Enalapril worldwide experience

Beta-Arrestins in the Treatment of Heart Failure Related to Hypertension: A Comprehensive Review

Heart failure (HF) is a complicated clinical syndrome that is considered an increasingly frequent reason for hospitalization, characterized by a complex therapeutic regimen, reduced quality of life, and high morbidity. Long-standing hypertension ultimately paves the way for HF. Recently, there have been improvements in the treatment of hypertension and overall management not limited to only conventional medications, but several novel pathways and their pharmacological alteration are also conducive to the treatment of hypertension. Beta-arrestin (β-arrestin), a protein responsible for beta-adrenergic receptors’ (β-AR) functioning and trafficking, has recently been discovered as a potential regulator in hypertension. β-arrestin isoforms, namely β-arrestin1 and β-arrestin2, mainly regulate cardiac function. However, there have been some controversies regarding the function of the two β-arrestins in hypertension regarding HF. In the present review, we try to figure out the paradox between the roles of two isoforms of β-arrestin in the treatment of HF.

Beta-Arrestins in the Treatment of Heart Failure Related to Hypertension: A Comprehensive Review

Heart failure (HF) is a complicated clinical syndrome that is considered an increasingly frequent reason for hospitalization, characterized by a complex therapeutic regimen, reduced quality of life, and high morbidity. Long-standing hypertension ultimately paves the way for HF. Recently, there have been improvements in the treatment of hypertension and overall management not limited to only conventional medications, but several novel pathways and their pharmacological alteration are also conducive to the treatment of hypertension. Beta-arrestin (β-arrestin), a protein responsible for beta-adrenergic receptors’ (β-AR) functioning and trafficking, has recently been discovered as a potential regulator in hypertension. β-arrestin isoforms, namely β-arrestin1 and β-arrestin2, mainly regulate cardiac function. However, there have been some controversies regarding the function of the two β-arrestins in hypertension regarding HF. In the present review, we try to figure out the paradox between the roles of two isoforms of β-arrestin in the treatment of HF.

Proline-dependent regulation of collagen metabolism

This review is focused on recent data on the role of proline (Pro) in collagen biosynthesis and cellular metabolism. It seems obvious that one of the main substrates for collagen biosynthesis Pro is required to form collagen molecule. The question raised in this review is whether the Pro for collagen biosynthesis is synthesized "de novo", comes directly from degraded proteins or it is converted from other amino acids. Recent data provided evidence that extracellular Pro (added to culture medium) had significant, but relatively little impact on collagen biosynthesis in fibroblasts (the main collagen synthesized cells) cultured in the presence of glutamine (Gln). However, extracellular Pro drastically increased collagen biosynthesis in the cells cultured in Gln-free medium. It suggests that Pro availability determines the rate of collagen biosynthesis and demand for Pro in fibroblasts is predominantly met by conversion from Gln. The potential mechanism of this process as well as possible implication of this knowledge in pharmacotherapy of connective tissue diseases is discussed in this review.

Simultaneous Determination of Rivaroxaban and Enalapril in Rat Plasma by UPLC-MS/MS and Its Application to A Pharmacokinetic Interaction Study

BACKGROUND AND OBJECTIVES

There have been no animal experiments and clinical studies on the pharmacokinetic interaction between rivaroxaban and enalapril. To investigate whether a potential pharmacokinetic interaction is present between rivaroxaban and enalapril, a rapid and sensitive Ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated to determine the concentration of rivaroxaban and enalapril in rat plasma and was then applied to a pharmacokinetic interaction study.

METHODS

The analytes were separated on an Acquity UPLC BEH C18 chromatography column (2.1 × 50 mm, 1.7 μm) with acetonitrile and 0.1% formic acid as the mobile phase with gradient elution. The mass spectrometer was operated in multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of 436.1 → 145.1 m/z for rivaroxaban, 377.3 → 234.2 m/z for enalapril and 285.2 → 193.1 m/z for diazepam (IS).

RESULTS

The method was validated over the concentration range of 1.0-200 ng/mL for rivaroxaban and 0.5-100 ng/mL for enalapril. The intra- and inter-day precision and accuracy of the quality control (QC) samples exhibited relative standard deviations (RSD) < 9.4% and the accuracy values ranged from - 8.3 to 9.6%. After co-administration of rivaroxaban and enalapril, the maximum plasma concentration (C_max) and area under the systemic drug concentration-time curve from time 0 to infinity (AUC_0-∞) of rivaroxaban were significantly increased by 19.6% (p < 0.05) and 21.3% (p < 0.05), respectively. On the contrary, the plasma clearance rate (CL/F) of rivaroxaban and enalapril was significantly decreased by 17.8% (p < 0.05) and 23.8% (p < 0.05), respectively.

CONCLUSIONS

The UPLC-MS/MS method was successfully applied to simultaneous determination of rivaroxaban and enalapril in rat plasma and applied to study the pharmacokinetic interaction between rivaroxaban and enalapril. The co-administration of rivaroxaban and enalapril resulted in a significant drug interaction in rats.

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.

Enalapril stimulates collagen biosynthesis through prolidase-dependent mechanism in cultured fibroblasts

The mechanism of a lower incidence of dermatological manifestations in patients treated with enalapril compared to patients treated with other ACE-inhibitors, e.g., captopril, is not known. The finding that prolidase plays an important role in collagen biosynthesis and that some angiotensin-converting enzyme inhibitors affect prolidase activity led us to evaluate its effect on collagen biosynthesis in cultured human skin fibroblasts. Since insulin-like growth factor (IGF-I) and transforming growth factor beta 1 (TGF-β1) are the most potent stimulators of both collagen biosynthesis and prolidase activity, and prolidase is regulated by β₁ integrin signaling, the effect of enalapril and enalaprilat on IGF-IR, TGF-β1, and β₁ integrin receptor expressions was evaluated. Cells were treated with milimolar concentrations (0.3 and 0.5 mM) of enalapril and enalaprilat for 24 h. The activity of prolidase was determined by colorimetic assay. Collagen biosynthesis was evaluated by radiometric assay. Expression of signaling proteins was evaluated using Western blot. It was found that enalapril- and enalaprilat-dependent increase in prolidase activity and expression was accompanied by parallel increase in collagen biosynthesis. The exposure of the cells to 0.5 mM enalapril and enalaprilat contributed to increase in IGF-IR and α₂β₁ integrin receptor as well as TGF-β1 and NF-κB p65 expressions. Enalapril- and enalaprilat-dependent increase of collagen biosynthesis in fibroblasts results from increase of prolidase activity and expression, which may undergo through activation of α₂β₁ integrin and IGF-IR signaling as well as upregulation of TGF-β1 and NF-κB p65, the inhibitor of collagen gene expression.

