Effect of carboxylesterase 1 c.428G > A single nucleotide variation on the pharmacokinetics of quinapril and enalapril.

AIM: The aim of the present study was to investigate the effects of the carboxylesterase 1 (CES1) c.428G > A (p.G143E, rs71647871) single nucleotide variation (SNV) on the pharmacokinetics of quinapril and enalapril in a prospective genotype panel study in healthy volunteers. METHODS: In a fixed-order crossover study, 10 healthy volunteers with the CES1 c.428G/A genotype and 12 with the c.428G/G genotype ingested a single 10 mg dose of quinapril and enalapril with a washout period of at least 1 week. Plasma concentrations of quinapril and quinaprilat were measured for up to 24 h and those of enalapril and enalaprilat for up to 48 h. Their excretion into the urine was measured from 0 h to 12 h. RESULTS: The area under the plasma concentration-time curve from 0 h to infinity (AUC0-∞) of active enalaprilat was 20% lower in subjects with the CES1 c.428G/A genotype than in those with the c.428G/G genotype (95% confidence interval of geometric mean ratio 0.64, 1.00; P = 0.049). The amount of enalaprilat excreted into the urine was 35% smaller in subjects with the CES1 c.428G/A genotype than in those with the c.428G/G genotype (P = 0.044). The CES1 genotype had no significant effect on the enalaprilat to enalapril AUC0-∞ ratio or on any other pharmacokinetic or pharmacodynamic parameters of enalapril or enalaprilat. The CES1 genotype had no significant effect on the pharmacokinetic or pharmacodynamic parameters of quinapril. CONCLUSIONS: The CES1 c.428G > A SNV decreased enalaprilat concentrations, probably by reducing the hydrolysis of enalapril, but had no observable effect on the pharmacokinetics of quinapril.

Pharmacokinetics and pharmacodynamics of enalapril and its active metabolite, enalaprilat, at four different doses in healthy horses.

Pharmacokinetic and pharmacodynamic of IV enalapril at 0.50 mg/kg, PO placebo and PO enalapril at three different doses (0.50, 1.00 and 2.00 mg/kg) were analyzed in 7 healthy horses. Serum concentrations of enalapril and enalaprilat were determined for pharmacokinetic analysis. Angiotensin-converting enzyme (ACE) activity, serum ureic nitrogen (SUN), creatinine and electrolytes were measured, and blood pressure was monitored for pharmacodynamic analysis. The elimination half-lives of enalapril and enalaprilat were 0.67 and 2.76 h respectively after IV enalapril. Enalapril concentrations after PO administrations were below the limit of quantification (10 ng/ml) in all horses and enalaprilat concentrations were below the limit of quantification in 4 of the 7 horses. Maximum mean ACE inhibitions from baseline were 88.38, 3.24, 21.69, 26.11 and 30.19% for IV enalapril at 0.50 mg/kg, placebo and PO enalapril at 0.50, 1.00 and 2.00 mg/kg, respectively. Blood pressures, SUN, creatinine and electrolytes remained unchanged during the experiments.

Greener bioanalytical approach for LC/MS-MS assay of enalapril and enalaprilat in human plasma with total replacement of acetonitrile throughout all analytical stages.

Green bioanalytical approaches are oriented toward minimization or elimination of hazardous chemicals associated to bioanalytical applications. LC/MS-MS assay of enalapril and enalaprilat in human plasma was achieved by elimination of acetonitrile from both sample preparation and chromatographic separation stages. Protein precipitation (PP) by acetonitrile addition was replaced by liquid-liquid extraction (LLE) in 1-octanol followed by direct large volume injection of the organic layer in the chromatographic column operated under reversed phase (RP) separation mechanism. At the mean time, acetonitrile used as organic modifier in the mobile phase was successfully replaced by a mixture of propylene carbonate/ethanol (7/3, v/v). Three analytical alternatives ((I) acetonitrile PP+acetonitrile based chromatographic elution; (II) 1-octanol LLE+acetonitrile based chromatographic elution; (III) 1-octanol LLE+propylene carbonate/ethanol based chromatographic elution) were validated and the quality characteristics were compared. Comparison between these alternative analytical approaches was also based on results obtained on incurred samples taken during a bioequivalence study, through application of the Bland-Altman procedure.

Rapid and sensitive liquid chromatography/tandem mass spectrometry method for simultaneous determination of enalapril and its major metabolite enalaprilat, in human plasma: application to a bioequivalence study.

