Relative lipophilicities and structural-pharmacological considerations of various angiotensin-converting enzyme (ACE) inhibitors

Babesia BdFE1 esterase is required for the anti-parasitic activity of the ACE inhibitor fosinopril

Effective and safe therapies for the treatment of diseases caused by intraerythrocytic parasites are impeded by the rapid emergence of drug resistance and the lack of novel drug targets. One such disease is human babesiosis, which is a rapidly emerging tick-borne illness caused by Babesia parasites. In this study, we identified fosinopril, a phosphonate-containing, FDA-approved angiotensin converting enzyme (ACE) inhibitor commonly used as a prodrug for hypertension and heart failure, as a potent inhibitor of Babesia duncani parasite development within human erythrocytes. Cell biological and mass spectrometry analyses revealed that the conversion of fosinopril to its active diacid molecule, fosinoprilat, is essential for its antiparasitic activity. We show that this conversion is mediated by a parasite-encoded esterase, BdFE1, which is highly conserved among apicomplexan parasites. Parasites carrying the L238H mutation in the active site of BdFE1 failed to convert the prodrug to its active moiety and became resistant to the drug. Our data set the stage for the development of this class of drugs for the therapy of vector-borne parasitic diseases.

Impact of drug treatment and drug interactions in post-stroke epilepsy

Stroke is a huge burden on our society and this is expected to grow in the future due to the aging population and the associated co-morbidities. The improvement of acute stroke care has increased the survival rate of stroke patients, and many patients are left with permanent disability, which makes stroke the main cause of adult disability. Unfortunately, many patients face other severe complications such as post-stroke seizures and epilepsy. Acute seizures (ASS) occur within 1 week after the stroke while later occurring unprovoked seizures are diagnosed as post-stroke epilepsy (PSE). Both are associated with a poor prognosis of a functional recovery. The underlying neurobiological mechanisms are complex and poorly understood. There are no universal guidelines on the management of PSE. There is increasing evidence for several risk factors for ASS/PSE, however, the impacts of recanalization, drugs used for secondary prevention of stroke, treatment of stroke co-morbidities and antiseizure medication are currently poorly understood. This review focuses on the common medications that stroke patients are prescribed and potential drug interactions possibly complicating the management of ASS/PSE.

Impact of Green Tea Catechin Ingestion on the Pharmacokinetics of Lisinopril in Healthy Volunteers

Lisinopril, a highly hydrophilic long‐acting angiotensin‐converting enzyme inhibitor, is frequently prescribed for the treatment of hypertension and congestive heart failure. Green tea consumption may reduce the risk of cardiovascular outcomes and total mortality, whereas green tea or its catechin components has been reported to decrease plasma concentrations of a hydrophilic β blocker, nadolol, in humans. The aim of this study was to evaluate possible effects of green tea extract (GTE) on the lisinopril pharmacokinetics. In an open‐label, randomized, single‐center, 2‐phase crossover study, 10 healthy subjects ingested 200 mL of an aqueous solution of GTE containing ~ 300 mg of (–)‐epigallocatechin gallate, a major catechin component in green tea, or water (control) when receiving 10 mg of lisinopril after overnight fasting. The geometric mean ratio (GTE/control) for maximum plasma concentration and the area under the plasma concentration‐time curve of lisinopril were 0.289 (90% confidence interval (CI) 0.226–0.352) and 0.337 (90% CI 0.269–0.405), respectively. In contrast, there were no significant differences in time to reach maximum lisinopril concentration (6 hours in both phases) and renal clearance of lisinopril (57.7 mL/minute in control vs. 56.9 mL/minute in GTE). These results suggest that the extent of intestinal absorption of lisinopril was significantly impaired in the presence of GTE, whereas it had no major effect on the absorption rate and renal excretion of lisinopril. Concomitant use of lisinopril and green tea may decrease oral exposure to lisinopril, and therefore result in reduced therapeutic efficacy.

An Unexpected Case of Lisinopril-Associated Severe Hyponatremia

Angiotensin-converting enzyme (ACE) inhibitors are a class of medications that have formed the backbone of hypertension management. Of these medications, lisinopril is one of the most commonly used. While known serious side effects of all ACE inhibitors include angioedema and hyperkalemia, ACE inhibitor-associated hyponatremia has been rarely reported. We present a patient with severe hyponatremia associated with lisinopril use and discuss the link between hyponatremia and ACE inhibitors.

ACE2 as a Therapeutic Target for COVID-19; its Role in Infectious Processes and Regulation by Modulators of the RAAS System

Angiotensin converting enzyme 2 (ACE2) is the recognized host cell receptor responsiblefor mediating infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). ACE2bound to tissue facilitates infectivity of SARS-CoV-2; thus, one could argue that decreasing ACE2tissue expression would be beneficial. However, ACE2 catalytic activity towards angiotensin I (AngI) and II (Ang II) mitigates deleterious effects associated with activation of the renin-angiotensinaldosteronesystem (RAAS) on several organs, including a pro-inflammatory status. At the tissuelevel, SARS-CoV-2 (a) binds to ACE2, leading to its internalization, and (b) favors ACE2 cleavage toform soluble ACE2: these actions result in decreased ACE2 tissue levels. Preserving tissue ACE2activity while preventing ACE2 shredding is expected to circumvent unrestrained inflammatoryresponse. Concerns have been raised around RAAS modulators and their effects on ACE2expression or catalytic activity. Various cellular and animal models report conflicting results invarious tissues. However, recent data from observational and meta-analysis studies in SARS-CoV-2-infected patients have concluded that RAAS modulators do not increase plasma ACE2 levels orsusceptibility to infection and are not associated with more severe diseases. This review presentsour current but evolving knowledge of the complex interplay between SARS-CoV-2 infection, ACE2levels, modulators of RAAS activity and the effects of RAAS modulators on ACE2 expression.