Effects of Hypertension on Abdominal Wall Healing: Experimental Study in Rats

PURPOSE

The aim of this study was to investigate the effects of untreated and treated hypertension on abdominal wall healing.

METHODS

Thirty-two spontaneously hypertensive rats (SHR) were randomly allocated into two groups: H (n = 16), untreated and E (n = 16), treated with enalapril (40 mg/kg per day). Group C (n = 16) was a nonhypertensive control group. The animals of each group were submitted to a midline laparotomy and randomly divided, according to the day on which they were killed (7th or 14th postoperative day), into subgroups of 8 animals, as follows: H-7, H-14, E-7, E-14, C-7 and C-14. On the day of their deaths, two strips of the anterior abdominal wall were collected. One strip was submitted to breaking strength measurement and the other to hydroxyproline determination.

RESULTS

No mortalities or complications were observed in the six subgroups. The breaking strength in E-7 subgroup was significantly lower than in C-7 (P < 0.05). The tissue hydroxyproline levels were similar in all six subgroups (P > 0.05).

CONCLUSIONS

Untreated hypertension had no effect on the abdominal wall healing of rats. Hypertensive animals treated with enalapril showed a significant decrease in abdominal wound-breaking strength on the 7th postoperative day.

Liquid chromatographic separation and UV determination of certain antihypertensive agents

Three antihypertensive agents were extracted and isolated from commercial formulations. These were purified and characterized by melting point, lambdamax and IR. The percentage recovery by extraction process was in the range 81-91%. Active ingredients from binary formulations were separated by RP-HPLC using methanol-water (50:50 v/v) and by TLC using CHCl3-CH3OH (6:1) as mobile phase. Detection was by UV at 210 nm in HPLC, and by iodine vapors in TLC. The solvent conditions from TLC were transferred to open column chromatographic separation. Quantitative determination was carried out using TLC and column chromatography supplemented with UV spectrophotometry. Recovery was in the range 82-93%. Two combination of drugs, viz. amlodipine+ramipril and amlodipine+enalapril, were separated by the three modes of liquid chromatography. The percentage recovery was in the range 80-92% by open column.

High-performance liquid chromatographic determination of enalapril in human plasma by enzyme kinetic analytical method

A high-performance liquid chromatographic method for indirect determination of enalapril in human plasma, was developed and validated. An exogenous angiotensin converting enzyme after drug inhibition was determined by reacting with hippuryl-histidyl-leucine to produce hippuric acid (HA) which was inversely proportional to the amount of enalaprilat in plasma. The HPLC was carried out on a Lichrosphere 60RP-select B, C18, 5 microm (125 mm x 4.0 mm i.d.) column at flow rate of 1.0 ml/min. The analysis time per injection was within 6.5 min. The lowest concentration of enalaprilat to be quantitated was 3.0 ng/ml with the acceptable accuracy and precision. This successfully developed method was practically and accurately used for pharmacokinetics and bioequivalent study of enalapril.

Angiotensin-converting enzyme inhibitors

ACE inhibitors have achieved widespread usage in the treatment of cardiovascular and renal disease. ACE inhibitors alter the balance between the vasoconstrictive, salt-retentive, and hypertrophic properties of angiotensin II (Ang II) and the vasodilatory and natriuretic properties of bradykinin and alter the metabolism of a number of other vasoactive substances. ACE inhibitors differ in the chemical structure of their active moieties, in potency, in bioavailability, in plasma half-life, in route of elimination, in their distribution and affinity for tissue-bound ACE, and in whether they are administered as prodrugs. Thus, the side effects of ACE inhibitors can be divided into those that are class specific and those that relate to specific agents. ACE inhibitors decrease systemic vascular resistance without increasing heart rate and promote natriuresis. They have proved effective in the treatment of hypertension, they decrease mortality in congestive heart failure and left ventricular dysfunction after myocardial infarction, and they delay the progression of diabetic nephropathy. Ongoing studies will elucidate the effect of ACE inhibitors on cardiovascular mortality in essential hypertension, the role of ACE inhibitors in patients without ventricular dysfunction after myocardial infarction, and the role of ACE inhibitors compared with newly available angiotensin AT1 receptor antagonists.

ACE inhibitor-induced angioedema. Incidence, prevention and management

Available information from 1980 to 1997 on angiotensin converting enzyme (ACE) inhibitor-induced angioedema and its underlying mechanisms are summarised and discussed. The incidence of angioedema is low (0.1 to 0.2%) but can be considered as a potentially life-threatening adverse effect of ACE inhibitor therapy. This adverse effect of ACE inhibitors, irrespective of the chemical structure, can occur early in treatment as well as after prolonged exposure for up to several years. The estimate incidence is quite underestimated. The actual incidence can be far higher because of poorly recognised presentation of angioedema as a consequence of its late onset in combination with usually long term therapy. Also, a spontaneous reporting bias can contribute to an actual higher incidence of this phenomenon. The incidence can be even higher (up to 3-fold) in certain risk groups, for instance Black Americans. Treatment includes immediate withdrawal of the ACE inhibitor and acute symptomatic supportive therapy followed by immediate (and long term) alternative therapy with other classes of drugs to manage hypertension and/or heart failure. Preclinical and clinical studies for the elucidation of the underlying mechanism(s) of ACE inhibitor-associated angioedema have not generated definite conclusions. It is suggested that immunological processes and several mediator systems (bradykinin, histamine, substance P and prostaglandins) are involved in the pathogenesis of angioedema. A great part of all reviewed reports suggest a relationship between ACE inhibitor-induced angioedema and increased levels of (tissue) bradykinin. However, no conclusive evidence of the role of bradykinin in angioedema has been found and an exclusive role of bradykinin seems unlikely. So far, no clear-cut evidence for an immune-mediated pathogenesis has been found. In addition, ACE gene polymorphism and some enzyme deficiencies are proposed to be involved in ACE inhibitor-induced angioedema. Progress in pharmacogenetic and molecular biological research should throw more light on a possible genetic component in the pathogenesis of ACE inhibitor-associated angioedema.