A rapid and most sensitive method for simultaneous determination of enalapril (ENP) and its metabolite, enalaprilat (ENPT), in human plasma using ESI-LC-MS/MS (electrospray ionization liquid chromatography tandem mass spectrometry) positive ion multiple reactions monitoring (MRM) mode, was developed and validated. The procedure involves a simple solid-phase extraction (SPE) followed by evaporation of the sample. Chromatographic separation was carried out on a Hypurity C(18) column (50 mm × 4.6 mm, 5 µm) with an isocratic mobile phase and a total run time of 2.0 min only. The MRM of ENP and ENPT is 377.10 → 234.20 and 349.20 → 206.10 respectively. The standard calibration curves showed excellent linearity within the range of 0.064 to 431.806 ng/mL for ENA and 0.064 to 431.720 ng/mL for ENPT (r ≥ 0.990). This is the only method which can quantitate upto 0.064 ng/mL for both ENP and ENPT in a single run with the shortest analysis time. In matrix effect experiment, this method shows a % CV (% coefficients of variation) of less than 5, which means that the proposed method is free from any kind of irregular ionization process. This method was successfully applied to a pharmacokinetic study after oral administration of enalapril maleate 20 mg tablet in Indian healthy male volunteers.

Determination of enalapril and enalaprilat in small human serum quantities for pediatric trials by HPLC-tandem mass spectrometry.

The angiotensin converting enzyme-inhibitor enalapril is the prodrug of enalaprilat and used in the treatment pediatric hypertension and chronic heart failure. Pharmacokinetic data are lacking to provide adequate dosing and for pediatric pharmacotherapeutical trials it is imperative to minimize sample volume. Therefore an HPLC-tandem mass spectrometry (MS) method for the determination of enalapril and enalaprilat in 100 µL of human serum was developed and validated with benazepril as internal standard (IS). After solid-phase extraction, chromatography was performed on a Luna(®) RP-C(18) (2) column with methanol-water-formic acid (65:35:1, v/v/v) as mobile phase and a flow rate of 0.4 mL/min. The MS was set to positive-mode electrospray ionization and multiple reaction monitoring, analyzing the m/z transitions channels 377.3 → 234.2, 349.3 → 206.1 and 425.3 → 351.2 for enalapril, enalaprilat and IS. Calibration curves were linear in the range of 1.61-206 ng/mL (enalapril) and 1.84-236 ng/mL (enalaprilat) with coefficients of determination >0.99. Relative standard deviations of intra- and inter-run precisions were below 7% and relative errors were below 6 ± 7% for both analytes. Also stabilities were acceptable for both analytes. As an application example, concentrations of enalapril and enalaprilat in serum after oral administration of 20 mg enalapril maleat in a healthy volunteer were determined.

A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using solid phase extraction for the simultaneous determination of plasma concentrations of enalapril and enalaprilate in hypertensive patients treated with different pharmaceutical formulations.

UNLABELLED: Enalapril maleate, available on the market in a variety of different pharmaceutical formulations, is commonly used for the control of systemic arterial hypertension. Many therapeutical failures have been reported thus far in clinical practice with respect to switching between different pharmaceutical formulations of the same product during pharmacological therapy. In the present study, plasma concentrations of enalapril and enalaprilate were measured in hypertensive patients undergoing treatment with different pharmaceutical formulations. MATERIALS AND METHODS: Pharmaceutical formulations studied included the reference brand product, a generic formulation, and a third drug product marketed as "similar"; plasma samples were obtained from 30 hypertensive volunteer patients. Drug was extracted from the plasma by solid phase extraction and determined by liquid chromatography-tandem mass spectrometry. The method was validated for the main analytical parameters. RESULTS: The analytical method developed in this study, using liquid chromatography-tandem mass spectrometry, was confirmed as suitable for application in the determination of plasma concentrations in patients and subsequently revealed statistically significant differences in plasma concentrations between the 3 treatment groups. CONCLUSIONS: Such differences reinforce the hypothesis that the bioequivalence tests currently proposed by the regulatory authorities to promote interchangeability between pharmaceutical formulations may not in fact represent a definitive parameter for guaranteeing similar plasma concentrations.

Simultaneous quantification of enalapril and enalaprilat in human plasma by high-performance liquid chromatography-tandem mass spectrometry and its application in a pharmacokinetic study.