Evaluation of self-nanoemulsifying drug delivery systems using multivariate methods to optimize permeability of captopril oral films

The present report demonstrates a quality by design approach to understand and optimize self-nanoemulsifying orodispersible films (SNEODF) of captopril for hypertension. A central composite experimental design was used to study the formulation parameters effects (primary emulsion, aqueous phase, and surfactant) on the film properties (globule size, film burst, adhesion, Young's moduli, disintegration time, tensile strength and dissolution). Principle component analysis (PCA) and principle component regression (PCR) were employed to identify and quantify the effects of formulation variables and physico-mechanical properties of the film on the drug permeability. PCA classified three distinct groups of film formulations based on their composition and properties. PCR quantified the impact of main variables, their interactions, and square effects on the drug permeability. The main effect of the aqueous phase exhibited a negative impact, while that of flux and tensile strength showed a positive impact on the permeability. Interactions of primary emulsions with disintegration time and tensile strength displayed a synergistic impact. Interactions of aqueous phase with flux, Young's moduli, and tensile strength, as well as between Young's moduli and tensile strength showed a significant positive effect on the permeability. A negative correlation of square effects of primary emulsion and flux, and a positive square effect of Young's moduli confirmed their non-linear influence on the drug permeability across porcine buccal mucosa. This research work demonstrates application of design of experiment and multivariate methods to achieve targeted product quality of captopril (SNEODF) having improved permeability and pH independent release profile.

Connecting the brain cholesterol and renin-angiotensin systems: potential role of statins and RAS-modifying medications in dementia

Millions of people worldwide receive agents targeting the renin-angiotensin system (RAS) to treat hypertension or statins to lower cholesterol. The RAS and cholesterol metabolic pathways in the brain are autonomous from their systemic counterparts and are interrelated through the cholesterol metabolite 27-hydroxycholesterol (27-OHC). These systems contribute to memory and dementia pathogenesis through interference in the amyloid-beta cascade, vascular mechanisms, glucose metabolism, apoptosis, neuroinflammation and oxidative stress. Previous studies examining the relationship between these treatments and cognition and dementia risk have produced inconsistent results. Defining the blood-brain barrier penetration of these medications has been challenging, and the mechanisms of action on cognition are not clearly established. Potential biases are apparent in epidemiological and clinical studies, such as reverse epidemiology, indication bias, problems defining medication exposure, uncertain and changing doses, and inappropriate grouping of outcomes and medications. This review summarizes current knowledge of the brain cholesterol and RAS metabolism and the mechanisms by which these pathways affect neurodegeneration. The putative mechanisms of action of statins and medications inhibiting the RAS will be examined, together with prior clinical and animal studies on their effects on cognition. We review prior epidemiological studies, analysing their strengths and biases, and identify areas for future research. Understanding the pathophysiology of the brain cholesterol system and RAS and their links to neurodegeneration has enormous potential. In future, well-designed epidemiological studies could identify potential treatments for Alzheimer's disease (AD) amongst medications that are already in use for other indications.

Efficacy and Safety of Zofenopril Versus Ramipril in the Treatment of Myocardial Infarction and Heart Failure: A Review of the Published and Unpublished Data of the Randomized Double-Blind SMILE-4 Study

Zofenopril is a lipophilic, sulfhydryl group-containing angiotensin-converting enzyme (ACE)-inhibitor, characterized by wide tissue distribution, long duration of action, and pleiotropic effects on endothelial dysfunction. Its clinical efficacy and safety have been described in the four randomized controlled trials of the SMILE program, which globally enrolled more than 3600 patients in post-acute myocardial infarction (AMI) setting. The SMILE-4 study specifically selected patients with left ventricular dysfunction at admission, and compared the effects of zofenopril or ramipril in combination with acetylsalicylic acid (ASA). Zofenopril demonstrated its superiority over ramipril in reducing the combined occurrence of death or hospitalization for cardiovascular causes both in the overall population included in the original study and in subgroups of patients at highest risk, namely hypertensive and diabetic subjects. The effects of the early treatment with zofenopril were sustained over time, and, after 5 years of follow-up, zofenopril increased the survival likelihood and reduced the hospitalization rate. Compared to ramipril, zofenopril was cost-effective with a number to treat of 13 and an incremental cost-effectiveness ratio (ICER) of 2125.45 euros for any additional event prevented. Furthermore, in real-world settings, zofenopril decreased the risk of death in patients with heart failure, particularly in men, and in subjects older than 76 years or with ejection fraction lower than 54%. These results support the early use of zofenopril immediately after AMI, even in the presence of comorbidities, and its maintenance over time to reduce the risk of heart failure.

FUNDING

Menarini International Operations Luxembourg S.A.

The Evaluation of Angiotensin-Converting Enzyme Inhibitors in Renal Elimination with Selected Molecular Descriptors

Angiotensin-converting enzyme (ACE) inhibitors modulate the function of the renin-angiotensin-aldosterone system, and they are commonly prescribed antihypertensive drugs especially in patients with renal failure. In this study, the relationships between several molecular properties of eight ACE inhibitors (enalapril, quinapril, fosinopril, ramipril, benazepril, perindopril, moexipril, trandolapril) and their renal elimination data, from relevant literature, were investigated. The ’molecular descriptors of the ACE inhibitors, which included aqueous solubility data (logS); an electronic descriptor, polar surface area (PSA);, a constitutional parameter, molecular mass (Mr); and a geometric descriptor, volume value (Vol), as well as lipophilicity descriptors (logP values), were calculated using different software packages. Simple linear regression analysis showed the best correlation between renal elimination data and lipophilicity descriptor AClogP values (R2 = 0.5742). In the next stage of the study, multiple linear regression was applied to assess a higher correlation between the ACE inhibitors’ renal elimination data and lipophilicity, AClogP, with one additional descriptor as an independent variable. Good correlations were established between renal elimination data from the literature and the AClogP lipophilicity descriptor using the constitutional parameter (molecular mass (R2 = 0.7425)) or the geometric descriptor (volume value (R2 = 0.7224)) as an independent variable. The application of computed molecular descriptors in evaluating drug elimination is of great importance in drug research.

Biowaiver Monographs for Immediate-Release Solid Oral Dosage Forms: Enalapril

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence testing for the marketing authorization of immediate-release, solid oral dosage forms containing enalapril maleate are reviewed. Enalapril, a prodrug, is hydrolyzed by carboxylesterases to the active angiotensin-converting enzyme inhibitor enalaprilat. Enalapril as the maleate salt is shown to be highly soluble, but only 60%-70% of an orally administered dose of enalapril is absorbed from the gastrointestinal tract into the enterocytes. Consequently, enalapril maleate is a Biopharmaceutics Classification System class III substance. Because in situ conversion of the maleate salt to the sodium salt is sometimes used in production of the finished drug product, not every enalapril maleate-labeled finished product actually contains the maleate salt. Enalapril is not considered to have a narrow therapeutic index. With this background, a biowaiver-based approval procedure for new generic products or after major revisions to existing products is deemed acceptable, provided the in vitro dissolution of both test and reference preparation is very rapid (at least 85% within 15 min at pH 1.2, 4.5, and 6.8). Additionally, the test and reference product must contain the identical active drug ingredient.