Drug-induced taste and smell disorders. Incidence, mechanisms and management related primarily to treatment of sensory receptor dysfunction

Drugs in every major pharmacological category can impair both taste and smell function and do so more commonly than presently appreciated. Impairment usually affects sensory function at a molecular level, causing 2 major behavioural changes--loss of acuity (i.e. hypogeusia and hyposmia) and/or distortion of function (i.e. dysgeusia and dysosmia). These changes can impair appetite, food intake, cause significant lifestyle changes and may require discontinuation of drug administration. Loss of acuity occurs primarily by drug inactivation of receptor function through inhibition of tastant/odorant receptor: (i) binding; (ii) Gs protein function; (iii) inositol trisphosphate function; (iv) channel (Ca++,Na++) activity; (v) other receptor inhibiting effects; or (vi) some combination of these effects. Distortions occur primarily by a drug inducing abnormal persistence of receptor activity (i.e. normal receptor inactivation does not occur) or through failure to activate: (i) various receptor kinases; (ii) Gi protein function; (iii) cytochrome P450 enzymes; or other effects which usually (iv) turn off receptor function; (v) inactivate tastant/odorant receptor binding; or (vi) some combination of these effects. Termination of drug therapy is commonly associated with termination of taste/smell dysfunction, but occasionally effects persist and require specific therapy to alleviate symptoms. Treatment primarily requires restoration of normal sensory receptor growth, development and/or function. Treatment which restores sensory acuity requires correction of steps initiating receptor and other pathology and includes zinc, theophylline, magnesium and fluoride. Treatment which inhibits sensory distortions requires reactivation of biochemical inhibition at the receptor or inactivation of inappropriate stimulus receptor binding and/or correction of other steps initiating pathology including dopaminergic antagonists, gamma-aminobutyric acid (GABA)-ergic agonists, calcium channel blockers and some orally active local anaesthetic, antiarrhythmic drugs.

CP-71,362: a pentapeptide renin inhibitor selective for the canine enzyme

Most renin inhibitors are primate-specific. In the present paper, we describe the effects of CP-71,362, a pentapeptide which preferentially inhibits canine (and to a lesser extent, rat) plasma renin. Vs. the canine enzyme, its affinity (IC50 = 3.3 x 10(-12) M) is 1000x greater than for rat renin (IC50 = 3.3 x 10(-9) M), and 1000x greater than for human (IC50 = 2.3 x 10(-8) M), cynomolgus monkey (IC50 = 1.6 x 10(-8) M), or guinea pig (IC50 = 5.2 x 10(-8) M) enzyme. In anesthetized, sodium-depleted dogs, intravenous infusion of CP-71,362 (ED50 = 1.1 micrograms/kg/min) resulted in dose-dependent decreases (up to -35 mm Hg) in mean arterial pressure (MAP). The maximum fall in MAP was equivalent to that produced by i.v. captopril (5 mg/kg). Similar falls in MAP were observed in conscious sodium-depleted SHR (ED50 = 5 micrograms/kg/min). Via bolus injection, the action of CP-71,362 was relatively brief in dog, guinea pig, and SHR. We conclude that CP-71,362 is a potent canine/rat renin inhibitor and causes profound MAP lowering in these species.

Angiotensin II receptor antagonists: a new approach to blockade of the renin-angiotensin system

A-II exerts its activity on various target tissues by binding to its receptors. The discovery of local RASs and A-II receptors within various tissues has generated interest in the clinical usefulness of RAS inhibition by directly blocking the action of A-II at the receptor level. Different A-II receptor subtypes have been identified and subsequently termed AT1 and AT2. AT1-receptor subtypes are the predominant receptor subtypes existing in most organs and, by coupling to a transmembrane G protein, seem to be the main subtypes participating in the vasoactive responses of A-II. Saralasin, a peptide with specific A-II receptor-antagonistic activity, had limited practical long-term usefulness as a result of its short half-life, significant agonistic properties, and lack of oral bioavailability. The discovery of simple benzyl-substituted imidazoles, which possess weak but highly selective A-II receptor antagonistic properties, led to the development of losartan (DuP 753). Losartan is a potent, orally active, specific, competitive nonpeptide A-II receptor antagonist that appears to be an effective antihypertensive agent both in animal studies and in preliminary clinical trials. The therapeutic usefulness of losartan, however, is not limited to its antihypertensive effects. The potential benefits of A-II receptor antagonists include roles in postmyocardial infarction therapy, slowing A-II-induced cardiac hypertrophy, 154, 155 slowing the progression of heart failure, preventing postangioplasty restenosis, and in slowing the progression of renal disease. Furthermore, losartan, a selective A-II type 1 (AT1) receptor antagonist, has also been a valuable pharmacologic probe for studying the mechanism of A-II stimulation of its receptors. A-II receptor antagonism appears to be as effective as ACE inhibition in the treatment of hypertension and other pathologic processes that involve the RAS and may offer an alternative to those patients who cannot tolerate ACE inhibitors because of their side effects.

Efficacy and dosage of enalapril in congenital and acquired heart disease

In a tertiary referral centre 63 patients underwent 67 treatment periods with enalapril. The median age was 5.4 months. All children had signs of heart failure: congestive cardiac failure with breathlessness at rest was present in 88%. Haemodynamic groups were left-to-right shunt (n = 15), impaired ventricular function (n = 14), after cardiac surgery (n = 23), valvar regurgitation (n = 12), and hypertension (n = 3). Serial clinical, radiological, and laboratory data were used to judge outcome. The mean (SD) maximal dose was 0.30 (0.21) mg/kg/day. Thirty nine (58%) patients improved, 20 (30%) showed no improvement, and eight (12%) had side effects requiring discontinuation of enalapril. Renal failure in eight patients was related to young age, low weight, and left-to-right shunt group. Three patients died in congestive heart failure with renal failure. Enalapril was clinically safe and effective for children with cardiac failure secondary to ventricular impairment, valvar regurgitation, or after cardiac surgery. Renal failure was a problem in young infants with left-to-right shunts.

