Advantages of automation in plasma sample preparation prior to HPLC/MS/MS quantification: application to the determination of cilazapril and cilazaprilat in a bioequivalence study.

An HPLC/MS/MS method characterized by complete automation and high throughput was developed for the determination of cilazapril and its active metabolite cilazaprilat in human plasma. All sample preparation and analysis steps were performed by using 2.2 mL 96 deep-well plates, while robotic liquid handling workstations were utilized for all liquid transfer steps, including liquid-liquid extraction. The whole procedure was very fast compared to a manual procedure with vials and no automation. The method also had a very short chromatographic run time of 1.5 min. Sample analysis was performed by RP-HPLC/MS/MS with positive electrospray ionization using multiple reaction monitoring. The calibration curve was linear in the range of 0.500-300 and 0.250-150 ng/mL for cilazapril and cilazaprilat, respectively. The proposed method was fully validated and proved to be selective, accurate, precise, reproducible, and suitable for the determination of cilazapril and cilazaprilat in human plasma. Therefore, it was applied to a bioequivalence study after per os administration of 2.5 mg tablet formulations of cilazapril.

Pharmacokinetics and haemodynamic effects of the angiotensin converting enzyme inhibitor cilazapril in hypertensive patients with normal and impaired renal function.

1. The pharmacokinetic and pharmacodynamic properties of the angiotensin converting enzyme (ACE) inhibitor cilazapril were studied in 30 hypertensive patients with various degrees of renal function. 2. After a single oral dose, apparent cilazaprilat clearance was dependent on renal function being 16.0 +/- 3.0, 11.1 +/- 3.0, 8.7 +/- 3.7 and 6.7 +/- 2.1 l h-1 (means +/- s.d.) in patients with creatinine clearances (CLcr) of > 100, 41-100, 21-40, and 8-20 ml min-1, respectively. .3 During 11 weeks of treatment with cilazapril, doses were adjusted to the CLcr and varied from 0.5 to 5.0 mg once daily. At 24 h after drug administration a clear antihypertensive response was seen only in the low clearance groups (CLcr < 40 ml min-1). In contrast, and despite higher once daily dosages, the decline of mean arterial pressure was small and cilazaprilat concentrations after 24 h were lower in the high clearance groups. 4. This study demonstrates that chronic once daily treatment with cilazapril is effective in patients with impaired renal function at dosages adjusted to creatinine clearance. No accumulation was seen. Since cilazaprilat clearance was high in the high creatinine clearance groups, a clear antihypertensive response in these groups was only seen at 3 h after drug administration.

A comparison of the pharmacokinetics and pharmacodynamics of cilazapril between Chinese and Caucasian healthy, normotensive volunteers.

METHODS: The pharmacokinetics and pharmacodynamics of the angiotensin converting enzyme (ACE) inhibitor cilazapril were studied in 12 Chinese and 13 Caucasian, healthy, normotensive volunteers on their normal diet. Cilazapril was given orally as a single 2.5 mg capsule. Plasma was sampled for assay of the active metabolite, cilazaprilat, plasma renin activity (PRA), aldosterone, angiotensin I (AI) and ACE-activity. Plasma concentrations of the active drug were measured by radioimmunoassay. Blood pressure and heart rate were measured at regular intervals. RESULTS: The pharmacokinetic parameters of cilazaprilat were similar in the two ethnic groups. No significant difference in plasma concentrations was found at any of the time points. However, the weight-adjusted plasma clearance was significantly higher in the Chinese group, which is compatible with their lower body weight. The effects on plasma hormones were also comparable, although there was a somewhat greater rise in PRA and greater fall in aldosterone levels in Chinese than in Caucasians. The effect of cilazapril on blood pressure and heart rate was greater than was previously reported in healthy volunteers. Systolic (SBP) and diastolic (DBP) blood pressure were significantly reduced in both groups, but there was a more prolonged reduction in DBP in Caucasians. In addition, heart rate (HR) was significantly increased from baseline from 5 h onwards in Chinese subjects and significantly higher in comparison with Caucasians at most time points from 1.5 h onwards. The pharmacokinetic parameters of cilazapril were essentially the same in healthy, normotensive Chinese and Caucasians. Cilazapril reduced blood pressure acutely in both groups, with good tolerance. The inhibition of ACE in relationship to time and the plasma concentrations of cilazaprilat were similar in the two groups, although the changes in PRA and aldosterone suggest an ethnic difference in the responses of the renin-angiotensin-aldosterone system.

