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

Pharmacokinetic Variability of Drugs Used for Prophylactic Treatment of Migraine

In this review, we evaluate the variability in the pharmacokinetics of 11 drugs with established prophylactic effects in migraine to facilitate 'personalized medicine' with these drugs. PubMed was searched for 'single-dose' and 'steady-state' pharmacokinetic studies of these 11 drugs. The maximum plasma concentration was reported in 248 single-dose and 115 steady-state pharmacokinetic studies, and the area under the plasma concentration-time curve was reported in 299 single-dose studies and 112 steady-state pharmacokinetic studies. For each study, the coefficient of variation was calculated for maximum plasma concentration and area under the plasma concentration-time curve, and we divided the drug variability into two categories; high variability, coefficient of variation >40%, or low or moderate variability, coefficient of variation <40%. Based on the area under the plasma concentration-time curve in steady-state studies, the following drugs have high pharmacokinetic variability: propranolol in 92% (33/36), metoprolol in 85% (33/39), and amitriptyline in 60% (3/5) of studies. The following drugs have low or moderate variability: atenolol in 100% (2/2), valproate in 100% (15/15), topiramate in 88% (7/8), and naproxen and candesartan in 100% (2/2) of studies. For drugs with low or moderate pharmacokinetic variability, treatment can start without initial titration of doses, whereas titration is used to possibly enhance tolerability of topiramate and amitriptyline. The very high pharmacokinetic variability of metoprolol and propranolol can result in very high plasma concentrations in a small minority of patients, and those drugs should therefore be titrated up from a low initial dose, depending mainly on the occurrence of adverse events.

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.

pH dependence of the hydrophobicity of beta-blocker amine compounds measured by counter-current chromatography

The octanol-water partition coefficients (Poct) of 17 antiadrenergic beta-blocker compounds were determined by counter-current chromatography (CCC). Since CCC uses a biphasic liquid system, the octanol-water liquid system was used with essentially an octanol stationary phase and aqueous buffer mobile phase. The Poct coefficients were obtained directly without any extrapolation. The measured Poct values were in the 0.0015-4070 range (-2.8 < log Poct < 3.6). Since the beta-blocking agents are ionizable compounds, the Poct values obtained were strongly dependent on the aqueous-phase pH. The apparent Poct coefficients of the beta-blockers were determined at three different pH values (approximately 3, 7 and 11) using 0.01 M ammonium phosphate buffers saturated with octanol. A model allowed us to obtain the molecular and ionic Poct value using the solute pKa with these three experimental octanol-water coefficients. Often, the Poct coefficients of the molecular forms obtained with the CCC method differ significantly from computed literature values and/or experimental values obtained by extrapolation. Relationships between biological properties and hydrophobicity were also examined.

Atenolol quantification in human plasma by high-performance liquid chromatography: application to bioequivalence study

An accurate, precise, and sensitive high-performance liquid chromatography (HPLC) assay was developed for the determination of atenolol in human plasma samples to compare the bioavailability of 2 atenolol tablet (50 mg) formulations in 24 volunteers of both sexes. The study had an open, randomized, 2-period crossover design with a 1-week washout period. Plasma samples were obtained over a 24-hour interval. Atenolol concentrations were analyzed by combined reversed phase liquid chromatography and fluorescence detection (lambda(EX) = 258 nm, lambda(EM) = 300 nm). From the atenolol plasma concentration versus time curves, the following pharmacokinetic parameters were obtained: AUC(0-24h), AUC(0- infinity ), and C(max). The geometric mean of test/reference 50-mg tablets individual percent ratio was 102.2% for AUC(0-24h), and 101.6% for C(max). The 90% confidence intervals (CI) were 100.2% to 105.4% and 100.9% to 103.5%, respectively. Since the 90% CI for both C(max) and AUC(0-24h) were within the 80% to 125% interval proposed by the Food and Drug Administration, it was concluded that atenolol (50-mg tablets) test formulation was bioequivalent to the reference formulation, with regard to both the rate and extent of absorption.

Colorimetric determination of beta-blockers in pharmaceutical formulations

A simple, accurate, precise and sensitive colorimetric method for the determination of some beta-blockers as atenolol (Ateno), metoprolol (Metop), sotalol (Sot) and nadolol (Nad) is described. This method is based on the formation of charge transfer complex with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) in methanolic-aqueous (for Ateno and Metop) or acetone-aqueous (for Sot and Nad) medium [30% (v/v)]. The orange color products are measured at 485, 470, 465 and 462 nm for Ateno, Metop, Sot and Nad, respectively. The optimization of various experimental conditions is described. Beer's law is obeyed in the range 0.4-60 microgram ml(-1) while that obtained applying Ringbom is 0.8-56 microgram ml(-1). The molar absorptivity, Sandell sensitivity, detection and quantification limits are calculated. The results obtained showed good recoveries of 99.5+/-1.1, 100.3+/-1.2, 100.5+/-1.0 and 99.3+/-1.1% with relative standard deviations of 0.74, 0.98, 1.15 and 0.87% for Ateno, Metop, Sot and Nad, respectively. Applications of the proposed method to representative pharmaceutical formulations are successfully presented.

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.