Stereoselective features of (R)- and (S)-atenolol: clinical pharmacological, pharmacokinetic, and radioligand binding studies

Non-β-blocker enantiomers of propranolol and atenolol inhibit vasculogenesis in infantile hemangioma

Propranolol and atenolol, current therapies for problematic infantile hemangioma (IH), are composed of R(+) and S(–) enantiomers: the R(+) enantiomer is largely devoid of beta blocker activity. We investigated the effect of R(+) enantiomers of propranolol and atenolol on the formation of IH-like blood vessels from hemangioma stem cells (HemSCs) in a murine xenograft model. Both R(+) enantiomers inhibited HemSC vessel formation in vivo. In vitro, similar to R(+) propranolol, both atenolol and its R(+) enantiomer inhibited HemSC to endothelial cell differentiation. As our previous work implicated the transcription factor sex-determining region Y (SRY) box transcription factor 18 (SOX18) in propranolol-mediated inhibition of HemSC to endothelial differentiation, we tested in parallel a known SOX18 small-molecule inhibitor (Sm4) and show that this compound inhibited HemSC vessel formation in vivo with efficacy similar to that seen with the R(+) enantiomers. We next examined how R(+) propranolol alters SOX18 transcriptional activity. Using a suite of biochemical, biophysical, and quantitative molecular imaging assays, we show that R(+) propranolol directly interfered with SOX18 target gene trans-activation, disrupted SOX18-chromatin binding dynamics, and reduced SOX18 dimer formation. We propose that the R(+) enantiomers of widely used beta blockers could be repurposed to increase the efficiency of current IH treatment and lower adverse associated side effects.

Survey of Pharmacological Activity and Pharmacokinetics of Selected β-Adrenergic Blockers in Regard to Their Stereochemistry

The present survey concentrates on pharmacodynamics and pharmacokinetics of selected β-adrenergic blockers from the point of view of their stereochemistry. It could be shown that the activity in the arylaminoethanol and aryloxyaminopropanol group of β-blockers is higher in their (–)-enantiomers as compared with the (+)-enantiomers. The stereoisomers differ also in other types of bioactivity as well as in toxicity. The particular pharmacokinetic stages such as resorption, distribution, and metabolism are discussed in regard to their stereochemistry.

Linking Aromatic Hydroxy Metabolic Functionalization of Drug Molecules to Structure and Pharmacologic Activity

Drug functionalization through the formation of hydrophilic groups is the norm in the phase I metabolism of drugs for the modification of drug action. The reactions involved are mainly oxidative, catalyzed mostly by cytochrome P450 (CYP) isoenzymes. The benzene ring, whether phenyl or fused with other rings, is the most common hydrophobic pharmacophoric moiety in drug molecules. On the other hand, the alkoxy group (mainly methoxy) bonded to the benzene ring assumes an important and sometimes essential pharmacophoric status in some drug classes. Upon metabolic oxidation, both moieties, i.e., the benzene ring and the alkoxy group, produce hydroxy groups; the products are arenolic in nature. Through a pharmacokinetic effect, the hydroxy group enhances the water solubility and elimination of the metabolite with the consequent termination of drug action. However, through hydrogen bonding, the hydroxy group may modify the pharmacodynamics of the interaction of the metabolite with the site of parent drug action (i.e., the receptor). Accordingly, the expected pharmacologic outcome will be enhancement, retention, attenuation, or loss of activity of the metabolite relative to the parent drug. All the above issues are presented and discussed in this review using selected members of different classes of drugs with inferences regarding mechanisms, drug design, and drug development.

Chiral pharmaceuticals: A review on their environmental occurrence and fate processes

