Determination of pindolol in biological fluids by electron-capture GLC

Knowledge-based system for the automated solid-phase extraction of basic drugs from plasma coupled with their liquid chromatographic determination. Application to the biodetermination of beta-receptor blocking agents

Techniques for the preparation of biological samples are often based nowadays on solid-phase extraction (SPE). The different SPE steps can be performed automatically on disposable extraction cartridges (DECs) by means of a sample processor. A knowledge-based system was developed to facilitate the development of fully automated methods for the solid-phase extraction of relatively hydrophobic basic drugs from plasma, coupled with their determination by high-performance liquid chromatography (HPLC). The DEC filled with 50 mg of cyanopropyl-bonded silica phase is first conditioned with methanol and buffer solution (pH 7.4). After sample application, the DEC sorbent is washed with the same buffer. The analytes are then desorbed with an appropriate eluent and the eluate is finally diluted with the same buffer as used in the HPLC mobile phase before injection. Under these conditions, only three variables are still to be optimized: the composition and volume of the elution solvent and the volume of buffer to be added to the eluate. On the basis of this general strategy, a decision tree providing information about suggested starting conditions and guidelines for the optimization of the three variables was developed and implemented by use of a hypermedia software. This didactic expert system was evaluated using several beta-receptor blocking agents as model compounds and the operating conditions obtained for the automated SPE of these compounds are presented. A method for the determination of propranolol in plasma using the SPE conditions deduced from the knowledge-based system was validated. The absolute recovery of propranolol is ca. 93% and the limit of detection is 1.3 ng ml-1. The mean within-day and between-day reproducibilities are 2.3 and 3.6%, respectively.

High-performance liquid chromatographic method for the determination of pindolol in human plasma

A sensitive, simple and highly reliable high-performance liquid chromatographic method using fluorescence detection is reported for the determination of pindolol in plasma. This method involves a single extraction of pindolol from alkalinized plasma into methyl tert.-butyl ether followed by a back-extraction into dilute hydrochloric acid. Injection of the dilute acid phase directly onto an octyl (LC-8) bonded-phase column provides the final separation, and detection of pindolol is achieved by monitoring the intrinsic fluorescence of pindolol at 315 nm following excitation at 255 nm. The method is sensitive enough to measure with confidence pindolol plasma concentrations of 2 ng/ml using a 2-ml sample. No internal standard is required. This method has been applied to the analysis of 1500 human plasma samples by two different laboratories.

Determination of pindolol in human plasma and urine by high-performance liquid chromatography with ultraviolet detection

This paper presents a rapid, simple and economical method for assaying pindolol concentrations in plasma and urine by high-performance liquid chromatography using ultraviolet detection. It is sensitive enough for use in single-dose pharmacokinetic studies and may also be used to determine pindolol concentrations in the plasma from patients taking the drug, provided that the patient is not taking any of the drugs which interfere with the method. Drugs which were found to interfere with the pindolol peak are quinidine, n-acetylprocainamide and lidocaine. Disopyramide, oxprenolol and levobunolol interfered with the internal standard peak.

Patients compliance in hypertension--the importance of number of tablets

The importance of number of tablets for patient compliance was investigated in 160 patients with mild-moderate essential hypertension treated with a beta-adrenoceptor blocker and a thiazide diuretic. Mean BP at entry 146 +/- 16/92 +/- 8 mm Hg. All patients were given pindolol 10 mg and clopamide 5 mg in one combination tablet or in separate tablets for 4 months respectively. Approximately 90% of the patients took greater than 90% of the prescribed dose throughout the study. Mean BP decreased progressively and heart rate increased slightly. Side effects were more frequently reported during the first month of the study than previously, and 30 patients discontinued the treatment. No differences in this respect were seen between 1 and 2 tablets daily. Approximately 75% of the patients preferred 1 tablet daily, but combining two drugs in one tablet had no effect upon compliance.

Derivatization reactions in the gas—liquid chromatographic analysis of drugs in biological fluids

Alkylation, acylation, silylation and other derivatization reactions applied to the gas chromatographic analysis of drugs in biological matrices are reviewed. Reaction conditions are discussed in relation to reaction mechanisms. Detector-oriented labelling of drugs, and derivatization with chiral reagents for the separation of enantiomers are surveyed. Data on the sample clean-up, derivatization and GLC analysis of more than 300 drugs and related compounds are listed.