Hemodynamic, hormonal, and pharmacokinetic aspects of treatment with lisinopril in congestive heart failure

Pharmacokinetic-pharmacodynamic model relating spiraprilat plasma concentrations to systemic and regional hemodynamic effects in congestive heart failure

The aim of this study was to investigate the relations between the plasma concentrations of spiraprilat (the active metabolite of the angiotensin-converting enzyme inhibitor spirapril) and its effects on plasma converting enzyme activity (PCEA), pulmonary capillary wedge pressure (PCWP), and brachial blood flow (BBF), after a single oral administration of 6 mg of spirapril in eight patients with severe congestive heart failure (CHF). Concentrations and effects were determined before and repeatedly during 48 h after drug intake. A sigmoid model was fitted to individual observations. Maximal effects, concentrations inducing half-maximal effects, and Hill coefficients were -99 +/- 2%, 3.9 +/- 1.9 ng/ml, and 2.4 +/- 0.7 for PCEA inhibition, -15 +/- 8 mm Hg, 11.8 +/- 9.2 ng/ml, and 2.6 +/- 1.3 for PCWP decrease, and 36 +/- 19 ml/min, 13.8 +/- 7.6 ng/ml, and 3.3 +/- 1.0 for BBF increase. In severe CHF, although a 14 ng/ml plasma concentration of spiraprilat may induce a 95% inhibition of PCEA, a 30 ng/ml plasma concentration is mandatory to normalize PCWP and BBF. This concentration corresponds to the peak achieved after a 6-mg oral dose of spirapril.

Beneficial effects of a single dose of quinapril on left ventricular performance in chronic mitral regurgitation

To evaluate the effect of a single dose of the angiotensin-converting enzyme inhibitor quinapril on left ventricular (LV) performance and size in patients with moderate to severe chronic mitral regurgitation (MR), 12 patients with angiographically proven isolated MR grade II to III and no evidence of coronary artery disease were studied. In all patients a baseline right heart catheterization and simultaneous radionuclide angiogram were performed at rest and during supine exercise (maximum 100 W) as well as 2 hours after oral administration of 10 mg of quinapril. Quinapril reduced heart rate slightly and lowered mean blood pressure at rest and during maximal exercise (p < 0.05). Systemic vascular resistance at rest was decreased from 1,484 +/- 505 to 1,150 +/- 427 dynes s cm-5 and with maximal exercise from 999 +/- 455 to 734 +/- 395 dynes s cm-5 (p < 0.005). Pulmonary capillary arterial pressure at rest decreased from 13 +/- 6 to 10 +/- 4 mm Hg (p = 0.01) and during maximal exercise from 29 +/- 10 to 20 +/- 7 mm Hg (p = 0.001). LV end-diastolic volume at rest (146 +/- 26 ml/m2) decreased after administration of quinapril to 128 +/- 24 ml/m2 (p = 0.001) and was also reduced during exercise (p = 0.001). LV end-systolic volume decreased from 63 +/- 43 to 49 +/- 35 ml/m2 at rest (p = 0.001) and with maximal exercise from 56 +/- 49 to 44 +/- 39 ml/m2 (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical pharmacokinetics of angiotensin converting enzyme (ACE) inhibitors in renal failure

