Food-induced reduction in bioavailability of atenolol

Evaluating Utilization of Tiny-TIM to Assess the Effect of Food on the Absorptions of Oral Drugs and Its Application on Biopharmaceutical Modeling

Safety and efficacy are the most critical factors for the development of modern medications. For oral drugs, evaluating drug exposure under various conditions is one of the most important outcomes for clinical trials. These data will help to better understand the safety and efficacy of new drugs. Studies involving potential drug-drug interactions, proton pump inhibitors, and intake of food are often conducted to assess the above. Among the above, the influence of food on exposure to the drug is one of the key data sets for regulatory submission. Since food may have either a positive or negative effect on drug exposure, it is important to obtain an early assessment of the food effect. To better forecast and plan for clinical studies, substantial efforts have been made in the industry to develop modeling and in-vitro and in-vivo assays. Despite the efforts, predicting the effect of food on exposure without integrating the dynamic of the gastrointestinal tract in the assessment remains challenging. In this study, we evaluated the utilization of the dynamic Gastro-Intestinal Model (Tiny-TIM) for the food effect of over 20 drugs/formulations in development or on the market that covers all BCS classes. In general, the Tiny-TIM predicted food effects were in good agreement with the reported data in humans. This suggests that Tiny-TIM can successfully capture the impact of physicochemical properties on absorption under the influence of food.

An International Multi-Center Cohort Study on β-blockers for the Treatment of Symptomatic Children with Catecholaminergic Polymorphic Ventricular Tachycardia

Background: Symptomatic children with catecholaminergic polymorphic ventricular tachycardia (CPVT) are at risk for recurrent arrhythmic events. Beta-blockers (BBs) decrease this risk, but studies comparing individual BBs in sizeable cohorts are lacking. We aimed to assess the association between risk for arrhythmic events and type of BB in a large cohort of symptomatic children with CPVT. Methods: From two international registries of patients with CPVT, RYR2 variant-carrying symptomatic children (defined as syncope or sudden cardiac arrest prior to BB initiation and age at start of BB therapy <18 years), treated with a BB were included. Cox-regression analyses with time-dependent covariates for BB and potential confounders were used to assess the hazard ratio (HR). The primary outcome was the first occurrence of sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter-defibrillator shock, or syncope. The secondary outcome was the first occurrence of any of the primary outcomes except syncope. Results: We included 329 patients (median age at diagnosis 12 [interquartile range, 7-15] years, 35% females). Ninety-nine (30.1%) patients experienced the primary and 74 (22.5%) experienced the secondary outcome during a median follow-up of 6.7 [interquartile range, 2.8-12.5] years. Two-hundred sixteen patients (66.0%) used a non-selective BB (predominantly nadolol [n=140] or propranolol [n=70]) and 111 (33.7%) used a β1-selective BB (predominantly atenolol [n=51], metoprolol [n=33], or bisoprolol [n=19]) as initial BB. Baseline characteristics did not differ. The HR for both the primary and secondary outcomes were higher for β1-selective compared with non-selective BBs (HR, 2.04 95% CI, 1.31-3.17; and HR, 1.99; 95% CI, 1.20-3.30, respectively). When assessed separately, the HR for the primary outcome was higher for atenolol (HR, 2.68; 95% CI, 1.44-4.99), bisoprolol (HR, 3.24; 95% CI, 1.47-7.18), and metoprolol (HR, 2.18; 95% CI, 1.08-4.40) compared with nadolol, but did not differ from propranolol. The HR of the secondary outcome was only higher in atenolol compared with nadolol (HR, 2.68; 95% CI, 1.30-5.55). Conclusions: B1-selective BBs were associated with a significantly higher risk for arrhythmic events in symptomatic children with CPVT compared with non-selective BBs, specifically nadolol. Nadolol, or propranolol if nadolol is unavailable, should be the preferred BB for treating symptomatic children with CPVT.

The Impact of Diet and Exercise on Drug Responses

It is well known that lifestyle changes can alter several physiological functions in the human body. For exercise and diet, these effects are used sensibly in basic therapies, as in cardiovascular diseases. However, the physiological changes induced by exercise and a modified diet also have the capacity to influence the efficacy and toxicity of several drugs, mainly by affecting different pharmacokinetic mechanisms. This pharmacological plasticity is not clinically relevant in all cases but might play an important role in altering the effects of very common drugs, particularly drugs with a narrow therapeutic window. Therefore, with this review, we provide insights into possible food–drug and exercise–drug interactions to sharpen awareness of the potential occurrence of such effects.