Discrepancies between clinic and ambulatory blood pressure responses to cilazapril therapy.

OBJECTIVE: To evaluate the antihypertensive effects of cilazapril, a new angiotensin-converting enzyme inhibitor, on clinic and ambulatory blood pressure (ABP) after first and last dose administrations. DESIGN: Four weeks randomized, double-blind, controlled trial of three regimens. SETTING: Six hypertensive research clinics in Canada. PATIENTS: After a two-week placebo run-in period, 130 patients aged 22 to 77 years with mild to moderate essential hypertension were randomized and evaluated. Exclusion criteria were secondary hypertension, childbearing potential and other significant diseases. INTERVENTION: Patients were assigned to cilazapril 2.5 mg (44 patients), cilazapril 5 mg (42) or placebo (44). Fourteen patients in each group were further evaluated in a substudy by 24 h ABP monitoring. MAIN RESULTS: Cilazapril in either dosage induced significant and similar antihypertensive effects on clinic blood pressure shortly after dosing (2 to 4 h), persisting during chronic treatment; however, no relevant effect persisted at the end of dosing (24 h). After four weeks, at the end of dosing, 22, 24 and 38% of patients were clinical responders (decrease in sitting diastolic blood pressure 10 mmHg or greater) on placebo, 2.5 or 5 mg (differences not significant). Conversely, both cilazapril regimens induced similar and significant (P < 0.01) falls in mean 24 h ABP compared with placebo. Moreover, 7, 50 and 48% of patients exhibited a reduction in mean 24 h diastolic blood pressure 10 mmHg or greater on placebo, cilazapril 2.5 or 5 mg, respectively. Furthermore, both regimens induced adequate trough:peak ratios on ABP.

Review of studies on the clinical pharmacodynamics of cilazapril.

Several studies were performed to evaluate the degree of inhibition of angiotensin-converting enzyme (ACE) by an ACE inhibitor by assessing the blood pressure response to a continuous i.v. infusion of increasing doses of angiotensin I in healthy volunteers. We assessed pharmacokinetic and pharmacodynamic interactions of the ACE inhibitor cilazapril and the beta-blocker propranolol in healthy volunteers and patients with essential hypertension. We also evaluated the effect of cilazapril on aortic compliance in hypertension by pulse-wave velocity along the aorta. We showed that single oral doses of cilazapril 4 mg, captopril 25 mg, or enalapril 10 mg shifted the angiotensin I dose-effect curve to the right and determined a pharmacologic half-life of about 4 h for cilazapril. Increasing single oral doses (1.25, 3.75, 10, and 30 mg) of cilazapril reduced diastolic blood pressure dose-dependently and shifted the angiotensin I dose-response curves to the right. The dose representing 50% inhibition of ACE activity (apparent Ki dose) was about 0.6 mg 3 h after cilazapril administration. Cilazapril and propranolol did not exhibit significant pharmacokinetic interaction in healthy volunteers; each drug reduced diastolic and systolic blood pressure by about 7 mm Hg, and this was doubled by the combination. Monotherapy with each drug reduced blood pressure, and combined administration enhanced the antihypertensive effect. The reduction in cardiac output and the increase in total peripheral resistance induced by propranolol were attenuated by the cilazapril-propranolol combination.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-converting enzyme (ACE)-inhibition in cirrhosis. Pharmacokinetics and dynamics of the ACE-inhibitor cilazapril (Ro 31-2848).

