Discordant responses to two classes of drugs acting on the renin-angiotensin system

Pooled Analysis of Multiple Crossover Trials To Optimize Individual Therapy Response to Renin-Angiotensin-Aldosterone System Intervention

BACKGROUND AND OBJECTIVES

In the treatment of CKD, individual patients show a wide variation in their response to many drugs, including renin-angiotensin-aldosterone system inhibitors (RAASi). To investigate whether therapy resistance to RAASi can be overcome by uptitrating the dose of drug, changing the mode of intervention (with drugs from similar or different classes), or lowering dietary sodium intake, we meta-analyzed individual responses to different modes of interventions.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Randomized crossover trials were analyzed to assess correlation of individual responses to RAASi and nonsteroidal anti-inflammatory drugs (NSAIDs; n=395 patients). Included studies compared the antialbuminuric effect of uptitrating the dose of RAASi (n=10 studies) and NSAIDs (n=1), changing within the same class of RAASi (e.g., angiotensin-converting enzyme inhibition to angiotensin receptor blockers; n=5) or NSAIDs (n=1), changing from RAASi to NSAIDs (n=2), and changing from high to low sodium intake (n=5). A two-stage meta-analysis was conducted: Deming regression was conducted in each study to assess correlations in response, and individual study results were then meta-analyzed.

RESULTS

The albuminuria response to one dose of RAASi or NSAIDs positively correlated with the response to a higher dose of the same drug (r=0.72; 95% confidence interval [95% CI], 0.66 to 0.78), changes within the same class of RAASi or NSAIDs (r=0.54; 95% CI, 0.35 to 0.68), changes between RAASi and NSAIDs (r=0.44; 95% CI, 0.16 to 0.66), and changes from high to moderately low salt intake (r=0.36; 95% CI, 0.22 to 0.48). Results were similar when the individual systolic BP and potassium responses were analyzed, and were consistent in patients with and without diabetes.

CONCLUSIONS

Individuals who show a poor response to one dose or type of RAASi also show a poor response to higher doses, other types of RAASi or NSAIDs, or a reduction in dietary salt intake. Whether other drugs or drug combinations targeting pathways beyond the renin-angiotensin-aldosterone system and prostaglandins would improve the individual poor response requires further study.

ACE Phenotyping as a Guide Toward Personalized Therapy With ACE Inhibitors

Background:

Angiotensin-converting enzyme (ACE) inhibitors (ACEI) are widely used in the management of cardiovascular diseases but with significant interindividual variability in the patient’s response.

Objectives:

To investigate whether interindividual variability in the response to ACE inhibitors is explained by the “ACE phenotype”—for example, variability in plasma ACE concentration, activity, and conformation and/or the degree of ACE inhibition in each individual.

Methods:

The ACE phenotype was determined in plasma of 14 patients with hypertension treated chronically for 4 weeks with 40 mg enalapril (E) or 20 mg E + 16 mg candesartan (EC) and in 20 patients with hypertension treated acutely with a single dose (20 mg) of E with or without pretreatment with hydrochlorothiazide. The ACE phenotyping included (1) plasma ACE concentration; (2) ACE activity (with 2 substrates: Hip-His-Leu and Z-Phe-His-Leu and calculation of their ratio); (3) detection of ACE inhibitors in patient’s blood (indicator of patient compliance) and the degree of ACE inhibition (ie, adherence); and (4) ACE conformation.

Results:

Enalapril reduced systolic and diastolic blood pressure in most patients; however, 20% of patients were considered nonresponders. Chronic treatment results in 40% increase in serum ACE concentrations, with the exception of 1 patient. There was a trend toward better response to ACEI among patients who had a higher plasma ACE concentration.

Conclusion:

Due to the fact that “20% of patients do not respond to ACEI by blood pressure drop,” the initial blood ACE level could not be a predictor of blood pressure reduction in an individual patient. However, ACE phenotyping provides important information about conformational and kinetic changes in ACE of individual patients, and this could be a reason for resistance to ACE inhibitors in some nonresponders.