Prediction of negative food effect induced by bile micelle binding on oral absorption of hydrophilic cationic drugs

The purpose of the present study was to quantitatively predict the negative food effect induced by bile micelle binding on the oral absorption of hydrophilic cationic drugs. The intrinsic membrane permeability and bile micelle unbound fraction of 12 model drugs (7 tertiary amines, 3 quaternary ammoniums, and 2 neutral drugs) were calculated from the experimental Caco-2 permeability data (P_app) under fasted and fed conditions. From these input data, the fraction of a dose absorbed (Fa) was predicted using the gastrointestinal unified theoretical framework, a mechanism-based oral absorption model. The predicted Fa ratio (fed/fasted) was then compared with the in vivo fed/fasted area under the plasma concentration-time curve ratio (AUCr). The AUCr values of tertiary amines and neutral drugs were appropriately predicted (absolute average fold error (AAFE) = 1.19), whereas those of quaternary ammoniums were markedly underestimated (AAFE = 4.70). The P_app ratio (fed/fasted) predicted AUCr less quantitatively (AAFE = 1.30 for tertiary amines and neutral drugs). The results of the present study would lead to a better understanding of negative food effect on oral drug absorption.

Pharmacokinetic variability of beta-adrenergic blocking agents used in cardiology

The aim of this study was to evaluate the pharmacokinetic variability of beta-adrenergic blocking agents used in cardiology by reviewing single-dose and steady-state pharmacokinetic studies from the literature. PubMed was searched for pharmacokinetic studies of beta-adrenergic blocking agents, both single-dose and steady-state studies. The studies included reported maximum plasma concentration (Cmax) and/or area under the concentration curve (AUC). The coefficient of variation (CV%) was calculated for all studies, and a CV% <40% was considered low or moderate variability, and a CV% >40% was considered high variability. The Cmax and AUC were reported a total of 672 times in 192 papers. Based on AUC, metoprolol, propranolol, carvedilol, and nebivolol showed high pharmacokinetic variability (highest first), whereas bisoprolol, atenolol, sotalol, labetalol, nadolol, and pindolol showed low to moderate variability (lowest first). We have shown a high interindividual pharmacokinetic variability that varies markedly in different beta-adrenergic blocking agents; the extreme being steady state ratios as high as 30 in metoprolol. A more personalized approach to the medical treatment of patients may be obtained by combining known pharmacokinetic information about variability, pharmaco-genetics and -dynamics, and patient characteristics, to avoid adverse events or lack of treatment effect.

Effect of lipid and cellulose based matrix former on the release of highly soluble drug from extruded/spheronized, sintered and compacted pellets

Background

The study was to develop an extended release (ER) encapsulated and compacted pellets of Atenolol using hydrophobic (wax based and polymeric based) and high viscosity grade hydrophilic matrix formers to control the release of this highly water soluble drug by extrusion/spheronization (ES). Atenolol is used for cardiovascular diseases and available as an immediate release (IR) tablet dosage form. The lipids, Carnauba wax (CW), Glyceryl monostearate (GMS) and cellulose based i.e. Hydroxypropyl methylcellulose (HPMC) and Ethyl cellulose (EC) were used in preparing Atenolol ER pellets. Thermal sintering and compaction techniques were also applied to control the burst release of Atenolol.

Method

For this purpose, thirty-six trial formulations (F1-F36) were designed by Response Surface Methodology (RSM), using Design-Expert 10 software, keeping (HPMC K4M, K15 M & K100 M), (EC 7FP, 10FP & 100FP), waxes (GMS, & CW), their combinations, sintering temperature and duration, as input variables. Dissolution studies were performed in pH, 1.2, 4.5 and 6.8 dissolution media. Drug release kinetics using different models such as zero order, first order, Korsmeyer-Peppas, Hixon Crowell, Baker-Lonsdale and Higuchi kinetics were studied with the help of DDsolver, an excel based add-in program.

Results

The formulations F35 and F36 showed compliance with Korsmeyer-Peppas Super case II transport model (R² = 0.975–0.971) in dissolution medium pH 4.5. No drug excipient interaction observed by FTIR. Stereomicroscopy showed that sintered combination pellets, (F35), were highly spherical (AR = 1.061, and sphericity = 0.943). The cross-sectional SEM magnification (at 7000X) of F34 and F35 showed dense cross-linking. The results revealed that the optimized formulations were F35 (sintered pellets) and F36 (compacted pellets) effectively controlling the drug release for 12 h.

Conclusion

Extended-release encapsulated, and compacted pellets were successfully prepared after the combination of lipids CW (10%) and GMS (20%) with EC (10FP 20% & 100FP 20%). Sintering and compaction, in addition, stabilized the system and controlled the initial burst release of the drug. Extended release (ER) Atenolol is an effective alternative of IR tablets in controlling hypertension and treating other cardiovascular diseases.

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.