More than 50% of pharmaceuticals in current use are chiral compounds. Enantiomers of the same pharmaceutical have identical physicochemical properties, but may exhibit differences in pharmacokinetics, pharmacodynamics and toxicity. The advancement in separation and detection methods has made it possible to analyze trace amounts of chiral compounds in environmental media. As a result, interest on chiral analysis and evaluation of stereoselectivity in environmental occurrence, phase distribution and degradation of chiral pharmaceuticals has grown substantially in recent years. Here we review recent studies on the analysis, occurrence, and fate of chiral pharmaceuticals in engineered and natural environments. Monitoring studies have shown ubiquitous presence of chiral pharmaceuticals in wastewater, surface waters, sediments, and sludge, particularly β-receptor antagonists, analgesics, antifungals, and antidepressants. Selective sorption and microbial degradation have been demonstrated to result in enrichment of one enantiomer over the other. The changes in enantiomer composition may also be caused by biologically catalyzed chiral inversion. However, accurate evaluation of chiral pharmaceuticals as trace environmental pollutants is often hampered by the lack of identification of the stereoconfiguration of enantiomers. Furthermore, a systematic approach including occurrence, fate and transport in various environmental matrices is needed to minimize uncertainties in risk assessment of chiral pharmaceuticals as emerging environmental contaminants.

Ganglionic GFAP + glial Gq-GPCR signaling enhances heart functions in vivo

The sympathetic nervous system (SNS) accelerates heart rate, increases cardiac contractility, and constricts resistance vessels. The activity of SNS efferent nerves is generated by a complex neural network containing neurons and glia. Gq G protein-coupled receptor (Gq-GPCR) signaling in glial fibrillary acidic protein-expressing (GFAP⁺) glia in the central nervous system supports neuronal function and regulates neuronal activity. It is unclear how Gq-GPCR signaling in GFAP⁺ glia affects the activity of sympathetic neurons or contributes to SNS-regulated cardiovascular functions. In this study, we investigated whether Gq-GPCR activation in GFAP⁺ glia modulates the regulatory effect of the SNS on the heart; transgenic mice expressing Gq-coupled DREADD (designer receptors exclusively activated by designer drugs) (hM3Dq) selectively in GFAP⁺ glia were used to address this question in vivo. We found that acute Gq-GPCR activation in peripheral GFAP⁺ glia significantly accelerated heart rate and increased left ventricle contraction. Pharmacological experiments suggest that the glial-induced cardiac changes were due to Gq-GPCR activation in satellite glial cells within the sympathetic ganglion; this activation led to increased norepinephrine (NE) release and beta-1 adrenergic receptor activation within the heart. Chronic glial Gq-GPCR activation led to hypotension in female Gfap-hM3Dq mice. This study provides direct evidence that Gq-GPCR activation in peripheral GFAP⁺ glia regulates cardiovascular functions in vivo.

Design, Development and Optimization of S (-) Atenolol Floating Sustained Release Matrix Tablets Using Surface Response Methodology

The objective of this present investigation was to develop and formulate floating sustained release matrix tablets of s (-) atenolol, by using different polymer combinations and filler, to optimize by using surface response methodology for different drug release variables and to evaluate the drug release pattern of the optimized product. Floating sustained release matrix tablets of various combinations were prepared with cellulose-based polymers: Hydroxypropyl methylcellulose, sodium bicarbonate as a gas generating agent, polyvinyl pyrrolidone as a binder and lactose monohydrate as filler. The 3² full factorial design was employed to investigate the effect of formulation variables on different properties of tablets applicable to floating lag time, buoyancy time, % drug release in 1 and 6 h (D_{1 h,}D_{6 h}) and time required to 90% drug release (t_90%). Significance of result was analyzed using analysis of non variance and P < 0.05 was considered statistically significant. S (-) atenolol floating sustained release matrix tablets followed the Higuchi drug release kinetics that indicates the release of drug follows anomalous (non-Fickian) diffusion mechanism. The developed floating sustained release matrix tablet of improved efficacy can perform therapeutically better than a conventional tablet.

