Metoprolol-controlled release, zero order kinetics

Beta-blockers for Atherosclerosis Prevention: a Missed Opportunity?

PURPOSE OF REVIEW

Current guidelines for the management of arterial hypertension endorse β-adrenergic receptor blocking agents (beta-blockers, BBs) as being particularly useful for hypertension in specific situations such as symptomatic angina, tachycardia, post-myocardial infarction, heart failure with reduced ejection fraction (HFrEF), and as an alternative to angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) in hypertensive women planning pregnancy or at least of child-bearing potential. One of the most common uses of BBs is in patients with a recent myocardial infarction, with or without hypertension. Although this one use is specifically in a setting of atherosclerotic cardiovascular disease (ASCVD), it is not primarily for atheroprevention, but rather for cases with impaired systolic function, and it is intended primarily to lessen adverse cardiac remodeling and worsening of congestive heart failure (CHF). The BB class consists of numerous agents which differ widely in pharmacologic properties and physiologic effects. These differences include selectivity for β-adrenergic receptors and their subtypes, hydro- or lipophilicity, effects on blood pressure and heart rate, influence on lipoprotein and glucose metabolism, and direct impact on the artery wall, including platelet reactivity, endothelial function, infiltration of inflammatory cells and on inflammation per se, and on smooth muscle cell proliferation. Importantly, BBs are not commonly used for prevention of atherosclerosis or ASCVD per se. Many studies of early-generation BBs showed adverse effects on lipoprotein levels and metabolism of glucose and insulin and thus discouraged their use in atheroprevention. Nevertheless, newer BBs often have neutral or favorable metabolic effects on these important factors in ASCVD pathophysiology, and recent scientific studies now document direct beneficial effects of BBs on the artery wall. This document reviews both types of newer data, not only to encourage consideration of BB treatment to reduce ASCVD in the present, but also to call for future research to better explore the clinical settings in which BBs may be proven to have additional benefit in preventing ASCVD when added to the better-established treatments for dyslipidemia and diabetes.

RECENT FINDINGS

Relatively recent publications have clarified the diversity among BBs regarding adverse, neutral, or favorable effects on lipoproteins (especially triglycerides (TG) and low-density lipoprotein (LDL)) and on glucose/insulin metabolism. Specifically, the newer BBs (metoprolol ER, carvedilol ER, bisoprolol, and nebivolol) are now documented to be metabolically beneficial. These new data are complex but instructive regarding potential mechanisms of the diverse effects of various BBs on metabolism. Further and more importantly, these new data refute the traditional, but now outmoded, concept that BBs are universally harmful metabolically and therefore must be used sparingly, if at all, for atheroprevention. Recent studies have also reported exciting new data regarding how certain BBs can reduce platelet adhesion and improve the function of the major cell types in the artery wall, including the endothelium, macrophages, and smooth muscle cells. Specifically, BBs can improve endothelial function by enhancing arterial vasodilation and by reducing monocyte adhesion and transmigration. Further, BBs can decrease numbers and activity of inflammatory cells, including decreasing proliferation of smooth muscle cells and their transformation into inflammatory cells. These data help with the crucial step of distinguishing among available BBs regarding their likely overall arterial effects, whether to accelerate or prevent the development of atherosclerosis. In this regard, there is even some limited published information beyond these intermediary steps, going directly to the clinically more important endpoints of atherosclerosis and ASCVD events. The negative metabolic effects observed with the use of traditional/earlier generations of BBs have discouraged use of any BBs to prevent ASCVD. These adverse effects are not seen, however, with newer BBs. Thus, BBs continue to be a useful component of combination regimens not only in the treatment of arterial hypertension, heart failure, and arrhythmia, but also potentially in the prevention of atherosclerosis and ASCVD. Despite this exciting potential, further research is greatly needed to better establish the possible benefits of the most promising BBs as they might work in combination with other better-established atheropreventive agents. Specifically, there is a need for randomized, prospective, cardiovascular outcome trials (CVOTs) in high-risk patients, adding a BB to background LDL-lowering (statins, etc.), TG-lowering (specifically icosapent ethyl, which reduces ASCVD in patients with high TG, although apparently not via TG-lowering), and/or anti-diabetic (sodium glucose transport-2 inhibitors, SGLT2i, and glucagon-like protein-1 receptor agonists, GLP1-RA) treatments, as indicated in a given subject population.

Carboxylic Acid Counterions in FDA-Approved Pharmaceutical Salts

Salification is one of the powerful and widely employed approaches to improve the biopharmaceutical properties of drugs. The FDA's eighty-year trajectory of new drug approvals depicts around one-third of the drugs clinically used as their pharmaceutical salts. Among various cationic and anionic counterions used in FDA-approved pharmaceutical salts, the carboxylic acids have significantly contributed. A total of 94 pharmaceutical salts discovered during 1943-2020 comprises carboxylic acids as counterions with a major contribution of acetate, maleate, tartrate, fumarate, and succinate. Hydrocodone tartrate is the first FDA-approved carboxylate salt approved in 1943. Overall, the analysis shows that fifteen carboxylic acid counterions are present in FDA-approved pharmaceutical salts with a major share of acetate (18 drugs). This review provides an account of FDA-approved carboxylate salts from 1939 to 2020. The decade-wise analysis indicates that 1991-2000 contributed a maximum number of carboxylate salts (24) and least (3) in 1939-1950. The technical advantage of carboxylate salts over free-base or other counterions is also discussed. Graphical Abstract.