Arterial hypertension occurs frequently in patients with chronic renal failure. Antihypertensive treatment of arterial hypertension with angiotensin converting enzyme (ACE) inhibitors has been shown to be effective with a low incidence of adverse effects compared with other drug classes. Furthermore, treatment with ACE inhibitors may slow the progression of renal function impairment in certain groups of patients, such as those with diabetes. Most ACE inhibitors are prodrugs which are converted by hepatic esterolysis to an active diacid metabolite. Only captopril and lisinopril have sufficient oral bioavailability and are given as active drugs. ACE inhibitors can be subdivided into 3 classes with regard to the active group: the majority of ACE inhibitors are carboxyl-containing drugs, a new class of ACE inhibitors possess a phosphoryl-group and captopril and related compounds are sulfhydryl-containing drugs. The predominant elimination pathway of ACE inhibitors is excretion via the kidneys. Therefore, renal insufficiency is associated with reduced elimination of most ACE inhibitors and, thus, altered pharmacokinetic properties. This is most evident in chronic renal failure when glomerular filtration rates (GFR) are < 30 to 40 ml/min (1.8 to 2.4 L/h). As renal clearance decreases, the peak plasma concentration and area under the plasma concentration-time curve of the active drugs or diacids are increased and time to peak concentrations and half-life are prolonged. However, there are large between-drug differences in the changes in pharmacokinetic parameters, resulting in different degrees of drug accumulation after consecutive administration. This leads, for example, to high accumulation rates for drugs such as lisinopril, or cilazaprilat. In contrast, fosinopril, which is also excreted to a large extent by the hepatobiliary pathway, does not seem to accumulate in renal failure. In general, pharmacokinetics and conversion of prodrugs seem to be slightly affected in chronic renal failure; however, these changes do not appear to be clinically relevant. Efficiency of clearance for prodrugs or active drugs and their respective metabolites by haemodialysis or peritoneal dialysis varies considerably. For some ACE inhibitors, such as captopril or enalapril, the high elimination fraction by haemodialysis necessitates a supplemental dose after dialysis. Other ACE inhibitors, such as quinapril or cilazapril, are only poorly eliminated by haemodialysis or peritoneal dialysis. Dosage recommendations for treatment with ACE inhibitors in chronic renal failure depend on the specific pharmacokinetic properties of the various agents. For most ACE inhibitors, dosage adjustment is recommended in moderate and severe impairment of renal function, with resultant dosages being 25 to 50% of those recommended for patients with normal renal function.

Drug-patient interactions and their relevance in the treatment of heart failure

The effects of congestive heart failure (CHF) on drug disposition and elimination are many and varied. Indeed, the pharmacokinetics of many of the drugs used to treat CHF are significantly altered by the patient's underlying condition. Reduced gastric emptying in CHF delays absorption and decreases the peak plasma concentrations of furosemide, bumetanide, and digoxin. Moreover, drugs that have a high hepatic extraction ratio (organic nitrates, morphine, prazosin, and hydralazine) achieve higher than expected plasma concentrations in patients with CHF. In contrast, drugs requiring biotransformation to active forms, e.g., angiotensin-converting enzyme (ACE) inhibitors such as enalapril, perindopril, quinapril, and ramipril, generally have lower than expected plasma concentrations. Nevertheless, ACE inhibitors can impair renal function in CHF, leading to an actual increase in plasma concentrations. However, decreases in absorption and first-pass metabolism are often offset by reduced hepatic and renal clearance. The overall absorption of lisinopril may be reduced in some CHF patients; consequently, the onset of effect is delayed but is often more prolonged.

Comparison of treatment with lisinopril versus enalapril for congestive heart failure

The effect of lisinopril 5-20 mg once daily or enalapril 5-20 mg once daily on exercise capacity, ventricular ectopic activity, and signs and symptoms of heart failure have been studied in 278 patients with mild-to-moderate (New York Heart Association [NYHA] classes II and III) heart failure in a randomized, double-blind, parallel-group study of 12 weeks' duration. Exercise duration was significantly increased by both angiotensin-converting enzyme (ACE) inhibitors after 6 and 12 weeks of treatment compared with their respective baseline values. There was a trend toward a greater increase in exercise duration on lisinopril after 12 weeks, although this did not reach statistical significance (p = 0.0748). There were no significant treatment differences with respect to the effect of the 2 drugs on ventricular ectopic counts, couplets, or nonsustained ventricular tachycardia. Both drugs were equally effective in improving NYHA grading and symptoms. Neither treatment had any significant effect on mean heart rate or mean blood pressures. Both treatments were equally well tolerated. The most commonly reported adverse events on both drugs were cough, dizziness, fall in blood pressure, vertigo, and myocardial infarction. The results of this study indicate that lisinopril 5-20 mg once daily is at least as effective and well tolerated as enalapril 5-20 mg once daily.