Systemic delivery of β-blockers via transdermal route for hypertension

Hypertension is the most common cardiovascular disease worldwide. Moreover, management of hypertension requires long-term treatment that may result in poor patient compliance with conventional dosage forms due to greater frequency of drug administration. Although there is availability of a plethora of therapeutically effective antihypertensive molecules, inadequate patient welfare is observed; this arguably presents an opportunity to deliver antihypertensive agents through a different route. Ever since the transdermal drug delivery came into existence, it has offered great advantages including non-invasiveness, prolonged therapeutic effect, reduced side effects, improved bioavailability, better patient compliance and easy termination of drug therapy. Attempts were made to develop the transdermal therapeutic system for various antihypertensive agents, including β-blockers, an important antihypertensive class. β-blockers are potent, highly effective in the management of hypertension and other heart ailments by blocking the effects of normal amounts of adrenaline in the heart and blood vessels. The shortcomings associated with β-blockers such as more frequent dose administration, extensive first pass metabolism and variable bioavailability, make them an ideal candidate for transdermal therapeutic systems. The present article gives a brief view of different β-blockers formulated as transdermal therapeutic system in detail to enhance the bioavailability as well as to improve patient compliance. Constant improvement in this field holds promise for the long-term success in technologically advanced transdermal dosage forms being commercialized sooner rather than later.

Chiral discrimination of drugs by DNA tetranucleotides under electrospray ionisation conditions

The DNA tetranucleotides, extended versions of GCA at the 3'-end or 5'-end, were used as chiral selectors for the chiral discrimination of atenolol, DOPA, tamsulosin, valacyclovir and zolmitriptan. Chiral discrimination was achieved by investigating the collision-induced dissociation spectra of the [X+Y-2H](2-) ion generated by electrospraying a solution mixture of tetranucleotide (X) and R- or S-analyte drug (Y). The relative abundances of the precursor ion and the product ion, resulting from the loss of drug, were considered for measuring the degree of chiral discrimination. Among all the tetranucleotides studied, AGCA showed the highest chiral discrimination. The present study emphasised the position of an adenine base in the tetranucleotide in chiral discrimination. The suitability of the method for the measurement of optical purity was also demonstrated in the case of zolmitriptan.

A comparative study of nebivolol and (S) atenolol on blood pressure and heart rate on essential hypertensive patients

Objectives:

To study the effect of nebivolol 5 mg once daily versus (S)-atenolol 25 mg once daily in patients with essential hypertension.

Materials and Methods:

A prospective study was conducted at RLJH and Research Centre which included 30 patients in each group with essential hypertension. The sex, age, presenting illness, and family history of the patients were recorded. Investigations such as blood sugar, urine analysis, kidney function test, lipid profile, and ECG were performed before starting the treatment. Any adverse effects during the treatment were noted. Blood pressure and heart rate were recorded at baseline and during follow-up. One group received nebivolol 5 mg once daily and other group (S)atenolol 25 mg once daily. Patients were followed-up every 15 days for 3 months.

Results:

Nebivolol group had 18 males and 12 females with mean age 50.6 ± 9.5 years, (S)-atenolol had 16 males and 14 females with mean age 54.4 ± 9 years. Patients receiving nebivolol and (S)-atenolol showed a significant fall (P <·0001) in systolic (SBP), diastolic blood pressure (DBP), and heart rate at the end of first, second, and third month when compared to baseline. The difference in fall in SBP and DBP was insignificant between the groups, but fall in heart rate was significant (P <·0001). Adverse effects such as headache, dizziness, and fatigue were reported with both drugs.

Conclusion:

Reduction of blood pressure with nebivolol and (S)atenolol was similar, but fall in blood pressure from baseline was highly significant in both groups.

3-[4-(2-Amino-2-oxoeth-yl)phen-oxy]-2-hy-droxy-N-isopropyl-propanaminium 1,1'-binaphthyl-2,2'-diyl phosphate

In the title salt, C₁₄H₂₃N₂O₃⁺·C₂₀H₁₂O₄P⁻, the dihedral angle between the two naphthyl ring systems in the anion is 57.77 (6)°. In the crystal, an O—H⋯O hydrogen bond links the components. The ammonium group engages in N—H⋯O hydrogen bonds, generating a layer structure.

Monitoring the effects of chiral pharmaceuticals on aquatic microorganisms by metabolic fingerprinting

The effects of the chiral pharmaceuticals atenolol and propranolol on Pseudomonas putida, Pseudomonas aeruginosa, Micrococcus luteus, and Blastomonas natatoria were investigated. The growth dynamics of exposed cultures were monitored using a Bioscreen instrument. In addition, Fourier-transform infrared (FT-IR) spectroscopy with appropriate chemometrics and high-performance liquid chromatography (HPLC) were employed in order to investigate the phenotypic changes and possible degradation of the drugs in exposed cultures. For the majority of the bacteria studied there was not a statistically significant difference in the organism's phenotype when it was exposed to the different enantiomers or mixtures of enantiomers. In contrast, the pseudomonads appeared to respond differently to propranolol, and the two enantiomers had different effects on the cellular phenotype. This implies that there were different metabolic responses in the organisms when they were exposed to the different enantiomers. We suggest that our findings may indicate that there are widespread effects on aquatic communities in which active pharmaceutical ingredients are present.

