Factors related to first dose hypotensive effect of captopril: prediction and treatment

Emerging insights and future prospects for therapeutic application of siRNA targeting angiotensinogen in hypertension

INTRODUCTION

Hypertension is the main global risk factor for cardiovascular disease. Despite this, less than half of treated hypertensive patients are controlled. One reason for this is nonadherence, a major unmet need in hypertension pharmacotherapy. Small interfering RNA (small interfering ribonucleic acid) therapies inhibit protein translation, and, when linked to N-acetylgalactosamine, allow liver-specific targeting, and durability over several months. Targeted knockdown of hepatic angiotensinogen, the source of all angiotensins, offers a precision medicine approach.

AREAS COVERED

This article describes the molecular basis for durability over months and the 24-h tonic target inhibition observed after one administration. We present an analysis of the published phase I trials using zilebesiran, a siRNA targeting hepatic angiotensinogen, which reduces blood pressure (BP) by up to 20 mmHg, lasting 24 weeks. Finally, we examine data evaluating reversibility of angiotensinogen knockdown and its relevance to the future clinical utility of zilebesiran.

EXPERT OPINION

Further studies should assess safety, efficacy, and outcomes in larger, more broadly representative groups. An advantage of zilebesiran is the potential for bi-annual dosing, thereby reducing nonadherence and improving control rates. It may also reduce nighttime BP due to 24-h tonic control. The provision of adherence assessment services will maximize the clinical value of zilebesiran.

Chemical Synthesis, Safety and Efficacy of Antihypertensive Candidate Drug 221s (2,9)

Hypertension is the main risk factor of cardiovascular and cerebrovascular diseases. In this paper, a novel compound known as 221s (2,9), which includes tanshinol, borneol and a mother nucleus of ACEI, was synthesized by condensation esterification, deprotection, amidation, deprotection, and amidation, with borneol as the initial raw material, using the strategy of combinatorial molecular chemistry. The structure of the compound was confirmed by ¹H NMR, ¹³C NMR, and high-resolution mass spectrometry, with a purity of more than 99.5%. The compound 221s (2,9) can significantly reduce the systolic and diastolic blood pressure of SHR rats by about 50 mmHg and 35 mmHg after 4 weeks of administration. The antihypertensive effect of 221s (2,9) is equivalent to that of captopril. The use of 221s (2,9) can reduce the content of Ren, Ang II and ACE in the serum of SHR rats, inhibit the RAAS and enhance the vascular endothelial function by upregulating the level of NO. Pathological studies in this area have shown that high dosage of 221s (2,9) can notably protect myocardial fibrosis in rats and reduce the degeneration and necrosis of myocardial fibers, inflammatory cell infiltration, and proliferation of fibrous tissue in the heart of rat. Therefore, the existing work provided a foundation for preclinical research and follow-up clinical research of 221s (2,9) as a new drug.

Treatment of Hypertension Among Non-Cardiac Hospitalized Patients

PURPOSE OF REVIEW

This review provides a contemporary perspective and approach for the treatment of hypertension (HTN) among patients hospitalized for non-cardiac reasons.

RECENT FINDINGS

Elevated blood pressure (BP) is a common dilemma encountered by physicians, but guidelines are lacking to assist providers in managing hospitalized patients with elevated BP. Inpatient HTN is common, and management remains challenging given the paucity of data and misperceptions among training and practicing physicians. The outcomes associated with intensifying BP treatment during hospitalization can be harmful, with little to no long-term benefits. Data also suggests that medication intensification at discharge is not associated with improved outpatient BP control. Routine inpatient HTN control in the absence of end-organ damage has not shown to be helpful and may have deleterious effects. Since routine use of intravenous antihypertensives in hospitalized non-cardiac patients has been shown to prolong inpatient stay without benefits, their routine use should be avoided for inpatient HTN control. Future large-scale trials measuring clinical outcomes during prolonged follow-up may help to identify specific circumstances where inpatient HTN control may be beneficial.

Safety and Prognostic Impact of Early Treatment with Angiotensin-Converting Enzyme Inhibitors or Angiotensin Receptor Blockers in Patients with Acute Heart Failure

BACKGROUND

Although angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) have been recommended for patients with heart failure, their clinical and prognostic impact in the very acute phase of acute heart failure (AHF) is unclear, mainly because data on their safety and efficacy are lacking.

METHODS

This study was a post hoc analysis of the REALITY-AHF trial. Patients with AHF who did not take an ACEI or ARB at admission were enrolled. Patients who received these medications within 48 h of admission were categorized as the ACEI/ARB group, and all other patients were categorized as the no ACEI/ARB group. The primary endpoint was a composite of all-cause death and heart failure readmission within 1 year of admission.

RESULTS

Of the 1682 patients in the REALITY-AHF cohort, 900 were enrolled in this study, and 288 (32%) were included in the ACEI/ARB group. After propensity score matching, 152 pairs were evaluated, and no significant difference was found for in-hospital mortality, worsening renal function, or length of hospital stay. The ACEI/ARB group had significantly higher event-free survival (hazard ratio 0.51; 95% confidence interval 0.32-0.82; p = 0.006).

CONCLUSIONS

Early initiation of ACEIs/ARBs within 48 h of admission for hospitalized patients with AHF was not associated with adverse events and correlated with improved outcomes at 1 year from admission.

