Ocular pharmacokinetics of atenolol, timolol and betaxolol cocktail: Tissue exposures in the rabbit eye.

Quantitative understanding of pharmacokinetics of topically applied ocular drugs requires more research to further understanding and to eventually allow predictive in silico models to be developed. To this end, a topical cocktail of betaxolol, timolol and atenolol was instilled on albino rabbit eyes. Tear fluid, corneal epithelium, corneal stroma with endothelium, bulbar conjunctiva, anterior sclera, iris-ciliary body, lens and vitreous samples were collected and analysed using LC-MS/MS. Iris-ciliary body was also analysed after intracameral cocktail injection. Non-compartmental analysis was utilized to estimate the pharmacokinetics parameters. The most lipophilic drug, betaxolol, presented the highest exposure in all tissues except for tear fluid after topical administration, followed by timolol and atenolol. For all drugs, iris-ciliary body concentrations were higher than that of the aqueous humor. After topical instillation the most hydrophilic drug, atenolol, had 3.7 times higher AUCiris-ciliary body than AUCaqueous humor, whereas the difference was 1.4 and 1.6 times for timolol and betaxolol, respectively. This suggests that the non-corneal route (conjunctival-scleral) was dominating the absorption of atenolol, while the corneal route was more important for timolol and betaxolol. The presented data increase understanding of ocular pharmacokinetics of a cocktail of drugs and provide data that can be used for quantitative modeling and simulation.

Novel electro self-assembled DNA nanospheres as a drug delivery system for atenolol.

We describe new method for preparing DNA nanospheres for a self-assembled atenolol@DNA (core/shell) drug delivery system. In this paper, we propose the electrochemical transformation of an alkaline polyelectrolyte solution of DNA into DNA nanospheres. We successfully electrosynthesized DNA nanospheres that were stable for at least 2 months at 4 °C. UV-visible spectra of the prepared nanospheres revealed a peak ranging from 372 to 392 nm depending on the DNA concentration and from 361 to 398.3 nm depending on the electrospherization time. This result, confirmed with size distribution curves worked out from transmission electron microscopy (TEM) images, showed that increasing electrospherization time (6, 12 and 24 h) induces an increase in the average size of DNA nanospheres (48, 65.5 and 117 nm, respectively). In addition, the average size of DNA nanospheres becomes larger (37.8, 48 and 76.5 nm) with increasing DNA concentration (0.05, 0.1 and 0.2 wt%, respectively). Also, the affinity of DNA chains for the surrounding solvent molecules changed from favorable to bad with concomitant extreme reduction in the zeta potential from -31 mV to -17 mV. Principally, the attractive and hydrophobic interactions tend to compact the DNA chain into a globule, as confirmed by Fourier transform infrared spectroscopy (FTIR) and TEM. To advance possible applications, we successfully electro self-assembled an atenolol@DNA drug delivery system. Our findings showed that electrospherization as a cost-benefit technique could be effectively employed for sustained drug release. This delivery system achieved a high entrapment efficiency of 68.03 ± 2.7% and a moderate drug-loading efficiency of 3.73%. The FTIR spectra verified the absence of any chemical interaction between the drug and the DNA during the electrospherization process. X-ray diffraction analysis indicated noteworthy lessening in atenolol crystallinity. The present findings could aid the effectiveness of electrospherized DNA for use in various other pharmaceutical and biomedical applications.

Intramuscular atenolol and levetiracetam reduce mortality in a rat model of paraoxon-induced status epilepticus.

Organophosphorus (OP) compounds are chemical threat agents and are irreversible inhibitors of the enzyme acetylcholinesterase that lead to a hypercholinergic response that could include status epilepticus (SE). SE particularly targets the heart and brain and despite existing therapies, it is still associated with significant mortality and morbidity. Here, we investigated the effect of intramuscular (i.m.) adjunct therapy consisting of atenolol (AT) and levetiracetam (LV) when administered after paraoxon (POX)-induced SE. The combination therapy was administered twice daily for 2, 7, or 14 days. POX exposure in rats produced rapid SE onset that was treated with atropine, pralidoxime chloride, and midazolam. Here, AT + LV therapy produced significant reductions in POX SE mortality assessed at 30 days post-SE. AT + LV therapy exhibited muscle pathology inflammation scores that were not significantly different from saline-treated controls. Pharmacokinetic analyses revealed that the i.m. route achieved faster and stabler plasma therapeutic levels for both AT and LV under OP SE conditions compared with oral administrations. Our data provide evidence of the safety and efficacy of i.m. AT + LV therapy for reducing mortality following POX SE.