Relaxations to beta-adrenoceptor subtype selective agonists in wild-type and NOS-3-KO mouse mesenteric arteries

We have investigated the role of nitric oxide (NO) in relaxations to beta-adrenoceptor agonists in mesenteric artery from wild-type (WT) and NO synthase-3 knockout (NOS-3-KO) mice. Isoprenaline, formoterol and BRL 37344 ((R(),R())-(+/-)-4-[2-[(2-(3-chlorophenyl)-2-hydroxyethyl)amino]propyl]phenoxyacetic acid) were chosen as non-selective and beta(2)- and beta(3)-adrenoceptor agonists, respectively. Atenolol, ICI 118,551 ((+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride) and SR59230A (1-(2-ethylphenoxy)-3-[[(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]-(2S)-2-propanol hydrochloride) were chosen as selective beta(1)-, beta(2)- and beta(3)-adrenoceptor antagonists, respectively. Experiments employing isoprenaline were carried out in the presence of prazosin (0.1 microM). Isoprenaline produced relaxations with a potency of 5.68+/-0.36 (-log M, n=6) in WT mice. Relaxations to isoprenaline were blocked by atenolol (10 microM) and were absent in vessels from NOS-3-KO animals. Formoterol produced relaxations with two components. ICI 118,551 (1 microM) abolished relaxations to low concentrations of formoterol (0.1-10 microM), but failed to affect relaxations to formoterol (100 microM). In NOS-3-KO mice only the highest concentration of formoterol (100 microM) produced relaxations: the relaxation was resistant to all of the beta-adrenoceptor antagonists employed. BRL 37344 (5.75+/-0.28, n=9) was approximately equipotent with isoprenaline but produced a smaller degree of relaxation, in WT mice. SR59230A (1 microM) abolished relaxations to BRL 37344 in WT mice. In NOS-3-KO mice, BRL 37344 produced concentration-dependent relaxations which were abolished by SR59230A. It is concluded that the predominant beta-adrenoceptor mediating relaxations in mouse mesenteric artery is beta(1), and relaxations involve NOS-3. In addition, beta(3)-adrenoceptors mediate smaller relaxations at least partly independent of NOS-3, and beta(2)-adrenoceptors may mediate smaller relaxations dependent on NOS-3.

Use of teicoplanin stationary phase for the enantiomeric resolution of atenolol in human urine by nano-liquid chromatography–mass spectrometry

Nano-liquid chromatography (nano-LC) was used for the enantiomeric resolution of atenolol employing a teicoplanin modified silica stationary phase prepared in our laboratory. Experiments were carried out in a fused silica capillary of 75 microm i.d. packed with chiral modified silica particles of 5 microm diameter. Separated enantiomers were revealed by on-line UV detector at 205 nm or electrospray-ion-trap mass spectrometer (ESI-MS). Atenolol enantiomers were eluted utilizing a mobile phase with the following composition: 500 mM ammonium acetate pH 4.5/methanol/acetonitrile 1:60:39 (v/v/v) allowing to achieve good enantioresolution in a reasonable analysis time (about 8 min) with a flow rate of about 900 nL/min. After comparing the sensitivity of the nano-LC method using a conventional UV detector for capillary electrophoresis, a zeta cell (3 nL volume) employed in nano-LC and the ion-trap MS the method was validated with the MS detector offering the highest sensitivity (limit of detection (LOD)=50 ng/mL; limit of quantification (LOQ)=400 ng/mL for each atenolol enantiomer). (-)-Psi-Nor-ephedrine was used as the internal standard. The method was successfully applied to the analysis of atenolol enantiomers present in human urine samples of a patient under atenolol therapy.

