Controlled release metoprolol formulations. A review of their pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension and ischaemic heart disease

Pediatric Beta Blocker Therapy: A Comprehensive Review of Development and Genetic Variation to Guide Precision-Based Therapy in Children, Adolescents, and Young Adults

Beta adrenergic receptor antagonists, known as beta blockers, are one of the most prescribed medications in both pediatric and adult cardiology. Unfortunately, most of these agents utilized in the pediatric clinical setting are prescribed off-label. Despite regulatory efforts aimed at increasing pediatric drug labeling, a majority of pediatric cardiovascular drug agents continue to lack pediatric-specific data to inform precision dosing for children, adolescents, and young adults. Adding to this complexity is the contribution of development (ontogeny) and genetic variation towards the variability in drug disposition and response. In the absence of current prospective trials, the purpose of this comprehensive review is to illustrate the current knowledge gaps regarding the key drivers of variability in beta blocker drug disposition and response and the opportunities for investigations that will lead to changes in pediatric drug labeling.

Physiologically Based Pharmacokinetic Modeling of Metoprolol Enantiomers and α-Hydroxymetoprolol to Describe CYP2D6 Drug-Gene Interactions

The beta-blocker metoprolol (the sixth most commonly prescribed drug in the USA in 2017) is subject to considerable drug–gene interaction (DGI) effects caused by genetic variations of the CYP2D6 gene. CYP2D6 poor metabolizers (5.7% of US population) show approximately five-fold higher metoprolol exposure compared to CYP2D6 normal metabolizers. This study aimed to develop a whole-body physiologically based pharmacokinetic (PBPK) model to predict CYP2D6 DGIs with metoprolol. The metoprolol (R)- and (S)-enantiomers as well as the active metabolite α-hydroxymetoprolol were implemented as model compounds, employing data of 48 different clinical studies (dosing range 5–200 mg). To mechanistically describe the effect of CYP2D6 polymorphisms, two separate metabolic CYP2D6 pathways (α-hydroxylation and O-demethylation) were incorporated for both metoprolol enantiomers. The good model performance is demonstrated in predicted plasma concentration–time profiles compared to observed data, goodness-of-fit plots, and low geometric mean fold errors of the predicted AUC_last (1.27) and C_max values (1.23) over all studies. For DGI predictions, 18 out of 18 DGI AUC_last ratios and 18 out of 18 DGI C_max ratios were within two-fold of the observed ratios. The newly developed and carefully validated model was applied to calculate dose recommendations for CYP2D6 polymorphic patients and will be freely available in the Open Systems Pharmacology repository.

Effect of Roux-en-Y gastric bypass on the bioavailability of metoprolol from immediate and controlled release tablets: a single oral dose study before and after surgery

Objective

Roux-en-Y gastric bypass (RYGB) surgery induces major changes in the gastrointestinal tract that may alter the pharmacokinetics of orally administered drugs. Results from pharmacokinetic studies are sparse. This study aimed to investigate the effect of RYGB on the bioavailability of metoprolol from immediate release (IR) and controlled release (CR) tablets in female patient volunteers before and after surgery.

Methods

An explorative, two-phase, single oral dose pharmacokinetic study of metoprolol in female patients undergoing RYGB was carried out. The dose was administered twice in each patient, 1 month before and 6 months after surgery. After intake of either 100 mg of metoprolol IR or CR tablet serum concentration-time profiles of metoprolol were determined. The endpoint was the ratio of AUC_after/AUC_before of metoprolol.

Results

Twelve patients were included in the study (metoprolol IR: 7; metoprolol CR: 5). After intake of a metoprolol IR tablet major intraindividual and interindividual differences for area under the serum concentration versus time curve (AUC) of metoprolol before and after surgery were observed (range ratio AUC_{0-10 hours after}/AUC_{0-10 hours before}: 0.74-1.98). For metoprolol CR tablets a significant reduction in bioavailability of metoprolol was observed after surgery (range ratio AUC_{0-24 hours after}/AUC_{0-24 hours before}: 0.43-0.77).

Conclusion

RYGB may influence the bioavailability of metoprolol from an IR tablet. The magnitude of changes in bioavailability after RYGB requires close monitoring of patients using metoprolol IR tablets and dose adjustment if deemed necessary. RYGB clearly reduces the bioavailability of metoprolol from a CR tablet. After RYGB clinicians may consider to increase the dose according to clinical response.