Medication adherence during laboratory workup for primary aldosteronism: pilot study

PURPOSE

Current hypertension guidelines stipulate that all incompatible medications be stopped before performing laboratory screening for aldosteronism, but patient adherence is unclear. We measured plasma drug concentrations to determine drug adherence and potential drug bias during biochemical tests.

PATIENTS AND METHODS

Plasma concentrations of 10 antihypertensive drugs were quantified by mass spectrometry in 24 consecutive ambulatory patients with uncontrolled hypertension routinely evaluated for aldosteronism. Drug screening was done before (first visit), and on the day of biochemical tests (second visit) after stopping all incompatible medications. Concentrations above those expected at trough dosing interval defined same-day dose intake.

RESULTS

On the first and second visits, 76% vs 77% of prescribed antihypertensive doses could be verified in plasma. A total of 33% of patients were found to be nonadherent and showed divergent plasma drug results relative to prescriptions (21% drugs not detected/13% unprescribed drugs found) on first visit, 25% on the second (0%/25%), and 46% for both. A total of 21% used medication incompatible with the biochemical tests on the second visit. Moreover, 17% of drug concentrations were below expected trough levels on the first vs 15% on the second visit. This analysis revealed additional four (17%) vs three (13%) nonadherent patients who failed same-day dose intake and remained undetected by qualitative drug tests.

CONCLUSION

Nonadherence was frequent during laboratory evaluations for aldosteronism advocating cautious interpretation of results. A multicenter study is desirable to set the stage for new screening protocols that should incorporate also incentives and checks of drug adherence.

Pharmacokinetic evaluation of guar gum-based three-layer matrix tablets for oral controlled delivery of highly soluble metoprolol tartrate as a model drug

The objective of the present study is to carry out pharmacokinetic evaluation of oral controlled release formulation (guar gum-based three-layer matrix tablets) containing highly soluble metoprolol tartrate as a model drug. Six healthy volunteers participated in the study, and a two-way crossover design was followed. The plasma concentration of metoprolol tartrate was estimated by reverse-phase HPLC. The pharmacokinetic parameters were calculated from the plasma concentration of metoprolol tartrate versus time data. The delayed T(max) lower C(max) decreased K(a) unaltered bioavailability and prolonged t(1/2) indicated a slow and prolonged release of metoprolol tartrate from guar gum three-layer matrix tablets in comparison with the immediate release tablet dosage form. The results of the study indicated that guar gum three-layer matrix tablets were able to provide oral controlled delivery of highly water-soluble drug such as metoprolol tartrate in humans.

A three-layer guar gum matrix tablet for oral controlled delivery of highly soluble metoprolol tartrate

The objective of the study is to design oral controlled drug delivery systems for highly water-soluble drugs using guar gum as a carrier in the form of a three-layer matrix tablet. Metoprolol tartrate was chosen as a model drug because of its high water solubility. Matrix tablets containing either 30 (M1), 40 (M2) or 50% (M3) of guar gum were prepared by wet granulation technique using starch paste as a binder. Three-layer matrix tablets of metoprolol tartrate were prepared by compressing on both sides of guar gum matrix tablet granules of metoprolol tartrate M1, M2 or M3 with either 50 (TL1M1, TL1M2 or TL1M3) or 75 mg (TL2M1, TL2M2 or TL2M3) of guar gum granules as release retardant layers. Both the matrix and three-layer matrix tablets were evaluated for hardness, thickness, drug content uniformity, and subjected to in vitro drug release studies. The amount of metoprolol tartrate released from the matrix and three-layer matrix tablets at different time intervals was estimated by using a HPLC method. Matrix tablets of metoprolol tartrate were unable to provide the required drug release rate. However, the three-layer guar gum matrix tablets (TL2M3) provided the required release rate on par with the theoretical release rate for metoprolol tartrate formulations meant for twice daily administration. The three-layer guar gum matrix tablet (TL2M3) showed no change either in physical appearance, drug content or in dissolution pattern after storage at 40 degrees C/75% RH for 6 months. The FT-IR study did not show any possibility of metoprolol tartrate/guar gum interaction with the formulation excipients used in the study. The results indicated that guar gum, in the form of three-layer matrix tablets, is a potential carrier in the design of oral controlled drug delivery systems for highly water-soluble drugs such as metoprolol tartrate.