Comparative bioavailability of two brands of atenolol 100 mg tablets (Tensotin and Tenormin) in healthy human volunteers

A bioequivalence study of two oral formulations of 100 mg atenolol was carried out in 24 healthy volunteers following a single dose, two-sequence, cross-over randomized design at the International Pharmaceutical Research Centre (IPRC), as a joint venture with Al-Mowasah Hospital, Amman, Jordan. The two formulations were Tensotin (Julphar, UAE) as test and Tenormin (Zeneca, UK) as reference product. Both test and reference tablets were administered with 240 ml of water to each subject after an overnight fast on 2 treatment days separated by a 1 week washout period. After dosing, serial blood samples were collected for a period of 36 h. Whole blood was analysed for atenolol by a sensitive, reproducible and accurate HPLC method with fluorescence detection capable of detecting atenolol in the range of 20-1600 ng/ml with a limit of quantitation of 20 ng/ml. Various pharmacokinetic parameters including AUC0-t, AUC0-proportional to), Cmax, Tmax, T1/2 and lambdaZ were determined from blood concentrations of both formulations and found to be in good agreement with reported values. AUC0-t, AUC0-proportional to), and Cmax were tested for bioequivalence after log-transformation of data using ANOVA and 90% confidence interval and were found within the acceptable range of 80%-125%. Based on these statistical inferences, it was concluded that Tensotin is bioequivalent to Tenormin.

Disposition kinetics of propranolol isomers in the perfused rat liver

The aim of this study was to define the determinants of the linear hepatic disposition kinetics of propranolol optical isomers using a perfused rat liver. Monensin was used to abolish the lysosomal proton gradient to allow an estimation of propranolol ion trapping by hepatic acidic vesicles. In vitro studies were used for independent estimates of microsomal binding and intrinsic clearance. Hepatic extraction and mean transit time were determined from outflow-concentration profiles using a nonparametric method. Kinetic parameters were derived from a physiologically based pharmacokinetic model. Modeling showed an approximate 34-fold decrease in ion trapping following monensin treatment. The observed model-derived ion trapping was similar to estimated theoretical values. No differences in ion-trapping values was found between R(+)- and S(-)-propranolol. Hepatic propranolol extraction was sensitive to changes in liver perfusate flow, permeability-surface area product, and intrinsic clearance. Ion trapping, microsomal and nonspecific binding, and distribution of unbound propranolol accounted for 47.4, 47.1, and 5.5% of the sequestration of propranolol in the liver, respectively. It is concluded that the physiologically more active S()-propranolol differs from the R(+)-isomer in higher permeability-surface area product, intrinsic clearance, and intracellular binding site values.

Enhanced bioavailability of atenolol by transdermal administration of the ethylene-vinyl acetate matrix in rabbits

The pharmacokinetics and bioavailability of atenolol, a antihypertensive, were studied to determine the feasibility of enhanced transdermal delivery of atenolol from the ethylene-vinyl acetate (EVA) matrix system containing polyoxyethylene-2-oleyl ether as an enhancer in rabbits. The atenolol-EVA matrix (20 mg/kg) was applied to abdominal skin of rabbits. Blood samples were collected via the femoral artery for 32 h and the plasma concentrations of atenolol were determined by high-performance liquid chromatography. Pharmacokinetic parameters was calculated using Lagran computer program. The area under the curve (AUC) was significantly higher in the enhancer group (12,402+/-3061 ng/ml.h) than that in the control group (8507+/-2092 ng/ml.h), showing about 46% increased bioavailability (P<0.05). The average C(max) was increased in the enhancer group (1361+/-340 ng/ml) compared with the control group (1168+/-293 ng/ml), but not significantly. The T(max) was significantly decreased in the enhancer group (1.3+/-0.36 h) compared with the control group (2.0+/-0.51 h). The elimination time (t(1/2)) and mean residence time were significantly increased in the transdermal group compared with the IV group. The absolute bioavailability was 19.7% in the control group, 28.6% in the enhancer group and 77.4% in the oral administration group compared with IV the group. As the atenolol-EVA matrix containing polyoxyethylene-2-oleyl ether as an enhancer and tributyl citrate as a plasticizer was administered to rabbits via the transdermal routes, the relative AUC% increased about 1.46-fold compared to the control group, showing a relatively constant, sustained blood concentration with minimal fluctuation. The results of this study show that atenolol-EVA matrix could be developed as a transdermal delivery system providing sustained plasma concentration.

