Versatile isocratic high-performance liquid chromatographic assay for propranolol and its basic, neutral and acidic metabolites in biological fluids

Fast determination of propranolol in urine and pharmaceutical preparations by stopped-flow and micellar-stabilized room-temperature phosphorescence: validation of the method

The stopped-flow mixing technique has been used to study the kinetic determination of propranolol by means of micellar-stabilized room-temperature phosphorescence. This mixing system diminishes the time required for the deoxygenation of micellar medium by sodium sulfite, allowing a kinetic curve that levels off within only 7s to be obtained. The phosphorescence enhancers thallium (I) nitrate, sodium dodecyl sulfate, and sodium sulfite were optimized to obtain maximum sensitivity and selectivity. A pH value of 6.54 was selected as adequate for phosphorescence development. The kinetic curves of propranolol phosphorescence were scanned at lambda(ex)=290 nm and lambda(em)=524 nm. The calibration graphs were linear for the concentration range from 25 to 400 ng mL(-1). The phosphorescence lifetime of propranolol is approximately 1210 micros. The detection limit calculated as proposed clayton was 13.53 ng mL(-1) and by applying the error propagation theory, the detection limit was 8.37 ng mL(-1). The repeatability was studied using 10 solutions of 200 ng mL(-1) of propranolol; if error propagation theory is assumed, the relative error is 1.94%. The standard deviation for a replicate sample was 4.0 ng mL(-1). This method was successfully applied to the determination of propranolol in commercial formulations and in urine. Suitable recovery values were obtained.

Control of propranolol intake by direct chromatographic detection of alpha-naphthoxylactic acid in urine

A rapid chromatographic procedure with a C18 column, a mobile phase of 0.15 M sodium dodecyl sulfate (SDS)-10% (v/v) 1-propanol at pH 3 (0.01 M phosphate buffer), and fluorimetric detection, is reported for the control of propranolol (PPL) intake in urine samples, which are injected directly without any other treatment than filtration. The peak of PPL was only observed in samples taken a few hours after ingestion of the drug due to its extensive conjugation and metabolisation. The detection of several unconjugated PPL metabolites was therefore considered: desisopropylpropranolol (DIP), propranolol glycol (PPG), alpha-naphthoxylactic acid (NLT) and alpha-naphthoxyacetic acid (NAC). NLT showed the best characteristics: it eluted at a much shorter retention time than PPL, its concentration in urine samples was greater and it did not present any interference from endogeneous compounds in urine, common drugs or drugs administered in combination with PPL. The limit of quantification, measured as the concentration of analyte providing a relative standard deviation of 20%, was 24 ng/ml, and the day-to-day imprecision was below 4% for concentrations above 200 ng/ml. The procedure allows the routine control of PPL at therapeutic urine levels. Urinary excretion studies showed that the detection of NLT is possible at least up to 20-30 h after oral administration.

Determination of propranolol concentration in small volume of rat plasma by HPLC with fluorometric detection

A simple, rapid and sensitive fluorescence high performance liquid chromatographic method was developed to determine propranolol concentration in the small volume of rat plasma without the solvent extraction step using pronethanol as the internal standard. The analysis was accomplished using a 5 microm CAPCELL PAK analytical cyano column at room temperature and a mobile phase consisted of 1% aqueous acetic acid containing 0.2% triethylamine and acetonitrile (65:35, v/v; pH 3.8). The flow-rate was kept at 0.5 mL/min and column effluent was monitored with a fluorescence detector at an excitation wavelength of 230 nm and an emission wavelength of 340 nm. Retention times for pronethalol and propranolol were 8.5 min and 10.5 min, respectively. Linear regressions for the standard curves were linear in the range 2-800 ng/mL, giving correlation coefficients above 0.998. The detection limit was 1.34 ng/mL. No analytical interference was observed from endogenous components in rat plasma. This simple and sensitive assay method was feasibly applied to the pharmacokinetic study of propranolol after intravenous administration of 2 mg/kg of propranolol to normal and carbon tetrachloride-induced liver cirrhotic rats.