Antioxidant and Cardioprotective Properties of the Sulphydryl Angiotensinconverting Enzyme Inhibitor Zofenopril

Zofenopril, a new potent sulphydryl angiotensin-converting enzyme (ACE) inhibitor, is characterized by high lipophilicity, selective cardiac ACE inhibition, and antioxidant and tissue protective activities. In vitro and in vivo experiments suggest that zofenopril exerts antioxidant properties at clinically achievable tissue concentrations. In endothelial cells, zofenopril enhances nitric oxide production, attenuates atherosclerotic lesion development and inhibits adhesion molecule expression by reducing reactive oxygen species. These peculiar characteristics are reflected in the drug's cardioprotective activity, which has been shown to be greater than that of non-sulphydryl ACE inhibitors. Cardiac hypertrophy was also reduced by chronic zofenopril administration, independently of its blood pressure-reducing effect. ACE inhibitors with a sulphydryl group could have an advantage in improving vascular function and reducing cardiac impairment compared with non-sulphydryl-containing ACE inhibitors. This could explain zofenopril's remarkable clinical efficacy post-infarction, and potentially beneficial use in prevention and therapy of cardiovascular diseases, such as atherosclerosis, thrombosis and heart failure.

The cough reflex is upregulated by lisinopril microinjected into the caudal nucleus tractus solitarii of the rabbit

We have previously shown that cough potentiation induced by intravenous administration of the AT1 receptor antagonist losartan is lower than that induced by the ACE inhibitor lisinopril in anesthetized and awake rabbits. Since losartan and lisinopril cross the blood-brain barrier, their central action on the cough reflex can be hypothesized. Mechanical stimulation of the tracheobronchial tree and citric acid inhalation were used to induce cough reflex responses in pentobarbital sodium-anesthetized, spontaneously breathing rabbits. Bilateral microinjections (30-50 nl) of losartan (5mM), lisinopril (1mM), bradykinin (0.05 mM), HOE-140 (0.2mM, a bradykinin B2 receptor antagonist) and CP-99,994 (1mM, an NK1 receptor antagonist) were performed into the caudal nucleus tractus solitarii, the predominant site of termination of cough-related afferents. Lisinopril, but not losartan increased the cough number. This effect was reverted by HOE-140 or CP-99,994. Cough potentiation was also induced by bradykinin. The results support for the first time a central protussive action of lisinopril mediated by an accumulation of bradykinin and substance P.

Absorption and cleavage of enalapril, a carboxyl ester prodrug, in the rat intestine: in vitro, in situ intestinal perfusion and portal vein cannulation models

In recent years prodrug strategy has been used extensively to improve the pharmacokinetic properties of compounds exhibiting poor bioavailability. Mechanistic understanding of the absorption and the role of intestine and liver in the activation of oral prodrugs is crucial. Enalapril, a carboxyl ester prodrug, is reported to be metabolized by human carboxylesterase-1 (CES1) but not by carboxylesterase-2 (CES2) to its active metabolite enalaprilat. Further, it has been reported that the small intestines of both rat and human contain mainly CES2. The objective of this work was to understand whether enalapril remains unchanged as it is absorbed through the intestine into the portal circulation. This was evaluated using different intestinal preparations, an in situ intestinal perfusion experiment and a portal vein cannulated rat model. No turnover of enalapril was seen with commercial rat intestinal S9 and microsomes, but reasonable turnover was observed with freshly prepared rat intestinal and mucosal homogenate and S9. In the intestinal perfusion study, both enalapril and enalaprilat were observed in the mesenteric plasma with the data suggesting 32% hydrolysis of enalapril in the intestine. In the portal vein cannulated rat, about 51% of enalapril absorbed into intestine was converted to enalaprilat. Overall, it was demonstrated that even though enalapril has been shown to be a specific substrate for CES1, it is converted to enalaprilat to a significant extent in the intestine. Such experimental techniques can be applied by other scientific groups who are working on prodrugs to determine the region and extent of activation. Copyright © 2015 John Wiley & Sons, Ltd.

The angiotensin converting enzyme inhibitor, captopril, prevents the hyperactivity and impulsivity of neurokinin-1 receptor gene 'knockout' mice: sex differences and implications for the treatment of attention deficit hyperactivity disorder

Mice lacking functional neurokinin-1 receptors (NK1R-/-) display behavioural abnormalities resembling attention deficit hyperactivity disorder (ADHD): locomotor hyperactivity, impulsivity and inattentiveness. The preferred ligand for NK1R, substance P, is metabolised by angiotensin converting enzyme (ACE), which forms part of the brain renin angiotensin system (BRAS). In view of evidence that the BRAS modulates locomotor activity and cognitive performance, we tested the effects of drugs that target the BRAS on these behaviours in NK1R-/- and wildtype mice. We first tested the effects of the ACE inhibitor, captopril, on locomotor activity. Because there are well-established sex differences in both ADHD and ACE activity, we compared the effects of captopril in both male and female mice. Locomotor hyperactivity was evident in male NK1R-/- mice, only, and this was abolished by treatment with captopril. By contrast, male wildtypes and females of both genotypes were unaffected by ACE inhibition. We then investigated the effects of angiotensin AT1 (losartan) and AT2 (PD 123319) receptor antagonists on the locomotor activity of male NK1R-/- and wildtype mice. Both antagonists increased the locomotor activity of NK1R-/- mice, but neither affected the wildtypes. Finally, we tested the effects of captopril on the performance of male NK1R-/- and wildtype mice in the 5-choice serial reaction-time task (5-CSRTT) and found that ACE inhibition prevented the impulsivity of NK1R-/- mice. These results indicate that certain behaviours, disrupted in ADHD, are influenced by an interaction between the BRAS and NK1R, and suggest that ACE inhibitors could provide a novel treatment for this disorder.

Pharmacokinetics and pharmacodynamics of enalapril and its active metabolite, enalaprilat, at four different doses in healthy horses

Pharmacokinetic and pharmacodynamic of IV enalapril at 0.50 mg/kg, PO placebo and PO enalapril at three different doses (0.50, 1.00 and 2.00 mg/kg) were analyzed in 7 healthy horses. Serum concentrations of enalapril and enalaprilat were determined for pharmacokinetic analysis. Angiotensin-converting enzyme (ACE) activity, serum ureic nitrogen (SUN), creatinine and electrolytes were measured, and blood pressure was monitored for pharmacodynamic analysis. The elimination half-lives of enalapril and enalaprilat were 0.67 and 2.76 h respectively after IV enalapril. Enalapril concentrations after PO administrations were below the limit of quantification (10 ng/ml) in all horses and enalaprilat concentrations were below the limit of quantification in 4 of the 7 horses. Maximum mean ACE inhibitions from baseline were 88.38, 3.24, 21.69, 26.11 and 30.19% for IV enalapril at 0.50 mg/kg, placebo and PO enalapril at 0.50, 1.00 and 2.00 mg/kg, respectively. Blood pressures, SUN, creatinine and electrolytes remained unchanged during the experiments.