Comparison of bisoprolol to a metoprolol CR/ZOK tablet for control of heart rate and blood pressure in mild-to-moderate hypertensive patients: the CREATIVE study

This open-label study investigated the long action of bisoprolol compared with metoprolol CR/ZOK for controlling the mean dynamic heart rate (HR) and blood pressure (BP) in patients with mild-to-moderate primary hypertension. Patients from seven centers in China were treated with either bisoprolol 5 mg or metoprolol CR/ZOK 47.5 mg once daily for 12 weeks. The primary end points were the mean dynamic HR reduction and the mean dynamic diastolic BP (DBP) control in the last 4 h of the treatment period. Secondary end points included ambulatory monitoring of the BP and HR, safety and compliance. A total of 186 patients, with 93 patients in each group, were enrolled and analyzed. In the last 4 h of the treatment period, patients receiving bisoprolol demonstrated a significantly greater reduction in the mean dynamic HR compared with patients receiving metoprolol CR/ZOK (least squares means (LSmeans) of difference: -3.79 b.p.m.; 97.5% confidence interval (CI): -7.45, -0.14; P=0.0202). Furthermore, in the last 4 h of the treatment period, bisoprolol demonstrated non-inferiority vs. metoprolol CR/ZOK in lowering the mean dynamic DBP (LSmeans of difference: -1.00; 97.5% CI: -4.79, 2.78; P=0.5495). Bisoprolol further significantly lowered the 24-h mean ambulatory, mean daytime and mean nighttime HR. The overall adverse event rate was similar between the two groups. Noncompliance was reported in 3 (3.53%) and 6 (7.32%) patients in the bisoprolol and metoprolol CR/ZOK groups, respectively. In conclusion, bisoprolol provided superior dynamic HR reduction and non-inferior dynamic BP reduction vs. metoprolol CR/ZOK in patients with mild-to-moderate hypertension. No new safety concerns were found.

Pharmacodynamics ofβ-Blockers in Heart Failure: Lessons from the Carvedilol Or Metoprolol European Trial

Heart failure is a growing public health problem in the United States, and the approach to the treatment of heart failure has undergone a radical transformation in the past decade. The use of β-blocker therapy in heart failure patients is now widely recommended, based on evidence from large-scale clinical trials demonstrating that bisoprolol, carvedilol, and extended-release metoprolol succinate significantly reduce morbidity and mortality in patients with heart failure. Although these agents appear to provide similar benefits, the question remains whether pharmacologic differences among them could translate to differences in clinical outcomes. The Carvedilol Or Metoprolol European Trial (COMET) compared nonselective blockade of the β1-/β2-/α1-adrenergic receptors with carvedilol versus selective β1-blockade with immediate-release metoprolol tartrate in patients with chronic heart failure. The trial found that carvedilol significantly reduced all-cause mortality compared with immediate-release metoprolol tartrate, although there were no differences in hospitalizations. Herein we review the pharmacokinetics and pharmacodynamics of metoprolol and carvedilol. In doing so, several issues regarding the design of COMET are identified that could alter the interpretation of the results of this trial. These include the choice of dose and dosage regimen of immediate-release metoprolol tartrate, a dosage form that has never been shown to reduce mortality in patients with heart failure. Additional studies are needed to fully understand whether there are any advantages of selective versus nonselective adrenergic blockade and whether there are any clinically meaningful differences in effectiveness between β-blockers with proven benefit in the management of chronic heart failure. The results of COMET demonstrate that all β-blockers and dosage forms are not interchangeable when prescribed for heart failure. Clinicians should choose only those agents (and dosage forms) that have been proven to reduce mortality in this patient population.

In Silico comparison between metoprolol succinate and bisoprolol on 24-hour systolic blood pressures

Objective

To compare the effects of bisoprolol and metoprolol CR/ZOK (metoprolol succinate controlled release) on systolic blood pressure (bp_sys) over a 24-h period in an in silico model.

Methods

On the basis of the observed data from ambulatory blood pressure measurements (ABPM), a model with an appropriate distribution and correlation structure was derived for simulation of 24-h bp_sys patterns during treatment with commonly studied doses, assumed to be equipotent, of bisoprolol and metoprolol CR/ZOK. Input into the simulations was aligned with the available data on the diurnal efficacy and pharmacology profiles of these substances. The validity of the model was tested in a bootstrap model.