Two reproducible and sensitive liquid chromatographic methods to quantify atenolol and propranolol in human plasma and determination of their associated analytical error functions

Two liquid chromatography (LC) methods with fluorimetric detection have been developed to measure atenolol and propranolol in human plasma. The same 5 microm Nucleosil RP-18 column, extraction procedure and mobile phase (containing acetonitrile, water, triethylamine and phosphoric acid, pH 3) were used. The linearity ranges were 25-800 ng/ml for atenolol and 3.13-100 ng/ml for propranolol. The coefficients of variation for validation assays were lower than 15% at the concentration assayed. The functions of the analytical error were linear: SD (ng/ml)=7.698+0.037C for atenolol and SD (ng/ml)=0.126+0.036C for propranolol.

Micellar liquid chromatography: a worthy technique for the determination of beta-antagonists in urine samples

Several beta-antagonists (acebutolol, atenolol, celiprolol, labetalol, metoprolol, nadolol, propranolol) were determined in urine samples with fluorometric detection after direct injection, in less than 15 min, with a micellar mobile phase of 0.1 M sodium dodecyl sulfate (SDS), 15% propanol, and 1% triethylamine at pH 3. The limits of detection (38 criterion) were usually between 3 and 30 ng/mL. The addition of propanol and triethylamine and the reduction of the pH of the mobile phase improved the efficiency of the chromatographic peaks that was rather low in pure micellar eluents. The selection of the composition of the mobile phase was easily performed through the use of an interpretive procedure which considered the retention times and peak shapes of the beta-antagonists in six chromatograms, obtained at varying concentrations of SDS (0.05-0.15 M) and propanol (5-15% v/v). The chromatograms of urine samples from healthy volunteers, which were administered atenolol, metoprolol, and propranolol, showed only one peak for the former drug and several peaks for the other two. These peaks corresponded to the parent drug and metabolites, which indicated the partial and the extensive degradation of metoprolol and propranolol, respectively.

Simplified high-performance liquid chromatographic method for propranolol and five metabolites in liver perfusate, rat serum and dog plasma

A new method has been developed for the analysis of propranolol plus five major metabolites in perfusate from isolated liver preparations, and also in rat serum and dog plasma. The regional isomers of hydroxypropranolol are clearly separated within a total run time of less than 15 min. The basic and neutral metabolites are extracted and analysed together, while the acidic metabolites are extracted in a second step. The new assay is more simple and time efficient than previously published methods.

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.

Differences of chronopharmacokinetic profiles between propranolol and atenolol in hypertensive subjects

Previous studies have shown that the absorption rate of a lipophilic, but not hydrophilic, agent is faster after the night dosage than after the morning dosage in nocturnal rodents. The present study examines whether such a difference in chronopharmacokinetic profiles between lipophilic and hydrophilic agents also exists in humans. Propranolol (20 mg), a lipophilic beta-blocker, or atenolol (50 mg), a hydrophilic beta-blocker, was given orally to 13 hypertensive patients at 9:00 AM (day trial) or 9:00 PM (night trial) by a crossover design. Plasma concentrations of propranolol and its metabolites, 4-hydroxypropranolol and naphthoxylactic acid, and atenolol were determined just before and at 0.5, 1, 1.5, 2, 3, 4, 6, 12, and 24 hours after treatment. Maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) of propranolol in the day trial were significantly greater than those in the night trial. Time to maximum plasma concentration (tmax) was significantly shorter in the day trial. No significant difference was observed in the elimination half-life between the two trials. There were similar administration time-dependent changes in the Cmax for 4-hydroxypropranolol and naphthoxylactic acid. On the other hand, although the Cmax of atenolol was greater and its tmax was shorter in the day trial, the differences did not reach significance. These results suggest that propranolol, but not atenolol is absorbed more rapidly after the morning dosage than after the night dosage. Based on these findings, the authors speculate that the absorption rate of a lipophilic, but not hydrophilic, agent is faster after the morning dosage than after the night dosage in humans.

Rapid high-performance liquid chromatographic method for the determination of propranolol levels in canine and feline plasma

A sensitive high-performance liquid chromatographic method that does not require organic extraction has been developed for the determination of propranolol levels in canine and feline plasma. Equal volumes of plasma and a mixture of methanol-acetonitrile-0.1 M sodium hydroxide (3:3:4, v/v/v) were added to a microseparation unit with a 10,000 molecular mass cut-off filter. The ultrafiltrate was analyzed by reversed-phase liquid chromatography with fluorimetric detection. The consistency of the recoveries obtained eliminated the need for an internal standard (coefficients of variation less than 4%). Linear regressions for the standard curves (2.5-100 ng/ml) gave correlation coefficients above 0.9955. The detection limit was 1 ng/ml. The assay retains high sensitivity while eliminating laborious sample preparation.