A rapid, selective and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed to simultaneously determine enalapril and enalaprilat in human plasma. With benazepril as internal standard, sample pretreatment involved in a one-step protein precipitation (PPT) with methanol of 0.2 ml plasma. Analysis was performed on an Ultimate XB-C(18) column (50 mm x 2.1 mm, i.d., 3 microm) with mobile phase consisting of methanol-water-formic acid (62:38:0.2, v/v/v). The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction-monitoring (MRM) mode via electrospray ionization (ESI) source. Each plasma sample was chromatographed within 2.5 min. The linear calibration curves for enalapril and enalaprilat were both obtained in the concentration range of 0.638-255 ng/ml (r(2) > or = 0.99) with the lower limit of quantification (LLOQ) of 0.638 ng/ml. The intra-day precision (R.S.D.) was below 7.2% and inter-day R.S.D. was less than 14%, while accuracy (relative error R.E.) was within +/-8.7 and +/-5.5%, determined from QC samples for enalapril and enalaprilat which corresponded to requirement of the guidance of FDA. The HPLC-MS/MS method herein described was fully validated and successfully applied to the pharmacokinetic study of enalapril maleate capsules in 20 healthy male volunteers after oral administration.

High-performance liquid chromatographic determination of enalapril in human plasma by enzyme kinetic analytical method.

A high-performance liquid chromatographic method for indirect determination of enalapril in human plasma, was developed and validated. An exogenous angiotensin converting enzyme after drug inhibition was determined by reacting with hippuryl-histidyl-leucine to produce hippuric acid (HA) which was inversely proportional to the amount of enalaprilat in plasma. The HPLC was carried out on a Lichrosphere 60RP-select B, C18, 5 microm (125 mm x 4.0 mm i.d.) column at flow rate of 1.0 ml/min. The analysis time per injection was within 6.5 min. The lowest concentration of enalaprilat to be quantitated was 3.0 ng/ml with the acceptable accuracy and precision. This successfully developed method was practically and accurately used for pharmacokinetics and bioequivalent study of enalapril.

Enalapril dosage in progressive chronic nephropathy: a randomised, controlled trial.

OBJECTIVE: In chronic renal failure, clearance of enalapril is reduced. Hence, a renoprotective effect may be achieved with lower doses than conventionally used. Since marked inter-patient variation in concentrations of enalaprilat has been shown in patients with renal failure despite equivalent dosage of enalapril, a direct comparison of the effect of high versus low plasma concentrations of enalaprilat on the progression of renal failure was undertaken. METHODS: Forty patients with a median glomerular filtration rate (GFR) of 17 (6-35) ml/min/1.73 m2 were studied in an open-label, randomised trial comparing patients with a high (>50 ng/ml) with patients with a low (<10 ng/ml) target trough plasma concentration of enalaprilat. The dose of enalapril was titrated accordingly. The patients were followed for 12 months or until they needed renal replacement therapy. GFR was measured at 3-month intervals by the plasma clearance of 51Cr-EDTA, and the individual rates of progression of renal failure were calculated as the slope of GFR versus time plot. RESULTS: In the high-concentration group, the median enalaprilat trough concentration was 92.9 ng/ml (21.8-371.0 ng/ml) and in the low-concentration group it was 9.1 ng/ml (2.5-74.8 ng/ml) at 3 months follow-up (P<0.001). The median daily doses of enalapril were 10 mg (2.5-30 mg) and 1.88 mg (1.25-5 mg) in the high and low groups, respectively (P<0.001). In the high-concentration group, the mean+/-SE decline in renal function was 6.1+/-1.5 ml/min/1.73 m2 per year and in the low-concentration group it was 4.3+/-14.4 ml/min/1.73 m2 per year (P=0.48). Five patients in the high-concentration group reached end-stage renal failure whereas none in the low-concentration group did (P=0.04). There were no statistically significant differences in blood pressure level, concomitant antihypertensive therapy or urinary albumin excretion. However, the high-enalaprilat concentration group had an overall higher plasma potassium concentration of 0.42 mmol/l than the low group (P<0.001). CONCLUSION: In patients with moderate to severe renal insufficiency, a low concentration of enalaprilat afforded the same degree of renoprotection, blood pressure control and minimisation of proteinuria as a high concentration, during 12 months of follow-up. The high-dosage treatment was associated with a more pronounced tendency to hyperkalaemia. Thus, there seems to be no indication for increasing the daily dose of enalapril beyond what achieves adequate blood pressure control in this group of patients.