Results

The simulation model reproduced the observed data with high congruence (p = 1.0). The mean 24-h bp_sys values did not significantly differ between the two simulated groups (estimated overall change in bp_sys [∆bp_sys] for metoprolol versus bisoprolol = 2.7 mmHg [95 % confidence interval −0.3 to 5.7 mmHg]; p = 0.08). There were clear diurnal differences, with bisoprolol being more effective earlier and metoprolol CR/ZOK being more effective later in the 24-h day. A validity test with 100 repeated samples gave an overall mean group difference of 1.4 ± 3.59 mmHg (p = 0.63 relative to simulation).

Conclusion

In a robust model for the simulation of 24-h ABPM, comparisons between bisoprolol and metoprolol CR/ZOK indicate a comparable overall blood pressure-lowering effect but different diurnal patterns, consistent with the pharmacokinetics of the two drugs. This difference may be of clinical relevance, given the recognized diurnal pattern of cardiovascular events.

The effect of metoprolol alone and combined metoprolol-felodipin on the digital microcirculation of patients with primary Raynaud's syndrome

OBJECTIVES

Calcium channel inhibitors have beneficial impact on microcirculation, but beta-blocker effect is controversial. Clinicians still do not agree on beta-blocker combination with other treatments in the management of impaired microcirculation. The aim of the present study was to describe the effects of beta-blocker metoprolol monotherapy and combined with calcium channel inhibitor felodipin on digital microcirculation in primary Raynaud's syndrome.

METHODS

We enrolled in this study 46 patients suffering from both hypertension and primary Raynaud's syndrome. Fifteen patients were treated with beta-blocker monotherapy (metoprolol), 13 received combined beta-blocker and calcium channel blocker therapy (felodipin and metoprolol), while 18 patients without any medications served as controls. Measurement of digital microcirculation was carried out with laser Doppler scanner.

RESULTS AND CONCLUSIONS

Our investigation concludes that the concurrent administration of beta-blockers with calcium channel inhibitors positively reduces symptoms in patients suffering from Raynaud's syndrome.

Influence of splitting on dissolution properties of metoprolol tablets

The objective of this work was to compare several profiles of dissolution data for metoprolol controlled release tablet formulations in order to identify possible changes in dissolution profiles of whole and scored tablets. Adequate design of score lines (on one or both sides) as well as the technology of preparation of tablet mixtures ensure forming a score line of adequate thickness, shape, size, curvature. According to the obtained results, this type of extended release formulation is eligible for splitting and use in therapy either as a whole or scored tablets.

Metoprolol succinate combination in the treatment of hypertension

Metoprolol is a selective beta(1)-adrenergic antagonist extensively used since 1975. Metoprolol has proven its efficacy in reducing cardiovascular events and mortality in patients with hypertension and coronary heart disease. A recently developed controlled release/ extended-release formulation of metoprolol succinate was designed to provide relatively constant metoprolol plasma concentrations and beta(1)-blockade while retaining the convenience of once daily administration. A 100-mg metoprolol controlled/extended-release tablet contains 95 mg of metoprolol succinate and is considered to have equivalent activity of 100 mg metoprolol tartrate. After ingestion, the tablet disintegrates into individual pellets and each pellet acts as a diffusion cell releasing the drug at a relatively constant rate over a period of approximately 20 hours. The aim of this review was to determine the pharmacokinetic and pharmacodynamic properties of metoprolol succinate and to apply those properties in combination with other drugs mainly diuretics in the treatment of hypertension.

The use of metoprolol CR/XL in the treatment of patients with diabetes and chronic heart failure

About 5 million Americans suffer from heart failure. Given the correlation of heart failure with age and the rising life expectancy, the prevalence of heart failure continues to increase in the general population. Sympathetic stimulation intensifies with progressive heart failure. The rationale to use β-blockers in individuals with impaired myocardial function is based on experimental evidence supporting the notion that prolonged α- and β-adrenergic stimulation leads to worsening heart failure. Until recently, safety concerns have precluded the use of β-blockers in patients with diabetes and heart failure. However, several large, randomized, placebo-controlled clinical trials such as Metoprolol Randomized Intervention Trial in Congestive Heart Failure (MERIT-HF) have shown that β-blockers can be safely used in patients with diabetes and heart failure. Moreover, β-blockers significantly improved morbidity and mortality in this population. Based on this evidence, it is now recommended to add β-blockers such as metoprolol CR/XL with an escalating dosage regimen to the treatment of patients with symptomatic heart failure who already are receiving a stable medical regimen including angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, diuretics, vasodilators, or digitalis.