Poly(Acrylic Acid)-Modified MoS2 Nanoparticle-Based Transdermal Delivery of Atenolol.

INTRODUCTION: Hypertension is a major health problem worldwide and is typically treated using oral drugs. However, the frequency of oral administration may result in poor patient compliance, and reduced bioavailability owing to the first-pass effect can also prove problematic. METHODS: In this study, we developed a new transdermal-drug-delivery system (TDDS) for the treatment of hypertension using atenolol (ATE) based on poly(acrylic acid) (PAA)-decorated three-dimensional (3D) flower-like MoS2 nanoparticles (PAA-MoS2 NPs) that respond to NIR laser irradiation. The PAA-modified MoS2 NPs were synthesized and characterized using attenuated total reflection Fourier-transform infrared spectroscopy, X-ray diffraction measurements, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, and the sedimentation equilibrium method. The drug-loading efficiency and photothermal conversion effect were also explored. RESULTS: The results showed that the colloidally stable PAA-MoS2 NPs exhibited a high drug-loading capacity of 54.99% and high photothermal conversion ability. Further, the capacity of the PAA-MoS2 NPs for controlled release was explored using in vitro drug-release and skin-penetration studies. The drug-release percentage was 44.72 ± 1.04%, and skin penetration was enhanced by a factor of 1.85 in the laser-stimulated group. Sustained and controlled release by the developed TDDS were observed with laser stimulation. Moreover, in vivo erythema index analysis verified that the PAA-MoS2 NPs did not cause skin irritation. DISCUSSION: Our findings demonstrate that PAA-MoS2 NPs can be used as a new carrier for transdermal drug delivery for the first time.

Functionalized MoS2-nanoparticles for transdermal drug delivery of atenolol.

Molybdenum disulfide (MoS2) has excellent photothermal conversion abilities, an ultra-high specific surface area, and has been extensively explored for use in biomedicine. However, the high toxicity associated with MoS2 has limited its biological applications for in vivo photothermal therapy and drug delivery systems. Herein, we have developed cationic hydroxyethyl cellulose (JR400) surface-modified MoS2 nanoparticles (NPs) that are responsive to near-infrared (NIR) laser irradiation as a transdermal drug delivery system (TDDS). Herein, we confirmed the preparation of hexagonal phase MoS2 with robust surface modification with JR400. The flower-like morphology of the NPs had an average diameter of 355 ± 69.3 nm limiting the absorption of the NPs through the stratum corneum. With the ability to efficiently load 90.4 ± 0.3% of the model drug atenolol (ATE), where 1 g of JR400-MoS2 NPs was able to load 3.6 g ATE, we assayed the controlled release capacity in vitro skin penetration studies. These JR400-MoS2 NPs showed further enhancement under NIR stimulation, with a 2.3-fold increase in ATE skin penetration. Furthermore, we verified in vivo that these JR400-MoS2 NPs do not cause skin irritation suggesting that they are promising new TDDS candidates for small molecule drugs.

Effect of Common Excipients on Intestinal Drug Absorption in Wistar Rats.

The aim of the present paper is to study the effect of common excipients on the permeability of atenolol (as drug absorbed mainly by passive diffusion) and rhodamine (as P-glycoprotein substrate). The apparent permeability was measured by an in situ perfusion method in Wistar rats using the closed loop Doluisio's method. Permeability values were characterized in the absence and presence of 18 commonly used excipients. Excipient concentrations were selected based on the amounts in oral immediate release dosage forms, which failed the test during the human bioequivalence studies. Atenolol was studied with and without excipients in the whole small intestine, whereas rhodamine was tested in three different intestinal segments to account for the differential expression of P-glycoprotein, and it was further on tested in the ileum, in the presence of excipients. Atenolol presented higher permeability values when it was administered with colloidal silica, croscarmellose, hydroxypropyl methylcellulose (HPMC), magnesium stearate, MgCO3, poly(ethylene glycol) 400, poly(vinylpyrrolidone), sorbitol, starch, and TiO2 rhodamine showed higher permeability values when it was administered with croscarmellose and HPMC. On the one hand, the mechanisms of action were not discernible with the proposed experiments. On the other hand, commercial formulations do not present a single excipient but several, which can counteract their effects. The in situ perfusion technique can be useful for a preliminary screening and risk analysis, while the in vivo pharmacokinetic results would be needed to define conclusive effects.