Use of the ACE inhibitor zofenopril in the treatment of ischemic heart disease

Zofenopril, an inhibitor of the angiotensin-converting enzyme (ACE), has recently been widely introduced into the pharmaceutical market. Its clinical safety and efficacy has been demonstrated in patients with hypertension and in patients with acute myocardial infarction (AMI). The Survival of Myocardial Infarction Long-term Evaluation (SMILE) project provided valuable information regarding the safety of early onset ACE inhibition with zofenopril after AMI and a greater perception of the early and late benefits. The SMILE-I study demonstrated that most benefits of ACE inhibition may be obtained early after AMI and persist after discontinuation of treatment. The SMILE-II study demonstrated that early zofenopril treatment (initiated <12 h) is safe and associated with a low rate of severe hypotension in thrombolyzed patients with acute myocardial infarction when administered in accordance with an adequate dose-titration scheme. Many other studies of clinical ACE-inhibitors (ACEIs) over the last 30 years have provided us with information in order to understand the effects of ACEIs and have demonstrated that patients benefit from ACEI treatment at different stages of the pathophysiological continuum of cardiovascular diseases. The current guidelines recommend that ACEIs should be used for routine secondary prevention in all patients with coronary artery disease and should be considered for all other patients with coronary or other vascular disease unless contraindicated.

An integrated physiology-based model for the interaction of RAA system biomarkers with drugs

The renin angiotensin aldosterone system (RAAS) is a paramount target for the pharmacological treatment of cardiovascular diseases. As modeling and simulation techniques are becoming increasingly utilized in cardiovascular research, our aim was to develop a physiology-based model that describes the effect of different drugs at different doses on the RAAS and integrates physiology-based description drug pharmacokinetics (PK). First, a basic RAAS model was developed in which equations for drug effects were included and missing parameters estimated. Next, a physiology-based PK model for enalapril and enalaprilat was developed and coupled to the RAAS model. Simulation of the effects of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and aliskiren administration on angiotensins I and II did not reveal significant overestimation or underestimation. For all drugs, the error numerics were acceptable. The model also encompassed the PK of intravenous and oral enalapril and its conversion to enalaprilat. In summary, we report a physiology-based model for the interaction of the RAAS biomarkers angiotensin I and II with enalapril, benazepril, aliskiren, and losartan that allows for an adequate description of the RAAS response after single administration of the drugs. Such a comprehensive description may lead to a better understanding of the effects of pharmacological interventions in the RAAS.

Angiotensin-converting enzyme inhibitors and incidence of mild cognitive impairment. The Italian Longitudinal Study on Aging

Midlife elevated blood pressure and hypertension contribute to the development of Alzheimer's disease (AD) and overall dementia. We sought to estimate whether angiotensin-converting enzyme inhibitors (ACE-Is) reduced the risk of developing mild cognitive impairment (MCI) in cognitively normal individuals. In the Italian Longitudinal Study on Aging, we evaluated 1,445 cognitively normal individuals treated for hypertension but without congestive heart failure from a population-based sample from eight Italian municipalities with a 3.5-year follow-up. MCI was diagnosed with current clinical criteria. Dementia, AD, and vascular dementia were diagnosed based on DSM-IIIR criteria, NINCDS-ADRDA criteria, and ICD-10 codes. Among 873 hypertension-treated cognitively normal subjects, there was no significant association between continuous exposure to all ACE-Is and risk of incident MCI compared with other antihypertensive drugs [hazard ratio (HR), 0.45, 95% confidence interval (CI), 0.16-1.28]. Captopril exposure alone did not significantly modify the risk of incident MCI (HR, 1.80, 95% CI, 0.39-8.37). However, the enalapril sub-group alone (HR, 0.17, 95% CI, 0.04 -0.84) or combined with the lisinopril sub-group (HR, 0.27, 95% CI, 0.08-0.96), another ACE-I structurally related to enalapril and with similar potency, were associated with a reduced risk of incident MCI. Study duration exposure to ACE-Is as a "class" was not associated with incident MCI in older hypertensive adults. However, within-class differences linked to different chemical structures and/or drug potencies may exist, with a possible effect of the enalapril and lisinopril sub-groups in reducing the risk of incident MCI.

Long-term clinical experience with zofenopril

Angiotensin-converting enzyme inhibitors are extensively used to improve clinical outcome of patients with several cardiovascular diseases. Zofenopril proved to be very effective in patients with coronary artery disease and myocardial infarction, thanks to its unique effective mechanism of action for improving blood pressure control, left ventricular function and myocardial ischemia burden, as well as angiotensin-converting enzyme inhibition. The SMILE project involved more than 3500 patients with coronary artery disease and demonstrated that zofenopril treatment may reduce mortality and morbidity in patients with myocardial infarction, also when combined with acetyl salicylic acid and to a greater extent than lisinopril and ramipril. In addition, the results of the SMILE-ISCHEMIA study have demonstrated an interesting anti-ischemic effect of zofenopril, and these properties largely contribute to the overall clinical benefit of the drug. The effects of zofenopril on blood pressure control and cardiovascular protection clearly support its primary role for prevention and treatment of cardiovascular diseases.