Benefits and harms of perioperative beta-blockade

Cardiac events in patients undergoing surgery may have serious consequences for both short- and long-term postoperative prognosis. Recently conducted trials have not demonstrated beneficial effects of perioperative beta-blockade, although originally small trials with methodological flaws did suggest this. We evaluate the evidence for using perioperative beta-blockade in both cardiac and non-cardiac surgery, and conclude that there is no statistically significant effect on mortality and insufficient evidence for a reduction of the incidence of mycocardial infarction in meta-analyses of all randomized trials. However, confidence intervals of the intervention effects in the meta-analyses are wide, leaving room for both benefits and harms. The largest observational study performed suggests that perioperative beta-blockade is associated with higher mortality in patients with low cardiac risk or diabetes, and with lower mortality in patients with high cardiac risk undergoing non-cardiac surgery. Larger randomized trials are needed to determine dosage, optimal duration, and safety of therapy, and to identify populations in whom-and how-perioperative beta-blockade may be beneficial.

Determination of metoprolol, and its four metabolites in dog plasma

Metoprolol and its metabolites alpha-hydroxymetoprolol, O-desmethylmetoprolol, metoprolol acid and deaminated metoprolol were quantified in dog plasma using an isocratic high-performance liquid chromatographic method (with a BetaBasic Cyano column) with fluorescence detection. A solid phase extraction technique (Oasis HLB, Waters) was used to extract metoprolol and its four metabolites from dog plasma with high recovery rates. The method was shown to be sensitive and reproducible and was used to determine the pharmacokinetic profile of metoprolol in dog. To the best of our knowledge, this is the only method that can extract and analyze metoprolol and its four metabolites in a single assay.

Influence of input rate on the stereospecific and nonstereospecific first pass metabolism and pharmacokinetics of metoprolol extended release formulations

The purpose of this study was to examine the influence of input rate on the stereoselective and nonstereoselective pharmacokinetics of metoprolol, alpha-hydroxymetoprolol, and its acid metabolite. Extended release formulations (100 mg) of metoprolol with varying release rates (e.g., slow (S), moderate (M), and fast (F)) and an oral solution (OS, 50 mg) were administered to normal, healthy extensive metabolizers. Serial blood samples were collected over 48 h, plasma was obtained, and subsequently analyzed by a validated HPLC method with fluorescence detection. The mean T(max) of metoprolol after the S, M, F (4.43, 4.00, 3.14 h, respectively) was found to be different ( P < 0.05) as compared to the OS (2.07 h). The ratio of alpha-hydroxymetoprolol/metoprolol was higher for the OS (1.26) vs. the S, M, and F (1.02, 0.96, 0.99). The S/R enantiomer ratios of the concentration for metoprolol, ACMB, and alpha-hydroxmetoprolol were calculated at each time point and showed a significant difference ( P < 0.05) in the absorption phase (1-4 h) vs. terminal phase (8-16 h) for fast input (solution and fast extended release formulations). Based on these results, it would appear that input rate influences the pharmacokinetics of metoprolol, its metabolites, and their enantiomers.

Metoprolol CR/XL in the Treatment of Chronic Heart Failure

Metoprolol CR/XL (metoprolol succinate extended-release tablets) is a beta1-selective agent that improved survival and reduced hospitalization among patients with New York Heart Association class II-IV heart failure in a randomized trial. Metoprolol CR/XL differs from conventional metoprolol tartrate with respect to pharmacokinetic and pharmacodynamic properties that may be clinically important in patients with heart failure. A thorough patient evaluation should be performed to determine optimal dosage and titration of this drug, as with any beta-blocker, and to assess the potential for drug-drug or drug-disease interactions. By applying knowledge of drug-specific characteristics and designing therapy for each individual patient, improvement in patient outcomes can be realized with metoprolol CR/XL.

Differential effects of beta-blockers in patients with heart failure: A prospective, randomized, double-blind comparison of the long-term effects of metoprolol versus carvedilol

BACKGROUND

Both metoprolol and carvedilol produce hemodynamic and clinical benefits in patients with chronic heart failure; carvedilol exerts greater antiadrenergic effects than metoprolol, but it is unknown whether this pharmacological difference results in hemodynamic and clinical differences between the 2 drugs.

