Overall tolerance and safety of quinapril in clinical trials

Benefit and risk evaluation of quinapril hydrochloride

INTRODUCTION

Angiotensin-converting enzyme (ACE) inhibitors are a mainstay of antihypertensive therapy. Quinapril hydrochloride, a less commonly used, and less-studied ACE inhibitor has been approved for its primary use in hypertension. Studies also indicate its off-label use for congestive heart failure and diabetic nephropathy. The ANDI and TREND trials have been pivotal in demonstrating the effectiveness of quinapril.

AREAS COVERED

The authors conducted a review of the literature analyzing the clinical efficacy and safety profile of quinapril. This review discusses the development of quinapril, provides an updated summary of the indications and contraindications, and presents a comparison with other ACE inhibitors.

EXPERT OPINION

Quinapril is a safe and well-tolerated antihypertensive medication with a favorable safety profile compared to other ACE inhibitors. However, a lack of ample recent clinical trials and post-marketing data investigating the efficacy of quinapril in large cohorts has resulted in limited use in clinical practice. Quinapril may be an effective antihypertensive option for elderly populations as well as those who cannot tolerate the side effects profiles of other ACE inhibitors and as an additional treatment option for patients with heart failure with preserved ejection fraction.

Calciotropic and Phosphaturic Hormones in End-Stage Heart Failure Patients Supported by a Left-Ventricular Assist Device

Background

Calcium and phosphate are central for myocardial contractility and energy metabolism, and low levels of the calciotropic hormone 1,25-dihydroxyvitamin D (1,25(OH)₂D), as well as high levels of the phosphaturic hormone fibroblast growth factor (FGF)-23, are independently associated with poor clinical outcome in heart failure (HF) patients. We therefore aimed to investigate the postoperative time course of the aforementioned hormones in HF patients supported with a left-ventricular assist device (LVAD) implant.

Methods

For the present study, stored biobank plasma samples of 69 patients, collected before LVAD implantation (t0) and 12 days (t1), 30 days (t2), 83 days (t3), and 300 days (t4) post-intervention, were used to measure circulating FGF-23, parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD), 1,25(OH)₂D, and kidney function.

Results

Most patients were male and had baseline INTERMACS levels and cardiac index values ≤ 3 and ≤ 2.7 L/min/m², respectively. There were significant time effects on estimated glomerular filtration rate (eGFR), FGF-23 and 1,25(OH)₂D, but not on PTH or 25OHD. Notably, eGFR values increased and FGF-23 levels decreased only transiently, whereas 1,25(OH)₂D increased continuously until t4. The rise in 1,25(OH)₂D was largely influenced by those patients who survived the first post-implant year, and was not seen in non-survivors. Variations in 1,25(OH)₂D levels could only partly be explained by eGFR values or FGF-23, 25OHD, and PTH levels (multiple R² = 0.305;P<0.001).

Conclusions

The present study indicates that LVAD implantation has only transient effects on circulating FGF-23 levels, but is associated with a continuous increase in circulating 1,25(OH)₂D levels, especially in survivors.

Effects of the ACE Inhibitor Quinapril on Echocardiographic Variables in Horses with Mitral Valve Insufficiency

Twenty horses with mitral valve insufficiency, but without signs of congestive heart failure, and five horses without signs of heart disease were examined before and after medication with an angiotensin-converting enzyme (ACE) inhibitor. The examination included echocardiography assessment as well as heart catheterization. The echocardiographic examination included B-mode, M-mode, conventional and colour Doppler techniques. For 8 weeks, all horses were treated with Accupro 20 (active substance: Quinapril) at an oral dose rate of 120 mg/horse/day. A follow-up of the horses with mitral valve insufficiency after 8 weeks revealed a statistically significant increase in the stroke volume and the cardiac output as well as a decrease in regurgitation velocity time integral (VTI). The regurgitation blood velocity remained the same. The severity of mitral valve insufficiencies revealed a moderate improvement in five horses, from moderate to mild, after therapy. Significant changes of cardiac dimension (B-mode) and shortening fraction (M-mode) before and after treatment could not be observed. The owners' judgement of the horses' performance was that of a minor improvement. In the horses without clinical findings the results of examination before and after treatment remained the same.

Low vitamin D status: a contributing factor in the pathogenesis of congestive heart failure?

OBJECTIVES

This study was designed to evaluate the association between vitamin D status and congestive heart failure (CHF).

BACKGROUND

Impaired intracellular calcium metabolism is an important factor in the pathogenesis of CHF. The etiology of CHF, however, is not well understood.