Enalapril clinical pharmacokinetics and pharmacokinetic-pharmacodynamic relationships. An overview

The conventional pharmacokinetic profile of the angiotensin converting enzyme (ACE) inhibitor, enalapril, is a lipid-soluble and relatively inactive prodrug with good oral absorption (60 to 70%), a rapid peak plasma concentration (1 hour) and rapid clearance (undetectable by 4 hours) by de-esterification in the liver to a primary active diacid metabolite, enalaprilat. Peak plasma enalaprilat concentrations occur 2 to 4 hours after oral enalapril administration. Elimination thereafter is biphasic, with an initial phase which reflects renal filtration (elimination half-life 2 to 6 hours) and a subsequent prolonged phase (elimination half-life 36 hours), the latter representing equilibration of drug from tissue distribution sites. The prolonged phase does not contribute to drug accumulation on repeated administration but is thought to be of pharmacological significance in mediating drug effects. Renal impairment [particularly creatinine clearance < 20 ml/min (< 1.2 L/h)] results in significant accumulation of enalaprilat and necessitates dosage reduction. Accumulation is probably the cause of reduced elimination in healthy elderly individuals and in patients with concomitant diabetes, hypertension and heart failure. Conventional pharmacokinetic approaches have recently been extended by more detailed descriptions of the nonlinear binding of enalaprilat to ACE in plasma and tissue sites. As a result of these new approaches, there have been significant improvements in the characterisation of concentration-time profiles for single-dose administration and the translation to steady-state. Such improvements have further importance for the accurate integration of the pharmacokinetic and pharmacodynamic responses to enalapril(at) in a concentration-effect model.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of treatment with lisinopril versus enalapril for congestive heart failure

The effect of lisinopril 5-20 mg once daily or enalapril 5-20 mg once daily on exercise capacity, ventricular ectopic activity, and signs and symptoms of heart failure have been studied in 278 patients with mild-to-moderate (New York Heart Association [NYHA] classes II and III) heart failure in a randomized, double-blind, parallel-group study of 12 weeks' duration. Exercise duration was significantly increased by both angiotensin-converting enzyme (ACE) inhibitors after 6 and 12 weeks of treatment compared with their respective baseline values. There was a trend toward a greater increase in exercise duration on lisinopril after 12 weeks, although this did not reach statistical significance (p = 0.0748). There were no significant treatment differences with respect to the effect of the 2 drugs on ventricular ectopic counts, couplets, or nonsustained ventricular tachycardia. Both drugs were equally effective in improving NYHA grading and symptoms. Neither treatment had any significant effect on mean heart rate or mean blood pressures. Both treatments were equally well tolerated. The most commonly reported adverse events on both drugs were cough, dizziness, fall in blood pressure, vertigo, and myocardial infarction. The results of this study indicate that lisinopril 5-20 mg once daily is at least as effective and well tolerated as enalapril 5-20 mg once daily.

Use of ACE inhibitors in the treatment of cardiovascular disease

ACE inhibitors have been available by prescription since the marketing of captopril in the early 1980s. Since that time, six additional ACE inhibitors have been marketed, four of which received approval from the Food and Drug Association in 1991. All but one of the new ACE inhibitors are carboxylic-acid compounds, and all of them maintain a pro-drug metabolic pathway. Initially, ACE inhibitors were approved only for the control of high blood pressure. More recently, captopril and enalapril have been approved for use in congestive heart failure. In 1988, ACE inhibitors were one of the recommended first-line therapies for mild-to-moderate hypertension. Their use in patients with hypertension has steadily increased, most likely because of their minimal effect on coexistent cardiovascular risk factors. In CHF, ACE inhibitors are the only single drug class that has been shown to reduce mortality and hospitalizations due to the disease without concomitant administration of another drug. ACE inhibitors are clearly drugs that should be used early in the treatment of most patients with CHF. Differences between ACE inhibitors are often difficult to define. As information regarding the clinical utility of tissue ACE inhibition is unveiled, the ability to use a selected ACE inhibitor based on individual patient characteristics may increase. The future for ACE inhibition looks promising and the cumulative clinical value of ACE inhibition appears to be just beginning.

Anaphylactoid reactions during hemodialysis and hemofiltration: role of associating AN69 membrane and angiotensin I-converting enzyme inhibitors

Over a 20-month period, we observed 15 anaphylactoid reactions in six patients undergoing hemodialysis and three others on hemofiltration with AN69 capillary dialyzers who were receiving angiotensin-converting enzyme (ACE) inhibitors. These reactions were severe in 11 cases. In eight patients, anaphylactoid reactions stopped when AN69 membrane was replaced by polysulfone membrane and ACE inhibitors were continued. In one case, reducing the dose of ACE inhibitors was sufficient to prevent new reactions. Anaphylactoid reactions did not occur in patients undergoing dialysis with another membrane (cellulosic or synthetic), nor in those on AN69 membrane without ACE inhibitor treatment. We conclude that back-filtration of endotoxin-contaminated dialysate does not play the main role in the origin of such reactions, since they occurred in patients on hemofiltration with sterile and pyrogen-free substitution liquids.

Adverse effects of angiotensin-converting enzyme inhibitors in antihypertensive therapy with focus on quinapril

Angiotensin-converting enzyme (ACE) inhibitors are useful first-line drugs in the therapy of mild and moderate hypertension. Adverse reactions to this drug class are rarely serious. Hypotension, cough, rash, and taste disturbance are uncommon; reduced glomerular filtration and hyperkalemia occur infrequently; angioedema is rare and neutropenia is extremely rare. Quinapril is a new ACE inhibitor that is converted to biologically active quinaprilat in the liver. This ACE inhibitor has a rapid onset of action and inhibits local tissue converting enzyme systems in kidney, heart, and brain, as well as in the circulating renin-angiotensin system. Clinically significant adverse effects of quinapril occur at low rates. In 1,771 patients receiving quinapril, the reported incidence of the first occurrence of orthostatic hypotension was comparable to that seen in patients receiving placebo. In other studies, headache was reported by up to 4.7% of patients receiving quinapril, which is comparable to reported incidences of headache in patients receiving other ACE inhibitors. Other adverse events reported at rates greater than 1% include cough with associated rhinitis and bronchitis, dizziness, and somnolence. Such adverse events have only rarely led to the withdrawal of patients from clinical studies of quinapril.