Could angiotensin-modulating drugs be relevant for the treatment of Trypanosoma cruzi infection? A systematic review of preclinical and clinical evidence

Although leucocytes are targets of renin-angiotensin system (RAS) effector molecules and RAS-modulating drugs exert immunomodulatory effects, their impact onTrypanosoma cruziinfection remains poorly understood. By using the framework of a systematic review, we integrated the preclinical and clinical evidence to investigate the relevance of angiotensin-inhibiting drugs onT. cruziinfections. From a comprehensive and structured search in biomedical databases, only original studies were analysed. In preclinical and clinical studies, captopril, enalapril and losartan were RAS-modulating drugs used. The mainin vitrofindings indicated that these drugs increased parasite uptake per host cells, IL-12 expression by infected dendritic cells and IFN-γby T lymphocytes, in addition to attenuating IL-10 and IL-17 production by CD8 + T cells. In animal models, reduced parasitaemia, tissue parasitism, leucocytes infiltration and mortality were often observed inT. cruzi-infected animals receiving RAS-modulating drugs. In patients with Chagas’ disease, these drugs exerted a controversial impact on cytokine and hormone levels, and a limited effect on cardiovascular function. Considering a detailed evaluation of reporting and methodological quality, the current preclinical and clinical evidence is at high risk of bias, and we hope that our critical analysis will be useful in mitigating the risk of bias in further studies.

Prolonged First-Dose Hypotension Induced by Sacubitril/Valsartan

Entresto was recommanded by major guidelines as the frontline therapy for heart failure with reduced ejection fraction since its clinical benefit was proved by the PARADIGM-HF trial. Angiotensin converting enzyme inhibitors are the cornerstone of the treatment of HF. Varying incidences of first-dose hypotension have been reported and recognized as a potential limiting factor for prescribing. According to previous reports, the onset of hypotension mostly occur 3-5 hours after the first dose. However, the pattern of entresto-related hypotension has not been reported. We present a case of HF, who had delay onset (about 8 to 18 hours) and prolonged (3 to 6 days) first-dose hypotension. Further investigation is required to illustrate this phenomenon.

Combined Angiotensin Receptor Antagonism and Neprilysin Inhibition

Heart failure affects ≈5.7 million people in the United States alone. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, β-blockers, and aldosterone antagonists have improved mortality in patients with heart failure and reduced ejection fraction, but mortality remains high. In July 2015, the US Food and Drug Administration approved the first of a new class of drugs for the treatment of heart failure: Valsartan/sacubitril (formerly known as LCZ696 and currently marketed by Novartis as Entresto) combines the angiotensin receptor blocker valsartan and the neprilysin inhibitor prodrug sacubitril in a 1:1 ratio in a sodium supramolecular complex. Sacubitril is converted by esterases to LBQ657, which inhibits neprilysin, the enzyme responsible for the degradation of the natriuretic peptides and many other vasoactive peptides. Thus, this combined angiotensin receptor antagonist and neprilysin inhibitor addresses 2 of the pathophysiological mechanisms of heart failure: activation of the renin-angiotensin-aldosterone system and decreased sensitivity to natriuretic peptides. In the Prospective Comparison of ARNI With ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure (PARADIGM-HF) trial, valsartan/sacubitril significantly reduced mortality and hospitalization for heart failure, as well as blood pressure, compared with enalapril in patients with heart failure, reduced ejection fraction, and an elevated circulating level of brain natriuretic peptide or N-terminal pro-brain natriuretic peptide. Ongoing clinical trials are evaluating the role of valsartan/sacubitril in the treatment of heart failure with preserved ejection fraction and hypertension. We review here the mechanisms of action of valsartan/sacubitril, the pharmacological properties of the drug, and its efficacy and safety in the treatment of heart failure and hypertension.

Angiotensin II, independent of plasma renin activity, contributes to the hypertension of autonomic failure

At least half of primary autonomic failure patients exhibit supine hypertension, despite profound impairments in sympathetic activity. Although the mechanisms underlying this hypertension are unknown, plasma renin activity is often undetectable, suggesting renin-angiotensin (Ang) pathways are not involved. However, because aldosterone levels are preserved, we tested the hypothesis that Ang II is intact and contributes to the hypertension of autonomic failure. Indeed, circulating Ang II was paradoxically increased in hypertensive autonomic failure patients (52±5 pg/mL, n=11) compared with matched healthy controls (27±4 pg/mL, n=10; P=0.002), despite similarly low renin activity (0.19±0.06 versus 0.34±0.13 ng/mL per hour, respectively; P=0.449). To determine the contribution of Ang II to supine hypertension in these patients, we administered the AT(1) receptor blocker losartan (50 mg) at bedtime in a randomized, double-blind, placebo-controlled study (n=11). Losartan maximally reduced systolic blood pressure by 32±11 mm Hg at 6 hours after administration (P<0.05), decreased nocturnal urinary sodium excretion (P=0.0461), and did not worsen morning orthostatic tolerance. In contrast, there was no effect of captopril on supine blood pressure in a subset of these patients. These findings suggest that Ang II formation in autonomic failure is independent of plasma renin activity, and perhaps Ang-converting enzyme. Furthermore, these studies suggest that elevations in Ang II contribute to the hypertension of autonomic failure, and provide rationale for the use of AT(1) receptor blockers for treatment of these patients.

