A enzyme (ACE) inhibitors are effective for the treatment of heart failure, but their pharmacology and precise hemodynamic effects have not yet been well defined in pediatric patients. The purpose of the present study, therefore, was to clarify acute pharmacologic characteristics and to determine the effective dose of cilazapril, an ACE inhibitor, along with its cardiovascular effects. We chose cilazapril because our preliminary experience in children and data in adults has shown that this ACE inhibitor may have a less renotoxic effect. The present study consisted of 2 steps: the first step was to determine the effective dose of cilazapril and the second step was to show its cardiovascular effects by using the stress-velocity index and aortic blood flow pattern. • • • The first step study included 20 patients, age range from 3 months to 13 years (4.5 3.5 years), who were hospitalized for either diagnostic or interventional cardiac catheterization; none had cyanosis. The 20 patients were divided randomly into 3 groups according to cilazapril dose; group 1 included 7 patients who were given 0.01 mg/kg; group 2 included 8 patients who were given 0.02 mg/kg; and group 3 included 5 patients who received 0.04 mg/kg. Age and body weight were not statistically different in these 3 groups. We determined plasma concentration of cilazaprilat, which is a diacid body and active metabolite of cilazapril, and ACE activity by prevalidated radioenzymatic assays, at 2, 6, 12, and 24 hours after a single oral dose of the medicine. The second step study consisted of 13 patients with congestive heart failure. Heart failure was clinically defined as the use of anticongestive medicine, such as diuretics and/or digoxin, because of persistent cardiomegaly, hepatomegaly, or reduced physical activity. Accordingly, all patients were on diuretics, 4 were on digoxin, and 5 were on isosorbide dinitrate. During the present study, doses of these medications were not changed. Twelve patients took part in the study 1 to 2 months after open heart surgery, and the remaining patient had dilated cardiomyopathy (Table 1). They were in stable heart failure with conventional therapy. Their age averaged 5.0 3.6 years. Cilazapril was administered orally twice a day. The dose was initially 0.01 mg/kg/day to avoid unexpected hypotension, which is often seen after the first dose, and it was gradually increased until apparent cardiovascular effects were confirmed or the dose reached 0.04 mg/kg/day. The 0.04 mg/kg/day dose was determined to be effective by the first step study. After 5 days on the final dose, plasma concentration of cilazaprilat, plasma ACE activity, and plasma renin activity were measured 2 hours after oral ingestion of the drug. By Bor M-mode echocardiography, we measured left ventricular (LV) diastolic and systolic dimensions, end-systolic LV posterior wall thickness, and LV preejection and ejection time according to standard methods. The RR interval was also measured on an electrocardiogram that was recorded simultaneously with echocardiogrpahic recordings. Fractional shortening (FS) and systolic time interval were also calculated as
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