METHODS AND RESULTS

We randomized 150 patients with heart failure (left ventricular ejection fraction </=0.35) to double-blind treatment with either metoprolol or carvedilol. When compared with metoprolol (124+/-55 mg/d), patients treated with carvedilol (49+/-18 mg/d) showed larger increases in left ventricular ejection fraction at rest (+10.9+/-11.0 versus +7.2+/-7.7 U, P=0.038) and in left ventricular stroke volume and stroke work during exercise (both P<0. 05) after 13 to 15 months of treatment. In addition, carvedilol produced greater decreases in mean pulmonary artery pressure and pulmonary wedge pressure, both at rest and during exercise, than metoprolol (all P<0.05). In contrast, the metoprolol group showed greater increases in maximal exercise capacity than the carvedilol group (P=0.035), but the 2 drugs improved symptoms, submaximal exercise tolerance, and quality of life to a similar degree. After a mean of 23+/-11 months of follow-up, 21 patients in the metoprolol group and 17 patients in the carvedilol group died or underwent urgent transplantation.

CONCLUSIONS

The present study demonstrates that during long-term therapy, carvedilol improves cardiac performance to a greater extent than metoprolol when administered to patients with heart failure in the doses shown to be effective in clinical trials. These differences were likely related to a greater antiadrenergic activity of carvedilol.

Felodipine/metoprolol: a review of the fixed dose controlled release formulation in the management of essential hypertension

The main objective of fixed dose combination therapy for hypertension is to improve blood pressure (BP) control with lower, better tolerated dosages of 2 antihypertensives rather than higher dosages of a single agent. Felodipine and metoprolol lower BP via different, but complementary, mechanisms and controlled release formulations of these 2 drugs are available as a fixed dose combination, felodipine/metoprolol. In clinical trials in patients with hypertension, felodipine/metoprolol was significantly more effective than placebo and the respective monotherapies administered at the same dosages. Mean BP was reduced to < 155/90 mm Hg in patients treated with combination therapy and controlled in approximately 70% of patients. In one study that titrated dosages to effect, fewer felodipine/metoprolol than felodipine or metoprolol monotherapy recipients required dosage increases to achieve BP control (45 vs 60 and 67%, respectively). Data from double blind comparative studies show that the antihypertensive efficacy of felodipine/metoprolol 5 to 10/50 to 100 mg/day is significantly greater than that of enalapril monotherapy or captopril plus hydrochlorothiazide and equivalent to nifedipine/atenolol and amlodipine. In comparisons with enalapril, fewer felodipine/metoprolol than enalapril recipients required dosage titration to achieve BP control. Compared with amlodipine, felodipine/metoprolol significantly reduced mean 24-hour average BP (8.9/5.5 vs 14.4/9.5 mm Hg after 6 weeks; p < 0.001). Both treatments preserved diurnal rhythm. Long term follow-up studies show that the antihypertensive effect of felodipine/metoprolol occurs mostly during the first month of treatment with small additional decreases in BP being observed in the second and third months, and a relatively constant effect thereafter. According to a validated questionnaire, quality of life was relatively similar during 12 weeks treatment with felodipine/metoprolol, enalapril or placebo. In a retrospective pharmacoeconomic analysis conducted in Sweden, felodipine/metoprolol was more cost effective than enalapril as initial treatment for hypertension. Peripheral oedema, headache and flushing were the most commonly reported adverse events with felodipine/metoprolol and felodipine monotherapy, whereas dizziness, fatigue, headache and respiratory infection were more frequent with metoprolol monotherapy. Dose-dependent adverse events such as oedema may occur less often in patients taking lower dosages in combination than in those taking higher dosages of felodipine monotherapy. Thus, patients with hypertension treated with felodipine/metoprolol experience greater control of BP, with less need for dosage titration, than those treated with felodipine, metoprolol or enalapril monotherapy. Importantly this greater efficacy does not appear to be associated with a higher incidence of adverse events relative to monotherapy. Additionally, in short term studies felodipine/metoprolol had a similar (minimal) effect on QOL to enalapril monotherapy but was more cost effective.

