Search

Most drugs acting on G-protein-coupled receptors target the orthosteric binding pocket where the native hormone or neurotransmitter binds. There is much interest in finding allosteric ligands for these targets because they modulate physiologic signaling and promise to be more selective than orthosteric ligands. Here we describe a newly developed allosteric modulator of the β2-adrenergic receptor (β2AR), AS408, that binds to the membrane-facing surface of transmembrane segments 3 and 5, as revealed by X-ray crystallography. AS408 disrupts a water-mediated polar network involving E1223.41 and the backbone carbonyls of V2065.45 and S2075.46. The AS408 binding site is adjacent to a previously identified molecular switch for β2AR activation formed by I3.40, P5.50 and F6.44. The structure reveals how AS408 stabilizes the inactive conformation of this switch, thereby acting as a negative allosteric modulator for agonists and positive allosteric modulator for inverse agonists.

G protein-coupled receptors (GPCRs) transduce pleiotropic intracellular signals in mammalian cells. Here, we report neuronal excitability of β-blockers carvedilol and alprenolol at clinically relevant nanomolar concentrations. Carvedilol and alprenolol activate β2AR, which promote G protein signaling and cAMP/PKA activities without action of G protein receptor kinases (GRKs). The cAMP/PKA activities are restricted within the immediate vicinity of activated β2AR, leading to selectively enhance PKA-dependent phosphorylation and stimulation of endogenous L-type calcium channel (LTCC) but not AMPA receptor in rat hippocampal neurons. Moreover, we have engineered a mutant β2AR that lacks the catecholamine binding pocket. This mutant is preferentially activated by carvedilol but not the orthosteric agonist isoproterenol. Carvedilol activates the mutant β2AR in mouse hippocampal neurons augmenting LTCC activity through cAMP/PKA signaling. Together, our study identifies a mechanism by which β-blocker-dependent activation of GPCRs promotes spatially restricted cAMP/PKA signaling to selectively target membrane downstream effectors such as LTCC in neurons.

Stereoselective dependence of active pharmaceutical ingredients for their pharmacokinetics inspired the researchers to develop new analytical methods for enantiomeric separation to enhance drug therapeutics. Enantiomeric separation of three β-blockers, namely, (RS)-pindolol, (RS)-alprenolol, and (RS)-sotalol has been achieved by direct thin-layer chromatographic approaches involving l-glutamic acid (l-Glu) as chiral selector. Three different approaches adopted were as follows: (i) chiral thin-layer plates were prepared by adding l-Glu in the silica gel slurry, (ii) mobile phase and stationary phases were achiral where chiral auxiliary was pre-mixed with active pharmaceutical ingredients solution in the specific ratio (1:3), and (iii) l-Glu was mixed in the mobile phase and plain plates without l-Glu were used. Several combinations of solvents were thriving in three different approaches for the enantioresolution of three pharmaceuticals. After optimizing successful resolution, spots of corresponding isomers were located using iodine as a detecting agent. The detection limits for each enantiomer were reported to be between 1.3 and 1.7 μg spot−1. [ABSTRACT FROM AUTHOR]

The sustained release of alprenolol, a ß-adrenergic antagonist, could be beneficial for the treatment of various heart diseases while reducing the side effects resulting from its continuous use. The novel and branched copolymers uniquely composed of biodegradable components (lactide and glycolide) have been synthesized using natural and therapeutically-efficient ß-aescin-initiator, and consequently characterized to determine their structures and physicochemical properties. The obtained matrices were not cyto- and genotoxic towards bacterial luminescence, protozoan, and Salmonella typhimurium TA1535. The copolymers release the drug in vitro in a sustained manner and without burst release. The value of the drug released was strongly dependent on the copolymer composition and highly correlated with the hydrolytic matrices’ degradation results.