Evaluation of fasted and fed state simulated and human intestinal fluids as solvent system in the Ussing chambers model to explore food effects on intestinal permeability

The Ussing chambers model is almost exclusively used in the presence of plain aqueous phosphate buffers as solvent system. In an attempt to further elucidate the effect of luminal ingredients and postprandial conditions on intestinal permeability, pooled fasted and fed state human intestinal fluids (FaHIFpool, FeHIFpool) were used. In addition, simulated intestinal fluids of both nutritional states (FaSSIF, FeSSIF) were evaluated as possible surrogate media for HIF. The use of FaHIFpool generated a broad range of Papp values for a series of 16 model drugs, ranging from 0.03×10(-6)cm/s (carvedilol) to 33.8×10(-6)cm/s (naproxen). A linear correlation was observed between Papp values using FaSSIF and FaHIFpool as solvent system (R=0.990), justifying the use of FaSSIF as surrogate medium for FaHIF in the Ussing chambers. In exclusion of the outlier carvedilol, a strong sigmoidal relationship was found between Papp and fahuman of 15 model drugs, illustrated by correlation coefficients of 0.961 and 0.936 for FaHIFpool and FaSSIF, respectively. When addressing food effects on intestinal permeability, the use of FeHIFpool resulted in a significantly lower Papp value for nine out of sixteen compounds compared to fasting conditions. FeSSIF as solvent system significantly overestimated Papp values in FeHIFpool. To conclude, the optimized Ussing chambers model using biorelevant media as apical solvent system holds great potential to investigate food effects in a more integrative approach, taking into account drug solubilisation, supersaturation and formulation effects.

Kidney function and population-based outcomes of initiating oral atenolol versus metoprolol tartrate in older adults

BACKGROUND

Atenolol and metoprolol tartrate are commonly prescribed β-blockers. Atenolol elimination depends on kidney function, whereas metoprolol tartrate does not. We hypothesized that compared to metoprolol tartrate, initiating oral atenolol treatment would be associated with more adverse events in older adults, with the association most pronounced in patients with lower baseline estimated glomerular filtration rates (eGFRs).

STUDY DESIGN

Population-based matched retrospective cohort study.

SETTING & PARTICIPANTS

Older adults (mean age, 75 years) in Ontario, Canada, prescribed oral atenolol versus metoprolol tartrate from April 2002 through December 2011. The 2 groups were well matched (n=75,257 in each group), with no difference in 31 measured baseline characteristics. Patients with end-stage renal disease were ineligible, and 4.6% of patients had chronic kidney disease (median eGFR, 38mL/min/1.73m(2) assessed through a database algorithm).

PREDICTORS

β-Blocker type and eGFR.

OUTCOMES

A composite outcome of hospitalization with bradycardia or hypotension and all-cause mortality were assessed in 90-day follow-up.

RESULTS

Compared to metoprolol tartrate, initiating atenolol treatment was not associated with higher risk of hospitalization with bradycardia or hypotension (incidence, 0.71% vs 0.79%; relative risk, 0.90; 95%CI, 0.80-1.01). Atenolol treatment initiation was associated with lower 90-day risk of mortality than metoprolol tartrate (incidence, 0.97% vs 1.44%; relative risk, 0.68; 95%CI, 0.61-0.74). Lower eGFR did not modify either association (P for interaction=0.5 and 0.6, respectively).

LIMITATIONS

Heart rate and blood pressure were not available in our data sources, and effects ascertained from observational studies are subject to residual confounding.

CONCLUSIONS

Contrary to our expectation, we found that atenolol versus metoprolol tartrate was associated with lower 90-day risk of mortality in patients regardless of eGFR, with no difference in risk of hospitalization with bradycardia or hypotension.

Polymers derived from Xanthomonas campesteris and Cyamopsis tetragonolobus used as retardant materials for the formulation of sustained release floating matrix tablet of atenolol

The objective of the present study was to develop, optimize, in vitro, and in vivo evaluation of floating matrix tablet of atenolol using polymer blend derived from Xanthomonas campesteris and Cyamopsis tetragonolobus that are characterized by release requirements of sustained-release product and to improve the oral bioavailability of the drug. A 3(2) full factorial design was employed to optimize the tablets, where content of polymer blend (X1) and ratio of xanthan gum-to-guar gum (X2) were considered as independent variables. The effects of independent variables on dependent variables, i.e. floating time, diffusion exponent, and time to release 50% of atenolol were evaluated. The in vivo pharmacokinetic parameters of the optimized formulation were compared with the marketed sustained release formulation of atenolol (Aten(®)). The optimized formulation containing 20% (w/w) of polymer blend and 50:50 ratio of xanthan gum-to-guar gum was able to float more than 12h and showed the desired sustained drug release from the tablets. In vivo retention studies in rabbit stomach showed the gastric residence of tablet up to 6h. The in vivo study of optimized tablets illustrated significant improvement in the oral bioavailability of atenolol in rabbits. It can be concluded that floating matrix tablet of atenolol prepared by using xanthan gum and guar gum has potential for sustained release of the drug as well as improved oral bioavailability through enhanced gastric residence time of formulation in stomach.