The angiotensin-converting enzyme (ACE)-inhibitor, cilazapril, is converted to its active metabolite, cilazaprilat, by ester hydrolysis in the liver. The pharmacokinetics and pharmacodynamics of a single 1 mg oral dose of cilazapril were investigated in 10 healthy volunteers and in 9 cirrhotic patients with compensated cirrhosis and portal hypertension. A significantly increased mean plasma peak concentration (40.0 +/- 13.6 ng/ml vs. 25.5 +/- 7.9 ng/ml; p < 0.05) and a decreased apparent oral clearance (7.8 +/- 6.0 l/h vs. 16.4 +/- 5.4 l/h; p < 0.05) of cilazapril were found in cirrhotic patients compared to healthy volunteers. The plasma concentration of cilazaprilat declined in 2 phases. In both phases the plasma half-life was significantly longer in patients with cirrhosis (1st phase: 2.5 +/- 0.8 h vs. 1.7 +/- 0.6 h; p < 0.05; 2nd phase: 46.2 +/- 16.6 h vs. 28.8 +/- 4.7 h; p < 0.001). Consequently, cilazaprilat concentrations at 24 h were higher in patients than in volunteers (1.42 +/- 0.33 ng/ml vs. 0.87 +/- 0.14 ng/ml; p < 0.001). The predose activity of the ACE (26.3 +/- 7.3 U/l vs. 16.8 +/- 4.5 U/l; p < 0.005) and plasma renin activity (3.3 +/- 3.2 ng/ml/h vs. 1.4 +/- 1.0 ng/ml/h) were higher in patients than in volunteers. Maximum ACE-inhibition occurred at similar times in patients (2.7 h) and volunteers (2.3 h). Maximum ACE-inhibition was slightly higher in volunteers (94.6%) than in patients (90.6%). At later time points (> 24 h), however, ACE-inhibition was more pronounced in patients (at 72 h: 39.6 +/- 6.9% vs. 23.5 +/- 8.2%; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Steady-state pharmacokinetics and pharmacodynamics of cilazapril in the presence and absence of cyclopenthiazide.

Twenty-two patients with essential hypertension received a single dose of 2.5 mg cilazapril and were then randomised into a double-blind parallel group study to receive either placebo, 1.25 mg cilazapril + 0.5 mg cyclopenthiazide (CPTZ), 2.5 mg cilazapril + 0.5 mg CPTZ, or 2.5 mg cilazapril alone for 1 month. After oral administration of a single dose of 2.5 mg cilazapril, the active diacid cilazaprilat appeared rapidly in the plasma (Tmax 2.0 +/- 0.2 h). With the radioinhibitor assay used in this study, a single elimination phase of cilazaprilat was evident, with a half-life (t1/2) of 2-3 h. At steady state, the pharmacokinetics of cilazaprilat were similar to single-dose administration and were not altered by CPTZ. The Cmax and area under the curve (AUC) of cilazaprilat were directly proportional to dose. Cilazapril administration in the dose range of 1.25-2.5 mg produced a dose-proportional inhibition of angiotensin-converting enzyme (ACE) activity that was maximum 2 h after drug administration. The degree of ACE inhibition correlated with the plasma concentration-time profile of cilazaprilat and the maximum decrease in blood pressure (BP). The EC50 for ACE inhibition by cilazaprilat was 7.7 ng/ml after acute treatment and was not significantly altered during chronic administration or by concomitant administration of CPTZ. There was no evidence of a dose-related antihypertensive effect of cilazapril at steady state and, with the small numbers of subjects used in this study, there was no evidence of 24-h BP control with monotherapy.

Comparison of the pharmacokinetics and pharmacodynamics of perindopril, cilazapril and enalapril.

1. The pharmacokinetic and pharmacodynamic responses to enalapril, perindopril and cilazapril have been studied in essential hypertensives (2, 4 and 8 mg perindopril and 2.5 mg cilazapril, single dose and steady state) and normotensive volunteers (10 mg enalapril, single dose). 2. Plasma levels of the active diacid compounds reached similar peaks after single dose administration of the drugs. However, perindoprilat levels persisted for 5 days whereas cilazaprilat levels were not detectable beyond 12 h. 3. The higher levels of perindoprilat were associated with a greater inhibition of plasma angiotensin-converting enzyme (ACE) activity in both acute and steady state studies. 4. The potency of the active diacids in inhibiting plasma ACE activity was perindoprilat greater than cilazaprilat greater than enalaprilat. 5. There was a close relationship between plasma concentration, ACE inhibition and blood pressure decrease. Although both cilazapril and perindopril administration reduced blood pressure in hypertensive subjects, only perindopril exerted 24 h blood pressure control at the doses used.