Ocular Intracameral Pharmacokinetics for a Cocktail of Timolol, Betaxolol, and Atenolol in Rabbits.

The mechanisms of drug clearance from the aqueous humor are poorly defined. In this study, a cocktail approach was used to simultaneously determine the pharmacokinetics of three ß-blocker agents after intracameral (ic) injection into the rabbit eyes. Aqueous humor samples were collected and analyzed using LC-MS/MS to determine drug concentrations. Pharmacokinetic parameters were obtained using a compartmental fitting approach, and the estimated clearance, volume of distribution, and half-life values were the following: atenolol (6.44 µL/min, 687 µL, and 73.87 min), timolol (19.30 µL/min, 937 µL, and 33.64 min), and betaxolol (32.20 µL/min, 1421 µL, and 30.58 min). Increased compound lipophilicity (atenolol < timolol < betaxolol) resulted in higher clearance and volume of distributions in the aqueous humor. Clearance of timolol and betaxolol is about 10 times higher than the aqueous humor outflow, demonstrating the importance of other elimination routes (e.g., uptake to iris and ciliary body and subsequent elimination via blood flow).

Effect of Osmolality on the Pharmacokinetic Interaction between Apple Juice and Atenolol in Rats.

A recent clinical study reported that the ingestion of apple juice (AJ) markedly reduced the plasma concentration of atenolol; however, our in vitro study showed that atenolol may not be a substrate of organic anion transporting polypeptide 2B1 (OATP2B1), so this AJ-atenolol interaction cannot be explained by inhibition of OATP2B1. On the other hand, we more recently showed that the solution osmolality influences gastrointestinal (GI) water volume, and this may indirectly affect intestinal drug absorption. In this study, we examined whether the osmolality dependence of water dynamics can account for AJ-atenolol interactions by evaluating the GI water volume and the atenolol aborption in the presence of AJ in rats. Water absorption was highest in purified water, followed by saline and isosmotic mannitol solution, and the lowest in AJ, confirming that water absorption is indeed osmolality-dependent. Interestingly, AJ showed apparent water secretion into the intestinal lumen. The intestinal concentration of FD-4, a nonpermeable compound, after administration in AJ was lower than the initial concentration, whereas that in purified water was greater than the initial concentration. Further, the fraction of atenolol absorbed in intestine was significantly lower in AJ or hyperosmotic mannitol solution (adjusted to the osmolality of AJ) than after administration in purified water. Comparable results were observed in an in vivo pharmacokinetic study in rats. Our results indicate that orally administered AJ has a capacity to modulate luminal water volume depending on the osmolality, and this effect may result in significant AJ-atenolol interactions.

Ion-pair approach coupled with nanoparticle formation to increase bioavailability of a low permeability charged drug.

Atenolol is a drug widely used for the treatment of hypertension. However, the great drawback it presents is a low bioavailability after oral administration. To obtain formulations that allow to improve the bioavailability of this drug is a challenge for the pharmaceutical technology. The objective of this work was to increase the rate and extent of intestinal absorption of atenolol as model of a low permeability drug, developing a double technology strategy. To increase atenolol permeability an ion pair with brilliant blue was designed and the sustained release achieved through encapsulation in polymeric nanoparticles (NPs). The in vitro release studies showed a pH-dependent release from NPs, (particle size 437.30 ±â€¯8.92) with a suitable release profile of drug (atenolol) and counter ion (brilliant blue) under intestinal conditions. Moreover, with the in vivo assays, a significant increase (2-fold) of atenolol bioavailability after administering the ion-pair NPs by oral route was observed. In conclusion, the combination of ion-pair plus polymeric NPs have proved to be a simple and very useful approach to achieve a controlled release and to increase the bioavailability of a low permeability charged drugs.