Enantioselective analysis of atenolol in biologic fluids: comparison of liquid-liquid and solid-phase extraction methods

In this study we evaluated a liquid-liquid extraction procedure and a solid-phase extraction procedure for sample preparation for the enantioselective analysis of atenolol in plasma and urine by high-performance liquid chromatography. A Chiralcel OD-H column was used for the resolution of atenolol enantiomers with hexane-ethanol (85:15, v/v) plus 0.1% diethylamine as the mobile phase. In the liquid-liquid extraction procedure, atenolol was extracted from alkalinized body fluids with 5 ml chloroform-2-propanol (4:1, v/v). In the solid-phase extraction procedure, atenolol was isolated from plasma using a C8 column and methanol. Both extraction procedures were efficient in recovering atenolol and removing endogenous interferents. The RSDs and deviation from nominal values were lower than 10% for both within-day and between-day assays. The results show that there were no statistically significant differences in between-day variation. The t-test showed that there were no significant differences between the real concentrations and the determined concentrations. The limit of quantitation was 10 ng/ml and the linear range was 10-5,000 ng/ml for both methods. These methods can be used in pharmacokinetic studies.

Enantioselective analysis of (R)- and (S)-atenolol in urine samples by a high-performance liquid chromatography column-switching setup

An HPLC column-switching method for the enantioselective determination of (R,S)-atenolol in human urine was developed and validated. Diluted urine samples were injected onto a LiChrospher ADS restricted access column and atenolol was separated from most of the matrix components using 0.01 M Tris buffer. The atenolol peak was sharpened by a step gradient of 30% acetonitrile and the atenolol-containing fraction was switched onto an enantioselective column. Separation of the atenolol enantiomers was carried out on a Chirobiotic T (Teicoplanin) column using acetonitrile-methanol-acetic acid-triethylamine (55:45:0.3:0.2, v/v/v/v) as eluent. Detection of the effluent was performed by fluorescence measurement. Several experiments were carried out to suppress the high blank reading, which was efficiently achieved using Tris buffer in the first dimension. For the enantioselective analysis of (R)- and (S)-atenolol in plasma under the same conditions the sample capacity of the ADS column is considerably lower.

Stereoselective increase of plasma concentrations of the enantiomers of propranolol and atenolol during exercise

OBJECTIVE

In vitro studies have shown that, like catecholamines, both propranolol and atenolol are taken up by and released from adrenergic cells. We performed this study to investigate whether this may also play a role in humans and whether stereoselective aspects are important.

METHODS

This was a randomized, double-blind, placebo-controlled, crossover study of two groups of 12 healthy volunteers. Subjects received single oral doses of 80 mg (R,S)-, 40 mg (R)-, and 40 mg (S)-propranolol; 100 mg (R,S)-, 50 mg (R)-, and 50 mg (S)-atenolol; and placebo at intervals of 1 week. Exercise was performed at 4 and 9 hours after drug intake, and blood samples were taken before and at the end of each exercise period. The plasma concentrations of the (R)- and (S)-enantiomers of propranolol and atenolol, as well as those of epinephrine and norepinephrine, were determined by HPLC.

RESULTS

Effects of exercise on the plasma levels of the enantiomers of propranolol and atenolol were similar. When the optically pure enantiomers were administered, exercise caused a marked and significant increase of the plasma concentrations of the (S)- but not of the (R)-enantiomers. When the drugs were administered in the racemic form, the plasma levels of both the (R)- and (S)-enantiomers were elevated to the same extent. The increase of norepinephrine levels during exercise was more pronounced than that of epinephrine and paralleled that of the (S)-enantiomers of the beta-blockers.

CONCLUSION

Bearing the in vitro data in mind, we conclude that (S)-propranolol and (S)-atenolol are taken up into and released from adrenergic cells together with norepinephrine during exercise. The reason why the plasma concentrations of (R)-propranolol and (R)-atenolol are increased only during exercise in the presence of the corresponding (S)-enantiomers remains to be determined.