Converting enzyme inhibition in mild and moderate essential hypertension. I. Acute effects on blood pressure, the renin-angiotensin system and blood bradykinin after a single dose of captopril

The acute effects of 25 mg captopril on blood pressure, heart rate, components of the renin-angiotensin system and blood concentration of bradykinin were followed in a single-blind placebo study of untreated (group A, n = 15) and thiazide-treated (group B, n = 13) patients with mild or moderate essential hypertension. A drug-related fall in blood pressure was seen in both groups. The blood pressure reduction was more marked in group B than in group A. Heart rate remained unchanged. Plasma concentrations of angiotensin II decreased significantly with concurrent increases in plasma concentrations of renin and angiotensin I, indicating the in vivo inhibition of converting enzyme. Blood concentrations of bradykinin showed no systemic changes. The magnitude of blood pressure reduction was correlated both with the pretreatment levels and the concurrent decreases in plasma angiotensin II. Inhibition of angiotensin II formation can explain a large part of the acute hypotensive pharmacological action of captopril. Other vasoactive systems may be involved. The kallikrein-kinin system does not appear to participate as indicated by the unchanged concentrations of kinin in blood.

Manipulation of the Renin Angiotensin System in Peripheral Arterial Disease

The Heart Outcomes Prevention Evaluation (HOPE) study has provided evidence for the use of ramipril for secondary cardiac prevention for patients with peripheral arterial disease. Despite this many vascular surgeons and general practitioners are reluctant to prescribe ACE inhibitors in a group of patients perceived to have a high incidence of renal artery stenosis. This review aims to review the pathophysiology of the renin-angiotensin system and make evidence based recommendations for commencing ACE inhibitors as part of a comprehensive delivery of best medical therapy to patients with peripheral arterial disease.

Chronic administration of losartan, an angiotensin II receptor antagonist, is not effective in reducing portal pressure in patients with preascitic cirrhosis

OBJECTIVES

Plasma angiotensin II (ANG II) concentrations are elevated in cirrhosis and have been implicated as a cause of portal hypertension. We aimed to study both the systemic and portal hemodynamics, and tolerability after chronic administration of losartan, an ANG II receptor antagonist.

METHODS

Twelve patients with preascitic cirrhosis were studied: mean age of 53.8 +/- 3.3 yr; average Child-Pugh score of 5.8 +/- 0.3; alcohol etiology (5), hepatitis B/C (1/3), primary biliary cirrhosis (3). No patients were on diuretics or vasoactive medication. Hemodynamic measurements were performed at baseline and 4 weeks after daily administration of 25 mg losartan.

RESULTS

There was no significant change in the hepatic venous pressure gradient (15.4 +/- 1.5 to 13.6 +/- 1.6 mmHg, -11.7%, p = NS), despite a significant reduction in the wedge hepatic venous pressure (20.3 +/- 1.8 to 17.3 +/- 1.8 mmHg, -14.8%, p < 0.05). Cardiac output, hepatic blood flow, systemic vascular resistance, creatinine clearance, and natriuresis were unaffected. The plasma renin activity increased significantly from 2.7 +/- 0.4 to 5.2 +/- 1.1 ng/ml/h (p < 0.05). There was a significant reduction in the mean arterial pressure from 96.9 +/- 3.3 to 89.3 +/- 3.5 mmHg, -7.8 +/- 3.0% (p = 0.02), with 1 patient experiencing symptomatic hypotension.

CONCLUSIONS

Chronic administration of low-dose losartan does not lead to a significant reduction in the portal pressure gradient. Losartan is unlikely to be useful in the management of patients with early cirrhosis, who are at risk of variceal bleeding.

Combined inhibition of neutral endopeptidase and angiotensin-converting enzyme by sampatrilat in essential hypertension

BACKGROUND

The antihypertensive response to angiotensin-converting enzyme (ACE) inhibitors may be attenuated by a compensatory decrease in atrial natriuretic factor production. If so, inhibition of atrial natriuretic factor breakdown by neutral endopeptidase (NEP) may enhance the antihypertensive effects of ACE inhibition. We compared effects of the combined ACE-NEP inhibitor sampatrilat, lisinopril, and placebo on blood pressure, plasma ACE, and renin activity and urinary cyclic guanosine monophosphate (cGMP) of patients with hypertension.

METHODS AND RESULTS

After a 4-week placebo run-in period, 124 patients with a mean blood pressure of 162/102 mm Hg were randomized in a double-blind parallel-group design to 1 of 5 treatments, given once daily for 10 days: 50 mg, 100 mg, or 200 mg sampatrilat; 20 mg lisinopril; or placebo. The first dose of sampatrilat did not lower clinic or ambulatory blood pressure. Lisinopril had an immediate antihypertensive effect that differed significantly from all doses of sampatrilat. After 10 days of treatment, sampatrilat lowered clinic and ambulatory blood pressure significantly at all doses, with a trend toward a dose response for systolic ambulatory blood pressure. Sampatrilat inhibited plasma ACE in a dose-dependent fashion but significantly less so than lisinopril on days 1 and 10 of treatment. Lisinopril but not sampatrilat significantly increased plasma renin activity, whereas sampatrilat but not lisinopril significantly increased urinary cGMP excretion.

CONCLUSION

The increasing efficacy of sampatrilat compared with lisinopril over 10 days could not be attributed to an increase in plasma ACE inhibition, suggesting that the NEP inhibitor activity of sampatrilat may have contributed to its antihypertensive action. NEP inhibition may enhance the antihypertensive effect of ACE inhibition.

Start of therapy with the angiotensin II antagonist losartan after immediate switch from pretreatment with an ACE inhibitor

AIMS

To evaluate initial blood pressure effects of the angiotensin II antagonist losartan (L) immediately after switching from an ACE inhibitor (captopril, C).

METHODS

Two-phase multicentre randomized study in 177 outpatients with mild to moderate essential hypertension. For 6 weeks all patients received 25 mg C twice daily. Then they were randomized double-blind to switch for another 6 weeks to 50 mg L once daily (n=110) or to maintain C (n=55). On the first day of the switch they underwent ambulatory blood pressure measurement (ABPM).