Design, synthesis, and in vitro kinetics study of atenolol prodrugs for the use in aqueous formulations

Based on DFT, MP2, and the density functional from Truhlar group (hybrid GGA: MPW1k) calculations for an acid-catalyzed hydrolysis of nine Kirby's N-alkylmaleamic acids and two atenolol prodrugs were designed. The calculations demonstrated that the amide bond cleavage is due to intramolecular nucleophilic catalysis by the adjacent carboxylic acid group and the rate-limiting step is determined based on the nature of the amine leaving group. In addition, a linear correlation of the calculated and experimental rate values has drawn credible basis for designing atenolol prodrugs that are bitterless, are stable in neutral aqueous solutions, and have the potential to release the parent drug in a sustained release manner. For example, based on the calculated B3LYP/6-31 G (d,p) rates, the predicted t_1/2 (a time needed for 50% of the prodrug to be converted into drug) values for atenolol prodrugs ProD 1-ProD 2 at pH 2 were 65.3 hours (6.3 hours as calculated by GGA: MPW1K) and 11.8 minutes, respectively. In vitro kinetic study of atenolol prodrug ProD 1 demonstrated that the t_1/2 was largely affected by the pH of the medium. The determined t_1/2 values in 1N HCl, buffer pH 2, and buffer pH 5 were 2.53, 3.82, and 133 hours, respectively.

Formulation and evaluation of fixed-dose combination of bilayer gastroretentive matrix tablet containing atorvastatin as fast-release and atenolol as sustained-release

The objective of the present study was to develop bilayer tablets of atorvastatin and atenolol that are characterized by initial fast-release of atorvastatin in the stomach and comply with the release requirements of sustained-release of atenolol. An amorphous, solvent evaporation inclusion complex of atorvastatin with β-cyclodextrin, present in 1 : 3 (drug/cyclodextrin) molar ratio, was employed in the fast-release layer to enhance the dissolution of atorvastatin. Xanthan gum and guar gum were integrated in the sustained-release layer. Bilayer tablets composed of sustained-release layer (10% w/w of xanthan gum and guar gum) and fast-release layer [1 : 3 (drug/cyclodextrin)] showed the desired release profile. The atorvastatin contained in the fast-release layer showed an initial fast-release of more than 60% of its drug content within 2 h, followed by sustained release of the atenolol for a period of 12 h. The pharmacokinetic study illustrated that the fast absorption and increased oral bioavailability of atorvastatin as well as therapeutic concentration of atenolol in blood were made available through adoption of formulation strategy of bilayer tablets. It can be concluded that the bilayer tablets of atorvastatin and atenolol can be successfully employed for the treatment of hypertension and hypercholesterolemia together through oral administration of single tablet.

A GENS-based approach to cardiovascular pharmacology: impact on metabolism, pharmacokinetics and pharmacodynamics

Pharmacological outcomes depend on many factors, with many of them being sexually dimorphic. Thus, physiological gender/sex (GENS) differences can influence pharmacokinetics, pharmacodynamics and, thus, bioavailability and resulting in efficacy of treatment, meaning GENS differences should be an important consideration in therapeutics. In particular, drug response can change according to different hormonal environments. Therefore, GENS-specific differences have a particular clinical relevance in terms of drug delivery, especially for those substances with a narrow therapeutic margin. Since adverse effects are more frequent among women, safety is a key issue. Overall, the status of women, from a pharmacological point of view, is often different and less studied than that of men and deserves particular attention. Further studies focused on women's responses to drugs are necessary in order to make optimal pharmacotherapeutic decisions.

Predictive models for drugs exhibiting negative food effects based on their biopharmaceutical characteristics

CONTEXT

A drug is defined to exhibit food effects if its pharmacokinetic parameter, area under the curve (AUC₀₋∞) is different when co-administered with food in comparison with its administration on a fasted stomach. Food effects of drugs administered in immediate release dosage forms were classified as positive, negative, and no food effects.

OBJECTIVE

In this study, predictive models for negative food effects of drugs that are stable in the gastrointestinal tract and do not complex with Ca²⁺ are reported.

METHODS

An empirical model was developed using five drugs exhibiting negative food effects and seven drugs exhibiting no food effects by multiple regression analysis, based on biopharmaceutical properties generated from in vitro experiments. An oral absorption model was adopted for simulating negative food effects of model compounds using in situ rat intestinal permeability.