Effects of a single oral dose of captopril on left ventricular performance in severe mitral regurgitation

For comparable decreases in systemic resistance, angiotensin-converting enzyme inhibitors produce a lesser increase in cardiac output than do previously used vasodilators. Although the reason for this is not yet clear, the possibility of a negative inotropic effect of angiotensin-converting enzyme inhibitors was demonstrated by intracoronary injection. The effects of an oral dose of captopril on systolic performance were assessed by examining left ventricular (LV) pressure-volume loops obtained with simultaneous cineangiography and micromanometer pressure recordings before and 90 minutes after administration of oral captopril (25 to 50 mg) in 18 patients with chronic, severe mitral regurgitation. Group 1 (n = 9) was given captopril alone, and group 2 (n = 9) was given captopril plus atropine (0.04 mg/kg intravenous) to assess the role of parasympathetic activity in mediating the effects of captopril. Captopril reduced heart rate (90 to 81 beats/min; p less than 0.002) and LV end-diastolic pressure (13 to 10 mm Hg; p = 0.03), despite a slight increase in end-diastolic volume (257 to 264 ml; p = not significant) that suggests improved diastolic properties. Despite a decrease in end-systolic pressure (103 to 90 mm Hg; p less than 0.001), ejection fraction did not increase (0.60 to 0.58; p = not significant) owing to an increase in end-systolic volume (107 to 114 ml; p = 0.008). Contractile performance, estimated from the end-systolic pressure/volume quotient, was consistently depressed by captopril, as was the relation of preload-corrected ejection fraction to end-systolic stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-term vasodilator effect of captopril in patients with severe mitral regurgitation is parasympathetically mediated

BACKGROUND

Few data exist regarding the effects of angiotensin converting enzyme inhibitors in patients with regurgitant valvular lesions. We postulated an immediate improvement in cardiac performance with captopril in mitral regurgitation, which, in a hemodynamically compensated group of patients, might be mediated through parasympathetic vasodilation rather than through blockade of angiotension converting enzyme.

METHODS AND RESULTS

Hemodynamics were examined before and 90 minutes after oral captopril (25-50 mg) in 18 patients (mean age, 31 years) with chronic, severe mitral regurgitation in New York Heart Association functional class II and III. One group of patients was given captopril alone (group 1, n = 9) and a second group was given captopril plus atropine 0.04 mg/kg i.v. (group 2, n = 9). Captopril alone (group 1) produced decreases in heart rate (90-81 beats/min, p less than 0.001), mean arterial pressure (90-73 mm Hg, p less than 0.001), systemic resistance (28-23 Wood units, p = 0.068), and pulmonary wedge pressure (19-14 mm Hg, p less than 0.001). There was no improvement in either arteriovenous oxygen difference or thermodilution cardiac output; in fact, the latter slightly declined (3.45-3.35 l/min, p = 0.002). Pretreatment with atropine (group 2) diminished the effects of captopril on heart rate (107-103 beats/min, p = 0.065 for atropine effect by two-way ANOVA), mean arterial pressure (88-82 mm Hg, p = 0.01 for atropine effect), and systemic resistance (26-27 Wood units, p = 0.04 for atropine effect).

CONCLUSIONS

In patients with chronic, severe mitral regurgitation, captopril reduced systemic arterial and left ventricular filling pressures but did not immediately augment cardiac output as expected. Furthermore, the modest systemic vasodilator effect of captopril was parasympathetically mediated.

Pharmacology of angiotensin-converting enzyme inhibitors as a guide to their use in congestive heart failure

The pharmacokinetics of the angiotensin-converting enzyme (ACE) inhibitors are difficult to assess for several reasons. First, these compounds exert their influence by inhibiting an intermediary enzyme of a cascade of enzymatic events, whose rate-limiting enzyme (renin) is not directly affected by ACE inhibition. Second, renin and angiotensin I accumulate during ACE inhibition and a change in the dose of an ACE inhibitor could produce sudden shifts of angiotensin I to angiotensin II. Third, components of the circulating renin system require the interaction of several organ systems and effector sites. Fourth, the kinetics of ACE inhibitors can be influenced by the organ systems responsible for drug absorption, metabolism and excretion, and the functional status of these systems can be affected by the heart failure process. Fifth, at least some portion of the cardiovascular effects of ACE inhibitors is influenced by the contributions of other systems whose physiologic effects may be of importance in some patients with congestive heart failure. Sixth, the potential impact of tissue-bound ACE is not yet fully understood. Finally, for appropriate drug dosing, the effects of aging on the heart failure process, the extent of renin system activity, and the disposition of ACE inhibitors need to be considered. Because of their complex pharmacokinetics, treatment with ACE inhibitors has been guided by their pharmacodynamic and clinical characteristics.