A new two-dimensional liquid chromatography (2D-LC) method using a column switching valve, with a restricted-access media (RAM) column in the first dimension was developed and validated for the quantification of two β-blockers in human plasma. Several parameters, such as sample collection, mobile phase composition and flow rate for sample cleanup, transference and analytical separation of the β-blockers were investigated and optimized. The developed method allowed for the simultaneous pre-treatment and quantification of alprenolol (ALP) and propranolol (PRO) in human plasma in less than 25 min. The method consisted in the injection of 100 μL of plasma samples on the RAM alkyl-diol-silica column (Lichrospher ® RP-18 ADS, 25 μm) with water/acetonitrile (98:2, v/v; at a flow rate of 2.0 mL/min) and then transferred (via a six-port valve) to the analytical column (Luna PFP (2), 150 × 4.6 mm ID, 100 Å, 3 μm) with 0.1% (v/v) triethylamine in water acidified with trifluoroacetic acid (pH = 3)/acetonitrile (74:26, v/v) at a flow rate of 0.6 mL/min in a back-flush mode. The column oven temperature was optimized to 42 °C and the fluorescence detector set at 280 nm and 310 nm (excitation and emission, respectively). The method was validated according to the European Medicines Agency’s guidelines and was linear (r 2 > 0.999) over a dynamic range of 5.0 – 200 ng/mL. Recoveries ranged from 90.2 and 107% and the lower limit of quantification was 5.0 ng/mL for both compounds. Precision was expressed as a percentage of relative standard deviation and did not exceed 11%. Finally, the method was successfully applied to determine the plasma concentration of PRO in four healthy volunteers. [ABSTRACT FROM AUTHOR]

Hemangioma is a benign vascular tumor that shouldbe treated in problematic situations. Propranolol efficacy, target dose, range of age, duration of treatment and complications arenot conclusive for treatment of pediatric hemangioma. Our goal was to study efficacy and safety of propranolol for hemangioma treating in children. A randomized, open label crossover trial with two twenty four-week treatment phases separated by a one-week washout period, was conducted in Amir-Kabir Hospital, Arak, Iran. Thirty two patients with age of 1 month to 15 years were randomized to receive either oral propranolol 2 mg/Kg/day or receivedno treatment. The primary outcome measure changed in hemangioma size assessed at baseline, day 3, day 7, and every month. At baseline, the mean surface area was 36.9 ± 36.3 cm2. After 1 week of treatment, a decrease was seen in size of hemangiomas. After one month, a significant reduction was seen in size of lesionsin treatment group compared to observation group (30 cm2vs 16 cm2, P < 0.01). Significant reductions were present at other intervals (P < 0.05). In the second phase of the study, a significant reduction was observed only after one month of treatment (P < 0.05). The trial suggested that 24 week treatment with oral propranolol was effective for treatment of pediatric hemangiomas with acceptable safety profile. [ABSTRACT FROM AUTHOR]

Cellulase (Cel) was immobilized onto aminopropyl-silica gels via its amino and carboxy groups, respectively, using N,N ′-disuccinimidyl carbonate, and 1-ethyl-3-(3′-dimethylaminopropyl)carbodimide and N -hydroxysulfosuccinimide. They were termed N -Cel and C -Cel, respectively. Despite their smaller retention factors on a C -Cel column, the enantioseparation factors and resolution of β-blockers, propranolol, alprenolol, oxprenolol and pindolol, were similar with N - and C -Cel columns. In addition, C -Cel was prepared using aminopropyl-silica gels, whose nominal particle diameters were 5 and 3, and 2.1 μm, respectively. A C -Cel column prepared with 2.1-μm aminopropyl-silica gels gave the highest enantioselectivity and column efficiency among three C -Cel columns. Furthermore, the influence of N , N -dimethyl- n -octylamine (DMOA) or cellobiose concentrations on the retentivity and enantioselectivity for β-blockers on a C -Cel column was investigated. The results indicate that single-site competition of β-blockers with DMOA or cellobiose on the catalytic binding site of Cel and the further bindings at the secondary site in a non-competitive fashion could occur. Furthermore, the enantioselective bindings of β-blockers could occur at the catalytic biding cite of Cel and at the secondary binding site. [ABSTRACT FROM AUTHOR]

Six selected β-blocker drugs (alprenolol, atenolol, metoprolol, nadolol, pindolol and propranolol) passing across 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer were studied using all-atom molecular dynamics simulation. The free energy profiles can be divided into two groups, according to their shapes: the free energy curve of group one (atenolol, nadolol and pindolol) has an obvious minimum while that of the other group (propranolol, metoprolol and alprenolol) is flat inside membrane. Energy analysis shows that electrostatic interaction plays an important role for the first group drugs. The hydrogen bond analysis results also certify that the first group drugs form more hydrogen bonds than the other β-blockers. The calculated permeability sequence agrees with the experimental ones. Our calculation suggests that the permeability model using potential of mean force (PMF) method can be also applied to chemically similar compounds besides chemically diverse compounds. [ABSTRACT FROM PUBLISHER]