RESULTS

Within 12 h of first dose, 31% of patients who switched to L had two consecutive systolic BP readings of 30 mmHg below their individual baseline value compared with 24% of patients who stayed on C. In 3% of patients with L and in 6% of the C patients systolic BP readings less than 100 mmHg were recorded within 12 h of first dose. The differences were not statistically significant. There were no clinical symptoms attributable to initial hypotension. During the 6 weeks double-blind therapy, 9% of L patients experienced at least one adverse event, compared with 16% of patients with C.

CONCLUSIONS

In this study the angiotensin II antagonist losartan was effective and generally well tolerated when administered immediately after pretreatment with an ACE inhibitor.

Determinants of the blood pressure response to the first dose of ACE inhibitor in mild to moderate congestive heart failure

AIMS

To investigate the relationship in patients with heart failure between BP response to the first dose of ACE inhibitor and (1) plasma drug concentration and (2) baseline clinical and laboratory variables.

METHODS

We studied individual placebo-corrected BP responses to initiation of treatment with one of a number ACE inhibitor preparations in 132 patients with mild to moderate CHF. Various pharmacokinetic/pharmacodynamic models were compared. We assessed the strength of association between baseline physiological and laboratory variables and the BP response as assessed directly from the AUC(0,10 h) and indirectly from the slope of the PK/PD relationship. Predictive models for response variables were developing using regression analysis.

RESULTS

BP response was primarily related to plasma drug concentration. The association between the fall in BP and baseline variables was weak. The strongest single predictor of BP response was baseline mean arterial pressure (r2 = 5.8%, P = 0.02). The best combinations of predictor variables contained mean arterial pressure, plasma renin activity, creatinine concentration and age (r2 = 14.4%, P = 0.37). When the choice of ACE inhibitor was added, the predictive power of the model increased (r = 23.6%, P < 0.01) but left the majority of the variability in response unexplained.

CONCLUSIONS

The first-dose blood pressure response to ACE inhibition cannot be accurately predicted from baseline pathophysiological variables in patients with mild to moderate CHF. The choice of ACE inhibitor accounts for a small proportion of the variability in response but wide inter-individual variability exists in the response to each treatment.

Use of angiotensin-converting enzyme inhibitors as monotherapy and in combination with diuretics and calcium channel blockers

Angiotensin-converting enzyme (ACE) inhibitors have earned an important place in medical therapy since their discovery about two decades ago. This family of drug has grown tremendously since the introduction of captopril in 1981. There are currently more than 14 ACE inhibitors in the world and 9 are available in the United States. Although these agents share many similarities, they differ in their pharmacokinetic properties, approved indications, and cost. This paper provides guidance for selection of ACE inhibitors by examining the pharmacokinetics, pharmacodynamics, drug interactions, adverse effects, and cost of these agents. Combination products of ACE inhibitors with either diuretics or calcium channel blockers also are reviewed.

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.

Optimal dosage of ACE inhibitors in older patients

Despite having lower levels of plasma renin activity than younger individuals, elderly patients with hypertension respond well to ACE inhibitors and the drugs have few adverse effects. Plasma concentrations of the active ACE inhibitor are generally higher in the elderly because of decreased renal clearance. These altered pharmacokinetics, combined with impairment of cardiovascular reflexes and the increasing prevalence of heart failure and renal impairment with age, render elderly patients more susceptible to first-dose hypotension. Although many studies have shown that standard dosages are well tolerated it is safer to use lower initial dosages of ACE inhibitors in elderly hypertensive patients because hypotensive reactions are not always predictable. The maintenance dosage may be determined more by the presence of renal disease or heart failure than by age per se. In elderly patients with heart failure, ACE inhibitors should be introduced even more cautiously, using low dosages and preferably under supervision. It may also be necessary to interrupt diuretic treatment for a few days to prevent severe hypotension. The ACE inhibitor dosage should then be titrated up to the maximum that is well tolerated, as this appears to offer the greatest benefit.

Dose-ranging study of the angiotensin II receptor antagonist irbesartan (SR 47436/BMS-186295) on blood pressure and neurohormonal effects in salt-deplete men

We characterised the blood pressure (BP) and hormonal responses to the oral angiotensin II (Ang II) receptor antagonist irbesartan (SR47436/BMS-186295) or placebo in normal men with an activated renin-angiotensin system (RAS) during salt depletion. We also evaluated safety and tolerability. Twelve healthy, normotensive male volunteers followed a standardised salt-depletion regimen for 3 days before each study day. Six different single oral doses of irbesartan (1, 5, 10, 25, 50, and 100 mg) were administered double-blind in a three-panel, dose escalation with placebo randomised in each panel. Supine and erect BP and heart rate (HR), serum and urinary electrolytes: plasma renin activity (PRA), and Ang II were measured at intervals. Urinary electrolytes were measured for the 24-h period before dosing (to confirm salt depletion) and for 24 h afterward. No drug-related side effects were noted. There was a dose-related decrease in supine and erect systolic and diastolic BP (SBP, DBP) with irbesartan from 10 mg and beyond, with no change in HR. Supine mean arterial pressure (MAP) decreased by 18.8 mm Hg. There was a dose-related reactive increase in PRA (to 35 ng/ml/h) and Ang II (to 450 pg/ml) with irbesartan. Irbesartan is an orally active AT1 receptor antagonist. In salt-deplete normal men, it has a dose-related haemodynamic, hormonal, and electrolyte profile characteristic of AT1 antagonists. The dose range studied did not show a plateau or maximum effect.