Comparación del efecto del aliskireno frente a controles negativos en la rigidez aórtica de los pacientes con síndrome de Marfan tratados con atenolol / Comparison of the effect of aliskiren versus negative controls on aortic stiffness in patients with Marfan Syndrome under treatment with atenolol

Introducción y objetivos: El objetivo del estudio es evaluar el efecto de aliskireno en la rigidez aórtica del paciente con síndrome de Marfan (SM). Métodos: Se reclutó a 28 pacientes con SM (media ± desviación estándar de edad, 32,6 ± 10,6 años) entre noviembre de 2009 y octubre de 2014. Todos estaban tratados con atenolol como terapia estándar con bloqueadores beta. Mediante un proceso prospectivo de aleatorización, se asignó a los participantes a tratamiento con aliskireno (150-300 mg/día vía oral) o sin tratamiento con aliskireno (controles negativos) en un diseño de etiquetado abierto. Se examinaron al inicio y a las 24 semanas la distensibilidad aórtica central y la velocidad de la onda de pulso (PWV) cuantificadas con resonancia magnética (RM), la PWV periférica, la presión aórtica central y el índice de aumento medidos por tonometría y la dilatación aórtica por ecocardiografía. El objetivo primario fue la distensibilidad aórtica central por RM. Resultados: En el análisis de la diferencia entre el examen basal y a las 24 semanas en el grupo tratado frente a los controles negativos, la distensibilidad aórtica central (general; p = 0,26) y la PWV central (0,2 ± 0,9 frente a 0,03 ± 0,7 m/s; p = 0,79) medidas con RM no fueron significativas. La presión sistólica central en la aorta era de 14 mmHg, menor en los pacientes tratados que en los controles (p = 0,09). Se observó una reducción significativa de la PWV periférica (brazo-tobillo) en el grupo tratado (-1,6 m/s) respecto a los controles (+0,28 m/s; p = 0,005). Conclusiones: En los pacientes con SM, la incorporación de aliskireno a los bloqueadores beta no mejora la rigidez de la aorta central a las 24 semanas de tratamiento

Introduction and objectives: The aim of this study was to evaluate the effect of aliskiren on aortic stiffness in patients with Marfan syndrome (MS). Methods: Twenty-eight MS patients (mean age ± standard deviation: 32.6 ± 10.6 years) were recruited from November 2009 to October 2014. All patients were receiving atenolol as standard beta-blocker therapy. A prospective randomization process was performed to assign participants to either aliskiren treatment (150-300 mg orally per day) or no aliskiren treatment (negative control) in an open-label design. Central aortic distensibility and central pulsed wave velocity (PWV) by magnetic resonance imaging (MRI), peripheral PWV, central aortic blood pressure and augmentation index by peripheral tonometry, and aortic dilatation by echocardiography were examined initially and after 24 weeks. The primary endpoint was central aortic distensibility by MRI. Results: In analyses of differences between baseline and 24 weeks for the aliskiren treatment group vs the negative control group, central distensibility (overall; P = .26) and central PWV (0.2 ± 0.9 vs 0.03 ± 0.7 [m/s]; P = .79) by MRI were not significantly different. Central systolic aortic blood pressure tended to be lower by 14 mmHg in patients in the aliskiren treatment group than in the control group (P = .09). A significant decrease in peripheral PWV (brachial-ankle PWV) in the aliskiren treatment group (-1.6 m/s) compared with the control group (+0.28 m/s) was noted (P = .005). Conclusions: Among patients with MS, the addition of aliskiren to beta-blocker treatment did not significantly improve central aortic stiffness during a 24-week period

ß-Blocker Dialyzability in Maintenance Hemodialysis Patients: A Randomized Clinical Trial.

BACKGROUND AND OBJECTIVES: There is a paucity of data available to describe drug dialyzability. Of the available information, most was obtained before implementation of modern hemodialysis membranes. Our study characterized dialyzability of the most commonly prescribed ß-blockers in patients undergoing high-flux hemodialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Patients on hemodialysis (n=8) were recruited to an open label, pharmacokinetic, four-way crossover trial. Single doses of atenolol, metoprolol, bisoprolol, and carvedilol were administered on separate days in random order to each patient. Plasma and dialysate drug concentrations were measured, and dialyzability was determined by the recovery clearance and arterial venous difference methods. RESULTS: Using the recovery clearance method, the dialytic clearance values for atenolol, metoprolol, bisoprolol, and carvedilol were 72, 87, 44, and 0.2 ml/min, respectively (P<0.001). Applying the arterial venous difference method, the dialytic clearance values of atenolol, metoprolol, bisoprolol, and carvedilol were 167, 114, 96, and 24 ml/min, respectively (P<0.001). CONCLUSIONS: Atenolol and metoprolol are extensively cleared by hemodialysis compared with the negligible dialytic clearance of carvedilol. Contrary to estimates of dialyzability on the basis of previous literature, our data indicate that bisoprolol is also dialyzable. This finding highlights the importance of conducting dialyzability studies to definitively characterize drug dialytic clearance.