Simultaneous determination of enalapril and enalaprilat in human plasma by liquid chromatography-tandem mass spectrometry.

A rapid, sensitive, and highly selective liquid chromatography-tandem mass spectrometry method was developed and validated for simultaneous determination of enalapril and its major active metabolite enalaprilat in human plasma. The analytes were extracted from plasma samples by liquid-liquid extraction, separated on a Zorbax Extend-C(18) column, and detected by tandem mass spectrometry with a Turbo IonSpray ionization interface. The method has a lower limit of quantification (LLOQ) of 0.1 ng/ml for both enalapril and enalaprilat. The chromatographic run time was approximately 3.5 min. The standard calibration curves for both enalapril and enalaprilat were linear in the concentration ranges of 0.10-100.0 ng/ml in human plasma. The intra- and inter-run precisions, expressed as the relative standard deviation (R.S.D.), were less than 7.7 and 7.8%, determined from QC samples for enalapril and enalaprilat, and accuracy was within +/-3.9 and +/-2.7% in terms of relative error, respectively. The method was successfully applied for the evaluation of the pharmacokinetics of enalapril and enalaprilat in 20 volunteers after an oral dose of 10 mg enalapril maleate.

Characterization of the pharmacokinetic and pharmacodynamic properties of the angiotensin-converting enzyme inhibitor, enalapril, in horses.

The pharmacokinetics of enalapril (0.5 mg/kg i.v.) and the pharmacodynamics of enalapril (0.5 mg/kg PO) in 5 mares were investigated. After single i.v. dosing, concentrations of enalapril and enalaprilat, its active metabolite, were measured. Two weeks later, enalapril was administered by nasogastric tube. Potassium, creatinine, blood urea nitrogen (BUN), enalapril, and enalaprilat concentrations and angiotensin converting enzyme (ACE) activity were measured in serum. In addition, heart rate, blood pressure, digital venous blood gases, and lactate were measured. Two weeks later, enalapril was again administered by nasogastric tube. To mimic activation of the renin-angiotensin-aldosterone system, angiotensin I (0.5 microg/kg) was administered at fixed intervals, followed by blood-pressure and heart-rate measurement. The elimination half lives of enalapril and enalaprilat were 0.59 and 1.25 hours, respectively, after i.v. administration. After PO administration, enalapril and enalaprilat were not detectable in serum. There was a tendency (P = .0625) toward a decrease in ACE activity 45-120 minutes after enalapril administration, but ACE activity suppression was never > 16%. There was a tendency (P = .0625) toward a decrease in mean arterial pressure (MAP) 6-8 hours after enalapril administration. Serum concentrations of potassium, creatinine, and BUN and digital venous blood gases and lactate concentrations did not change. In response to angiotensin I, there was a tendency (P = .0625) toward a decrease in the MAP response 4-24 hours after enalapril administration. Single-dose enalapril at 0.5 mg/kg PO did not demonstrate significant availability, pharmacodynamic effect, or substantial suppression of ACE activity.

Bioequivalence study of two brands of enalapril tablets after single oral administration to healthy volunteers.

OBJECTIVE: To compare the relative bioavailability and bioequivalence of 2 enalapril tablet formulations in healthy volunteers under fasting conditions. METHODS: An open-label, single-dose, randomized, two-period, crossover trial with a 1-week washout period in 24 healthy volunteers. The 2 enalapril 20 mg tablet formulations used were Antiprex (Elpen, Greece) as test and Renitec (Vianex, Greece) as reference preparation. Serial blood samples were collected at 19 points for 36 h. Plasma samples were analyzed for enalaprilat, the pharmacologically active metabolite of enalapril, by a validated GC/MS assay. Pharmacokinetic parameters, such as AUC(0-infinity), AUC(0-t), C(max) T(max), t1/2 and MRT were calculated from plasma concentrations for both formulations. Statistical comparisons (ANOVA and 90% confidence intervals) of AUC(0-infinity), AUC(0-t) and C(max) data were evaluated after logarithmic transformation, and differences of T(max) were tested non-parametrically. RESULTS: The parametric 90% confidence intervals of the geometric mean values of the test/reference ratios were 88.0 - 117.6% (point estimate: 101.8%) for AUC(0-infinity), 88.7 - 118.9% (point estimate: 102.7%) for AUC(0-t), and 91.0% - 123.4% (point estimate: 106.0%) for C(max) No statistically significant differences were found between the 2 preparations for T(max) t1/2 and MRT values. CONCLUSIONS: From the results of the present study, it is concluded that the test and reference tablet formulations of enalapril are bioequivalent for both the extent and the rate of absorption and therefore the 2 products can be considered to be interchangeable in clinical practice.