Clinical pharmacokinetics of the newer ACE inhibitors. A review

The orally active angiotensin-converting inhibitors (ACE inhibitors) such as captopril and enalapril represent a significant therapeutic advance in the treatment of hypertension and congestive heart failure. Enalapril differs from captopril in several respects. It is a prodrug converted by hepatic esterolysis to the active (but more poorly absorbed) diacid, enalaprilat. Enalaprilat is more potent than captopril, more slowly eliminated and does not possess a sulfhydryl (SH) group. Enalapril was rapidly followed by a number of newer ACE inhibitors, the majority of which are similar to enalapril in that they are prodrugs, converted by hepatic esterolysis to a major active but poorly absorbed diacid metabolite. In one case (delapril) there are 2 active metabolites; in another (alacepril) the prodrug is converted in vivo to captopril. Lisinopril is an exception in that it is an enalaprilat-like diacid but with acceptable oral bioavailability, so that the prodrug route is not employed. The newer ACE inhibitors are at widely different stages of development, and it is not yet clear how many will reach regular clinical use. Of these newer drugs, lisinopril is the longest established and is the subject of the widest published literature. For a number there is as yet little published pharmacokinetic information. A variety of assay methods have been employed to characterise the pharmacokinetics of the ACE inhibitors, including enzymatic techniques, radioimmunoassay and chromatography. The peak plasma concentrations of the prodrugs are generally observed at around 1 hour and those of the diacid metabolites at about 2 to 4 hours. However, there is considerable variation within and between drugs, with benazepril and benazeprilat reaching peak concentrations early and enalapril and enalaprilat typical of later times to peak. Absorption of the active diacids is generally poor, and moderate (typically 30 to 70%) for the prodrugs. The bioavailability of lisinopril is about 25%. It is difficult to talk meaningfully about half-lives of the active drugs. The declines in their plasma concentrations are polyphasic and, if analytical sensitivity allows, active drug may be found at 48 hours or more following administration. This may reflect binding to ACE in plasma. Half-lives of accumulation are of the order of 12 hours; protein binding varies from little (lisinopril) to 90% (benazeprilat). Elimination is mostly renal but there may be biliary elimination for some, such as benazeprilat and fosinopril. The half-lives of the prodrugs are short. Impaired renal function decreases the elimination rate of the diacids.(ABSTRACT TRUNCATED AT 400 WORDS)

Lisinopril: a new angiotensin-converting enzyme inhibitor

Lisinopril is a synthetic, nonsulfhydryl, angiotensin-converting enzyme inhibitor. Its bioavailability is approximately 25% and is not affected by food. Hepatic metabolism is not required for pharmacologic effect, which occurs 1 hour after administration. Peak serum concentration and effect are delayed, occurring 6-8 hours after a single dose and lasting for at least 24 hours. The drug is eliminated primarily by the kidneys. The elimination half-life is 12.6 hours and is prolonged in renal impairment. Lisinopril 10-80 mg once a day is effective in lowering blood pressure in all grades of essential and renovascular hypertension. It is as effective as hydrochlorothiazide, atenolol, metoprolol, and nifedipine. Combining lisinopril with hydrochlorothiazide produces a greater degree of blood pressure reduction. Patients with congestive heart failure have demonstrated immediate and prolonged beneficial hemodynamic effects and increased exercise tolerance. Lisinopril is well tolerated. Clinically significant drug interactions have not been reported, but caution should be used when lisinopril is administered with diuretics, nifedipine, or agents that may increase concentrations of potassium. The usual initial oral dosage of lisinopril is 10 mg once a day (range 20-40 mg/day). Lower dosages may be necessary in patients with renal impairment or congestive heart failure, elderly persons, and those receiving diuretics.