A detailed physiologically based model to simulate the pharmacokinetics and hormonal pharmacodynamics of enalapril on the circulating endocrine Renin-Angiotensin-aldosterone system

The renin-angiotensin-aldosterone system (RAAS) plays a key role in the pathogenesis of cardiovascular disorders including hypertension and is one of the most important targets for drugs. A whole body physiologically based pharmacokinetic (wb PBPK) model integrating this hormone circulation system and its inhibition can be used to explore the influence of drugs that interfere with this system, and thus to improve the understanding of interactions between drugs and the target system. In this study, we describe the development of a mechanistic RAAS model and exemplify drug action by a simulation of enalapril administration. Enalapril and its metabolite enalaprilat are potent inhibitors of the angiotensin-converting-enzyme (ACE). To this end, a coupled dynamic parent-metabolite PBPK model was developed and linked with the RAAS model that consists of seven coupled PBPK models for aldosterone, ACE, angiotensin 1, angiotensin 2, angiotensin 2 receptor type 1, renin, and prorenin. The results indicate that the model represents the interactions in the RAAS in response to the pharmacokinetics (PK) and pharmacodynamics (PD) of enalapril and enalaprilat in an accurate manner. The full set of RAAS-hormone profiles and interactions are consistently described at pre- and post-administration steady state as well as during their dynamic transition and show a good agreement with literature data. The model allows a simultaneous representation of the parent-metabolite conversion to the active form as well as the effect of the drug on the hormone levels, offering a detailed mechanistic insight into the hormone cascade and its inhibition. This model constitutes a first major step to establish a PBPK-PD-model including the PK and the mode of action (MoA) of a drug acting on a dynamic RAAS that can be further used to link to clinical endpoints such as blood pressure.

Fosinopril and zofenopril, two angiotensin-converting enzyme (ACE) inhibitors, potentiate the anticonvulsant activity of antiepileptic drugs against audiogenic seizures in DBA/2 mice

The renin-angiotensin system (RAS) exists in the brain and it may be involved in pathogenesis of neurological and psychiatric disorders including seizures. The aim of the present research was to evaluate the effects of some angiotensin-converting enzyme inhibitors (ACEi; captopril, enalapril, fosinopril and zofenopril), commonly used as antihypertensive agents, in the DBA/2 mice animal model of generalized tonic-clonic seizures. Furthermore, the co-administration of these compounds with some antiepileptic drugs (AEDs; carbamazepine, diazepam, felbamate, gabapentin, lamotrigine, phenobarbital, phenytoin, topiramate and valproate) was studied in order to identify possible positive interactions in the same model. All ACEi were able to decrease the severity of audiogenic seizures with the exception of enalapril up to the dose of 100mg/kg, the rank order of activity was as follows: fosinopril>zofenopril>captopril. The co-administration of ineffective doses of all ACE inhibitors with AEDs, generally increased the potency of the latter. Fosinopril was the most active in potentiating the activity of AEDs and the combination of ACEi with lamotrigine and valproate was the most favorable, whereas, the co-administrations with diazepam and phenobarbital seemed to be neutral. The increase in potency was generally associated with an enhancement of motor impairment, however, the therapeutic index of combined treatment of AEDs with ACEi was predominantly more favorable than control. ACEi administration did not influence plasma and brain concentrations of the AEDs studied excluding pharmacokinetic interactions and concluding that it is of pharmacodynamic nature. In conclusion, fosinopril, zofenopril, enalapril and captopril showed an additive anticonvulsant effect when co-administered with some AEDs, most notably carbamazepine, felbamate, lamotrigine, topiramate and valproate, implicating a possible therapeutic relevance of such drug combinations.

Design, synthesis and characterization of captopril prodrugs for enhanced percutaneous absorption

Most drugs are designed primarily for oral administration, but the activity and stability profiles desirable for this route often make them unsuitable for transdermal delivery. We were therefore interested in designing analogues of captopril, a model drug with poor percutaneous penetration, for which the sustained steady-state blood plasma level associated with transdermal delivery (and which is unattainable orally) would be particularly beneficial. Quantitative structure—permeability relationships (QSPRs) predicted that ester and thiol prodrug derivatives of captopril would have lower maximal transdermal flux (Jm) than the parent drug, since the increases in permeability coefficient (kp) of prodrugs would be outweighed by the reductions in aqueous solubility. Therefore, the aim of this study was to synthesize a series of prodrugs of captopril and to determine if a QSPR model could be used to design therapeutically viable prodrugs. Molecules with the highest predicted kp values were synthesized and characterized, and Jm measured in Franz diffusion cells from saturated aqueous donor across porcine skin (fresh and frozen). In-vitro metabolism was also measured. Captopril and the prodrugs crossed the skin relatively freely, with Jm being highest for ethyl to butyl esters. Substantial first-order metabolism of the prodrugs was observed, suggesting that their enhanced percutaneous absorption was complemented by their metabolic performance. The results suggested that QSPR models provided excellent enhancements in drug delivery. This was not seen at higher lipophilicities, suggesting that issues of solubility need to be considered in conjunction with any such use of a QSPR model.

Use of angiotensin receptor blockers and risk of dementia in a predominantly male population: prospective cohort analysis

OBJECTIVE

To investigate whether angiotensin receptor blockers protect against Alzheimer's disease and dementia or reduce the progression of both diseases.

DESIGN

Prospective cohort analysis.

SETTING

Administrative database of the US Veteran Affairs, 2002-6. Population 819 491 predominantly male participants (98%) aged 65 or more with cardiovascular disease.

MAIN OUTCOME MEASURES

Time to incident Alzheimer's disease or dementia in three cohorts (angiotensin receptor blockers, lisinopril, and other cardiovascular drugs, the "cardiovascular comparator") over a four year period (fiscal years 2003-6) using Cox proportional hazard models with adjustments for age, diabetes, stroke, and cardiovascular disease. Disease progression was the time to admission to a nursing home or death among participants with pre-existing Alzheimer's disease or dementia.

RESULTS

Hazard rates for incident dementia in the angiotensin receptor blocker group were 0.76 (95% confidence interval 0.69 to 0.84) compared with the cardiovascular comparator and 0.81 (0.73 to 0.90) compared with the lisinopril group. Compared with the cardiovascular comparator, angiotensin receptor blockers in patients with pre-existing Alzheimer's disease were associated with a significantly lower risk of admission to a nursing home (0.51, 0.36 to 0.72) and death (0.83, 0.71 to 0.97). Angiotensin receptor blockers exhibited a dose-response as well as additive effects in combination with angiotensin converting enzyme inhibitors. This combination compared with angiotensin converting enzyme inhibitors alone was associated with a reduced risk of incident dementia (0.54, 0.51 to 0.57) and admission to a nursing home (0.33, 0.22 to 0.49). Minor differences were shown in mean systolic and diastolic blood pressures between the groups. Similar results were observed for Alzheimer's disease.

CONCLUSIONS

Angiotensin receptor blockers are associated with a significant reduction in the incidence and progression of Alzheimer's disease and dementia compared with angiotensin converting enzyme inhibitors or other cardiovascular drugs in a predominantly male population.