Simultaneous quantitation of enalapril and enalaprilat in human plasma by 96-well solid-phase extraction and liquid chromatography/tandem mass spectrometry.

A sensitive and rapid method based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) combined with rapid solid-phase extraction (SPE) has been developed and validated for the quantitative determination of enalapril and its active metabolite enalaprilat in human plasma. After addition of internal standard to human plasma, samples were extracted by 96-well SPE cartridge. The extracts were analyzed by HPLC with the detection of the analyte in the multiple reaction monitoring (MRM) mode. This method for the simultaneous determination of enalapril and enalaprilat was accurate and reproducible, with respective limits of quantitation of 0.2 and 1.0 ng/mL in plasma. The standard calibration curves for both enalapril and enalaprilat were linear (r(2) = 0.9978 and 0.9998) over the concentration ranges 0.2-200 and 1.0-100 ng/mL in human plasma, respectively. The intra- and inter-day precision over the concentration range for enalapril and enalaprilat were lower than 13.3 and 15.4% (relative standard deviation, %RSD), and accuracy was between 89.2-105.0 and 91.9-104.7%, respectively.

Determination of enalapril and enalaprilat by enzyme linked immunosorbent assays: application to pharmacokinetic and pharmacodynamic analysis.

We have developed two enzyme linked immunosorbent assay (ELISA) methods for determining enalapril and enalaprilat in plasma. In this study, 48 healthy subjects received an oral dose of either 10 or 20 mg of enalapril and plasma concentrations of enalapril and enalaprilat were determined by their specific ELISA methods. These plasma concentrations and blood pressure measurements were applied to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) parameters of both enalapril and enalaprilat. The enalapril values for the area under the curve (AUC(0)--> infinity ) were 480 +/- 216 and 832 +/- 325 ngh/mL, maximum plasma concentrations (C(max)) were 310 +/- 187 and 481 +/- 185 ng/mL, and times required to reach the maximum concentration t(max) were 1.13 +/- 0.22 and 1.09 +/- 0.33 h for 10 and 20 mg doses, respectively. The enalaprilat values for AUC(0)--> infinity were 256 +/- 122 and 383 +/- 158 ngh/mL, C(max) values were 57 +/- 29 and 72.9 +/- 33.6 ng/mL and t(max) values were 4.28 +/- 1.45 and 4.05 +/- 01.22 h for 10 and 20 mg doses, respectively. The C(max) values of enalapril were approximately 10 times higher than those in the literature, which were determined by angiotensin converting enzyme (ACE) inhibition assays following alkaline hydrolysis, but similar to those of enalaprilat. The PD profiles revealed a significant correlation between enalaprilat concentrations in plasma and the decrease in systolic and diastolic blood pressures (r = -0.95 with P < 0.001 and r = -0.95 with P < 0.001), respectively, following a single oral dose of enalapril. These ELISA methods have the advantage of being simple, accurate, sensitive, and do not depend on enalaprilat binding to ACE. Such methods can be used for analysis and kinetic testing of enalapril and enalaprilat in biological fluids.

The pharmacokinetics of enalapril in children and infants with hypertension.

Forty children with hypertension between the age of 2 months and 15 years received 0.07 to 0.14 mg/kg of enalapril as a single daily dose. Enalapril was administered orally as a novel extemporaneous suspension in children younger than 6 years of age and as tablets in older children. First-dose and steady-state pharmacokinetics were estimated in children ages 1 to 24 months, 25 months to < 6 years, 6 to < 12 years, and 12 to < 16 years. Maximum serum concentrations for enalapril occurred approximately 1 hour after administration. Serum concentrations of enalaprilat, the active metabolite of enalapril, peaked between 4 and 6 hours after the first dose and 3 and 4 hours after multiple doses. The area under the concentration versus time curve (AUC), adjusted for body surface area, did not differ between age groups. Based on comparison of first-dose and steady-state AUCs, the accumulation of enalaprilat in children ranged from 1.13- to 1.45-fold. For children ages 2 to 15 years, mean urinary recovery of total enalaprilat ranged from 58.3% in children ages 6 to < 12 years to 71.4% in children ages 12 to < 16 years. Urinary recovery for children ages 2 to < 6 years was 66.8%. The mean percentage conversion of enalapril to enalaprilat ranged from 64.7% for children ages 1 to 24 months to 74.6% for children ages 6 to < 12 years. The median effective half-life for accumulation ranged from 14.6 hours in children ages 12 to < 16 years to 16.3 hours in children ages 6 to < 12 years. There were two serious adverse events, neither of which was attributed to enalapril or resulted in discontinuation of the study drug. The extemporaneous suspension used in this study was tolerated well. The pharmacokinetics of enalapril and enalaprilat in hypertensive children ages 2 months to 15 years with normal renal function appears to be similar to that previously observed in healthy adults.