Effects of acute and chronic angiotensin converting enzyme inhibition by spirapril on cardiovascular regulation in essential hypertensive patients. Assessment by spectral analysis and haemodynamic measurements

1. The effects of a first dose and of chronic treatment with spirapril, a novel angiotensin converting enzyme (ACE) inhibitor, on short-term blood pressure and heart rate fluctuations were assessed by fast Fourier spectral analysis. The effects on systemic haemodynamics in supine and standing position were also studied. We treated 11 patients with 3 mg and 13 patients with 12 mg spirapril for 8 weeks. 2. Overall blood pressure variability was not changed by spirapril. By spectral analysis the changes in blood pressure and heart rate variability in various frequency bands can be assessed, which may be related to changes in activity of the autonomic nervous system. The relative power in the mid-frequency band (0.08-0.12 Hz) of supine systolic pressure was 23 +/- 10% during placebo and decreased during treatment with 12 mg to 11 +/- 4% (P < 0.01 vs placebo, first dose) and to 13 +/- 6% (P < 0.01, chronic treatment). Standing systolic mid-frequency power was 38 +/- 12% during placebo and decreased to 27 +/- 9% (P < 0.01 vs placebo) after the first dose of 12 mg, but it did not decrease after chronic treatment (29 +/- 13%). Treatment with 3 mg induced no changes in mid-frequency blood pressure variability. A decrease in power of the mid-frequency band may point to a decrease in sympathetic vascular drive. The power in the high-frequency band (0.15-0.40 Hz) of heart rate did not change after treatment, suggesting that there is no change in the vagal cardiac drive. 3. Supine blood pressure decreased by a decrease in vascular resistance by 16 +/- 23% (3 mg) and 14 +/- 19% (12 mg) after 8 weeks treatment. Heart rate, stroke volume and cardiac output did not change. No orthostatic hypotension occurred after the first dose. In the 12 mg group the orthostatic induced rise in heart rate (compared with supine) increased from + 9 +/- 5 beats min-1 (placebo) to + 14 +/- 4 beats min-1 (P < 0.05) after the first dose. No changes in the orthostatic heart rate increase occurred in the 3 mg group. The orthostatic changes in stroke volume, cardiac output and vascular resistance were not influenced by spirapril. 4. In conclusion, the decrease in mid-frequency blood pressure variability may suggest an inhibitory effect of acute and chronic ACE inhibition upon sympathetic vasomotor control. Vagal activity was not influenced as high-frequency heart rate variability did not change. Acute and chronic ACE inhibition did not blunt important cardiovascular reflexes, as the haemodynamic response to orthostasis remained intact.

ACE inhibitors. Differential use in elderly patients with hypertension

High blood pressure (BP) in the elderly must not be ignored as a normal consequence of aging. The criteria for the diagnosis of hypertension and the necessity to treat it are the same in elderly and younger patients. The aim of treatment of elderly hypertensive patients is to decrease BP safely and to reduce risk factors associated with cerebrovascular, cardiovascular and renal morbidity and mortality. The treatment of elderly hypertensive patients should be adjusted according to the needs of the individual, based upon age, race, severity of hypertension, co-existing medical problems, other cardiovascular risk factors, target-organ damage, risk-benefit considerations and costs. In addition to the elevated BP, other cardiovascular risk factors include smoking, glucose intolerance, hyperinsulinaemia, dyslipidaemia, hypercreatininaemia, peripheral vascular disease, left ventricular hypertrophy, and microalbuminuria (or albuminuria). Thus, the choice of initial antihypertensive therapy in elderly hypertensive patients should be based not only on the expected response, but also on the effects of therapy on lipid, potassium, glucose and uric acid levels, and left ventricular anatomy and function. Co-existing medical conditions (such as asthma, diabetes mellitus, heart failure, renal failure, gout, coronary artery disease, hyperlipidaemia and peripheral vascular disease) are major determinants for the selection of antihypertensive medications. With previous therapies (diuretics, beta-blockers, etc.), good BP control in the elderly was associated with clear and statistically significant reductions in stroke-related morbidity and mortality, but the overall effects on cardiovascular and renal complications of hypertension was either more variable or less obvious. Angiotensin converting enzyme (ACE) inhibitors are not only efficacious antihypertensive agents in the elderly, but also appear promising in counteracting some of the cardiovascular and renal consequences of hypertension. They are well tolerated and have a relatively low incidence of adverse effects. ACE inhibitors possess ancillary characteristics that are potentially beneficial for many elderly patients, including reduction of left ventricular mass, lack of metabolic and lipid disturbances, no adverse CNS effects, no risk of induction of heart failure, and a low risk of orthostatic hypotension. Since ACE inhibitors may improve perfusion to the heart, kidney and brain, they are well worth considering for the treatment of elderly patients with hypertensive target organ damage, especially in patients with heart failure, and diabetic patients with early nephropathy.

Invasive hemodynamic evaluation of sublingual captopril and nifedipine in patients with arterial hypertension after abdominal aortic surgery

OBJECTIVES

To examine the central hemodynamic and blood gas responses to sublingual captopril and nifedipine administration in patients with arterial hypertension after abdominal aortic surgery.

DESIGN

Prospective, randomized, parallel-group clinical study.

SETTING

Twenty-nine-bed medical-surgical intensive care unit in a university hospital.

PATIENTS

Twenty patients with arterial hypertension (mean arterial pressure of > or = 115 mm Hg) the day after abdominal aortic surgery. Patients with bilateral renal artery stenoses, identified with the preoperative angiogram, were excluded.

INTERVENTIONS

Pressures were measured using intravascular catheters and cardiac output was determined by thermodilution for 2 hrs after captopril 25 mg (n = 10) or nifedipine 10 mg (n = 10) was administered by the sublingual route.