Temperature-dependent specific transport of levofloxacin in human intestinal epithelial LS180 cells

It was reported previously that specific levofloxacin uptake in Caco-2 cells was inhibited by nicotine, enalapril, L-carnitine and fexofenadine. The aim of the present study was to characterize the cellular uptake of levofloxacin using another human intestinal cell line, LS180. Levofloxacin uptake in LS180 cells was temperature-dependent and optimal at neutral pH, but was Na(+)-independent. The rank order of inhibitory effects of the four compounds on [(14)C] levofloxacin uptake in LS180 cells was nicotine>enalapril>L-carnitine>fexofenadine, which is consistent with that in Caco-2 cells. The mRNA levels of OATP1A2, 1B1, 1B3 and 2B1 in LS180 cells were markedly different from those in Caco-2 cells, and OATP substrates/inhibitors had no systematic effect on the levofloxacin uptake. The mRNA levels of OCTN1 and 2 in LS180 cells were similar to those in Caco-2 cells. However, the inhibitory effect of nicotine on L-[(3)H]carnitine uptake was much less potent than that of unlabeled L-carnitine. These results indicate that the specific uptake system for levofloxacin in LS180 cells is identical/similar to that in Caco-2 cells, but that OATPs and OCTNs contribute little to levofloxacin uptake in the human intestinal epithelial cells.

Inhibition of renin-angiotensin system in experimental acute pancreatitis in rats: a new therapeutic target?

OBJECTIVE

Pancreatic renin-angiotensin system has been implied to play a role in the regulation of pancreatic functions and could be a new therapeutic target in acute pancreatitis. The aim of this study was to evaluate the therapeutic potential of angiotensin-converting-enzyme inhibition by captopril and angiotensin II type 1 receptor inhibition by L-158809 and losartan experimentally in acute pancreatitis.

DESIGN

Rats were randomly divided into 15 groups. Acute edematous pancreatitis was induced by injection of cerulein 20microg/kg SC four times at hourly intervals. Severe necrotizing pancreatitis was induced by retrograde injection of 3% taurocholate into the biliary-pancreatic duct.

INTERVENTIONS

Captopril, L-158809 and losartan were given intraperitoneally. Main outcome features: pancreatic pathology, pancreatic myeloperoxidase activity and serum amylase activity were assessed.

RESULTS

Captopril decreased serum amylase (10,809+/-1867 vs. 4085+/-1028U/L, p<0.01), myeloperoxidase activity (3.5+/-0.5 vs. 1.5+/-0.1, p<0.05) and histopathological score (5.0+/-0.4 vs. 1.1+/-0.5, p<0.01) in acute edematous pancreatitis. In taurocholate induced severe necrotizing pancreatitis captopril ameliorated histopathological score (10.1+/-1.2 vs. 3.4+/-0.5, p<0.01), pancreatic parenchymal necrosis (4.5+/-0.6 vs. 0.0+/-0.0, p<0.001), fatty necrosis (2.8+/-0.9 vs. 0.1+/-0.1, p<0.01) and edema (2.1+/-0.3 vs. 1.4+/-0.3, p<0.05). However, L-158809 did not have similar beneficial effects on acute pancreatitis in rats while losartan decreased pancreatic parenchymal necrosis and neutrophil infiltration.

CONCLUSIONS

This study not only demonstrated the differential effects of captopril, losartan and L-158809 in acute pancreatitis but also showed that there is still much to investigate about pancreatic renin-angiotensin system. Inhibition of angiotensin-converting enzyme should be evaluated carefully as a potential new therapeutic target in acute pancreatitis.

Chromatography methods in investigation of lipophilicity of the biological active substances

This paper presents the review of the methods used in research of the biological active substances hydrophobicity, a very important property. The biological activity of some substances depends on their pharmacokinetics and pharmacodynamics. These processes depend on the molecule's capability to interact with two different media: aqueous (cells interior) and non-aqueous (cells membrane), or on the molecule lipophilicity. Today, great attention is given to investigation and systematic determination of drugs lipophilicity. In these researches chromatography methods have an important role.

Does aldosterone upregulate the brain renin-angiotensin system in rats with heart failure?

The brain renin-angiotensin system (RAS) contributes to increased sympathetic drive in heart failure (HF). The factors upregulating the brain RAS in HF remain unknown. We hypothesized that aldosterone (ALDO), a downstream product of the systemic RAS that crosses the blood-brain barrier, signals the brain to increase RAS activity in HF. We examined the relationship between circulating and brain ALDO in normal intact rats, in adrenalectomized rats receiving subcutaneous infusions of ALDO, and in rats with ischemia-induced HF and sham-operated controls. Brain ALDO levels were proportional to plasma ALDO levels across the spectrum of rats studied. Compared with sham-operated controls rats, HF rats had higher plasma and hypothalamic tissue levels of ALDO. HF rats also had higher expression of mRNA and protein for angiotensin-converting enzyme and angiotensin type 1 receptors in the hypothalamus, increased reduced nicotinamide-adenine dinucleotide phosphate oxidase activity and superoxide generation in the paraventricular nucleus of the hypothalamus, increased excitation of paraventricular nucleus neurons, and increased plasma norepinephrine. HF rats treated for 4 weeks with intracerebroventricular RU28318 (1 microg/h), a selective mineralocorticoid receptor antagonist, had less hypothalamic angiotensin-converting enzyme and angiotensin type 1 receptor mRNA and protein, less reduced nicotinamide-adenine dinucleotide phosphate-induced superoxide in the paraventricular nucleus, fewer excited paraventricular nucleus neurons, and lower plasma norepinephrine. RU28318 had no effect on plasma ALDO or on angiotensin-converting enzyme or angiotensin type 1 receptor expression in brain cortex. The data demonstrate that ALDO of adrenal origin enters the hypothalamus in direct proportion to plasma levels and suggest that ALDO contributes to the upregulation of hypothalamic RAS activity and sympathetic drive in heart failure.

Acidity, lipophilicity, solubility, absorption, and polar surface area of some ACE inhibitors

Computational chemical methods have been used to correlate the molecular properties of the 10 ACE inhibitors (captopril, enalapril, perindopril, lisinopril, ramipril, trandolapril, quinapril, fosinopril, benazepril, and cilazapril) and some of their active metabolites (enalaprilat, perindoprilat, ramiprilat, trandolaprilat, quinaprilat, fosinoprilat, benazeprilat, and cilazaprilat). The computed pK a values correlate well with the available experimental values. In the dicarboxylic ACE inhibitors, the carboxyalkyl carboxylate group of the ACE inhibitors studied is more acidic than the C-terminal carboxylate. However, at physiological pH = 7.4 both carboxyl groups of ACE inhibitors are completely ionized and the dicarboxyl-containing ACE inhibitors behave as strong acids. The available experimental partition coefficients of these ACE inhibitors investigated are well reproduced by the neural network-based ALOGPs and the fragment-based KoWWiN methods. All parent drugs (and prodrugs), with the exception of fosinopril, are compounds with low lipophilicity. Calculated pK a, lipophilicity, solubility, absorption, and polar surface area of the most effective ACE inhibitors for the prevention of myocardial infarction, perindopril and ramipril, were found similar. Therefore, it is probable that the experimentally observed differences in the survival benefits in the first year after acute myocardial infarction in patients 65 years of age or older correlate closely to the physicochemical and pharmacokinetic characteristics of the specific ACE inhibitor that is used.