RESULTS

Analysis of selected model drugs indicated that percent food effects correlated to their dissociation constant, K (K(a) or K(b)) and Caco-2 permeabilities. The obtained predictive equation was: Food effect (%)=(2.60 x 10⁵·P(app))--(2.91 x 10⁵·K)--8.50. Applying the oral absorption model, the predicted food effects matched the trends of published negative food effects when the two experimental pH conditions of fed and fasted state intestinal environment were used.

CONCLUSION

A predictive model for negative food effects based on the correlation of food effects with dissociation constant and Caco-2 permeability was established and simulations of food effects using rat intestinal permeability supported the drugs? published negative food effects. Thus, an empirical and a mechanistic model as potential tools for predicting negative food effects are reported.

Effect of food intake on the oral absorption of poorly water-soluble drugs: in vitro assessment of drug dissolution and permeation assay system

The aim of the present work was to establish appropriate conditions for the dissolution/permeation system (D/P system) to estimate the effect of food intake on oral drug absorption. The D/P system is an in vitro assay system to evaluate the drug dissolution and permeation processes after oral administration. Caco-2 monolayer was used as a model membrane of the intestinal epithelium. In this study, two types of simulated intestinal fluid reflecting the fasted and the fed state conditions of the human gastrointestinal tract were used. Drugs were applied to the D/P system as a powder, then, permeated amounts of drugs into the basal side were monitored. A sigmoidal correlation was obtained between in vivo oral absorption (% absorbed of dose) and in vitro permeated amount (% of dose/2 h) under both states. From the D/P system, the estimated absorption of albendazole in both states was found to correspond well with in vivo observation. Moreover, the D/P system could estimate the effect of self-emulsifying formulation on the oral absorption of danazol, quantitatively. In conclusion, the D/P system was proved to be a useful assay system not only for the oral absorption of drugs, but also for the food effect on the absorption.

Oral sustained delivery of atenolol from floating matrix tablets-formulation and in vitro evaluation

Floating matrix tablets of atenolol were developed to prolong gastric residence time and increase drug bioavailability. Atenolol was chosen as a model drug because it is poorly absorbed from the lower gastrointestinal tract. The tablets were prepared by direct compression technique, using polymers such as hydroxypropyl methylcellulose (HPMC K15M, K4M), guargum (GG), and sodium carboxymethylcellulose (SCMC), alone or in combination, and other standard excipients. Tablets were evaluated for physical characteristics viz. hardness, swelling index, floating capacity, thickness, and weight variation. Further, tablets were evaluated for in vitro release characteristics for 8 hr. The effect of effervescent on buoyancy and drug release pattern was also studied. In vitro release mechanism was evaluated by linear regression analysis. GG- and SCMC-based matrix tablets showed significantly greater swelling indices compared with other batches. The tablets exhibited controlled and prolonged drug release profiles while floating over the dissolution medium.

Effects of orange juice on the pharmacokinetics of atenolol

OBJECTIVE

Fruit juices can significantly change the pharmacokinetics of several drugs. Our objective was to investigate the effect of orange juice on the pharmacokinetics of the beta-blocking agent atenolol.

METHODS

In a randomized cross-over study with two phases and a washout of 2 weeks, ten healthy volunteers took either 200 ml orange juice or water thrice daily for 3 days and twice on the fourth day. On the morning of day 3, each subject ingested 50 mg atenolol with an additional amount of either 200 ml orange juice or water. The plasma concentrations of atenolol and the cumulative excretion of atenolol into urine were measured up to 33 h after its dosing. Systolic and diastolic blood pressures and heart rate were recorded in a sitting position before the intake of atenolol and 2, 4, 6, and 10 h after.

RESULTS

Orange juice decreased the mean peak plasma concentration (C(max)) of atenolol by 49% (range 16-59%, P<0.01), and the mean area under the plasma atenolol concentration-time curve (AUC(0-33 h)) by 40% (range 25-55%, P<0.01). The time of the peak concentration (t(max)) and the elimination half-life (t(1/2)) of atenolol remained unchanged by orange juice. The amount of atenolol excreted into urine was decreased by 38% (range 17-60%, P<0.01), but the renal clearance remained unaltered. The average heart rate was slightly higher during the orange juice+atenolol phase than during the water+atenolol phase.

CONCLUSIONS

Orange juice moderately interferes with the gastrointestinal absorption of atenolol. This food-drug interaction can be of clinical significance.