Selective alpha 1-adrenoreceptor blockers in the treatment of hypertension: should we be using them more?

It has become apparent in recent years that in the treatment of essential hypertension, reduction of blood pressure alone is not sufficient to reduce significantly the morbidity and mortality from ischaemic heart disease. Since the emergence of a multifactorial approach to the prevention of cardiovascular disease, the potential interaction between antihypertensive therapy and metabolic factors, such as control of blood glucose and lipid levels, has become an important consideration. Abnormal function of the sympathetic nervous system may contribute to both the initiation, or maintenance, of hypertension and the associated metabolic disturbances. The new generation of selective alpha 1-adrenoreceptor blockers, besides lowering blood pressure, appear to have favourable effects on lipid and glucose metabolism. The use of these drugs and their place in the treatment of hypertension are discussed.

Impact of age, race, and obesity on hypertensive mechanisms and therapy

Despite the demonstrated efficacy of traditional antihypertensive therapy in reducing blood pressure, hypertension continues to be a major cause of cardiovascular disease morbidity and mortality. Stepped-care therapy is a nonphysiologic approach that, due to potential metabolic derangements and stimulation of undesirable reflex responses, may not substantially reduce the cardiovascular and renal complications associated with hypertension or improve long-term survival in many hypertensive patients. Because of fundamental hemodynamic differences related to the age, race, and weight of hypertensive patients, drug treatment often elicits varying responses. Certain classes of drugs are not only more effective but also more appropriate from a physiologic standpoint in specific types of patients. Therapy selection based in part on hemodynamic mechanisms and demographic patterns is a more rational approach to patient management and may contribute to a better overall outcome than has been observed with conventional treatment.

Quinapril: a new second-generation ACE inhibitor

Quinapril is a new non-sulfhydryl angiotensin-converting enzyme (ACE) inhibitor. The drug undergoes hepatic hydrolysis into its major active diacid metabolite, quinaprilat, and two minor inactive metabolites. On a weight basis quinaprilat is three times as potent an ACE inhibitor as quinapril. Approximately 60 percent of an oral dose of quinapril is absorbed. In contrast with captopril, the absorption of quinapril is unaffected by food. Peak serum concentrations of quinapril and quinaprilat are achieved within one and two hours, respectively. Approximately 61 percent of an orally administered dose is excreted in the urine, principally as quinaprilat. The elimination half-life of quinaprilat is three hours, but is prolonged up to 11 hours in patients with renal dysfunction. Quinapril dose reduction is recommended in patients with a creatinine clearance of 0.50 mL/sec or less. In the elderly the elimination of quinaprilat is reduced and correlates well with renal function. In patients with cirrhosis the hydrolysis of quinapril to quinaprilat is impaired resulting in lower plasma quinaprilat concentrations and up to a two-fold increase in quinapril half-life. Quinaprilat has a strong binding capacity to tissue ACE allowing for once-daily dosing. The recommended starting dose for quinapril is 20 mg/d. The nature and incidence of adverse reactions to quinapril are similar to those of enalapril and captopril. Quinapril's antihypertensive efficacy is equal to that of captopril and enalapril. A small number of patients with congestive heart failure (CHF) have been treated with quinapril. Preliminary data indicate that quinapril is an equally effective therapeutic alternative to presently available ACE inhibitors in the treatment of CHF.(ABSTRACT TRUNCATED AT 250 WORDS)

Agranulocytosis associated with enalapril

An 83-year-old patient developed agranulocytosis following six months of enalapril 10 mg/d. The patient also had received verapamil for three years. Upon discontinuation of both drugs the white blood cell count was rapidly restored. Cases of agranulocytosis due to angiotensin-converting enzyme inhibitors, mainly captopril, have been previously described. We could, however, find no single case associated with verapamil. This, and the very long exposure of the patient to verapamil, support the assumption that this life-threatening complication might have been caused by enalapril.

Newer antihypertensive agents

Three recent additions to the list of antihypertensive agents have been approved for use as monotherapy or in combination with other drugs. Betaxolol hydrochloride (Kerlone) maintains its effect for 24 hours, making it a true once-a-day beta blocker. Penbutolol sulfate (Levatol) is as effective as other beta blockers and diuretics. Doxazosin mesylate (Cardura), a selective alpha 1 blocker, also allows once-a-day dosing and has produced favorable changes in lipid profiles. Two new drug delivery systems, one for verapamil hydrochloride (Verelan) and one for extended-release nifedipine (Procardia XL), allow less frequent dosing and may offer other advantages, such as greater compliance and a more tolerable side-effect profile.

Intravenous enalaprilat therapy for hypertension

The angiotensin-converting enzyme inhibitor enalapril is available for intravenous administration in the form of enalaprilat. Intravenous enalaprilat is indicated for the management of hypertension when oral therapy is not feasible. However, there are no reports of intravenous enalaprilat therapy exceeding one week in duration. We report the case of a critically ill, 39-year-old woman who received intravenous enalaprilat for the management of hypertension for a period of 21 days. The patient's blood pressure and heart rate were controlled adequately on a regimen of enalaprilat 1.25 mg iv piggyback q6h without any apparent adverse effects.

Efficacy of enalapril in essential hypertension and its comparison with atenolol

The effect of enalapril was evaluated in 67 patients with essential hypertension, and its therapeutic efficacy was compared with atenolol in a placebo run-in, single-blind, cross-over trial. Enalapril significantly reduced blood pressure in all grades of essential hypertension. As monotherapy it 'normalized' blood pressure in 88%, 50% and 25% of patients with mild, moderate and severe hypertension respectively. Optimal dose for most of the patients was 20 to 40 mg/day. Comparison with atenolol revealed almost parallel efficacy of the two drugs, although enalapril produced a significantly greater reduction in systolic blood pressure in patients with mild and moderate hypertension (P less than 0.01 in each group). No serious side effects were encountered with either drug. Enalapril, therefore, has a potent and slightly superior antihypertensive effect to that of atenolol, and may be used as a 'first-step' drug in the treatment of hypertensive patients.