Effects of angiotensin-converting-enzyme inhibitors in combination with diuretics on blood pressure and renal injury in nitric oxide-deficiency-induced hypertension in rats

The present study investigates the effects of chronic administration of ACEIs (angiotensin-converting-enzyme inhibitors; either zofenopril or enalapril) in combination with a diruetic (hydrochlorothiazide) on BP (blood pressure) increase and renal injury induced by L-NAME (NG-nitro-L-arginine methyl ester), an inhibitor of NO (nitric oxide) synthesis. Rats were untreated or received L-NAME alone, L-NAME+zofenopril+hydrochlorothiazide or L-NAME+enalapril+hydrochlorothiazide for 8 weeks. L-NAME treatment resulted in marked elevation in BP and mortality. Treatment with either ACEI and diuretic prevented the increase in BP induced by L-NAME, reduced the death rate and improved excretory parameters. Renal injury in the L-NAME group was severe, but, in the groups treated with either ACEI and diuretic, glomerular and tubulointerstitial lesions were not observed and the intensity, number and size of vessels affected was reduced. However, the efficacy of zofenopril+diuretic was superior to that of enalapril+diuretic in reducing vascular alterations. Oxidative stress indices and the expression of NO synthase and nitrotyrosine were normalized by the treatments. In conclusion, the combined treatment of zofenopril or enalapril with hydrochlorothiazide completely prevented the development of arterial hypertension induced by L-NAME. Renal morphological and functional alterations in the hypertensive animals were also almost completely normalized, but the treatment with zofenopril+diuretic produced a more complete organ protection. The protective effect is related to an activation of endothelial NO synthase expression and to a normalization of the oxidative stress parameters due to the inhibition of angiotensin II.

Human physiologically based pharmacokinetic model for ACE inhibitors: ramipril and ramiprilat

Background

The angiotensin-converting enzyme (ACE) inhibitors have complicated and poorly characterized pharmacokinetics. There are two binding sites per ACE (high affinity "C", lower affinity "N") that have sub-nanomolar affinities and dissociation rates of hours. Most inhibitors are given orally in a prodrug form that is systemically converted to the active form. This paper describes the first human physiologically based pharmacokinetic (PBPK) model of this drug class.

Methods

The model was applied to the experimental data of van Griensven et. al for the pharmacokinetics of ramiprilat and its prodrug ramipril. It describes the time course of the inhibition of the N and C ACE sites in plasma and the different tissues. The model includes: 1) two independent ACE binding sites; 2) non-equilibrium time dependent binding; 3) liver and kidney ramipril intracellular uptake, conversion to ramiprilat and extrusion from the cell; 4) intestinal ramipril absorption. The experimental in vitro ramiprilat/ACE binding kinetics at 4°C and 300 mM NaCl were assumed for most of the PBPK calculations. The model was incorporated into the freely distributed PBPK program PKQuest.

Results

The PBPK model provides an accurate description of the individual variation of the plasma ramipril and ramiprilat and the ramiprilat renal clearance following IV ramiprilat and IV and oral ramipril. Summary of model features: Less than 2% of total body ACE is in plasma; 35% of the oral dose is absorbed; 75% of the ramipril metabolism is hepatic and 25% of this is converted to systemic ramiprilat; 100% of renal ramipril metabolism is converted to systemic ramiprilat. The inhibition was long lasting, with 80% of the C site and 33% of the N site inhibited 24 hours following a 2.5 mg oral ramipril dose. The plasma ACE inhibition determined by the standard assay is significantly less than the true in vivo inhibition because of assay dilution.

Conclusion

If the in vitro plasma binding kinetics of the ACE inhibitor for the two binding sites are known, a unique PBPK model description of the Griensven et. al. experimental data can be obtained.

Hydrochlorothiazide increases plasma or tissue angiotensin-converting enzyme-inhibitor drug levels in rats with myocardial infarction: Differential effects on lisinopril and zofenopril

Sodium depletion with diuretics augments the efficacy of angiotensin-converting enzyme-inhibitor therapy for hypertension and renal dysfunction, and possibly for left ventricular dysfunction after myocardial infarction. Underlying mechanisms may involve altered angiotensin-converting enzyme-inhibitor pharmacokinetics. We hypothesized that the diuretic hydrochlorothiazide causes increased steady-state levels of the angiotensin-converting enzyme-inhibitors lisinopril and zofenopril in rats with myocardial infarction. Rats were subjected to coronary ligation to induce myocardial infarction. After 1 week, rats were randomized to 50 mg/kg/day hydrochlorothiazide or control treatment for 3 weeks. The last week, rats received lisinopril or zofenopril in equipotentent dosages (3.3 and 10 mg/kg/day, respectively). Rats were sacrificed at Tmax after the last dose of angiotensin-converting enzyme-inhibitor, and tissues were collected for analysis of drug concentrations. Lisinopril concentrations in plasma were significantly increased by hydrochlorothiazide, at unchanged tissue concentrations. This increase could be fully explained by decreased renal function, as evidenced by increased plasma creatinine levels (lisinopril + hydrochlorothiazide 82+/-5 microM versus lisinopril 61+/-5 microM, P < 0.001). In contrast, zofenoprilat levels in kidney and non-infarcted left ventricle were markedly increased by hydrochlorothiazide, whereas plasma concentrations were unchanged. Although hydrochlorothiazide tended to increase plasma creatinine in zofenopril-treated rats as well, this increase was less pronounced (zofenopril + hydrochlorothiazide 61+/-3 microM versus zofenopril 54+/-2 microM, P = 0.15). Hydrochlorothiazide increases steady-state angiotensin-converting enzyme-inhibitor drug levels, most likely by affecting their renal clearance. Notably, the lipophilic angiotensin-converting enzyme-inhibitor zofenopril accumulated in tissue, whereas the hydrophilic lisinopril increased in plasma. Whether combining different angiotensin-converting enzyme-inhibitors with hydrochlorothiazide translates into distinct clinical profiles requires further study.