Hydrophilic interaction liquid chromatographic tandem mass spectrometric determination of atenolol in human plasma

A hydrophilic interaction liquid chromatographic method with tandem mass spectrometry for the determination of atenolol, a beta-blocking agent, in human plasma has been developed and validated over the curve range of 10--2000 ng/mL. The assay was based on protein precipitation followed by evaporation of the extraction solvent, reconstitution with acetonitrile, and chromatography on an Hypersil silica column (50 x 4.6 mm) using a low aqueous--high organic mobile phase. The mobile phase consists of 85% acetonitrile, 15% water, 0.5% acetic acid and 0.04% trifluoroacetic acid and runs isocratically at a flow rate of 2.0 mL/min. The column ef fluent was split so that 50% of it was transferred into the LC-MS/MS interface operated in positive electrospray ionization mode. The chromatographic run time was 2.0 min per injection. Atenolol and the internal standard, atenolol-d(7), showed a retention time of 1.0 min. The inter-day and intra-day precision and accuracy of the quality control samples were <5.3% relative standard deviation and <8.0% relative error, respectively. To explore the application of the current method for the analysis of other beta-blocking agents, propranolol and metoprolol were tested under the same chromatographic conditions with retention times of 0.68 and 0.75 min, respectively. The present method could be used for therapeutic drug monitoring, pharmacokinetic and drug--drug interaction studies of beta-blocking agents.

Comparative pharmacokinetic study of a floating multiple-unit capsule, a high-density multiple-unit capsule and an immediate-release tablet containing 25 mg atenolol

The purpose of this study was to evaluate the possible advantages of floating and high-density dosage forms and their influence on pharmacokinetic parameters. Atenolol was chosen as a model drug because of its poor absorption in the lower gastrointestinal tract. Three formulations containing 25 mg atenolol, a floating multiple-unit capsule, a high-density multiple-unit capsule, and an immediate-release tablet were compared with respect to estimated pharmacokinetic parameters. The two multiple-unit dosage forms were composed of compressed minitablets and had sustained release properties. The bioavailability of the two gastroretentive preparations with sustained release characteristics was significantly decreased when compared to the immediate-release tablet. The floating minitablets seemed to be retained longer in the stomach than the high-density dosage form. The first atenolol concentration detectable in the plasma and the time to peak Tmax were delayed for the floating dosage form. For the parameters Cmax and AUC 0-infinity, the lower limit of the 90% confidence interval was outside the bioequivalence range (0.80-1.25). This study showed that it was not possible to increase the bioavailability of a poorly absorbed drug such as atenolol using gastroretentive formulations. Atenolol absorption was delayed and the maximum plasma concentration was diminished.

Mechanisms and variations in the food effect on propranolol bioavailability

Mechanisms and variations in the food-induced increase in the bioavailability of propranolol were assessed by single-dose (80 mg) studies in healthy volunteers who took the drug on an empty stomach, immediately after a protein-rich breakfast, and together with a carbohydrate-rich, protein-poor breakfast. Concomitant intake of the protein-rich, but not the carbohydrate-rich, protein-poor breakfast, increased the bioavailability of propranolol in most, but not all, subjects. The food (protein) effect displayed much inter-individual variation, from a decrease to a 250% increase, which could be explained, at least in part, by a correlation between the oral clearance of propranolol and the food-induced increase in its bioavailability. The food effect was not associated with decreased total availability, but with delayed appearance, of the oxidative metabolites 4-OHP, NLA and PG. Hence the food (protein) effect does not seem to be caused by enzyme inhibition, but rather it is due to reduced hepatic extraction of propranolol, probably consequent to an increase hepatic entry rate. When taken together with the protein-rich breakfast, propranolol usually appeared in systemic blood at least as early as when taken on an empty stomach, implying that gastric absorption of propranolol may be possible in the presence of protein-rich food. Within the individual the food effect was reproducible, but its magnitude showed an intraindividual variation that may reflect its dependence upon the rates of gastrointestinal absorption and splanchnic-hepatic blood flow, and hence upon the rate of hepatic drug entry.

Oral bioavailability of atenolol

The bioavailability of two formulations of atenolol was compared in an open, randomized crossover study. Each film-coated tablet contained 100 mg of active drug. The plasma concentrations of atenolol were determined using a newly developed and specific high-performance liquid chromatography procedure. The areas under the concentration-time curves (AUC) were calculated, as were pair differences and ratios for individual AUC values and for maximum plasma levels. The latter were determined (Cmax.(m] and calculated (Cmax.(c] at the corresponding time values (tmax.) for test and reference formulations, and were then tested for statistical significance. The 95% confidence limits for both test and reference preparations, taken according to Westlake or Wilcoxon, were found to be 80.0-114.7% for AUC, 80.2-119.9% for Cmax. and 74.5-132.8% for tmax. In terms of pharmacokinetic target criteria, therefore, it can be seen that there were no substantial differences between the two film-coated tablets. The two atenolol preparations, therefore, may be classified as bioequivalent.