Background and Purpose: Our previous studies have shown the β2 -adrenoceptor and its endogenous ligand, adrenaline, are required for development of the asthma phenotype in murine asthma models. Chronic administration of some, but not other, β-blockers attenuated the asthma phenotype and led us to hypothesize that biased signalling was the basis of their differential effects, experimentally and clinically.Experimental Approach: We used mice with no detectable systemic adrenaline (PNMT(-/-) ) and wild-type (WT) mice to study the effects of four β-blockers, alprenolol, carvedilol, propranolol and nadolol, in an ovalbumin sensitization and challenge (Ova S/C) murine model of asthma. The parameters measured were inflammatory cell infiltration, mucous metaplasia and airway hyperresponsiveness. To interpret the pharmacological action of these ligands quantitatively, we conducted computer simulations of three-state models of receptor activation.Key Results: Ova S/C PNMT(-/-) mice do not develop an asthma phenotype. Here, we showed that administration of alprenolol, carvedilol or propranolol in the absence of interference from adrenaline using Ova S/C PNMT(-/-) mice resulted in the development of an asthma phenotype, whereas nadolol had no effect. Ova S/C WT mice did develop an asthma phenotype, and administration of alprenolol, propranolol and carvedilol had no effect on the asthma phenotype. However, nadolol prevented development of the asthma phenotype in Ova S/C WT mice. Computer simulations of these four ligands were consistent with the isolated three-state receptor model.Conclusion and Implications: β-Blockers have different effects on the murine asthma phenotype that correlate with reported differences in activation or inhibition of downstream β2 -adrenoceptor signalling pathways. [ABSTRACT FROM AUTHOR]

The sustained release of alprenolol, a β-adrenergic antagonist, could be beneficial for the treatment of various heart diseases while reducing the side effects resulting from its continuous use. The novel and branched copolymers uniquely composed of biodegradable components (lactide and glycolide) have been synthesized using natural and therapeutically-efficient aescin-initiator, and consequently characterized to determine their structures and physicochemical properties. The obtained matrices were not cyto- and genotoxic towards bacterial luminescence, protozoan, and Salmonella typhimurium TA1535. The copolymers release the drug in vitro in a sustained manner and without burst release. The value of the drug released was strongly dependent on the copolymer composition and highly correlated with the hydrolytic matrices' degradation results. [ABSTRACT FROM AUTHOR]

Optically pure epoxides are essential chiral precursors for the production of (S)-propranolol, (S)-alprenolol, and other β-adrenergic receptor blocking drugs. Although the enzymatic production of these bulky epoxides has proven difficult, here we report a method to effectively improve the activity of BmEH, an epoxide hydrolase from Bac;7/us megaterium ECU1001 toward a-naphthyl glycidyl ether, the precursor of (S)-propranolol, by eliminating the steric hindrance near the potential product-release site. Using X-ray crystallography, mass spectrum, and molecular dynamics calculations we have identified an active tunnel for substrate access and product release of this enzyme. The crystal structures revealed that there is an independent product-release site in BmEH that was not included in other reported epoxide hydrolase structures. By alanine scanning, two mutants, F128A and M145A, targeted to expand the potential product-release site displayed 42 and 25 times higher activities toward a-naphthyl glycidyl ether than the wild-type enzyme, respectively. These results show great promise for structure-based rational design in improving the catalytic efficiency of industrial enzymes for bulky substrates. [ABSTRACT FROM AUTHOR]

A vancomycin-bonded silica monolithic column for capillary electrochromatography (CEC) was prepared by a single-step in situ sol-gel approach. This sol-gel process incorporates a synthetic sol-gel precursor which contains a macrocyclic antibiotic, vancomycin, to form a porous silica network inside a fused-silica capillary. To avoid degradation of vancomycin during the column fabrication, a mild step was adopted into the sol-gel process. The performance of the vancomycin chiral stationary phase was investigated by CEC in both the reversed-phase mode and the normal-phase mode. The vancomycin chiral stationary phase was optimized with respect to vancomycin loading in the reversed-phase mode for chiral separation of thalidomide enantiomers. The best efficiency and resolution values of 94600plates/m and 5.79, respectively, were achieved. The optimized column was further applied to chiral separation of alprenolol enantiomers. A plate height of less than 7µm for the first eluted enantiomer of alprenolol was obtained in an aqueous mobile phase at a flow rate of 0.74mm/s. Using enantiomers of seven β-blockers and some other basic enantiomers as test analytes, separation efficiencies of up to 148100plates/m in the reversed-phase mode and up to 138100plates/m in the normal-phase mode were achieved. [ABSTRACT FROM AUTHOR]