Exploring the Role of Different Drug Transport Routes in Permeability Screening

The influence of different drug transport routes in intestinal drug permeability screening assays was studied. Three experimental models were compared: the small-intestine-like 2/4/A1 cell model, which has a leaky paracellular pathway, the Caco-2 cell model, which has a tighter paracellular pathway, and artificial hexadecane membranes (HDMs), which exclusively model the passive transcellular pathway. The models were investigated regarding their ability to divide passively and actively transported compounds into two permeability classes and to rank compounds according to human intestinal absorption. In silico permeability models based on two-dimensional (2D) and three-dimensional (3D) molecular descriptors were also developed and validated using external test sets. The cell-based models classified 80% of the acceptably absorbed compounds (FA >/= 30%) correctly, compared to 60% correct classifications using the HDM model. The best compound ranking was obtained with 2/4/A1 (r(s) = 0.74; r(s) = 0.95 after removing actively transported outliers). The in silico model based on 2/4/A1 permeability gave results of similar quality to those obtained when using experimental permeability, and it was also better than the experimental HDM model at compound ranking (r(s) = 0.85 and 0.47, respectively). We conclude that the paracellular transport pathway present in the cell models plays a significant role in models used for intestinal permeability screening and that 2/4/A1 in vitro and in silico models are promising alternatives for drug discovery permeability screening.

Pharmacokinetics and pharmacokinetic/pharmacodynamic relationships for angiotensin-converting enzyme inhibitors

The pharmacokinetic (PK) properties and the pharmacokinetic/pharmacodynamic (PK/PD) relationships for the angiotensin-converting enzyme (ACE) inhibitors (ACEIs), such as enalaprilat, benazeprilat, imidaprilat and ramiprilat, differ from those of conventional drugs. This is because of their immediate and saturable binding to an ACE pool which is partly circulating (and contributing to the measured plasma concentration), and partly noncirculating (tissular), being anchored to the endothelium of vessels and not measurable by the analytical technique. A physiologically based model is required to allow appropriate interpretation of the different phases of the disposition curve of ACEI. The protracted terminal phase observed for all ACEIs is not a conventional elimination phase but a phase dependent on ACEI dissociation from ACE. In contrast, the phase which reflects ACEI elimination (and which is interpreted as a distribution phase for a conventional drug) has a short half-life, thus explaining the absence of drug accumulation during repeated dosing and mild kidney failure. ACE inhibition is the surrogate endpoint generally selected for establishing a PK/PD relationship and for simulating dosage regimen scenarios in order to decide on the appropriate dosage regimen for ACEIs.

Brain angiotensin-converting enzyme activity and autonomic regulation in heart failure

Several recent studies suggest an important role for the brain renin-angiotensin system in the pathogenesis of heart failure. Angiotensin-converting enzyme (ACE) activity and binding of angiotensin type 1 (AT1) receptors, which mediate the central effects of ANG II, are increased in heart failure. The present study examined the relationship between brain ACE activity and the autonomic dysregulation characteristic of rats with congestive heart failure. Rats with heart failure (HF) induced by coronary artery ligation and sham-operated control (SHAM) rats were treated with chronic (28 days) third cerebral ventricle [intracerebroventricular (ICV)] or intraperitoneal (IP) infusion of a low dose of the ACE inhibitor enalaprilat (ENL) or vehicle (VEH). VEH-treated HF rats had increased sodium consumption, reduced urine sodium and urine volume, and increased sympathetic nerve activity with impaired baroreflex regulation. These responses were minimized or prevented by ICV ENL started 24 h after coronary ligation. IP ENL at the low dose used in these studies had no beneficial effects on HF rats. Neither IP nor ICV ENL had any substantial effect on the SHAM rats. The findings confirm a critically important contribution of the brain renin-angiotensin system to the pathophysiology of congestive heart failure.

Chronic effects of angiotensin-converting enzyme inhibition on kinin receptor binding sites in the rat spinal cord

With the use of in vitro receptor autoradiography, this study aims at determining whether the higher level of kinin B(2) receptor density in the spinal cord of the spontaneously hypertensive rat (SHR) is secondary to arterial hypertension and whether chronic treatment with angiotensin I-converting enzyme inhibitors (ACEI) can regulate neuronal B(1) and B(2) receptors. SHR received, from the age of 4 wk, one of the two ACEI (lisinopril or zofenopril, 10 mg x kg(-1) x day(-1)) or for comparison, the selective AT(1) antagonist (losartan, 20 mg x kg(-1) x day(-1)) in their drinking water for a period of 4, 12, and 20 wk. Age-matched untreated SHR and Wistar-Kyoto rats (WKY) were used as controls. B(2) receptor binding sites in most laminae were higher in SHR than in WKY from the age of 8 to 24 wk. Whereas B(1) receptor binding sites were significantly present in young SHR and WKY, they were barely detectable in adult rats. ACEI (16 and 24 wk) and AT(1) antagonist (24 wk) enhanced the number of B(2) without changing B(1) receptor binding sites. However, at 8 wk the three treatments significantly increased B(1) and decreased B(2) receptors in lamina I. It is concluded that 1) the higher density of B(2) receptors in the spinal cord of SHR is not due to hypertension, 2) kinin receptors are regulated differently by ACEI in neuronal and vascular tissues, and 3) aging may have a profound impact on levels of B(1) and B(2) receptors in the rat spinal cord.

Neuropsychiatric effects of cardiovascular drug therapy

Various cardiovascular drugs have been shown to have neuropsychiatric effects that can be harmful or therapeutically beneficial to patients. As an example, both sedation and mental depression have been described in patients receiving centrally acting antihypertensive drugs and beta-adrenergic blockers, related to their antiadrenergic actions. In contrast, because of these antiadrenergic actions, agents like clonidine have been used to treat opiate, alcohol, and nicotine withdrawal, while beta blockers have been used to treat symptoms of performance anxiety, migraine, and psychocardiac disorders. Some antiarrhythmic drugs have been associated with delirium, and digitalis toxicity has been shown to cause hallucinations, mania, euphoria, and depression. The calcium-channel blocker verapamil has been used as an adjunctive treatment in patients with bipolar disorders. Since neuropsychiatric symptoms are seen in patients with cardiovascular disease, clinicians should be aware of the possible relationship between these symptoms and concurrent cardiovascular drug therapy.