Buccal patches of atenolol formulated using fenugreek (Trigonella foenum-graecum L.) seed mucilage.

BACKGROUND: The use of mucoadhesive natural polymers in designing mucoadhesive patch systems has received much attention. OBJECTIVES: The study involved the development and evaluation of buccal patches of atenolol using fenugreek (Trigonella foenum-graecum L.) seed mucilage with hydroxylpropyl methyl cellulose (HPMC K4M) and a backing membrane (ethyl cellulose 5% w/v). MATERIAL AND METHODS: These atenolol-releasing buccal patches were prepared using a solvent casting technique. The buccal patches prepared were evaluated for average weight, thickness, drug content, folding endurance and moisture content. Ex vivo mucoadhesive strength, force of adhesion and bonding strength were determined using porcine buccal mucosa. The mucosal permeation of atenolol through the porcine buccal mucosa was carried out using a Franz diffusion cell in phosphate buffer saline, pH 6.8. These buccal patches were also characterized by SEM and FTIR spectroscopy. RESULTS: The average weight, thickness, drug content, folding endurance and moisture content of these atenolol-releasing buccal patches were found satisfactory for all the patches. Amongst all, the F-4 buccal patch showed maximum mucoadhesive strength (31.12 ±1.86 g), force of adhesion (30.53 × 10-2 N) and bond strength (1748.89 N/m2). Ex vivo atenolol permeation from the buccal patches showed drug permeation across the excised porcine buccal mucosa over 12 h. The F-4 buccal patch showed maximum permeation flux (29.12 µg/cm2/h). CONCLUSIONS: The developed atenolol-releasing buccal patches can be beneficial over the conventional drug delivery systems to decrease the dosing frequency and enhance patient compliance.

Revisiting atenolol as a low passive permeability marker.

BACKGROUND: Atenolol, a hydrophilic beta blocker, has been used as a model drug for studying passive permeability of biological membranes such as the blood-brain barrier (BBB) and the intestinal epithelium. However, the extent of S-atenolol (the active enantiomer) distribution in brain has never been evaluated, at equilibrium, to confirm that no transporters are involved in its transport at the BBB. METHODS: To assess whether S-atenolol, in fact, depicts the characteristics of a low passive permeable drug at the BBB, a microdialysis study was performed in rats to monitor the unbound concentrations of S-atenolol in brain extracellular fluid (ECF) and plasma during and after intravenous infusion. A pharmacokinetic model was developed, based on the microdialysis data, to estimate the permeability clearance of S-atenolol into and out of brain. In addition, the nonspecific binding of S-atenolol in brain homogenate was evaluated using equilibrium dialysis. RESULTS: The steady-state ratio of unbound S-atenolol concentrations in brain ECF to that in plasma (i.e., Kp,uu,brain) was 3.5% ± 0.4%, a value much less than unity. The unbound volume of distribution in brain (Vu, brain) of S-atenolol was also calculated as 0.69 ± 0.10 mL/g brain, indicating that S-atenolol is evenly distributed within brain parenchyma. Lastly, equilibrium dialysis showed limited nonspecific binding of S-atenolol in brain homogenate with an unbound fraction (fu,brain) of 0.88 ± 0.07. CONCLUSIONS: It is concluded, based on Kp,uu,brain being much smaller than unity, that S-atenolol is actively effluxed at the BBB, indicating the need to re-consider S-atenolol as a model drug for passive permeability studies of BBB transport or intestinal absorption.

Facile formation of co-amorphous atenolol and hydrochlorothiazide mixtures via cryogenic-milling: Enhanced physical stability, dissolution and pharmacokinetic profile.

The development of poorly water-soluble drugs faces the risk of low bioavailability and therapeutic efficacy. The co-amorphous drug delivery system has recently gained considerable interest because it offers an alternative approach to modify properties of poorly water-soluble drugs. Herein, we developed a co-amorphous system of atenolol (ATE) and poorly water-soluble hydrochlorothiazide (HCT) by means of cryogenic milling. The co-administration of ATE and HCT has been reported to show therapeutic advantages for patients with uncomplicated hypertension. The co-amorphous ATE-HCT sample with 1:1 molar ratio showed excellent physical stability, which could be attributed to the formation of strong molecular interactions between ATE and HCT as evidenced by FT-IR spectra. Compared to the pure crystalline form, amorphous form and physical mixture, HCT in the co-amorphous form exhibited the significantly increased intrinsic dissolution rate, as well as the enhanced bioavailability in the pharmacokinetic study. It was found that the enhanced bioavailability of HCT in the co-amorphous formulation was achieved by the synergistic effect of amorphized HCT and the water-soluble coformer ATE. The present study provides an improved approach to implement the combination therapy of ATE and HCT for potential clinical treatments.

