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

High-performance liquid chromatographic analysis of pindolol enantiomers in human serum and urine using a reversed-phase cellulose-based chiral column

Simple, sensitive and reliable high-performance liquid chromatographic methods are reported for the determination of pindolol enantiomers in human serum and urine. The methods involved a solid-phase extraction of serum and a direct injection of urine samples. The separation of R(+)- and S(-)-pindolol was accomplished on a reversed-phase cellulose-based chiral column with a mobile phase of 40:60 (v/v) acetonitrile-0.3 M aqueous sodium perchlorate at a flow-rate of 0.5 ml/min. The detection was achieved by monitoring the fluorescence emission of pindolol enantiomers at 310 nm with excitation at 270 nm. The limits of detection were 1.2 ng/ml of R(+)- and 4.3 ng/ml of S(-)-pindolol in serum, and 21 ng/ml of R(+)- and 76 ng/ml of S(-)-pindolol in urine. The external standard method was used for quantitation. The methods have been applied to the analysis of human serum and urine samples in a pharmacokinetic study.

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.

Simultaneous determination of clopamide-pindolol combination in tablets by zero-crossing derivative spectrophotometry

A first-derivative spectrophotometric method, using a 'zero-crossing' technique of measurement has been used for determining clopamide-pindolol mixture in tablets. In the first-derivative mode the zero-crossing points of clopamide and pindolol occur at 272.6 and 262.4 nm, respectively. The relative ease offered by this technique for the quantification of these drugs with closely overlapping bands was demonstrated. The linearity of the calibration curves was satisfactory (r = 0.9998) and the precision (RSD%) better than 1.89. Detection limits were 0.50 and 0.44 micrograms ml-1 for pindolol and clopamide, respectively. No spectral interferences from tablet excipients were found. Applications are given for the assay of commercial tablets and content uniformity test. The procedures proved to be suitable for rapid and reliable quality control.

High-performance liquid chromatographic determination of nifedipine, nicardipine and pindolol using a carbon fibre flow-through amperometric detector

The electrochemical properties of the calcium-channel blockers, nifedipine and nicardipine, and the beta-blocking agent, pindolol, have been exploited for the determination of their concentrations in plasma samples. High-performance liquid chromatography (HPLC) separation was carried out on a cyanopropyl modified column and the drugs were detected in a flow-through carbon fibre microelectrode cell. The chromatographic system was coupled to a column-switching arrangement in order to perform on-line solid-phase extraction of the drugs from spiked human plasma. Preliminary investigations showed the response of the method to be linear over a range of 20-500 ng ml-1 in plasma with a limit of detection of approximately 15 ng ml-1 for each compound.

Chromatography of beta-adrenergic blocking agents

The determination of beta-blockers has posed pharmaceutical analysts with a variety of problems arising from the essential characteristics of these compounds as bases and the variability of physicochemical properties of individual drugs. Liquid chromatography has become the favoured method of analysis and to a certain extent there is a standardised approach to analysis based on either solvent or solid-phase extraction and reversed-phase high-performance liquid chromatography coupled to fluorescence detection. The analyst must be aware of interactions occurring during extraction stages. All manipulations should be fully evaluated for individual drugs and metabolites prior to use. Other analytical options are chosen for specific or more demanding applications. The use of unmodified silicas for the liquid chromatography of beta-blockers (and other basic drugs) is an example of a potential alternative mode of chromatography. The stereoselectivity of the pharmacology of beta-blockers has spawned a great deal of literature describing the resolution of enantiomers by chromatographic methods. It is envisaged that this area will achieve greater prominence in the future as drug development pursues optical purity. The demand for the availability of enantiomerically pure pharmaceutical preparations will certainly see developments for preparative-scale separations as well as analytical methods and will surely promote developments in new and established methods of chromatography.

High-performance liquid chromatographic determination of beta-adrenoceptor blocking agents in body fluids

Several reports have been published reviewing high-performance liquid chromatographic (HPLC) methods for the determination of beta-adrenoceptor blocking agents (beta-blockers) in biological materials (Flouvat et al., 1981; Mehta, 1983; Marko and Soltés, 1984; Ahnoff et al., 1985; Tkaczyková and Safarík, 1987). Of these, the paper by Mehta (1983) briefly summarizes the interrelationship between physiocochemical properties of beta-blockers with prechromatographic treatment of biological samples, as well as with the HPLC methods used for the determination of 12 beta-adrenoceptor blocking drugs. The work by Ahnoff et al. (1985) concerning the monitoring of cardiovascular drugs also deals with HPLC assays of 18 beta-blockers in plasma. The Appendix to this report presents the great majority of HPLC methods for determining 30 beta-blockers in various body fluids. HPLC methods providing resolution and determination of individual beta-blocker enantiomers have not been included since this topic is being covered by Walle and Walle (1989). The Appendix is just a guide to the methods reviewed for the HPLC determination of parent beta-blockers as well as some of their metabolites co-assayed in various body fluids. It does not include details such as the internal standard, recovery, setting of the detector, limit of determination, etc., given in the individual methods listed. The isolation technique of the drug(s) from the given body fluid represents the main step in the sample work-up procedure. Along with this information, only the type of the HPLC column packing and the detection principle used by each method's developers are given.

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.

Hemodynamic-inotropic response to beta-blocker with intrinsic sympathomimetic activity in patients with congestive cardiomyopathy

The rest and exercise hemodynamic-inotropic response to administration of the beta-blocker pindolol was evaluated in 10 patients with congestive cardiomyopathy to determine whether the intrinsic sympathomimetic activity (ISA) of this agent may preserve ventricular function in the setting of beta-blockade. A significant (p less than .05) rise in systemic and pulmonary vascular resistance and a decline in stroke volume and cardiac index was observed after a single 10 mg dose. The change in cardiac index was negatively correlated with free drug concentration (r = -.59, p less than .01); the change in pulmonary and systemic vascular resistance showed a positive correlation with plasma concentration (r = .67, r = .57, respectively; all p less than .05). The response to exercise reflected a predominant beta-blocking effect, with a significant decrease in peak heart rate and cardiac index and an increase in pulmonary vascular resistance. There were no significant changes in variables of right or left ventricular inotropy after administration of the drug. The mean baseline plasma norepinephrine concentration for the population was 609 +/- 172 pg/ml (normal = 196 +/- 7 pg/ml) and was markedly elevated in two patients (931 and 2053 pg/ml) who developed severe pindolol-induced hypotension. Renin increased markedly in these two patients, but decreased in each of the remaining eight patients. These data indicate that although inotropy is not adversely affected by pindolol, increased afterload, which appears to be mediated by peripheral beta-blockade, results in a reduction in ventricular performance.(ABSTRACT TRUNCATED AT 250 WORDS)