MEASUREMENTS AND MAIN RESULTS

Captopril administration and nifedipine administration decreased mean arterial pressure (from 121 +/- 1 to 94 +/- 4 mm Hg and from 121 +/- 2 to 94 +/- 2 [sem] mm Hg, respectively), pulmonary arterial pressure, pulmonary artery occlusion pressure, and right atrial pressure (p < .001 for all variables). Changes in heart rate and in cardiac output were not significant. PaO2 decreased after nifedipine, from 101 +/- 8 to 81 +/- 3 torr [13.5 +/- 1.1 to 10.8 +/- 0.4 kPa] (p < .01), but not after captopril (104 +/- 9 to 100 +/- 7 torr [13.9 +/- 1.2 to 13.3 +/- 0.9 kPa]). Excessive or symptomatic decreases in blood pressure were not observed, nor was deterioration in renal function observed.

CONCLUSIONS

Sublingual captopril and nifedipine were equally effective for the treatment of arterial hypertension after abdominal aortic surgery. Nifedipine, but not captopril, caused a deterioration in pulmonary gas exchange.

Tissue angiotensin generation and regulation of vascular tone

The renin-angiotensin system is intimately involved in the control of sodium and water balance, the activity of the sympathetic nervous system, mitogenesis and the regulation of vascular tone. There is evidence that many of these effects may be controlled at a local level by independent tissue renin-angiotensin systems. Drugs that are specific inhibitors of the cascade have proved powerful tools for dissecting the physiology of the renin-angiotensin system, and are of major benefit in the treatment of hypertension and chronic heart failure. Recent evidence suggests that variations in the genes coding for components of the system may affect the risk of developing hypertension and ischaemic heart disease.

Clinical problem-solving in geriatric medicine: obstacles to rehabilitation

This case illustrates how multifactorial medical, neurological and psychiatric conditions can synergistically effect the functional status of elderly individuals. This case also illustrates how iatrogenically induced illness, most commonly in the form of drug therapy, can significantly affect patients' conditions and their progress in rehabilitative therapies. This case also illustrates how the atypical presentation of disease in the elderly, as well as the medical ramifications of rehabilitative therapies, need to be strongly considered during trials at functional rehabilitation. More importantly, however, this case demonstrates how even a community-based geriatrician can be instrumental in recognizing the need of more appropriate evaluations in elderly patients with functional disabilities and how even in the setting of a multidisciplinary team there can still be a consulting relationship, with each person seeing the patient individually and communicating with other members of the team as necessary. Although each team member may have a specific area of expertise, there is still a very important role for the geriatrician to play in making sure that all the different components of the rehabilitation and the medical care proceed in a way that will provide the most favorable outcome for the patient.

Changes in the renin-angiotensin-aldosterone axis in later life

The renin-angiotensin-aldosterone system (RAAS) is one of the main systems involved in the regulation of blood pressure and sodium homeostasis. In animal experiments and in humans, the plasma renin activity and aldosterone levels are reduced with aging. The age-related differences in plasma renin activity and aldosterone are more pronounced in stimulated conditions (when sitting in an upright position, when salt intake is restricted and when plasma volume is depleted) than under basal conditions. Age-related alterations of the kidney (glomerulosclerosis, decreased number of functional nephrons) might account for the age-related differences in the active to inactive plasma renin ratio. In the same way, a diminished synthesis of angiotensinogen by the liver could contribute to the decrease in the activity of the RAAS in aging. This is partially compensated for by increases in the density of angiotensin II receptors reported in elderly patients. Furthermore, aging is associated with a reduced adrenal responsiveness to angiotensin II, contributing to lower production of aldosterone and alterations of sodium homeostasis. Estradiol and progesterone help stimulate the secretion of renin. Reduced levels of these hormones at menopause also lead to reduced plasma renin activity. In relation to these findings, several studies have shown that reductions in blood pressure, induced by short or long term treatment with angiotensin converting enzyme (ACE) inhibitors, were more pronounced in old than young hypertensive patients. An insertion/deletion polymorphism in the ACE gene has been described; the genotype deletion/deletion of this gene has been reported to be closely associated with longevity. This result was unexpected since the same deletion polymorphism was also shown to represent a potent risk factor for myocardial infarction.

Responses to low dose intravenous perindoprilat infusion in salt deplete/salt replete normotensive volunteers

1. Intravenous ACE inhibitor therapy appears to have a role in the treatment of acute heart failure and early after myocardial infarction. Practical experience with intravenous administration with activation of renin is limited. We report responses to perindoprilat (Pt, 0.67 mg) or placebo (P) infused over 4 h in normotensive male volunteers (n = 12, 19-28 years, 53-77 kg) with double-blind, placebo controlled salt depletion (SD) or salt repletion (SR) as a model of the activated renin system. 2. Salt depletion caused no significant fall in serum sodium (P, 139.4 +/- 2.4; Pt, 138.3 +/- 1.9) compared with salt replete preparation (P, 139.9 +/- 1.2; Pt, 139.7 +/- 0.9) but elevation of plasma renin activity 2-3-fold. Pretreatment baseline systolic blood pressure following salt depletion (P, 121 +/- 9.3/71 +/- 7.9; Pt, 121.5 +/- 9.6/69 +/- 8.1) was higher than following salt replete preparation (P, 114 +/- 9.5/61 +/- 7.2; Pt, 116.9 +/- 6.9/67 +/- 7.2). 3. Baseline corrected supine SBP fell significantly and to a similar extent following active treatment regardless of activation of the renin system (SD, -14.6 +/- 9.5/-9.4 +/- 6.4; SR, -12 +/- 14/-10.1 +/- 6.6) compared with placebo (SD, -6.1 +/- 6/-3.7 +/- 5.6; SR, -4.7 +/- 10/-1.3 +/- 6.5). Heart rate was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Determinants of the initial effects of captopril on blood pressure, glomerular filtration rate, and natriuresis in mild-to-moderate chronic congestive heart failure secondary to coronary artery disease