High serum enalaprilat in chronic renal failure.

BACKGROUND: Most angiotensin-converting enzyme (ACE) inhibitors and their metabolites are excreted renally and doses should hence be reduced in renal insufficiency. We studied whether the dosage of enalapril in daily clinical practice is associated with drug accumulation of enalaprilat in chronic renal failure. METHODS: Fifty nine out-patients with plasma creatinine >150 micromol/L and chronic antihypertensive treatment with enalapril were investigated, in a cross-sectional design. RESULTS: Median glomerular filtration rate (GFR) was 23(range 6-60) ml/minute/1.73 m2. The daily dose of enalapril was 10 (2.5-20) mg and the trough serum concentration of enalaprilat was 31.8 (<2.5-584.7)ng/ml. Ninety percent of the patients had higher serum concentrations of enalaprilat than has been reported in subjects with normal kidney function, and a marked elevation of serum enalaprilat was observed in patients with GFR <30 ml/minute. All but three patients had serum ACE activity below the reference range. The ACE genotype did not influence the results. Additional pharmacokinetic studies were done in nine patients in whom GFR was 23 (10-42)ml/minute/1.73 m2. The median clearance of enalaprilat was 28 (16-68) ml/minute and correlated linearly with GFR (r=0.86, p=0.003). Intra-subject day-to-day variation in trough concentrations was 19.7%. CONCLUSION: Patients with chronic renal failure given small or moderately high doses of enalapril may thus have markedly elevated levels of serum enalaprilat. Whether this affords extra renoprotection, or on the contrary may inappropriately impair renal function, is not known, and should be investigated in prospective, controlled studies.

Comparison of the pharmacokinetics of fosinoprilat with enalaprilat and lisinopril in patients with congestive heart failure and chronic renal insufficiency.

AIMS: To compare the serum pharmacokinetics of fosinoprilat with enalaprilat and lisinopril after 1 and 10 days of dosing with fosinopril, enalapril and lisinopril. METHODS: Patients with congestive heart failure (CHF, NYHA Class II-IV) and chronic renal insufficiency (creatinine clearance

Within-patient comparison of effects of different dosages of enalapril on functional capacity and neurohormone levels in patients with chronic heart failure.

BACKGROUND: Angiotensin-converting enzyme (ACE) inhibitors are established as first-line therapy in chronic heart failure (CHF). However, conflicting results exist regarding the dose-effect relation of ACE inhibitors. METHODS: We investigated 45 patients (age 55 +/- 10 years) with stable CHF who presented with a maintenance dosage of enalapril of either 5 mg given twice daily (E10; n = 16), 10 mg given twice daily (E20; n = 18), or 20 mg given twice daily (E40; n = 11). This dosage was changed 3 times to treat all patients with lower, higher, and the initial dosages for 4 weeks each. Neurohormones (atrial natriuretic peptide [ANP], brain natriuretic peptide [BNP], and norepinephrine) and enalaprilat trough levels were measured, and ergospirometry was performed. RESULTS: Changes in enalapril dose and enalaprilat level were concordant in 82% of patients, indicating good compliance. After augmentation of enalapril to 40 mg daily, patients in the E10 group showed an increase in maximal oxygen consumption and a decrease in neurohormonal stimulation, whereas the opposite changes were observed after reduction of enalapril to 10 mg daily in patients in the E20 and E40 groups (maximal oxygen consumption: Delta1.1 +/- 2.0 vs -1.0 +/- 1.9 mL. kg(-1). min(-1), P <.01; ANP: Delta-63 +/- 106 vs 19 +/- 54 pg/mL, P <.01; BNP: Delta-62 +/- 104 vs 18 +/- 89 pg/mL, P <.05; norepinephrine: Delta-1.3 +/- 2.9 vs 0.6 +/- 1.8, P <.05). Within-patient comparison showed that neurohormone levels were higher and exercise capacity lower while patients were receiving 10 mg of enalapril per day than when they were receiving 40 mg per day (ANP: 172 +/- 148 vs 139 +/- 122 pg/mL, P <.01; BNP: 193 +/- 244 vs 152 +/- 225 pg/mL, P <.005; norepinephrine: 4.2 +/- 2.2 vs 3.5 +/- 1. 6 nmol/L, P <.05; maximal oxygen consumption 22.0 +/- 4.4 vs 21.3 +/- 4.3 mL. kg(-1). min(-1) P <.05). Similar differences were observed when comparing these variables, and patients had lowest and highest enalaprilat trough levels. CONCLUSIONS: High doses of enalapril resulted in an improvement of exercise capacity and reduction of neurohumoral stimulation, whereas these parameters worsened after reduction of enalapril dose. Thus patients with congestive heart failure may benefit from increasing dosage of ACE inhibitors.