A comparative study of the electrochemical conversion and the biotransformation performed by the cytochrome P450 (CYP450) obtained by rat liver microsomes has been achieved to elucidate the oxidation mechanism of both acebutolol and alprenolol. For this purpose, a wide range of reactions such as N-dealkylation, O-dealkoxylation, aromatic hydroxylation, benzyl hydroxylation, alkyl hydroxylation, and aromatic hydroxylation have been examined in this study, and their mechanisms have been compared. Most of the results of the electrochemical oxidation have been found to be in accordance with those obtained by incubating acebutolol and alprenolol in the presence of CYP450, i.e., N-dealkylation, benzyl hydroxylation, and O-dealkoxylation reactions catalyzed by liver microsomes were found to be predicted by the electrochemical oxidation. The difficulty for the electrochemical process to mimic both aromatic and alkyl hydroxylation reactions has also been discussed, and the hypothesis for the absence of aromatic hydroxylated and alkyl hydroxylated products, respectively, for alprenolol and acebutolol, under the anodic oxidation has been supported by theoretical calculation. The present study highlights the potential and limitation of coupling of electrochemistry-liquid chromatography-high-resolution mass spectrometry for the study of phase I and phase II reactions of acebutolol and alprenolol. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Biodegradation of chiral pharmaceuticals in the environment can be enantioselective. Thus quantification of enantiomeric fractions during the biodegradation process is crucial for assessing the fate of chiral pollutants. This work presents the biodegradation of alprenolol and propranolol using an activated sludge inoculum, monitored by a validated enantioselective HPLC method with fluorescence detection. The enantioseparation was optimized using a vancomycin-based chiral stationary phase under polar ionic mode. The method was validated using a minimal salts medium inoculated with activated sludge as matrix. The method was selective and linear in the range of 10–800ng/ml, with a R 2>0.99. The accuracy ranged from 85.0 percent to 103 percent, the recovery ranged from 79.9 percent to 103 percent, and the precision measured by the relative standard deviation (RSD) was <7.18 percent for intra-batch and <5.39 percent for inter-batch assays. The limits of quantification and detection for all enantiomers were 10ng/ml and 2.5ng/ml, respectively. The method was successfully applied to follow the biodegradation of the target pharmaceuticals using an activated sludge inoculum during a fifteen days assay. The results indicated slightly higher biodegradation rates for the S-enantiomeric forms of both beta-blockers. The presence of another carbon source maintained the enantioselective degradation pattern while enhancing biodegradation extent up to fourteen percent. [Copyright &y& Elsevier]

Abstract: Counter-current chromatography (CCC) was applied for preparative enantioseparation of three β-blocker drugs, including propranolol, pindolol and alprenolol. The two-phase solvent system was composed of chloroform–0.05molL−1 acetate buffer containing 0.10molL−1 boric acid (1:1, v/v), in which 0.10molL−1 di-n-hexyl l-tartrate was added in the organic phase as chiral selector. Influence factors in the enantioseparation of propranolol were investigated. The chromatographic retention mechanism based on borate coordination complex was proposed. 116mg of racemic propranolol was completely enantioseparated using conventional high speed CCC in a single run, yielding 48mg of (+)-propranolol with HPLC purity of 98.9% and 47mg of (−)-propranolol with HPLC purity of 96.3%. Recovery for propranolol enantiomers from CCC fractions was in the range of 75–82%. pH-zone-refining CCC was also successfully applied in enantioseparation of propanolol and it was found that 356mg of racemic propranolol could be completely enantioseparated. 145mg of (+)-enantiomer with HPLC purity of 95.6% and 148mg of (−)-enantiomer with HPLC purity of 98.2% were recovered from pH-zone-refining mode. Separation mechanism about chiral separation by pH-zone-refining CCC was discussed. [Copyright &y& Elsevier]