Effectiveness, safety and cost of drug substitution in hypertension

Cost-containment measures in healthcare provision include the implementation of therapeutic and generic drug substitution strategies in patients whose condition is already well controlled with pharmacotherapy. Treatment for hypertension is frequently targeted for such measures. However, drug acquisition costs are only part of the cost-effectiveness equation, and a variety of other factors need to be taken into account when assessing the impact of switching antihypertensives. From the clinical perspective, considerations include maintenance of an appropriate medication dose during the switching process; drug equivalence in terms of clinical effectiveness; and safety issues, including the diverse adverse-event profiles of available alternative drugs, differences in the 'inactive' components of drug formulations and the quality of generic formulations. Patients' adherence to and persistence with therapy may be negatively influenced by switching, which will also impact on treatment effectiveness. From the economic perspective, the costs that are likely to be incurred by switching antihypertensives include those for additional clinic visits and laboratory tests, and for hospitalization if required to address problems arising from adverse events or poorly controlled hypertension. Indirect costs and the impact on patients' quality of life also require assessment. Substitution strategies for antihypertensives have not been tested in large outcome trials and there is little available clinical or economic evidence on which to base decisions to switch drugs. Although the cost of treatment should always be considered, careful assessment of the human and economic costs and benefits of antihypertensive drug substitution is required before this practice is recommended.

Intraindividual Blood Pressure Responses to Angiotensin‐Converting Enzyme Inhibition and Angiotensin Receptor Blockade

This study aims to test the hypothesis that in some hypertensive subjects the blood pressure (BP) response to angiotensin-converting enzyme inhibition differs from that to angiotensin receptor blockade (ARB); a responder to angiotensin-converting enzyme inhibition may not respond to ARB or the opposite. A randomized, open-label, crossover, comparative trial of lisinopril 20 mg compared with telmisartan 80 mg (5 weeks per treatment period) was conducted in 32 untreated hypertensives using 24-hour ambulatory BP monitoring. Subjects were classified as "responders" and "nonresponders" using an arbitrary threshold of ambulatory BP response (> or =10 mm Hg systolic or > or =5 diastolic) or the median response achieved by each drug. No difference was detected between the drugs in their effect on ambulatory BP (mean difference 1.2+/-7.1/0.7+/-5.1 mm Hg, systolic/diastolic). Significant correlations were found between the antihypertensive responses to the two drugs (r=0.77, p<0.001). Using the arbitrary response criterion, there was a difference between the drugs in the responses in 28%/13% of subjects (9/4 patients) for systolic/diastolic BP (19%/25% using the median response criterion). These data suggest that in some hypertensive patients the BP response to angiotensin-converting enzyme inhibition may fail to predict the response to ARB. It appears that there are differences in the antihypertensive action of angiotensin-converting enzyme inhibitors and ARBs that may be clinically important.

Candesartan

Candesartan cilexetil is the prodrug of candesartan, an angiotensin II receptor antagonist. Candesartan binds selectively and non-competitively to the angiotensin II receptor type 1, thus preventing the actions of angiotensin II. Clinical trials have demonstrated its efficacy at a dose range of 2 to 32 mg once daily in hypertension of all grades, heart failure, in reducing urinary albumin excretion in diabetes mellitus and in coexisting hypertension and renal failure. Pharmacokinetic properties of candesartan cilexetil in elderly patients are not significantly different from those in younger individuals. Hepatic impairment does not change pharmacokinetics of candesartan cilexetil at doses up to 12 mg/day. No dose adjustment is necessary in patients with mild or moderate renal impairment. Tolerability of candesartan cilexetil is not much different from that of placebo. All adverse events are usually of mild to moderate severity and not dose-related. The most common adverse events were headache, upper respiratory tract infection, back pain, and dizziness. The incidence of these adverse effects, as well as of cough, was similar in patients treated with candesartan cilexetil or placebo. The incidence of adverse events in long-term trials was not different from that in short-term trials. Tolerability of candesartan cilexetil does not differ with either age or gender.

Angiotensin-converting enzyme activity is involved in the mechanism of increased endogenous nitric oxide synthase inhibitor in patients with type 2 diabetes mellitus

The renin-angiotensin system plays an important role in the elevation of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, in hypertensive patients, so the present study was designed to examine whether angiotensin-converting enzyme (ACE) activity is also involved in the mechanism of ADMA elevation in type 2 diabetes mellitus (NIDDM). A crossover study was performed to determine if ACE inhibition with perindopril (4 mg/day) for 4 weeks decreases serum ADMA concentration and plasma von Willebrand factor (vWF) level (a marker of endothelial injury) in 11 patients with NIDDM. None of the patients was treated with insulin or oral hypoglycemic drugs, and none had major diabetic complications. Before the protocol began, serum ADMA and plasma vWF were significantly higher in the 11 NIDDM patients, when compared with 8 control subjects without diabetes. Perindopril did not affect blood pressure or glucose metabolism, but did significantly decrease serum ADMA and plasma vWF. These results suggest that endothelial injury associated with ADMA elevation may be present even in patients with non-complicated NIDDM, and that increased activity of ACE may be involved in such endothelial dysfunction.