Whereas angiotensin-converting enzyme inhibitors are now indicated for all grades of chronic heart failure, the 2 adverse effects that limit use of these drugs are systemic hypotension and renal dysfunction. The recognized clinical correlates such as hyponatremia and high diuretic dose, which predict occurrence of these adverse effects in severe chronic congestive heart failure (CHF), are rarely evident in patients with mild-to-moderate CHF. Accordingly, we studied 36 patients with stable, moderate CHF in a double-blind, placebo-controlled, crossover fashion to evaluate by multiple discriminate regression analysis the pathophysiologic determinants of changes in blood pressure, glomerular filtration rate, and urinary sodium excretion after initial converting enzyme inhibition with captopril 25 mg. A captopril-mediated decrease in mean arterial pressure was predicted by 3 factors (r2 = 0.74): the decrease in serum angiotensin II (F ratio = 10.3, p < 0.01), the decrease in plasma norepinephrine (F = 8, p = 0.02), and, inversely by pretreatment mean arterial pressure (F = 5.6, p = 0.04), patients with higher initial values exhibiting greater decreases in response to captopril. A captopril-mediated decline in glomerular filtration rate, determined by radioisotope elimination, was also predicted by 3 factors (r2 = 0.67): a decrease in renal plasma flow (F = 48.6, p < 0.01), low pretreatment glomerular filtration rate (F = 11.1, p < 0.01), and low absolute post-treatment serum angiotensin II (F = 5, p = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

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)

The effects of age on the pharmacokinetics and pharmacodynamics of single oral doses of benazepril and enalapril

1. Eighteen healthy, normotensive subjects (nine young and nine elderly) participated in a double-blind, 3-way, crossover study to compare aspects of the pharmacokinetics and pharmacodynamics of single oral doses of 10 mg benazepril, 10 mg enalapril and placebo. 2. The hypotensive effect was similar after both drugs but the absolute reductions were greater in the elderly who had higher initial levels of blood pressure. 3. The AUCs for both benazeprilat and enalaprilat were higher in the elderly but by a significantly greater amount for enalaprilat (+ 113% vs 40%; P < 0.01). 4. The AUCs for both drugs tended to be highest in subjects with the lowest creatinine clearance. 5. The changes in kinetics and dynamics observed in the elderly after benazepril are qualitatively similar to those with other ACE inhibitors. The clinical significance of the quantitative differences requires further investigation.

Drug therapy of renovascular hypertension

The renin-angiotensin system is responsible for renovascular hypertension resulting from narrowing of the renal arteries. Inhibitors of angiotensin-converting enzyme (ACE) interrupt the conversion of angiotensin I to angiotensin II, causing a reduction in blood pressure. Several drugs of this family have been introduced since captopril was launched, including enalapril, lisinopril, ramipril and others. While they are effective antihypertensive agents, they can in some cases lead to deterioration of renal function, especially in patients with bilateral renal artery stenosis or stenosis of a solitary kidney. ACE inhibitors must also be administered with caution to sodium-depleted patients. Calcium antagonists, presumed to be ideal for the treatment of low renin hypertension, have also proved to be effective in patients with renal artery stenosis, many of whom have severe refractory hypertension. These agents, in common with ACE inhibitors, may be useful for determining the lateralisation index used to establish the kidney responsible for hypertension.

Haemodynamic and hormonal responses to oral enalapril in salt depleted normotensive man

A combination of dietary sodium restriction (40 mmol day-1) and frusemide pretreatment has been used to activate the renin angiotensin system (RAS) in order to characterise the haemodynamic and hormonal responses to enalapril in young normotensives. Enalapril significantly reduced supine blood pressure with a mean maximum fall of 19 +/- 7.6, compared with 6.5 +/- 6.8 mm Hg with placebo. Similar but greater responses were seen in erect blood pressure. Mean maximal plasma ACE inhibition (78 +/- 5.7%) was associated with a significant increase in PRA from 5.2 +/- 2.1 ngAI ml-1 h-1 to a peak of 29.1 +/- 6 ngAI ml-1 h-1. This simple well tolerated regimen produced consistent RAS activation and gave readily measurable falls in blood pressure following enalapril. This model may be used to undertake detailed assessments of ACE inhibition, renin inhibition and angiotensin receptor blockade.

Long-range safety and protective benefits of angiotensin-converting enzyme inhibitors for hypertension. Do we need more clinical trials?

Inhibition of the renin-angiotensin system is being applied with considerable success to the treatment of hypertension and heart failure. Angiotensin-converting enzyme (ACE) inhibitors are the only currently available agents that can achieve this objective. In general, the major therapeutic effects of these agents in the treatment of mild to moderate hypertension or of heart failure are exerted on the vascular tissue through inhibition of the renin-angiotensin system and, secondarily, of the sympathetic nervous system. When cardiovascular functional reserve is diminished and autoregulation of regional and systemic blood flow is strained, however, ACE inhibitors may affect other organ functions (heart, kidneys, and possibly brain), hormones other than the renin system, and local tissue humoral systems. The interrelations between the renin-angiotensin system and several other vasoactive systems--including circulating and locally generated tissue hormones and centrally acting neurohormonal factors--are complex and unclear. A better understanding of these mechanisms and interrelations would allow for a more rational therapeutic use of these agents. Unknown also are the clinical effects of prolonged ACE inhibition. Whether the use of ACE inhibitors can provide primary cardiorenal protection requires proof through definitive clinical trials.