Abstract: Carvedilol, a non-selective β-adrenergic blocker, is widely used for the treatment of angina pectoris and hypertension. We examined the action of carvedilol on cloned Kv1.5 expressed in CHO cells, using the whole-cell patch clamp technique. Carvedilol reduced the peak amplitude of Kv1.5 and accelerated the inactivation rate in a concentration-dependent manner with an IC 50 of 2.56μM. Using a first-order kinetics analysis, we calculated k +1 =19.68μM−1 s−1 for the association rate constant, and k −1 =44.89s−1 for the dissociation rate constant. The apparent K D (k −1/k +1) was 2.28μM, which is similar to the IC 50 value. Other β-adrenergic blockers (alprenolol, oxprenolol and carteolol) had little or no effect on Kv1.5 currents. Carvedilol slowed the deactivation time course, resulting in a tail crossover phenomenon. Carvedilol-induced block was voltage-dependent in the voltage range for channel activation, but voltage-independent in the voltage range for full activation. The voltage dependences for both steady-state activation and inactivation were unchanged by carvedilol. Carvedilol affected Kv1.5 in a use-dependent manner. When stimulation frequencies were increased to quantify a use-dependent block, however, the block by carvedilol was slightly increased with IC 50 values of 2.56μM at 0.1Hz, 2.38μM at 1Hz and 2.03μM at 2Hz. Carvedilol also slowed the time course of recovery from inactivation of Kv1.5. These results indicate that carvedilol blocks Kv1.5 in a reversible, concentration-, voltage-, time-, and use-dependent manner, but only at concentrations slightly higher than therapeutic plasma concentrations in humans. These effects are probably relevant to an understanding of the ionic mechanism underlying the antiarrhythmic property of carvedilol. [Copyright &y& Elsevier]

Abstract: To fully utilize the extended contact time of gel formulations a novel formulation with drug containing catanionic aggregates offering prolonged drug release and skin penetration were investigated. This study aimed to further explore the drug release process from catanionic vesicles in gels. Catanionic vesicles were formed from alprenolol and sodium dodecyl sulphate. Physical gels composed of catanionic vesicles and a SoftCAT polymer were used as well as covalent Carbopol gels. Drug release was measured in vitro using a modified USP paddle method and the skin penetration was studied using dermatomized pig ear skin mounted in horizontal Ussing chambers. The aggregate structure was visualized with cryo-TEM during the drug release and skin penetration process. The study results show that catanionic vesicles are present in the formulations throughout the drug release process and during the clinically relevant skin application time. Hence, the decreased skin penetration rate stems from the prolonged release of drug substance from the gels. The rheological investigation shows that the gel structure of the physically cross-linked gels is maintained even as the drug substance is released and the gel volume is decreased. These findings indicate that the applicability of formulations like these is a future possibility. [Copyright &y& Elsevier]

The growing practice of exploiting noninvasive fluorescence-based techniques to study G protein-coupled receptor pharmacology at the single cell and single molecule level demands the availability of high-quality fluorescent ligands. To this end, this study evaluated a new series of red-emitting ligands for the human β-adrenoceptor family. Upon the basis of the orthosteric ligands propranolol, alprenolol, and pindolol, the synthesized linker-modified congeners were coupled to the commercially available fluorophore BODIPY 630/650-X. This yielded high-affinity β-adrenoceptor fluorescent ligands for both the propranolol and alprenolol derivatives; however, the pindolol-based products displayed lower affinity. A fluorescent diethylene glycol linked propranolol derivative (18a) had the highest affinity (log KDof −9.53 and −8.46 as an antagonist of functional β2- and β1-mediated responses, respectively). Imaging studies with this compound further confirmed that it can be employed to selectively label the human β2-adrenoceptor in single living cells, with receptor-associated binding prevented by preincubation with the nonfluorescent β2-selective antagonist 3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]butan-2-ol (ICI 118551) (J. Cardiovasc. Pharmacol.1983, 5, 430–437.) [ABSTRACT FROM AUTHOR]

How drugs bind to their receptors-from initial association, through drug entry into the binding pocket, to adoption of the final bound conformation, or "pose"-has remained unknown, even for G-protein-coupled receptor modulators, which constitute one-third of all marketed drugs. We captured this pharmaceutically critical process in atomic detail using the first unbiased molecular dynamics simulations in which drug molecules spontaneously associate with G-protein-coupled receptors to achieve final poses matching those determined crystallographically. We found that several beta blockers and a beta agonist all traverse the same well-defined, dominant pathway as they bind to the β1- and β2-adrenergic receptors, initially making contact with a vestibule on each receptor's extracellular surface. Surprisingly, association with this vestibule, at a distance of 15 Å from the binding pocket, often presents the largest energetic barrier to binding, despite the fact that subsequent entry into the binding pocket requires the receptor to deform and the drug to squeeze through a narrow passage. The early barrier appears to reflect the substantial dehydration that takes place as the drug associates with the vestibule. Our atomic-level description of the binding process suggests opportunities for allosteric modulation and provides a structural foundation for future optimization of drug-receptor binding and unbinding rates. [ABSTRACT FROM AUTHOR]