A novel approach for constant rate delivery of highly soluble bioactives from a simple monolithic system

A novel monolithic drug delivery system for highly water-soluble bioactive agents to follow pH-independent zero-order kinetics is described. The system utilizes a hydrophilic gel-based swellable polymeric material (polyethylene oxide), a model drug (metoprolol tartrate, 100% water soluble at 25 degrees C) and different electrolytes, such as sodium carbonate and/or pentasodium tripolyphosphate. Based on the induction of in situ intra-gel chemical reactions between different ionic species, drug and polymer, a heterogeneous structure manifested as 'peripheral boundary stiffening,' is accomplished. The consequence of these interactions essentially include the development of gradient-controlled matrix swelling as elucidated through textural profiling, which may contribute to inhibition of drug solubility and its outward diffusion. Analysis of textural profiles and photomicroscopy distinctly provides information on the disposition of peripheral boundary densification for the electrolyte-containing matrices. Electrolytic conductivity measurements performed with the simultaneous analysis of matrix swelling showed that sodium carbonate forms a highly reactive matrix within the first 3 h of medium penetration. On the other hand, larger molecules such as pentasodium tripolyphosphate maintain a constant conductivity level, which may be related to its lower solubility and diffusion in comparison to sodium carbonate. Based on model fitting and statistical analysis, it is shown that drug release kinetics were adequately described by M(t)/M(infinity)=k(0)t, with zero-order release rate constant k(0) of 0.054 h(-1). This novel approach in formulation development could potentially be used for constant rate delivery of highly soluble bioactive agents over an extended period for specific biopharmaceutical needs.

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

Conventional formulations of metoprolol have become well established in cardiovascular medicine and are particularly useful in the management of hypertension and ischaemic heart disease. Recently developed controlled release metoprolol delivery systems (metoprolol CR/ZOK and metoprolol OROS) were designed to overcome the drug delivery problems of matrix-based sustained release forms by releasing the drug at a relatively constant rate over a 24-hour period, and thus producing sustained and consistent metoprolol plasma concentrations and beta 1-blockade while retaining the convenience of once daily administration. Clinically and statistically significant reductions in blood pressure have been observed with metoprolol CR/ZOK and metoprolol OROS 24 hours after administration in mildly or moderately hypertensive patients. Studies in patients with mild to moderate hypertension have demonstrated that a similar or higher percentage of patients achieved a goal response with metoprolol CR/ZOK compared with matrix-based sustained release formulations of metoprolol, or conventional atenolol or bisoprolol, while metoprolol OROS achieved an equal or greater response rate compared with conventional or matrix-based sustained release metoprolol preparations. In patients with stable effort angina pectoris, once daily administration of metoprolol CR/ZOK provided at least equal antianginal efficacy as conventional metoprolol in divided doses, while metoprolol OROS reduced the mean number of anginal attacks by the same margin as atenolol. Controlled release metoprolol formulations have been well tolerated in clinical trials. Metoprolol CR/ZOK was associated with a similar or lesser degree of adverse effects related to the central nervous system compared with atenolol or long acting propranolol. Metoprolol CR/ZOK also demonstrated less pronounced beta 2-mediated bronchoconstrictor effects than atenolol in asthmatics, and less general fatigue and leg fatigue in healthy subjects. Metoprolol OROS produced less pronounced bronchoconstrictor effects than atenolol, matrix-based sustained release metoprolol or long acting propranolol in patients with asthma or obstructive airways disease, and healthy volunteers. These results are presumably due to the beta 1-selectivity of metoprolol in addition to the relatively low plasma concentrations maintained by metoprolol CR/ZOK and metoprolol OROS, and the avoidance of high peak plasma concentrations with these agents. Despite the relative safety of the controlled release forms of metoprolol, the use of all beta-adrenoceptor antagonists should be avoided in patients with a history of bronchospasm. Thus, controlled release metoprolol formulations offer the potential to maximise the confirmed benefits of this agent in the management of hypertension and angina, by maintaining clinically effective plasma concentrations within a narrow therapeutic range over a 24-hour dose interval.

Beta-adrenoceptor blockade and CNS-related subjective symptoms: a randomized, double-blind, placebo-controlled comparison of metoprolol CR/ZOK, atenolol and propranolol LA in healthy subjects

The effect of once daily treatment with atenolol (100 mg), metoprolol CR/ZOK (100 mg) and propranolol LA (160 mg) for one week on CNS-related subjective symptoms was compared with that of placebo using a randomised, double-blind cross-over design in 12 healthy volunteers. The symptoms were recorded using a previously documented self-administered questionnaire (MSE-profile), which included three dimensions: Contentment, Vitality and Sleep. Compared to placebo, all three beta-adrenoceptor antagonists reduced the exercise heart rate at 24 hours but a somewhat more pronounced effect was found with propranolol LA. No significant difference in any of the dimensions was detected between placebo and either metoprolol CR/ZOK or atenolol tablets. Following propranolol LA treatment a deterioration in the dimensions Vitality and Sleep was observed compared with both placebo and the beta 1-selective drugs. Difference in lipophilicity between the beta 1-selective agents metoprolol and atenolol has little bearing on the occurrence of the CNS-related symptoms, in comparison to the marked effects of the lipophilic and nonselective compound propranolol.