Angiotensin-converting enzyme inhibitors in heart failure

Recognition of the importance of the renin-angiotension-aldosterone system in heart failure, along with an appreciation of the hemodynamic benefits of vasodilator therapy has led to the widespread use of angiotensin-converting enzyme (ACE) inhibitors in the treatment of heart failure. The ACE inhibitors are the only class of vasodilator agents shown to have a significant protective effect against mortality in patients with heart failure.

Angiotensin-converting enzyme inhibitors. Relationship between pharmacodynamics and pharmacokinetics

The inter-relationship between the pharmacokinetic and pharmacodynamic behaviour of ACE inhibitors is reviewed. First, some of the methods which have been used to assess the pharmacodynamics of ACE inhibitors in humans are presented. They include humoral assays (e.g. ACE activity in plasma, renin activity, etc.), haemodynamic changes (blood pressure, total peripheral resistance, etc.) and agonist challenges (angiotensin I infusions). Subsequently a pharmacokinetic-dynamic model is described, based on biochemical processes obtained after ACE inhibition, which seems to be useful for the interpretation of the complex processes. The various correlations between plasma drug concentration on the one hand and plasma ACE activity, angiotensin II concentration in plasma or blood pressure on the other, are discussed on the basis of this model. From the model obtained it becomes obvious that under many circumstances the release of the inhibitor from ACE binding is the step which in fact determines the pharmacodynamically relevant elimination rate of the drug at low concentrations, whereas at high concentrations the elimination of the drug is mainly dependent on kidney (and/or liver) elimination rate. The dynamic-kinetic correlations are then presented for some ACE inhibitors in various disease states: arterial hypertension, heart failure, old age, renal failure, liver disease. In a final section the kinetic and dynamic relevance of interactions of ACE inhibitors with food and other drugs is described (e.g. prostaglandin inhibitors, diuretics, digoxin and cimetidine). Despite the great body of literature which deals with the kinetic and/or dynamic properties of ACE inhibitors, precise knowledge of the relationship between their kinetic and dynamic behaviour is rather limited and there is a clear need for further studies to elucidate this complex topic, thereby improving therapeutic possibilities with these useful new compounds.

The multifacetted role of angiotensin converting enzyme inhibitors in congestive heart failure

The angiotensin converting enzyme (ACE) inhibitors constitute a major breakthrough in the medical management of congestive heart failure. The incidence of side effects with these agents is surprisingly low when they are used in the appropriate dosage. They produce sustained beneficial hemodynamic and symptomatic improvement in most patients with congestive heart failure and may produce greater symptomatic benefit than digoxin when given as second-line therapy to patients with heart failure on diuretics. Their neurohumoral effects generally are advantageous, resulting in normalization of sodium and potassium balance and a reduction in ventricular arrhythmias. The ACE inhibitors may improve survival in patients with congestive heart failure, and recent data suggest that they may prevent or delay the development of left ventricular dilatation and overt heart failure in patients with asymptomatic left ventricular dysfunction.