Abstract: A novel fluorescent labeling method for alprenolol was developed based on Mizoroki–Heck coupling reaction. We designed and synthesized fluorescent aryl iodide, 4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIBI) as a labeling reagent. DIBI has a lophine skeleton carrying an iodide atom acting as fluorophore and reactive center, respectively. In order to evaluate the usefulness of DIBI, a high-performance liquid chromatography (HPLC) with fluorescence detection method was developed for the determination of alprenolol as a model compound of terminal double bond. The fluorescent labeling of alprenolol with DIBI was achieved in the presence of palladium acetate as a catalyst, and the labeled alprenolol was detected fluorometrically. In addition, it was found that the fluorescence of DIBI derivative increased and red shifted when compared with that of DIBI. Furthermore, the proposed method could be applied to determine the alprenolol concentration in rat plasma after administration of alprenolol without interferences from biological components. The detection limit (S/N=3) for alprenolol in rat plasma was 0.74ng/mL (30fmol on column). [Copyright &y& Elsevier]

Abstract: Neurotransmission is strongly affected after ischaemic insult. It is postulated that modulatory neurotransmitter systems and their receptors play a role in experience-dependent and restoration plasticity. In this study, muscarinic cholinergic, serotonergic 5-HT2A/2C, dopaminergic D1 and noradrenergic β1 receptors were examined after focal cerebral ischaemia in different brain regions, using quantitative in vitro autoradiography. There were six evaluated time points: 4h, 1, 4, 7, 28 and 60 days after the insult. Rats received unilateral ischaemic lesions through photothrombosis in the primary somatosensory cortex. In the lesion core, 5-HT2A/2C, D1 and β1 receptor binding values return to control levels 28 days after displaying initial decreases, while muscarinic binding remains very low, at 30% of controls. From 4h to 60 days post-stroke no changes are observed in the perilesional tissue. In contrast, in remote brain regions, a bilateral increase of serotonergic 5-HT2A/2C receptor binding in the somatosensory cortex at the striatum level is observed after 4h and after 7 days post-stroke. In addition, a bilateral decrease of muscarinic cholinergic receptor binding in the hippocampus is observed at each time point examined. This study points to a complex and remote reaction of modulatory systems in response to ischaemic lesions. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to explore if mixtures of drug containing catanionic vesicles and polymers give rise to gel formation, and if so, if drug release from these gels could be prolonged. Catanionic vesicles formed from the drug substances alprenolol or tetracaine, and the oppositely charged surfactant sodium dodecyl sulphate were mixed with polymers. Three polymers with different properties were employed: one bearing hydrophobic modifications, one positively charged and one positively charged polymer bearing hydrophobic modifications. The structure of the vesicles before and after addition of polymer was investigated by using cryo-TEM. Gel formation was confirmed by using rheological measurements. Drug release was studied using a modified USP paddle method. Gels were observed to form only in the case when catanionic vesicles, most likely with a net negative charge, were mixed with positively charged polymer bearing lipophilic modifications. The release of drug substance from these systems, where the vesicles are not trapped within the gel but constitute a founding part of it, could be significantly prolonged. The drug release rate was found to depend on vesicle concentration to a higher extent than on polymer concentration. [Copyright &y& Elsevier]

Abstract: A fast, sensitive, and enantioselective LC–MS/MS bioanalytical method was developed and validated for the direct determination of individual alprenolol enantiomers in human plasma using cellobiohydrolase (CBH) chiral stationary phases (CSP) along with supported liquid extraction (SLE) procedures. Complete baseline separation of enantiomeric alprenolol was achieved within 2min in reversed phase chromatography at 0.9ml/min. SLE in a 96-well plate format was used for sample extraction. The method validation was conducted over the curve range of 0.500–500ng/ml for each alprenolol enantiomer using 0.0500ml of plasma sample. The intra- and inter-day precision and accuracy of the quality control samples at low, medium, and high concentration levels showed ≤7.3% relative standard deviation (RSD) and −6.2 to 8.0% relative error (RE) for both alprenolol enantiomers. [Copyright &y& Elsevier]