Propranolol oxidation by human liver microsomes--the use of cumene hydroperoxide to probe isoenzyme specificity and regio- and stereoselectivity

1. Three oxidations of the enantiomers of propranolol were studied in human liver microsomes under two reaction conditions. Previous in vitro studies had established that two of the livers were from poor metaboliser (PM) phenotypes for the debrisoquine 4-hydroxylase (cytochrome P-450IID6) and the remaining seven were from extensive metaboliser (EM) phenotypes. 2. In the presence of NADPH and oxygen 4- and 5-hydroxylation of propranolol occurred in microsomes from all nine livers, as did propranolol N-desisopropylation. R(+)-propranolol was oxidized preferentially along the three pathways, although enantioselectivity observed for N-desisopropylation may have arisen not only from stereoselectivity in formation rates, but also from stereoselectivity in subsequent microsomal metabolism, possibly by monoamine oxidase. The involvement of monoamine oxidase in the further microsomal metabolism of N-desisopropylpropranolol was indicated by inhibition of the metabolism of this compound when incubated with phenelzine. 3. Cumene hydroperoxide has been proposed to support only the activity of cytochrome P450IID6. This is consistent with the observations that a) propranolol 4- and 5-hydroxylation occurred in microsomes from the EM livers only and b) side-chain oxidation was not observed under these conditions in either PM or EM livers. 4. Using cumene hydroperoxide to support the reactions, the 4-hydroxylation of propranolol showed little enantioselectivity, whereas S(-)-propranolol was 5-hydroxylated about twice as fast as the R(+)-enantiomer. There were highly significant correlations between the rates of 4- and 5-hydroxylation of R(+)-propranolol (r = 0.96, P less than 0.001, n = 7 livers) and of S(-)-propranolol (r = 0.98, P less than 0.001). Both oxidations were described by single-site Michaelis-Menten kinetics. 5. The findings suggest that P450IID6 is involved in both the 4- and 5-hydroxylations of propranolol, but that these metabolites can also be formed by other P450 isoenzymes. It is confirmed that P450IID6 does not contribute to the N-desisopropylation of propranolol. Furthermore, the finding that mephenytoin did not inhibit the appearance of this metabolite is not consistent with the results of in vivo studies suggesting the involvement of the same enzyme in the side-chain oxidation of propranolol and the 4-hydroxylation of mephenytoin.

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.

Bioavailability of propranolol following oral and transdermal administration in rabbits

The systemic bioavailability of propranolol was evaluated following oral and transdermal administration in rabbits. Using a four-way crossover study, the bioavailability of propranolol following oral administration was determined to be 12.3 +/- 5.9%, indicating that propranolol is subject to extensive hepatic first-pass metabolism in rabbits. Transdermal delivery of propranolol, via an adhesive delivery device, resulted in a bioavailability of 74.8 +/- 10.1%, indicating that the transdermal delivery of propranolol can significantly increase systemic bioavailability over oral administration. Skin irritation studies indicated that neither propranolol nor the adhesive used in the device caused any appreciable skin irritation.

Simultaneous determination of propranolol and 4-hydroxypropranolol enantiomers after chiral derivatization using reversed-phase high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method is described, which allows the simultaneous quantification of propranolol and 4-hydroxypropranolol enantiomers in human plasma. After extraction from plasma (pH 10.5) using ethyl acetate, the enantiomers are derivatized with R-(+)-phenylethylisocyanate as chiral derivatization reagent and triethylamine as basic catalyst in chloroform. Ascorbic acid is used to prevent 4-hydroxypropranolol from oxidation during the extraction. Chromatographic separation on ODS columns and fluorescence detection (228 nm/greater than 340 nm) allows sensitive quantitation of all derivatives. Incubation of the plasma samples with beta-glucuronidase/arylsulfatase and the use of the specific beta-glucuronidase inhibitor saccharo-1,4-lactone allows the quantitation of both the sulfate and glucuronide conjugates of the enantiomers. The method was applied to human plasma samples from a subject after administration of 60 mg racemic propranolol three times daily.