Antianginal effects of YM430, a novel calcium entry-blocking and beta-adrenoceptor-blocking agent in several experimental angina models

1. We evaluated the antianginal effects of YM430 in several experimental models in vitro and in vivo. 2. In isolated dog coronary artery, YM430 (10(-8)-10(-6) M) inhibited 3,4-diaminopyridine-induced rhythmic contractions with an IC50 value of 59.2 nM. 3. In anesthetized rats, YM430 (10-100 mg/kg PO) inhibited arginine vasopressin-induced ST-segment depression with an IC50 value of 36.6 mg/kg PO. 4. In anesthetized dogs, YM430 (0.3 mg/kg IV) significantly inhibited ST-segment elevation induced by coronary artery occlusion. 5. These findings suggest that YM430 may be of value in the treatment of various types of angina pectoris such as variant and stable angina.

The effect on 24 h blood pressure control of an angiotensin converting enzyme inhibitor (perindopril) administered in the morning or at night

OBJECTIVE

To determine the clinic and ambulatory blood pressure when the same dose of perindopril (4 mg) is administered in the morning (0900 h), or at night (2100 h), in particular, to determine whether the early morning blood pressure rise, the duration of effect and the pattern of response differed.

METHODS

Twenty male patients with diastolic blood pressure 95-110 mmHg when seated and 24 h mean ambulatory diastolic blood pressure > 85 mmHg after 4 weeks' placebo were allocated randomly to be administered 4 mg perindopril at 0900 h or at 2100 h. Clinic blood pressure (with the patient seated and erect) was measured 2 and 4 weeks after the therapy had been started and ambulatory blood pressure monitoring with a SpaceLabs device was performed for 26 h during week 4. The patients then crossed over to the other time of dosage and the measurements were repeated. The study was conducted from a hospital clinic.

RESULTS

The clinic analysis concerned all 20 patients but the ambulatory analysis concerned 18 patients because the ambulatory blood pressure monitor data sets were inadequate for two patients. Compliance was high (97 +/- 3%), with a suggestion that it was better with the 0900 h dose. Clinic blood pressure (with the patient seated and erect) was lower under both regimes and the blood pressure with night-time administration of perindopril tended to be lower than that with daytime administration (P = 0.05-0.10). Twenty-four-hour mean, daytime and night-time means were lower with both doses than they were with placebo and did not differ. Both regimes reduced the early morning peak blood pressure rise and the effect tended to be greater with the 2100 h dose (P = 0.05-0.10). The 0900 h dose had an effect that persisted for > 24 h but the effect of the 2100 h dose had dissipated 18 h after the dose. There was no excessive night-time fall in blood pressure with the 2100 h dose. The trough : peak ratio with the 0900 h dose was 0.86 for systolic and 0.70 for diastolic blood pressure.

CONCLUSION

The early morning blood pressure rise is reduced more when 4 mg perindopril is administered at 2100 h. However, the 2100 h dose regime does not reduce blood pressure over 24 h whereas 24 h control is achieved with the 0900 h dose. In clinical practice the 2100 h dose would have been titrated to the next dose range in more patients. This study indicates that the response profile obtained with an angiotensin converting enzyme inhibitor cannot be transformed from one dose time to another automatically and that chronobiology has important effects on a drug's action.

Effects of 100 mg of controlled-release metoprolol and 100 mg of atenolol on blood pressure, central nervous system-related symptoms, and general well being

Central nervous system (CNS)-related symptoms and quality of life during treatment with controlled-release (CR) metoprolol and a standard formulation of atenolol were compared in a double-blind crossover study in 60 patients with mild to moderate hypertension. After a 4-week placebo run-in period, each beta 1-adrenoceptor blocker was administered at a dosage of 100 mg once daily for 6 weeks. Quality of life was assessed regularly during the active treatment phases by use of two standardized self-administered questionnaires, the minor symptom evaluation (MSE) profile, and the psychologic general well-being (PGWB) index. Both questionnaires have previously been shown to be effective in detecting CNS symptoms and changes in well being produced by beta-blockers. Blood pressure and heart rate were monitored to assess the antihypertensive efficacy of the two drugs. Metoprolol CR and atenolol produced equivalent, clinically effective reductions in systolic and diastolic blood pressures measured 24 hours after administration. The drugs were found to exert similar effects on general well being, as assessed by the PGWB index, and there were no significant differences between the two treatments with regard to the three dimensions of the MSE profile, contentment, vitality, and sleep. Thus, at equivalent antihypertensive dosages, metoprolol CR and atenolol are clinically comparable with regard to the degree of CNS-related symptoms produced and effects on general well being. Because these agents differ markedly in lipophilicity, other factors, such as beta 1-selectivity/nonselectivity, may be more important determinants of whether these subjective symptoms occur during therapy with beta-blockers.