The medial prefrontal cortex (PFC) receives stress-sensitive dopamine (DA) and noradrenergic (NE) projections from the ventral tegmental area and locus coeruleus, respectively, and evidence from various sources point to a complex functional interaction between these two systems. Stress will also stimulate DA transmission in the nucleus accumbens (NAcc), and our previous work has shown that this response is under the indirect inhibitory control of a DA-sensitive mechanism in PFC. We examined the possibility that the NAcc DA stress response is also modulated by prefrontal cortical NE. We used voltammetry to study in freely behaving rats the effects of local applications of alpha1 (benoxathian 0.1, 1, 10 nmol), alpha2 (SKF86466), and beta1/2 (alprenolol) receptor selective antagonists into the PFC on the NAcc DA response to tail-pinch stress. The NAcc DA stress response was dose-dependently inhibited by local PFC blockade of alpha1 receptors. Additional tests revealed, however, that the DA stress response in NAcc is unaffected after local alpha1 receptor activation with cirazoline. Furthermore, at equivalent doses, neither alpha2 nor beta1/2 receptor blockade significantly affected the NAcc DA stress response. These data indicate that stress-induced activation of subcortical DA transmission is modulated by the NE input to PFC acting at alpha1 receptors. They suggest that, under normal circumstances, this system exerts a facilitatory or enabling influence on the NAcc DA stress response. [ABSTRACT FROM AUTHOR]

Two modern, fundamentally different methods were used for a detailed investigation of enantioselective drug-protein interactions, a surface plasmon resonance (SPR)-based Biacore 2000 biosensor assay and the previously validated HPLC perturbation method (HPLC-PM). This is the first time SPR has been used for this purpose. The fundamental features of the two methods were investigated, and the consequences for operation and data evaluation were addressed. With HPLC-PM, chiral data could be obtained directly from the racemic mixture, whereas a separate analysis of each pure enantiomer was required to obtain chiral data with SPR. It was shown that if chirality is not attributed in the SPR analysis, misleading average racemic binding constants will be obtained. Both drug and protein consumption were considerably higher with HPLC-PM. HPLC-PM was found to be best suited for measurements of weak affinity interactions, whereas the SPR method was best for strong interactions. With both methods, the presence of DMSO in the samples severely affected the interactions, introducing errors. The binding of the β-blockers alprenolol and propranolol to Ce17a cellulase was used as a model system. These methods gave results that agreed quite well qualitatively, but considerable quantitative deviations were sometimes obtained. [ABSTRACT FROM AUTHOR]

The influence of the pH on the complexation equilibria between (S)- or (R)-alprenolol and the cellulase Cel7A was investigated by isothermal titration calorimetry. The results obtained agree with those of previous, similar studies of the same equilibria in which the protein was immobilized on silica particles, packed in a chromatographic column. The association constant and the complexation enthalpy and entropy of the (S)-enantiomer increase with increasing pH. For (R)-alprenolol, the binding is endothermic at all pH values. Thus, for both enantiomers in the pH range 5.5–6.8, the binding is an entropically driven process. [Copyright &y& Elsevier]

The electrophoretic mobilities of alprenolol have been determined in a mixed solvent background electrolyte system containing sodium acetate (40 mM)+acetic acid (40 mM) as buffering agent and different volume fractions of water, methanol and ethanol using capillary electrophoresis. The mobility of alprenolol has been used to test the prediction capability of a model trained by previously reported mobility data of five beta-blocker drugs at the same electrophoretic conditions. The average percentage mean deviations (APMD) between experimental and predicted values were used as an accuracy criterion. The APMD (±SD) obtained for alprenolol data in binary/ternary solvent electrolyte system employing the mobility values in mono-solvent buffers was 4.37 (±3.50)% and the corresponding value for an ab initio prediction method was 7.65 (±4.30)%. [Copyright &y& Elsevier]

1. We have studied the effects of three betaAR ligands (carvedilol, alprenolol, and ICI-118551) with different pharmacological profiles and negative efficacy at the beta2AR on cardiac in vivo, in vitro, biochemical and gene expression parameters in mice with permanent occlusion of the left anterior descending coronary artery. 2. Cardiac in vivo parameters were determined using Doppler studies. Mitral-wave E peak velocity (EPV) and aortic peak velocity (AoPV) decreased in the first 2 weeks postocclusion. After 3 weeks of drug treatment, EPV was improved in the carvedilol group to preocclusion values; however, a further reduction in EPV in the alprenolol and control permanent occlusion group was measured and there was no change after ICI-118551 treatment. AoPV was unchanged between weeks 2 and 5 in all groups. 3. The left atria were isolated to record isometric tension responses to isoprenaline. Permanent occlusion significantly reduced the maximum isoprenaline response to 30% of control and carvedilol increased the maximum response to isoprenaline significantly to 60%. 4. The biochemical and gene expression studies revealed different effects of the three betaAR ligands. Most notably, carvedilol reduced gene expression of myosin heavy chain beta. 5. These results indicate that chronic treatment with carvedilol is beneficial in a mouse model of myocardial damage resulting from ischaemia. We hypothesise that these beneficial effects of the drug may be because of the negative efficacy at the beta2AR, combined with beta1AR antagonism. [ABSTRACT FROM AUTHOR]