Angiotensin-converting enzyme inhibitors: a comparative review

The chemistry, pharmacology, pharmacokinetics, adverse effects, and dosages of the three currently available angiotensin-converting enzyme (ACE) inhibitors are reviewed. This class of agents effectively inhibits the conversion of angiotensin I to the active vasoconstrictor angiotensin II, a hormone that also promotes, via aldosterone stimulation, increased sodium and water retention. The ACE inhibitors, therefore, are capable of lowering blood pressure primarily by promoting vasodilatation and reducing intravascular fluid volume. Captopril, the first orally active, commercially available ACE inhibitor, is a sulfhydryl-containing compound. Captopril was followed by the introduction of enalapril and lisinopril, two non-sulfhydryl ACE inhibitors. The pharmacokinetic profiles of these three ACE inhibitors differ. Captopril has rapid onset with relatively short duration of action, whereas enalapril and lisinopril have slower onset and relatively long duration of action. Captopril is an active ACE inhibitor in its orally absorbable parent form. In contrast, enalapril must be deesterified in the liver to the metabolite enalaprilat in order to inhibit the converting enzyme; this accounts for its delayed onset of action. Lisinopril does not require metabolic activation to be effective; however, a slow and incomplete absorption pattern explains the delay in onset of activity. Captopril and its disulfide metabolites are primarily excreted in the urine with minor elimination in the feces. Approximately two-thirds of an administered enalapril dose is excreted in the urine as both the parent drug and the metabolite enalaprilat; the remainder of these two substances are excreted in the feces. Lisinopril does not undergo measurable metabolism and approximately one-third is excreted unchanged in the urine with the remaining parent drug being excreted in the feces. The ACE inhibitors lower systemic vascular resistance with a resultant decrease in blood pressure. Their efficacy is comparable to diuretics and beta-blockers in treating patients with mild, moderate, or severe essential and renovascular hypertension. In those patients with severe congestive heart failure (CHF) the ACE inhibitors produce a reduction in systemic vascular resistance, blood pressure, pulmonary capillary wedge pressure, and pulmonary artery pressure. These drugs may produce improvement in cardiac output and stroke volume and, with chronic administration, may promote regression of left ventricular hypertrophy. The antihypertensive effects of the ACE inhibitors are enhanced when these agents are combined with a diuretic. Captopril and enalapril have been shown to be of particular benefits as adjunctive therapy in patients with congestive heart failure, both in terms of subjective improvement of patient symptoms, and in improving overall hemodynamic status.(ABSTRACT TRUNCATED AT 400 WORDS)

Renal effects of angiotensin converting enzyme inhibitors: nondiabetic chronic renal disease

Based on studies in the rat remnant kidney model, it has been proposed that glomerular hypertension is responsible for the progressive nature of chronic renal disease. In that model, therapy with angiotensin converting enzyme (ACE) inhibitors reduced glomerular pressures. As a result, glomerular injury was reduced and the rate of progression of renal disease was slowed. Thus, alterations in hemodynamics may play an important role in glomerular injury. However, it is now evident that a variety of metabolic and other factors affect the progression of renal disease. Moreover, recent studies suggest that ACE inhibitors may also have beneficial effects that are independent of alterations in glomerular pressure. In humans, the glomerular hemodynamic response to renal disease cannot be measured, and it is not known whether or under which conditions glomerular capillary pressure might be elevated. Treatment with ACE inhibitors safely lowers blood pressure without adversely affecting renal function in most patients with nondiabetic chronic renal failure. Although proteinuria and the rate of progression of renal disease may decrease in some patients, these effects are inconsistently seen. Identification of the factors that modulate this variability in response to ACE inhibition may provide new insight into the pathogenesis and treatment of progressive renal disease in humans.

Effect of salt balance on the renal and hemodynamic actions of benazepril in normal men

Renal and hemodynamic effects of diet alone and of single oral doses of the nonsulphydryl angiotensin converting enzyme (ACE) inhibitor, benazepril (10 mg), were investigated in eight healthy volunteers under stable conditions of high salt intake (300 mmol NaCl/day) and low salt intake (10 mmol NaCl/day), in a double blind, placebo controlled study. There were no changes in blood pressure between the two dietary extremes either during the run-in period or once sodium balance had been achieved. Mean renal plasma flow was higher, by approximately 10% and renal vascular resistance lower by 15%, on high salt diet compared to low salt diet. Glomerular filtration rates were found to be similar irrespective of the state of salt balance. Both plasma urate concentration and plasma renin activity were significantly elevated in the low salt compared to high salt state. Benazepril caused a greater fall in blood pressure in the sodium depleted state. Significant increases in the mean renal plasma flow, in the order of 15-20%, were seen over 6 h postbenazepril when compared with placebo response, regardless of the level of salt intake. Glomerular filtration rate over the same period remained unaltered. Benazepril doubled the urinary excretion of sodium over the first 4 hours after dosing whilst on the low salt diet; the equivalent increase during salt loading was approximately 20%. These results suggest that benazepril may exert direct effects on renal tubular function additional to those achieved through ACE blockade.

A comparison of the efficacy and safety of quinapril with that of enalapril in the treatment of mild to moderate essential hypertension

This twenty-eight-week double-blind study in patients with mild to moderate essential hypertension showed quinapril (10, 20, and 40 mg/day) to be similarly effective to enalapril at the same doses in producing clinically significant reductions in sitting DBP. Hydrochlorothiazide could be safely added to quinapril therapy in nonresponders. Quinapril and enalapril were well tolerated. Both agents can safely be administered as first-line therapy.