Mass Spectrometry Imaging proves differential absorption profiles of well-characterised permeability markers along the crypt-villus axis.

Knowledge about the region-specific absorption profiles from the gastrointestinal tract of orally administered drugs is a critical factor guiding dosage form selection in drug development. We have used a novel approach to study three well-characterized permeability and absorption marker drugs in the intestine. Propranolol and metoprolol (highly permeable compounds) and atenolol (low-moderate permeability compound) were orally co-administered to rats. The site of drug absorption was revealed by high spatial resolution matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) and complemented by quantitative measurement of drug concentration in tissue homogenates. MALDI-MSI identified endogenous molecular markers that illustrated the villi structures and confirmed the different absorption sites assigned to histological landmarks for the three drugs. Propranolol and metoprolol showed a rapid absorption and shorter transit distance in contrast to atenolol, which was absorbed more slowly from more distal sites. This study provides novel insights into site specific absorption for each of the compounds along the crypt-villus axis, as well as confirming a proximal-distal absorption gradient along the intestine. The combined analytical approach allowed the quantification and spatial resolution of drug distribution in the intestine and provided experimental evidence for the suggested absorption behaviour of low and highly permeable compounds.

Osmolality of Orally Administered Solutions Influences Luminal Water Volume and Drug Absorption in Intestine.

Intestinal water absorption is reportedly influenced by luminal osmolality. In this study, we examined whether differences in the osmolality of the vehicle used for oral administration of drugs influence luminal water volume and drug absorption in the gastrointestinal (GI) tract, by means of in situ rat intestinal closed loop studies using solutions of fluorescein isothiocyanate dextran 4000 (a non-absorbable compound), atenolol (a low-permeability drug), and antipyrine (a high-permeability drug) in various solvents. Determination of the remaining fraction of water revealed the following rank order for water absorption in rat jejunum: purified water > saline > phosphate buffer = isosmotic mannitol solution. The luminal concentration of fluorescein isothiocyanate-dextran 4000 after administration in purified water was significantly increased to 2.5 times the initial dosing concentration. Thus, osmolality-dependent changes in GI water absorption can cause significant changes of drug concentration in the GI fluid, potentially resulting in altered drug absorption characteristics. Indeed, the fraction absorbed of atenolol in jejunum was significantly greater when the drug was administered in purified water than in isosmotic solution. In contrast, no significant change in fraction absorbed of antipyrine was observed. Our results indicate that osmolality-dependent changes in GI water volume may influence drug absorption, especially of low-permeability drugs.

Regional Intestinal Permeability of Three Model Drugs in Human.

Currently there are only a limited number of determinations of human Peff in the distal small intestine and none in the large intestine. This has hindered the validation of preclinical models with regard to absorption in the distal parts of the intestinal tract, which can be substantial for BCS class II-IV drugs, and drugs formulated into modified-release (MR) dosage forms. To meet this demand, three model drugs (atenolol, metoprolol, and ketoprofen) were dosed in solution intravenously, and into the jejunum, ileum, and colon of 14 healthy volunteers. The Peff of each model drug was then calculated using a validated deconvolution method. The median Peff of atenolol in the jejunum, ileum, and colon was 0.45, 0.15, and 0.013 × 10(-4) cm/s, respectively. The corresponding values for metoprolol were 1.72, 0.72, and 1.30 × 10(-4) cm/s, and for ketoprofen 8.85, 6.53, and 3.37 × 10(-4) cm/s, respectively. This is the first study where the human Peff of model drugs has been determined in all parts of the human intestinal tract in the same subjects. The jejunal values were similar to directly determined values using intestinal single-pass perfusion, indicating that the deconvolution method is a valid approach for determining regional Peff. The values from this study will be highly useful in the validation of preclinical regional absorption models and in silico tools.

Regional Intestinal Permeability in Dogs: Biopharmaceutical Aspects for Development of Oral Modified-Release Dosage Forms.