Single dose pharmacokinetics of (S)-atenolol administered orally as a single enantiomer formulation and as a racemic mixture (Tenormin)

The purpose of this study was to describe the pharmacokinetics of and heart rate and blood pressure responses to (S)-atenolol (SATN) and (R)-atenolol (RATN) after oral administration of (S)-atenolol and (R,S)-atenolol (Tenormin) in man. Eight male subjects were given single oral doses of 50 mg of SATN as a single enantiomer formulation (SEF) and 100 mg of Tenormin (TMN) using a randomized, double-blind, 2-period, complete crossover study design. Subjects performed exercise tolerance tests (Bruce Protocol) before and 2, 4, 6, 8, 12, and 24 h after drug administration. Plasma samples were obtained 2 min before and 30 min, 1, 1.5, 2, 3, 4, 5, 6, 8, 10, 12, 16, and 24 h after dosing. Urine was collected for the first 48 h after dosing. Plasma and urine samples were analyzed for SATN and RATN by an enantioselective HPLC method. SEF and Tenormin attenuate exercise-induced increases in heart rate and systolic blood pressure. Mean changes in exercise heart rates 4 h after dosing were -38 +/- 3 bpm and -37 +/- 3 bpm for SEF and TMN, respectively, P = 0.792. Mean changes in exercise systolic blood pressure were -42 +/- 12 mm Hg and -55 +/- 14 mm Hg for SEF and TMN, respectively, P = 0.484. Mean area under the plasma level time curve (AUC0-24) and mean Cmax for SATN for SEF were significantly lower than for SATN after TMN.(ABSTRACT TRUNCATED AT 250 WORDS)

Enantioselective bioanalysis of beta-blocking agents: focus on atenolol, betaxolol, carvedilol, metoprolol, pindolol, propranolol and sotalol

The recent developments in enantioselective HPLC-separation techniques are impressive and are driven by industrial and academic interests; thus there is for instance a high demand for developing stereoselective assays for chiral drugs in biological fluids. The beta-blocking agents, which possess an amino-propanol- or -ethanol side chain with at least one chiral centre, represent one of the most intensively investigated groups of more than 40 drugs introduced world wide. Seven of the most popular beta-blockers were chosen as representatives: atenolol; betaxolol; carvedilol; metoprolol; pindolol; propranolol; and sotalol, these span the whole range of lipophilicity to hydrophilicity (polarity). Enantioselective HPLC bioassays for these beta-blockers published so far, including techniques based on chiral derivatizing agents (CDAs), chiral stationary phases (CSPs) and chiral mobile phase additives (CMPAs) have been reviewed and documented in the light of general aspects together with pharmacokinetic and pharmacodynamic considerations.

Stereoselective HPLC bioanalysis of atenolol enantiomers in plasma: application to a comparative human pharmacokinetic study

An enantioselective HPLC bioassay has been developed relying on extraction of (R)- and (S)-atenolol from alkalinized plasma or serum (pH > 12) into dichloromethane containing 5% (v/v) 1-butanol followed by an achiral derivatization of the drug with phosgene leading to (R)- and (S)-oxazolidine-2-one derivatives. Under these conditions there was quantitative conversion of the acetamido group to the corresponding nitrile. These stable derivatives were separated on a (R,R)-diaminocyclohexane-dinitrobenzoyl chiral stationary phase [(R,R)-DACH-DNB] using dichloromethane/methanol 98/2 as mobile phase. Determination limits of 0.5 ng for (R)- and 0.6 ng for (S)-atenolol could be achieved using fluorimetric detection. The assay was applied to a human pharmacokinetic study which was performed in a randomized cross-over, double-blind fashion in 12 healthy volunteers, administering single oral doses of 100 mg (R,S)-, 50 mg (R)-, and 50 mg (S)-atenolol. AUC0-24 and Cmax values of (R)-atenolol were slightly but significant higher than those of (S)-atenolol. The R/S ratios were 1.09 for AUC(R)/AUC(S) and 1.03 for Cmax (R)/Cmax(S) (P < 0.01) respectively after administration of the racemic drug. However, there were no difference between AUC, Cmax, and t1/2 values of each enantiomer, whether they were administered as single enantiomers or in the form of its racemic mixture.