Inhibition and active-site modelling of prolidase

Consideration of the active-site model of prolidase led us to examine azetidine, pyrrolidine and piperidine substrate analogs as potential in vivo inhibitors of the enzyme. One of these, N-benzyloxycarbonyl-L-proline, was shown to be a potent competitive inhibitor of porcine kidney prolidase (Ki = 90 microM); its rapid protein-mediated permeation of human and sheep erythrocytes suggests that it may be effective in vivo. The higher homolog, N-benzyloxycarbonyl-L-pipecolic acid, was also a potent inhibitor of the enzyme while the antihypertensive drugs, captopril and enalaprilat, were shown to have mild and no inhibitory effects, respectively. Analysis of inhibitor action and consideration of X-ray crystallographic data of relevant Mn2+ complexes allowed the active-site model of prolidase to be further refined; a new model is presented in which the substrate acts as a bidentate ligand towards the active-site manganous ion. Various aspects of the new model help to explain why Mn2+ has been 'chosen' by the enzyme in preference to other biologically available metal ions.

Hypertension

An estimated 58 million Americans are at increased risk of morbidity and premature death due to high blood pressure (BP) and require some type of therapy or systematic monitoring. This article focuses on recent advances in our understanding of the pathogenesis of hypertension, new approaches to the diagnosis and treatment of secondary hypertension, and current views of the most appropriate nonpharmacologic and pharmacologic therapy for essential hypertension. In view of the extremely high prevalence of the disorder, emphasis is placed on efficient and cost-effective strategies for diagnosing and managing the hypertensive patient. Recent evidence indicates that nonpharmacologic therapy, including dietary potassium and calcium supplements, reduction of salt intake, weight loss for the obese patient, regular exercise, a diet high in fiber and low in cholesterol and saturated fats, smoking cessation, and moderation of alcohol consumption produces significant sustained reductions in BP while reducing overall cardiovascular risk. Accordingly, nonpharmacologic antihypertensive therapy should be included in the treatment of all hypertensive patients. In persons with mild hypertension, nonpharmacologic approaches may adequately reduce BP, thereby avoiding the expense and potential side effects of drug therapy. In patients with more severe hypertension, nonpharmacologic therapy, used in conjunction with pharmacologic therapy, can reduce the dosage of antihypertensive medications necessary for BP control. Patients treated with nonpharmacologic therapy only should be followed closely, and if BP control is not satisfactory, drug therapy should be added. The large number of drugs available for use in hypertension treatment, coupled with our rapidly expanding knowledge of the pathophysiology of hypertension and of the adverse effects of these drugs in individual patient groups, make it possible to individualize antihypertensive treatment. When used as monotherapy, most agents effectively lower BP in the majority of patients with mild or moderate essential hypertension. Thus, a single agent from one of four classes: diuretics, angiotensin-converting enzyme inhibitors, calcium channel blockers, and beta-adrenergic blockers, usually provides effective BP control with minimal side effects in most patients. Therapy should be initiated with the agent most likely to be effective in BP lowering and best tolerated. If the initial agent is ineffective at maximal recommended therapeutic doses or has undue side effects, an alternative agent from another class should be tried. When monotherapy is unsuccessful, a second agent, usually of a different mechanism of action, should be

Angiotensin-converting enzyme inhibitors in heart failure

Recognition of the importance of the renin-angiotension-aldosterone system in heart failure, along with an appreciation of the hemodynamic benefits of vasodilator therapy has led to the widespread use of angiotensin-converting enzyme (ACE) inhibitors in the treatment of heart failure. The ACE inhibitors are the only class of vasodilator agents shown to have a significant protective effect against mortality in patients with heart failure.

Mild hypertension in the elderly. A comparison of prazosin and enalapril

In a single-blind, crossover study, prazosin and enalapril monotherapies were evaluated in 15 patients, aged 55 years or older (average age, 64 years), with mild hypertension (sitting diastolic blood pressure between 90 and 104 mm Hg). After eight weeks of placebo administration, patients were randomly assigned to treatment with prazosin or enalapril and then treated with the alternate drug after a second eight-week placebo washout period. The dose was titrated from 1 mg to a maximum of 10 mg twice daily of prazosin and from 2.5 mg to a maximum of 20 mg twice daily of enalapril to achieve a reduction in diastolic blood pressure to less than 85 mm Hg, with a decrease of at least 10 mm Hg based on clinical measurements of blood pressure. Patients received maintenance therapy with each medication for at least eight weeks. The response to therapy was then evaluated with two-hour periods of automated blood pressure monitoring. Average systolic and diastolic blood pressures for all patients during these two-hour monitoring periods decreased by 10.3 +/- 1.9/8.3 +/- 1.5 mm Hg during prazosin therapy and by 9.0 +/- 5.1/5.8 +/- 3.4 mm Hg during enalapril therapy. All patients responded to one of the two drugs, but only 50 percent responded to both. Side effects were generally mild and transient, and no significant metabolic effects were observed. Both prazosin and enalapril were effective and well tolerated in this population of elderly patients with mild hypertension.

Angiotensin converting enzyme inhibitors. II. Clinical use

Since their introduction in clinical practice in 1980, ACE inhibitors have been found useful in the treatment of hypertension and CHF. In hypertension, they are effective as monotherapy in 40% to 50% of the patients, and in combination with diuretics or calcium antagonists, they are effective in up to 85% of the patients. They are well tolerated, are not associated with depression, impotence, bronchospasm or metabolic derangements such as hypokalemia, hyperuricemia or hyperglycemia, and do not have adverse effects on the quality of life. As a result, they are preferred in hypertensive patients with CHF, left ventricular dysfunction, mental depression, older age, coronary artery disease, metabolic disorders, chronic destructive pulmonary disease, and peripheral vascular disease. In CHF they cause long-lasting hemodynamic and symptomatic improvement, improve exercise tolerance, and may lower mortality in certain patient subsets. Evolving new indications for ACE inhibitors include the diagnosis of renovascular hypertension, the prediction of surgical success, the treatment of scleroderma renal crisis, the reduction of proteinuria, renal protection, cardioprotection, the improvement of arterial compliance, in Bartter's syndrome and idiopathic edema, etc. ACE inhibitors are usually well tolerated but in some instances they may cause class-specific side effects such as hypotension; usually reversible azotemia or renal failure, especially in patients with renal artery stenosis or with CHF with low blood pressure; cough; angioedema; and hyperkalemia. Differences among ACE inhibitors are emerging and include chemical class (e.g., zinc ligand), biotransformation, potency, pharmacokinetics, prodrugs, tissue effects, additional pharmacologic properties, and drug interactions.