Effect of propranolol on the myocardial contractility of normotensive and spontaneously hypertensive rabbits: relationship of pharmacokinetics and pharmacodynamics

Myocardial contractility of normotensive and spontaneously hypertensive rabbits was determined following an iv bolus injection of propranolol HCl. Left ventricular pressure and dimension were used to calculate the contractility parameters of (dP/dt)max, maximum fiber shortening velocity (Vcf), and the slope of the end systolic pressure-end systolic volume line (ESP-ESV line). Hypertension was induced by a methoxamine HCl iv infusion which mimicked the cardiac effects seen in essential hypertension. Propranolol caused a significant decrease in all contractility parameters (p less than 0.05) within 15 min after administration, with a peak effect occurring after 30-35 mins. The pharmacokinetics and pharmacodynamics of propranolol were fit using Hill's equation in conjunction with the concentration of drug in the theoretical effect compartment. The normotensive group of rabbits had a calculated EC(50) of 12.7 ng/ml, while the hypertensive group had an EC(50) of 6.9 ng/ml, indicating that the hypertensive rabbits were much more sensitive to the propranolol than the normotensive group. In addition, the normotensive group of rabbits demonstrated a much different pharmacokinetic-pharmacodynamic relationship than that of the hypertensive group, indicating that the hypertensive state of the animal has a significant effect upon the concentration-effect relationship.

Determination of total and free concentration of propranolol in human plasma by displacement electrophoresis in a two-layer polyacrylamide gel using fluorimetric detection

A new method based on displacement electrophoresis has been developed for the determination of the total and free concentration of propranolol, a beta-adrenergic blocker drug, in plasma. To determine the total concentration the drug is extracted from human plasma into a chloroform + heptane mixture in the presence of ammonia. After evaporation of the solvent mixture the residue is submitted to displacement electrophoresis in a glass tube containing a two-layer polyacrylamide gel. When the propranolol electrophoretically leaves the gel column it is transferred by a buffer flow to the cuvette of a fluorimeter for continuous detection and quantification. The concentration of the free non-protein bound drug can be determined by the same displacement electrophoresis technique following extraction of the plasma sample into the above organic solvent mixture in the absence of ammonia. Alternatively the extraction procedure can be exchanged for dialysis for 1 h. To decrease the risk that large size material might comigrate with propranolol two layers of polyacrylamide are used, one having small pores to retard such material. In addition, we use fluorimetric detection which means that many possible contaminants are not recorded and therefore do not affect a quantitative determination of propranolol.

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.

Propranolol metabolism by Cunninghamella bainieri

1. Incubations of racemic propranolol alone or in the presence of either quinidine or sparteine were performed with Cunninghamella bainieri. 2. Five mammalian metabolites of propranolol (4-hydroxypropranolol, desisopropyl-propranolol, 1-naphthoxylactic acid, propranolol glycol and 1-naphthoxyacetic acid) were present in unhydrolysed extracts of the incubation medium according to h.p.l.c. and g.l.c. analyses. The relative proportion of 4-hydroxypropranolol increased after enzymic treatment. 3. Propranolol not only had a fungistatic effect, but also caused morphological changes in the organism, which were accompanied by decomposition of 4-hydroxypropranolol and formation of a greenish-brown colour in the incubation medium. 4. Drug interaction experiments yielded results which paralleled those reported in mammals. 5. The findings indicate that C. bainieri may be a useful microbial model for drug disposition and interaction studies.

Alteration in the disposition and metabolism of S(-)-propranolol in rats with active respiratory viral infection

Viral illness elicited marked changes in the disposition and metabolism of S(-)-propranolol in rats during the course of a recent viral outbreak in our rodent colony. A slower rate of gastrointestinal absorption and a much higher clearance of orally-administered S(-)-propranolol were observed. The apparent increase in metabolic clearance is partly attributed to a decrease in the serum protein binding of S(-)-propranolol. A direct stimulation of microsomal oxidative metabolism was also suggested by an increase in urinary recovery of the monohydroxyl metabolites of S(-)-propranolol. In addition, a greater portion of the phenolic metabolites were present in urine as the glucuronic acid conjugates, which may be explained by a concomitant stimulation in conjugative reaction. These observations are unusual in that existing reports indicate that viral illness in man and animals generally leads to an inhibition of oxidative drug metabolism.