ACE inhibitors and their influence on inflammation, bronchial reactivity and cough

The immunomodulatory effects of antihypertensive therapy: A review

Hypertension remains the leading preventable risk factor for stroke and coronary artery disease, significantly contributing to all-cause global mortality and predisposing patients to renal and heart failure, as well as peripheral vascular disease. Due to the widespread usage of antihypertensive drugs, global mean blood pressure has remained unchanged or even slightly decreased over the past four decades. However, considering the broad spectrum of mechanisms involved in the action of antihypertensive drugs and the prevalence of their target receptors on immune cells, possible immunomodulatory effects which may exert beneficial effects of lowering blood pressure but also potentially alter immune function should be considered. In this review, we attempt to assess the consequences to immune system function of administering the five most commonly prescribed groups of antihypertensive drugs and to explain the mechanisms behind those interactions. Finally, we show potential gaps in our understanding of the effects of antihypertensive drugs on patient health. With regard to the widespread use of these drugs in the adult population worldwide, the discussed results may be of vital importance to evidence-based decision-making in daily clinical practice.

Efficacy and safety of spirapril in mild-to-moderate hypertension

Spirapril is a new angiotensin-converting enzyme (ACE) inhibitor. It is a prodrug with a resorption of about 50%. The active metabolite spiraprilat reaches maximal plasma concentration within 2-3 h after oral administration. Spirapril can be administered once daily because of its long duration of action caused by an elimination half-life of about 40 h. It undergoes renal and hepatic elimination. In contrast to other ACE inhibitors it has a narrow dose range; therefore, the recommended dose is 6 mg for most patients without the need for dose titration. Spirapril has no relevant drug interactions. In several studies, spirapril was given to patients with mild-to-moderate essential hypertension at doses of 1-24 mg/day. There was an identical blood pressure lowering effect at doses of 6-24 mg/day; doses of 1-3 mg/day were less effective. Twenty-four-hour blood pressure monitoring showed a trough:peak ratio up to 0.84. In studies comparing the effect of spirapril with enalapril, lisinopril, trandolapril or captopril, spirapril was at least as effective as the other substances. Besides treating uncomplicated mild-to-moderate essential hypertension, spirapril can be used in patients with diseases accompanying hypertension such as heart and renal diseases, diabetes mellitus, and lipid disturbances. Possible advantages of spirapril compared to other ACE inhibitors are the dual mechanism of elimination, the lack of need for dose titration and a low incidence of cough.

Use of losartan in the treatment of hypertensive patients with a history of cough induced by angiotensin-converting enzyme inhibitors

The objective of this study was to determine the incidence of dry cough in hypertensive patients with a history of angiotensin-converting enzyme (ACE) inhibitor-induced cough after treatment with losartan (an angiotensin II-receptor antagonist), lisinopril (an ACE inhibitor), or placebo. One hundred patients from 16 outpatient treatment centers in the United States were included in this double-masked, randomized, parallel-group, active- and placebo-controlled study, with stratification according to sex. After a challenge phase with lisinopril and a placebo washout phase, patients were randomly allocated to receive losartan 50 mg once daily, lisinopril 20 mg once daily, or placebo for a maximum of 8 weeks. The primary efficacy end point of the study was the presence or absence of dry cough during the double-masked period, as rated by the patient at each visit using a validated symptom assessment questionnaire. A secondary end point was the frequency of dry cough, as measured at each visit using a visual analogue scale (VAS). The incidence of dry cough was significantly higher in the lisinopril group than in the losartan and placebo groups (87.5% vs 36.7% and 31.4%, respectively) at the end of the double-masked treatment period; there was no statistically significant difference between the losartan and placebo groups. Mean VAS scores showed that patients treated with lisinopril rated themselves as having a significantly higher frequency of cough than did patients treated with losartan or placebo (4.0 vs 1.2 and 1.5, respectively). Again, the difference between the losartan and placebo groups was not statistically significant. All treatments were otherwise well tolerated, and no serious clinical or laboratory adverse events were reported during the double-masked phase of the study. These results demonstrate that the incidence, severity, and frequency of dry cough in patients with a history of ACE inhibitor-induced dry cough are significantly lower in those treated with losartan than in those treated with lisinopril and are similar to the incidence, severity, and frequency of dry cough in those receiving placebo.

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.

ACE inhibitor-induced cough and bronchospasm. Incidence, mechanisms and management

A dry, tickly and often bothersome cough is the most common adverse effect of ACE inhibitors. Recent studies indicate that cough may develop in around 10% of the patients treated with ACE inhibitors. In half of these patients, the ACE inhibitor has to be discontinued. Cough has emerged as a class effect occurring with all ACE inhibitors with no clear difference between the single substances. While ACE inhibition is safe in the vast majority of patients with obstructive airways disease, asthmatic symptoms or exacerbation of asthma as well as a rise in bronchial reactivity have been occasionally reported. ACE inhibition increases the cough reflex. The mechanisms underlying ACE inhibitor-induced cough are probably linked to suppression of kininase II activity, which may be followed by an accumulation of kinins, substance P and prostaglandins. Physicians should be aware that a dry cough is the most common adverse effect of ACE inhibitors and that this symptom may occur not necessarily shortly after institution of therapy but months or even a year later. Replacement by another ACE inhibitor should not be tried, since the cough will almost always recur on rechallenge with the same or another ACE inhibitor. After withdrawal of the ACE inhibitor, which is the treatment of choice, cough will resolve usually within a few days.

Pharmacokinetics of losartan, an angiotensin II receptor antagonist, and its active metabolite EXP3174 in humans

The pharmacokinetics of the angiotensin II receptor antagonist losartan potassium and its active carboxylic acid metabolite EXP3174 were characterized in 18 healthy male subjects after administration of intravenous losartan, intravenous EXP3174, and oral losartan. In these subjects, the average plasma clearance of losartan was 610 ml/min, and the volume of distribution was 34 L. Renal clearance (70 ml/min) accounted for 12% of plasma clearance. Terminal half-life was 2.1 hours. In contrast, the average plasma clearance of EXP3174 was 47 ml/min, and its volume of distribution was 10 L. Renal clearance was 26 ml/min, which accounted for 55% of plasma clearance; terminal half-life was 6.3 hours. After oral administration of losartan, peak concentrations of losartan were reached in 1 hour. Peak concentrations of EXP3174 were reached in 3 1/2 hours. The area under the plasma concentration-time curve of EXP3174 was about four times that of losartan. The oral bioavailability of losartan tablets was 33%. The low bioavailability was mainly attributable to first-pass metabolism. After intravenous or oral administration of losartan the conversion of losartan to the metabolite EXP3174 was 14%.