Clinical pharmacokinetics in heart failure. An updated review

Pharmacokinetics is the study of the effect that the body has on drug absorption, distribution, metabolism and excretion. The pharmacokinetics of a specific drug are assessed by the volume of distribution, bioavailability, clearance and elimination half-life. Elimination half-life is directly related to the volume of distribution and inversely related to clearance. Any 1 or more of these parameters may be altered by physiological changes such as ageing, or disease states such as congestive heart failure. Congestive heart failure is associated with hypoperfusion to various organs including the sites of drug clearance, i.e. the liver and kidneys. It also leads to organ congestion as seen in the liver and gut. The main changes in drug pharmacokinetics seen in congestive heart failure are a reduction in the volume of distribution and impairment of clearance. The change in elimination half-life consequently depends on whether both clearance and the apparent volume of distribution change, and the extent of that change. Pharmacokinetic changes are not always predictable in congestive heart failure, but it seems that the net effect of reduction in the volume of distribution and impairment of clearance is that plasma concentrations of drugs are usually higher in patients with congestive heart failure than in healthy subjects. The changes in pharmacokinetics assume importance only in the case of drugs with a narrow therapeutic ratio (e.g. digoxin) and some of the antiarrhythmics such as lignocaine (lidocaine), procainamide and disopyramide. This necessitates reduction in both the loading and maintenance doses. Prolongation of the elimination half-life leads to delay in reaching steady-state, and therefore dose increments must be made more gradually. Plasma concentration measurements of the drugs concerned are a good guide to therapy and help to avoid toxicity. Pharmacokinetic changes are of less importance in the case of drugs with immediate clinical response, e.g. diuretics and intravenous vasodilators such as nitrates and phosphodiesterase inhibitors. The dose in the latter group can be titrated to the desired effect. Not all adverse reactions to drugs that may occur in heart failure are the result of alterations in pharmacokinetics; rather, some may be due to important drug interactions. An interaction may occur directly e.g. reduction of renal clearance of digoxin by captopril and quinidine; or indirectly, e.g. through diuretic-induced hypokalaemia, which exacerbate arrhythmias associated with digoxin and antiarrhythmics such as quinidine and procainamide.

Modulation of hemodynamic effects with a converting enzyme inhibitor: acute hemodynamic dose-response relationship of a new angiotensin converting enzyme inhibitor, lisinopril, with observations on long-term clinical, functional, and biochemical responses

The hemodynamic effects of varying oral doses of the long-acting converting enzyme inhibitor lisinopril were studied in an acute, single-blind, parallel fashion in 55 patients with moderate to severe congestive heart failure. Doses of 2.5, 5.0, and 10 mg produced a significant increase in cardiac index and significant reductions in pulmonary capillary wedge, right atrial, pulmonary arterial, and systemic arterial pressures and systemic vascular resistance. The changes were present up to 24 hours after dosing for most parameters. There was a clear-cut dose-response relationship observed. Forty-seven patients were followed over a 3-month period, during which functional status and exercise tolerance improved. Although 26% showed some evidence of renal dysfunction with lisinopril, these changes could be normalized by decreasing either the lisinopril or the diuretic dose. These data demonstrate that the hemodynamic changes with the long-acting converting enzyme inhibitor lisinopril can be modulated with dose adjustment in patients with congestive heart failure. They also suggest that renal function changes may be normalized by adjustment of either the dose of lisinopril or the diuretic dose.

Lisinopril: a new angiotensin-converting enzyme inhibitor

Lisinopril is a new, nonsulfhydryl angiotensin-converting enzyme inhibitor approved for the treatment of hypertension. After oral administration, 25-29 percent of the dose is absorbed intact; biotransformation is not required for pharmacological activity. Onset of action occurs one to two hours after administration, with effects still present 24 hours later. The major route of elimination is through renal excretion and an elimination half-life of 12.6 hours has been reported in normotensive individuals. In patients with impaired renal function (creatinine clearance less than or equal to 30 ml/min) a longer half-life and accumulation have been observed. Lisinopril 20-80 mg/d has been shown to be as effective as hydrochlorothiazide, nifedipine, and beta-blocking agents in the treatment of essential hypertension. Its efficacy in renovascular hypertension has also been demonstrated. In congestive heart failure (CHF) doses of 2.5-20 mg/d appear to provide hemodynamic effects comparable to those of captopril. Dizziness and cough have been the most frequently reported side effects; rash and proteinuria have also been reported in a small number of patients. Interactions with diuretics, potassium supplements, and possibly with nonsteroidal antiinflammatory agents may occur. Lisinopril appears to be similar in efficacy to other antihypertensive agents in the treatment of essential hypertension and to captopril in the treatment of CHF. Whether lisinopril is safer or more effective than captopril or enalapril in the treatment of hypertension or CHF requires further investigation. Prolonged duration of action of lisinopril allows once daily dosing, unlike captopril for which dosing is required every 8-12 hours or enalapril which may necessitate twice daily dosing.