Plasma levels of enalaprilat in chronic therapy of heart failure: relationship to adverse events.

Angiotensin-converting enzyme (ACE) inhibitors are established as first-line therapy in chronic heart failure (CHF). However, little is known about the dosage-plasma-level relationship of ACE inhibitors in CHF and its relation to drug-induced adverse effects. We investigated 45 patients (age 55 +/- 10 years) with stable CHF who presented with a maintenance dosage of enalapril of either 5 mg b.i.d. (E10, n = 16), 10 mg b.i.d. (E20, n = 18), or 20 mg b.i.d. (E40, n = 11). This dosage was changed three times to treat all patients with lower, higher, and, finally, the initial dosage for 4 weeks each. Patients were examined clinically, by questionnaire, and by spiroergometry. In addition, neurohormones (atrial and brain natriuretic peptide and norepinephrine), enalaprilat trough levels, and serum potassium and creatinine were measured. Enalaprilat trough levels differed significantly between the three groups at study entry but also varied markedly within each group. In addition to the dose of enalapril, serum creatinine, severity of CHF, basal metabolic rate, and body weight significantly influenced enalaprilat trough levels (R2 =.84, p <.001). Within-patient comparisons revealed that serum creatinine (107 +/- 26 versus 102 +/- 20 micromol/liter) and potassium (3.8 +/- 0.4 versus 3.7 +/- 0. 3mmol/liter) were higher, cough was more common (scored on a scale of 0-8: 1.7 +/- 2.1 versus 1.4 +/- 1.8), and blood pressure was lower (systolic, 112 +/- 14 versus 117 +/- 13 mm Hg; diastolic, 66 +/- 9 versus 69 +/- 11 mm Hg) on the highest than on the lowest enalaprilat trough level (all p <.05). Highly variable enalaprilat trough levels and the fact that adverse effects were more common on high enalaprilat trough levels provide a rationale for individually adjusting ACE-inhibitor dose in case of adverse effects.

ACE (I/D) genotype as a predictor of the magnitude and duration of the response to an ACE inhibitor drug (enalaprilat) in humans.

BACKGROUND: We have investigated the possible effects of contrasting ACE (I/D) genotypes on the responses to the ACE inhibitor enalaprilat in normotensive men. METHODS AND RESULTS: Subjects with DD (n=12) and II (n=11) ACE genotypes received an intravenous infusion of enalaprilat or placebo. Pressor responses to stepwise, incremental doses of angiotensin I were measured at 1 and 10 hours after dosing. The dose required to raise mean blood pressure by 20 mm Hg (PD20) was calculated individually, and the ratio of PD20 during enalaprilat to that during placebo (dose ratio, DR) was used for assessment of the extent of ACE inhibition. The pressor response was significantly attenuated at 1 hour after enalaprilat in both groups, but significant attenuation was evident at 10 hours after dose only in the II subjects. The DRs at both 1 hour (median, 5.43 versus 2.82, P=0.0035) and 10 hours (2.06 versus 0.84, P=0.0008) after enalaprilat were significantly higher in II subjects than in DD subjects. CONCLUSIONS: The effect of enalaprilat was significantly greater and lasted longer in normotensive men homozygous for the II ACE genotype. By multivariate analysis, ACE (I/D) genotype and plasma angiotensin II levels were predictive of >50% of the variation in response to ACE inhibition.