano(3,4-c)pyridi n-5-one (CI-923) (1) in human plasma. The drug and internal standard (2) were extracted from plasma (pH 10.5) with ether, and the secondary amines were derivatized with fluorescein-6-isothiocyanate (F6ITC) (3). The derivatives were isolated from the mixture by on-line HPLC column switching and were quantified with fluorometric detection (Ex: 484 nm; Em: 518 nm). Linearity was observed over the range 0.5-50.0 ng/mL of 1, and the recovery of drug from plasma was greater than 86%. The precision of the method was 3.7-5.2% RSD based on the analysis of seeded control pools containing 0.8, 20.0 and 40.0 ng/mL of 1. The accuracy of the method was +/- 3.3% relative error for the same three pools.