The influence of food on the oral absorption of bevantolol

The bioavailability of bevantolol was compared in 12 healthy volunteers given single doses of the drug as the HCl salt after an overnight fast, or 15 minutes before or after a standardized breakfast in a nonblind, randomized crossover design. Bevantolol was rapidly absorbed in all three treatment groups, with maximum concentrations (Cmax) observed at 1.0, 0.9, and 1.8 hours for the fasting, before breakfast, and after breakfast groups, respectively. Time to Cmax was significantly longer than fasting only when bevantolol was given after breakfast. Food ingestion did not significantly affect Cmax, total of absorbed drug, or the drug elimination rate. Since food only slightly decreases the drug absorption rate and has no measurable effect on the extent of drug absorption, the relationship of bevantolol administration to meals is not expected to influence therapeutic efficacy.

Effect of food intake on plasma levels and antihypertensive response during maintenance therapy with endralazine

A sensitive HPLC assay has been used to determine the effect of food on plasma endralazine levels in 8 patients with essential hypertension. Subjects were investigated whilst on maintenance therapy with endralazine combined with a fixed antihypertensive baseline treatment for at least 4 weeks, samples being collected after the usual oral morning dose of endralazine (5 mg and 10 mg), on two occasions at least 7 days apart. Endralazine was administered with the concomitant therapy in randomised order once 90 min before and once immediately after a standard breakfast. Acetylator status did not affect its pharmacokinetics in the postprandial study after a 5 mg dose, the peak endralazine concentration averaged 57.5% lower and the AUC had fallen significantly by 49.9%, whereas after 10 mg the postprandial peak level and the AUC were 82.9% and 64.7%, lower. In the 5 mg study the mean arterial blood pressure was decreased by 30 mm Hg in the fasting subjects and by 21 mm Hg in the postprandial group. For the 10 mg dose the corresponding values were 35 and 24 mm Hg. The blood pressure lowering effect was only weakly correlated with the food--related reduction in the plasma endralazine levels. The results suggest that endralazine has a similar kinetic interaction with food as that found for hydralazine.

Interactions affecting drug absorption

The influence of drug-drug and drug-food interactions affecting the absorption of orally administered medication is reviewed. Drug-drug interactions can be classified in terms of indirect effects by one drug on gastrointestinal tract physiology influencing the absorption of other drugs, or direct interactions involving altered pH, adsorption, absorption, or chelation. Most, but not all, drug-drug interactions result in reduced or delayed systemic drug availability. Drug-food interactions may result in reduced, delayed, or increased systemic drug availability. The absorption of only a small number of drugs is unaffected by concomitant food intake. The degree of interaction and whether it positively or negatively affects drug absorption depends on a number of factors including the physical and chemical nature of the drug, the formulation, the type of meal, and the time interval between eating and dosing. Mechanisms of drug-food interactions are not well characterised. They clearly involve both direct and indirect factors in a similar fashion to drug-drug interactions, but indirect factors probably predominate. Reduced or delayed drug absorption is generally attributed, at least in part, to delayed stomach-emptying due to food. Increased absorption may also result from delayed stomach-emptying facilitating greater drug dissolution before it passes from the stomach into the small intestine. Increased bioavailability of some drugs, e.g. propranolol, metoprolol and labetalol, may be related to reduced presystemic clearance. The potential clinical implications of drug-drug and drug-food interactions must be taken into account with oral medications in order to minimise variations in systemic drug availability and hence in clinical efficacy.