The use of l-(+)-tartaric acid as a chiral mobile phase additive (CMPA) has been investigated in a packed-column SFC system. The CMPA, carbon dioxide, and methanol, containing a high concentration of aliphatic amine additive, were used as the mobile phase and Hypercarb as support [Gyllenhaal O., Karlsson A., SFC of metoprolol and other amino alcohols on Hypercarb (in preparation)].Good enantioselectivities were obtained for tertiary amine homologues of 2-amino alcohols, used as β-adrenoreceptor-blocking drugs. Moderate selectivities were observed for aromatic compounds having a second substituent in the ortho-position. The overall retention was influenced by the aromaticity of the analytes as well as the presence of free electron pairs in the molecule. Increased concentrations of CMPA gave higher retention and also increased the enantioselectivity.The practical utility of this present enantioselective system was demonstrated on one batch of (S)-metoprolol that was N-methylated with methyl iodide. The enantiomeric separation was accomplished within 10 min. [Copyright &y& Elsevier]

In a pharmaceutical industry, several cases of allergic contact eczema caused by the β-adrenergic blocking agent alprenolol (Aptin) have appeared. This report deals with 12 men and two women who developed eczema during work with the substance. In 13 of the 14 cases, the induction time for sensitization was less than 1 year. The skin reactions were very florid. After heating they could be reproduced by very small quantities of the substance. In one case, eczema could also be produced after ingestion or Aptin tablets. All the cases were transferred to other work within the factory. An intensive programme was implemented to remove dust from the working areas. Despite this, isolated new cases still appear. Some employees in contact with the substance also experienced mucous membrane symptoms. These symptoms could not be shown to have an allergic aetiology, but were considered to be irritant reactions, Alprenolol must be considered a very strong contact allergen. [ABSTRACT FROM AUTHOR]

Serum levels of T, T rT and resin T uptake were followed for 5 days in 40 patients with acute myocardial infarction (AMI) allocated to early treatment either with alprenolol or placebo. There was a significant fall in T (P<0.05) and an increase in rT (P<0.05) without any significant difference between the alprenolol - ( n=19) and placebo - ( n=21) treated groups. The risk of missing a further 20% change in se-T and se-rT after alprenolol compared to placebo treatment (β) was <0.10 and <0.50, respectively. In patients with a severe clinical course, the fall in T and increase in rT was significantly greater than in patients without complications. No change in T was observed either with respect to the clinical course nor following alprenolol. The data suggest that alprenolol can be given in the acute phase of myocardial infarction without causing any additional disturbance in the serum levels of T and T. [ABSTRACT FROM AUTHOR]

The effect of long-term treatment with alprenolol on left ventricular function was investigated in a controlled double-blind study of 15 patients with ischaemic heart disease (alprenolol 6, placebo 9), by measurement of systolic time intervals (STI). Significant prolongation of QSI was observed in patients treated with alprenolol ( p<0.05), while changes in PEPI, LVETI and PEP/LVET were all insignificant. The heart rate x systolic blood pressure product (RPP) was significantly reduced in the alprenolol group ( p<0.05). The data suggest that long-term treatment with alprenolol did not impair left ventricular function as evaluated by STI, and that myocardial oxygen demand, assessed by RPP, was reduced during the treatment. [ABSTRACT FROM AUTHOR]

The binding of 8 β-adrenergic blocking drugs to human serum albumin, to α-acid glycoprotein and to serum from normal volunteers and from patients with rheumatoid arthritis was studied. Protein binding was determined in vitro using equilibrium dialysis of labelled drug at 25° C. Oxprenolol and propranolol were highly bound to serum, alprenolol, pindolol and timolol to a lesser degree, and atenolol, metoprolol and sotalol were negligibly bound. For the five compounds which were appreciably bound, the mean binding was significantly higher in serum from patients with rheumatoid arthritis than in serum from normal volunteers. For those drugs, binding to α-acid glycoprotein was higher than to human serum albumin, and binding to a mixture of both proteins approached that to serum from healthy volunteers. For each of these drugs there was a strong correlation between the serum α-glycoprotein concentration and the percentage binding. [ABSTRACT FROM AUTHOR]