The development of oral modified-release (MR) dosage forms requires an active pharmaceutical ingredient (API) with a sufficiently high absorption rate in both the small and large intestine. Dogs are commonly used in preclinical evaluation of regional intestinal absorption and in the development of novel MR dosage forms. This study determined regional intestinal effective permeability (Peff) in dogs with the aim to improve regional Peff prediction in humans. Four model drugs, atenolol, enalaprilat, metoprolol, and ketoprofen, were intravenously and regionally dosed twice as a solution into the proximal small intestine (P-SI) and large intestine (LI) of three dogs with intestinal stomas. Based on plasma data from two separate study occasions for each dog, regional Peff values were calculated using a validated intestinal deconvolution method. The determined mean Peff values were 0.62, 0.14, 1.06, and 3.66 × 10(-4) cm/s in the P-SI, and 0.13, 0.02, 1.03, and 2.20 × 10(-4) cm/s in the LI, for atenolol, enalaprilat, metoprolol, and ketoprofen, respectively. The determined P-SI Peff values in dog were highly correlated (R(2) = 0.98) to the historically directly determined human jejunal Peff after a single-pass perfusion. The determined dog P-SI Peff values were also successfully implemented in GI-Sim to predict the risk for overestimation of LI absorption of low permeability drugs. We conclude that the dog intestinal stoma model is a useful preclinical tool for determination of regional intestinal permeability. Still, further studies are recommended to evaluate additional APIs, sources of variability, and formulation types, for more accurate determination of the dog model in the drug development process.

Melatonin Pathway and Atenolol-Related Glucose Dysregulation: Is There a Correlation?

Lower melatonin level, melatonin receptor gene variations, and atenolol treatment are associated with glucose dysregulation. We investigated whether atenolol-related glucose and melatonin changes are correlated, and whether single nucleotide polymorphisms (SNPs) in melatonin candidate genes contribute to interindividual variation in glucose change. Hypertensive Caucasians (n = 232) from the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) study treated with atenolol for 9 weeks were studied. Urinary 6-sulfatoxymelatonin (aMT6s) was measured pre- and posttreatment and normalized to urinary creatinine. Pharmacogenetic effects on glucose change of 160 SNPs in 16 melatonin candidate genes were assessed with multiple linear regression. Atenolol was associated with increased glucose (1.8 ± 10.1mg/dl, P = 0.02) and decreased aMT6s (-4.5 ± 10.1 ng/mg, P < 0.0001). However, the aMT6s change was not correlated with post-atenolol glucose change. SNP rs11649514 in PRKCB was associated with glucose change (P = 1.0×10(-4)). PRKCB is involved in the melatonin-insulin regulatory pathway, and may be important in mediating clinically meaningful atenolol-related hyperglycemia.

Simultaneous quantification of atenolol and chlorthalidone in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry.

A simple, sensitive and reproducible ultra-performance liquid chromatography-tandem mass spectrometry method has been developed for the simultaneous determination of atenolol, a ß-adrenergic receptor-blocker and chlorthalidone, a monosulfonamyl diuretic in human plasma, using atenolol-d7 and chlorthalidone-d4 as the internal standards (ISs). Following solid-phase extraction on Phenomenex Strata-X cartridges using 100 µL human plasma sample, the analytes and ISs were separated on an Acquity UPLC BEH C18 (50 mm × 2.1 mm, 1.7 µm) column using a mobile phase consisting of 0.1% formic acid-acetonitrile (25:75, v/v). A tandem mass spectrometer equipped with electrospray ionization was used as a detector in the positive ionization mode for both analytes. The linear concentration range was established as 0.50-500 ng/mL for atenolol and 0.25-150 ng/mL for chlorthalidone. Extraction recoveries were within 95-103% and ion suppression/enhancement, expressed as IS-normalized matrix factors, ranged from 0.95 to 1.06 for both the analytes. Intra-batch and inter-batch precision (CV) and accuracy values were 2.37-5.91 and 96.1-103.2%, respectively. Stability of analytes in plasma was evaluated under different conditions, such as bench-top, freeze-thaw, dry and wet extract and long-term. The developed method was superior to the existing methods for the simultaneous determination of atenolol and chlorthalidone in human plasma with respect to the sensitivity, chromatographic analysis time and plasma volume for processing. Further, it was successfully applied to support a bioequivalence study of 50 mg atenolol + 12.5 mg chlorthalidone in 28 healthy Indian subjects.