Influence of food intake on presystemic clearance of drugs

Many drugs have a low degree of oral bioavailability even though their gastrointestinal absorption is complete. This is because they undergo extensive presystemic metabolic transformation during the first passage of the drug through the gastrointestinal mucosa and the liver. In addition to effects on the absorption of some drugs, food intake has been found to influence the bioavailability of drugs with extensive presystemic metabolic clearance. Extensive presystemic clearance occurs commonly with compounds that are lipophilic bases, e.g. propranolol and amitriptyline, but rarely if ever with lipophilic acids, e.g. salicylic acid and penicillin, except for esters of such acids, e.g. acetylsalicylic acid (aspirin) and pivampicillin. While presystemic clearance of (esterified) acidic drugs is unaffected by food, concurrent food intake markedly reduces presystemic clearance, and thus enhances bioavailability, of several lipophilic bases. Among these are propranolol, metoprolol, labetalol, dixyrazine and hydralazine, which are presystemically metabolised by hydroxylation, glucuronidation and acetylation enzymes systems. In contrast, the bioavailability of lipophilic bases which undergo presystemic dealkylation (amitriptyline, codeine, dextropropoxyphene, prazosin, zimelidine) is unaffected by concurrent food intake. Food intake reduces presystemic clearance of hydralazine and propranolol when these drugs are administered in conventional rapid-release tablets but not when they are given in slow-release formulations. Likewise, coadministration of hydralazine reduces presystemic clearance of rapid-release but not slow-release propranolol. These and other observations favour the view that food may reduce presystemic clearance of (certain) lipophilic basic drugs via transient, complex effects on splanchnic-hepatic blood flow and/or shunt processes, and that the extent of this effect is influenced by the rate of drug delivery to the liver. In addition, these findings refute the notion that the reduced presystemic clearance results from (long-lasting) hepatic enzyme inhibition by some nutrient. On the other hand, repeated intake of specific nutrients (protein) and food contaminants (benzpyrene) can enhance presystemic drug clearance by enzyme induction. Thus, food may exert a dual effect on presystemic drug clearance. A complete evaluation of the influence of food on presystemic drug clearance necessitates bioavailability studies carried out following both single and repeated meals, including different kinds of food prepared by various cooking methods. The influence of food on the presystemic clearance of drugs is most likely to be clinically relevant with drugs having narrow therapeutic margins and/or steep dose-response curves.

Comparison between atenolol and nadolol in essential hypertension at rest and on exercise

1 The effects of 4 week treatment periods of once-daily atenolol 100 mg, nadolol 80 mg, nadolol 160 mg and placebo on resting and exercise heart rate and blood pressure were compared in a single-blind crossover trial in fifteen patients with essential hypertension. 2 Both atenolol and nadolol, irrespective of dose, reduced resting and exercise blood pressures to the same extent. 3 Nadolol caused a greater bradycardia both at rest and during exercise than did atenolol, thereby effecting a greater reduction in double-product. 4 During progressive treadmill exercise neither atenolol nor nadolol prevented a linear increase in heart rate and blood pressure which were parallel to, but at a lower level than, that produced by placebo. 5 In each individual patient the magnitude of the hypotensive effect produced by one drug was similar to that produced by the other. 6 All the treatment periods resulted in the same linear increase in the patients' perceived exertion scores during exercise despite marked differences in haemodynamic responses evoked by the beta-adrenoceptor blockers compared with placebo. 7 Neither atenolol or nadolol produced any significant change in peak expiratory flow rate compared with placebo.

Clinical pharmacokinetics of atenolol--a review

Atenolol is a hydrophilic betareceptor blocking drug, which is predominantly eliminated via the kidneys, only about 5% of the atenolol is metabolised by the liver. After oral administration atenolol is incompletely absorbed from the intestine, so about 50% of the beta blocker are finally biovailable. In plasma only 3% of atenolol are protein-bound. There exists a linear relationship between the atenolol plasma levels and the degree of beta blocking effect measured by inhibition of the exercise-induced tachycardia. No correlation was found between plasma levels of atenolol and blood pressure lowering activity of the drug. After oral administration elimination half life of atenolol is calculated from 6 to 9 h by different authors. In patients with impaired renal function elimination half life of atenolol gradually increases to values of 36 h in uraemic patients (glomerular filtration rate (GFR) less than 10 ml/min). Between GFR and atenolol plasma clearance as well as renal clearance a close significant correlation is described. Prolongation of elimination half life requires a dosage adjustment of atenolol in patients with renal failure. A marked interaction of atenolol is found when calcium or aluminium hydroxide are concurrently administered with the beta blocker whereas cimetidine does not influence atenolol kinetics.

Influence of food intake on the absorption and effect of glipizide in diabetics and in healthy subjects

The influence of a standardized breakfast on the single dose (5 mg) kinetics and effects of glipizide was examined in 9 healthy volunteers and in 14 diabetics not previously exposed to a sulfonylurea. In the volunteers, glipizide caused an increase in plasma insulin and a reduction in blood glucose both during continued fasting and when the drug was taken with the breakfast. Food intake did not influence the peak concentration, the elimination half-life or the bioavailability of the drug. However, food intake significantly delayed the absorption of glipizide by about 0.5 h. In the patients. glipizide produced a significant increase in plasma glucose in response to the meal. Starting at breakfast and for 45 min thereafter serum glipizide concentrations were significantly higher when the drug was taken 0.5 h before the meal, than when ingested concurrently with it. With the former treatment, the increase in plasma insulin occurred earlier and the blood glucose reduction was pronouncedly greater than with the latter treatment. As the absorption of glipizide may be delayed by concurrent breakfast, this may help to explain, why the administration of glipizide 0.5 h before breakfast led to a more appropriate relation between the serum concentration of the drug and the metabolic impact of the meal, thereby promoting more appropriate insulin release and better glucose disposition than after concurrent intake of the drug and breakfast.