Angiotensin-converting enzyme inhibitors

There is convincing evidence that ACE inhibitors, alone or in combination with a diuretic, effectively lower blood pressure in patients with all grades of essential or renovascular hypertension and that they are of particular benefit as adjunctive therapy in patients with congestive heart failure. The hemodynamic, hormonal and clinical effects of the presently available ACE inhibitors, captopril and enalapril, are comparable and their side effect profiles are extremely favorable. One important difference between the two oral ACE inhibitors, however, is their pharmacokinetics; enalapril's action is slower to begin and is of longer duration. Compared with other agents, ACE inhibitors offer important advantages, among them an improved feeling of well being. It is, therefore, expected that ACE inhibitors will gain greater acceptance by patients and physicians in the future.

Recent issues in antihypertensive drug therapy

Results of recent large scale treatment trials have demonstrated that aggressive management of high blood pressure prevents progression of mild hypertension to the accelerated or malignant phase and reduces incidence of stroke, congestive heart failure, and left ventricular hypertrophy. These trials mostly have utilized a diuretic-based, stepped-care approach to drug therapy, however, and have not shown a consistent beneficial effect of treatment on coronary heart mortality. In addition, the results of studies such as MRFIT have raised questions about serious risks of diuretic treatment in selected patients. These concerns have led to increased use of nonpharmacologic approaches to lowering blood pressure in patients with mild hypertension, but most patients ultimately require drug therapy. Alternative agents to diuretics now being employed as monotherapy in mild hypertension include beta-blockers, calcium channel blockers, ACE inhibitors, alpha-blockers, alpha- and beta-blockers, and, to a lesser extent, centrally-acting sympatholytics and peripheral adrenergic antagonists. Rational use of these agents primarily is based on a careful evaluation of concomitant medical conditions (see Table 3), as well as their mode of action, relative side effects, ease of administration, and cost. Age and race recently have been found to be important determinants of antihypertensive response to agents such as diuretics, beta-blockers, calcium channel blockers, and ACE inhibitors (see Table 3) and appreciation of these relative differences may affect drug selection. When these factors are taken into account, an effective and well tolerated regimen can be tailored to the individual patient. It is hoped that aggressive treatment of hypertension in the future will cause a further decline in cardiovascular mortality in the United States.

Angiotensin converting enzyme inhibitors. Properties and side effects

The purpose of this brief review is to separate the characteristic properties and side effects attributable to the pharmacology of the whole class of angiotensin converting enzyme (ACE) inhibitors from those attributable to the chemical structure and kinetics of each particular ACE inhibitor. The former would be predictable and probably similar for all agents and, therefore, would be expected to recur with each agent, whereas the latter are likely to be characteristic of individual compounds and may be avoidable by changing to another compound with similar pharmacology but different molecular structure.

Demographic considerations in the selection of antihypertensive therapy

Because of the growing number of antihypertensive agents that are suitable for initial therapy in mild and moderate hypertension, it is important to identify factors that influence the response to various medications. Although individual patient considerations, such as associated illnesses and potential side effects, are of primary importance in choosing therapy, the influence of demographic factors has received increasing attention. The effect of age, race and gender on the response to antihypertensive therapy will be examined. Several studies have indicated that the beta blockers and angiotensin converting enzyme (ACE) inhibitors are more effective in younger than in older patients. Conversely, there is a trend toward greater responses in older subjects to the diuretics and calcium antagonists. In the few studies available that have compared agents in various classes, it appears that diuretics, and probably calcium antagonists, are significantly more effective than beta blockers or ACE inhibitors in patients over 60 years of age. However, the interdrug differences in young patients are probably less important. With regard to race, the relative lack of effect of beta blockers and ACE inhibitors in blacks is well accepted; in comparative studies, diuretics proved significantly better. From the few available studies, it does not appear that the calcium antagonists are more potent in either racial group, but they may be superior to the beta blockers and ACE inhibitors in blacks. Far less information is available concerning differences in antihypertensive responses between men and women. There is some suggestion that women may be less responsive to beta blockers than men.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of hyponatremia as a risk factor for the development of functional renal insufficiency during converting enzyme inhibition in severe chronic heart failure

To identify patients with severe chronic heart failure who are at greatest risk of developing functional renal insufficiency during converting enzyme inhibition, creatinine clearance was measured in 59 patients before and after long-term therapy with captopril (39 patients) or enalapril (20 patients), while digitalis and diuretic therapy was kept constant. Creatinine clearance increased or remained constant in 33 of the 59 patients (Group I), but declined in the remaining 26 patients (Group II). The two groups were similar with respect to the cause of heart failure, pretreatment renal function and all pretreatment hemodynamic variables. Patients in Group II, however, had lower values for serum sodium concentration (134.8 +/- 1.0 versus 137.0 +/- 0.6 mmol/liter) and higher values for plasma renin activity (10.6 +/- 3.4 versus 3.0 +/- 0.5 ng/ml per hour), received larger doses of furosemide (108 +/- 11 versus 84 +/- 6 mg/day), were more frequently diabetic (42 versus 15%) and were more frequently treated with enalapril (50 versus 21%) than were patients in Group I (all p less than 0.05). By stepwise logistic analysis, only hyponatremia (or an elevated plasma renin activity) and enalapril therapy independently predicted the decline in creatinine clearance during converting enzyme inhibition. These observations could not be explained by changes in systemic blood pressure. In patients with a normal serum sodium concentration (greater than or equal to 137 mmol/liter), creatinine clearance increased with captopril (+21%, p less than 0.05), but not with enalapril (-6%, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Enalapril: a long-acting angiotensin-converting enzyme inhibitor

The development of angiotensin-converting enzyme (ACE) inhibitors is of landmark importance in the understanding and treatment of cardiovascular disorders, particularly hypertension and congestive heart failure. Enalapril has recently joined captopril as an approved, orally active ACE inhibitor. Like captopril, it has been effective in the treatment of hypertension and congestive heart failure, with minimal adverse reactions noted. Differences in pharmacology exist between enalapril and captopril which may prove to be of clinical significance.