The clinical pharmacology of angiotensin converting enzyme inhibitors in chronic heart failure

ACE inhibitors (ACEIs) have now been shown to improve symptoms and survival in patients with mild, moderate and severe chronic heart failure. Their mechanism of action is thought to be a combination of RAAS suppression and augmentation of bradykinin and prostaglandins. Although ACE inhibitors improve hemodynamics post myocardial infarction, we do not yet have consistent data on their effects on symptoms or survival in these particular patients. One other potential benefit is their effects on reperfusion injury and free radicals. As yet only minor differences have been found to exist between different ACEIs but increasing attention is now being focussed in this direction.

The response to the first dose of an angiotensin converting enzyme inhibitor in uncomplicated hypertension--a placebo controlled study utilising ambulatory blood pressure recording

1. The importance of total dose to the initial hypotensive response with an angiotensin converting enzyme inhibitor (quinapril) was assessed using a suggested 'maintenance' dose (20 mg) or matched placebo in a randomised double-blind study in patients with uncomplicated hypertension. 2. Thirty-two patients were recruited who were not on therapy or had not received diuretic therapy in their existing drug treatment in the preceding 4 weeks. Secondary causes of hypertension had previously been excluded and sustained clinic blood pressures of SBP greater than 160 mmHg and/or DBP greater than 90 mmHg were taken as indications for a trial of adjuvant or monotherapy with an ACE inhibitor. 3. After uneventful supervised therapy with quinapril in an open pilot study (n = 5) 27 patients entered a double-blind, randomised, crossover study of quinapril or placebo using ambulatory monitoring to assess BP response. 4. All patients remained asymptomatic and both therapy and monitoring were well tolerated. A smooth onset of antihypertensive effect was noted with an overall 24 h placebo corrected fall in systolic BP of 9.9 mmHg (7.2-12.6 95% CI) and diastolic BP of 6.4 mmHg (4.2-8.8) with no significant effect on heart rate. Individual placebo corrected maximal responses during the first 8 h following quinapril showed a wide range for both systolic (+1.56 to 44.0 mmHg) and diastolic (+2.3 to -35.6 mmHg) pressure. Larger falls tended to be associated with higher baseline pretreatment pressures but in no case did absolute systolic pressure fall below 100 mmHg during the first 8 h following administration of placebo or quinapril.(ABSTRACT TRUNCATED AT 250 WORDS)

Interventions in renal scintigraphy

Physiological and pharmacological intervention for the purpose of determining organ functional reserve is a familiar concept in medical testing and in nuclear medicine. Nephrourologic applications include established procedures such as diuretic scintigraphy for determination of urinary outflow obstruction and captopril scintigraphy for determination of renovascular hypertension. Subtle renal dysfunction may exist among some individuals with essential hypertension, induced by provocative exercise renography, and not observed at rest. The strength of nuclear medicine resides in its ability to assess disorders of organ function for the diagnostic, prognostic, or pathophysiological information provided. Nephrourologic interventions are reviewed with an emphasis on the functional changes caused by the intervention.

Tissue and plasma angiotensin converting enzyme and the response to ACE inhibitor drugs

1. There is a body of circumstantial and direct evidence supporting the existence and functional importance of a tissue based RAS at a variety of sites. 2. The relation between circulatory and tissue based systems is complex. The relative importance of the two in determining haemodynamic effects is unknown. 3. Despite the wide range of ACE inhibitors already available, it remains unclear whether there are genuine differences related to tissue specificity. 4. Pathological states such as chronic cardiac failure need to be explored with regard to the contribution of tissue based ACE activities in generating acute and chronic haemodynamic responses to ACE inhibitors. 5. The role of tissue vs plasma ACE activity may be clarified by study of the relation between drug concentration and haemodynamic effect, provided that the temporal dissociation is examined and linked to circulating and tissue based changes in ACE activity, angiotensin peptides and sympathetic hormones.

Once-daily lisinopril compared with twice-daily captopril in the treatment of mild to moderate hypertension: assessment of office and ambulatory blood pressures

This multicenter, double-blind, parallel-group study compared the antihypertensive effects of two angiotensin-converting enzyme inhibitors, lisinopril and captopril, in 70 patients (35 lisinopril, 35 captopril) with mild-to-moderate essential hypertension. Doses of 10, 20, and 40 mg once-daily lisinopril or 25, 50, and 100 mg bid captopril were increased at biweekly intervals until patients responded to treatment, as defined by a decrease in office diastolic pressure to less than 90 mm Hg or at least a 10 mm Hg decrease from baseline. Patients who responded to a 2-week titration dose remained at that dose for another 2 weeks. Blood pressure assessments were made using both office and ambulatory blood pressure monitoring. Area under the curve analysis of ambulatory blood pressure reductions showed significant differences between treatment groups for both systolic (P = .023) and diastolic (P = .007) blood pressures, with lisinopril-treated patients showing the most significant reduction in pressure. Greater reductions (P less than .05) were also noted in patients receiving lisinopril at hours 10 to 12, suggesting two blood pressure troughs for those receiving captopril. Both drugs were well tolerated, and no patients withdrew from either treatment group. The authors concluded that after at least 4 weeks of therapy, once-daily lisinopril administration was more effective than twice-daily captopril administration in reducing blood pressure, when measured by 24-hour ambulatory blood pressure monitoring.