METHODS

Twenty patients age <50 years and 34 patients age >/=50 years with New York Heart Association classes >/=2 and 34 control subjects age >/=50 years were recruited. N-terminal pro-atrial natriuretic peptide (NT-proANP), a predictor of CHF severity; vitamin D metabolites; and parameters of calcium metabolism were measured in fasting blood samples collected between November 2000 and March 2001.

RESULTS

Both groups of CHF patients had markedly increased serum levels of NT-proANP (p < 0.001), increased serum phosphorus levels (p < 0.001), and reduced circulating levels of both 25-hydroxyvitamin D (p < 0.001) and calcitriol (p < 0.001). Albumin-corrected calcium levels were reduced and parathyroid hormone levels were increased in the younger CHF patients compared with the controls (both p values <0.001). Moreover, parathyroid hormone levels tended to be higher in the elderly CHF patients than in the controls (p = 0.074). In a nonlinear regression analysis 25-hydroxyvitamin D and calcitriol were inversely correlated with NT-proANP (r(2) = 0.16; p < 0.001 and r(2) = 0.12; p < 0.01, respectively). The vitamin D genotype at the BmsI restriction site did not differ between the study groups.

CONCLUSIONS

The low vitamin D status can explain alterations in mineral metabolism as well as myocardial dysfunction in the CHF patients, and it may therefore be a contributing factor in the pathogenesis of CHF.

Clinical pharmacokinetics of vasodilators. Part I

Understanding the mechanism of action and the pharmacokinetic properties of vasodilatory drugs facilitates optimal use in clinical practice. It should be kept in mind that a drug belongs to a class but is a distinct entity, sometimes derived from a prototype to achieve a specific effect. The most common pharmacokinetic drug improvement is the development of a drug with a half-life sufficiently long to allow an adequate once-daily dosage. Developing a controlled release preparation can increase the apparent half-life of a drug. Altering the molecular structure may also increase the half-life of a prototype drug. Another desirable improvement is increasing the specificity of a drug, which may result in fewer adverse effects, or more efficacy at the target site. This is especially important for vasodilatory drugs which may be administered over decades for the treatment of hypertension, which usually does not interfere with subjective well-being. Compliance is greatly increased with once-daily dosing. Vasodilatory agents cause relaxation by either a decrease in cytoplasmic calcium, an increase in nitric oxide (NO) or by inhibiting myosin light chain kinase. They are divided into 9 classes: calcium antagonists, potassium channel openers, ACE inhibitors, angiotensin-II receptor antagonists, alpha-adrenergic and imidazole receptor antagonists, beta 1-adrenergic agonist, phosphodiesterase inhibitors, eicosanoids and NO donors. Despite chemical differences, the pharmacokinetic properties of calcium antagonists are similar. Absorption from the gastrointestinal tract is high, with all substances undergoing considerable first-pass metabolism by the liver, resulting in low bioavailability and pronounced individual variation in pharmacokinetics. Renal impairment has little effect on pharmacokinetics since renal elimination of these agents is minimal. Except for the newer drugs of the dihydropyridine type, amlodipine, felodipine, isradipine, nilvadipine, nisoldipine and nitrendipine, the half-life of calcium antagonists is short. Maintaining an effective drug concentration for the remainder of these agents requires multiple daily dosing, in some cases even with controlled release formulations. However, a coat-core preparation of nifedipine has been developed to allow once-daily administration. Adverse effects are directly correlated to the potency of the individual calcium antagonists. Treatment with the potassium channel opener minoxidil is reserved for patients with moderately severe to severe hypertension which is refractory to other treatment. Diazoxide and hydralazine are chiefly used to treat severe hypertensive emergencies, primary pulmonary and malignant hypertension and in severe preeclampsia. ACE inhibitors prevent conversion of angiotensin-I to angiotensin-II and are most effective when renin production is increased. Since ACE is identical to kininase-II, which inactivates the potent endogenous vasodilator bradykinin, ACE inhibition causes a reduction in bradykinin degradation. ACE inhibitors exert cardioprotective and cardioreparative effects by preventing and reversing cardiac fibrosis and ventricular hypertrophy in animal models. The predominant elimination pathway of most ACE inhibitors is via renal excretion. Therefore, renal impairment is associated with reduced elimination and a dosage reduction of 25 to 50% is recommended in patients with moderate to severe renal impairment. Separating angiotensin-II inhibition from bradykinin potentiation has been the goal in developing angiotensin-II receptor antagonists. The incidence of adverse effects of such an agent, losartan, is comparable to that encountered with placebo treatment, and the troublesome cough associated with ACE inhibitors is absent.

31P-NMR determinations of cytosolic phosphodiesters in turtle hearts

As part of our ongoing research on cardiac hypoxia tolerance we have conducted 31P nuclear magnetic resonance (NMR) studies of isolated, perfused, working hearts from freshwater turtles, animals that are well known for their ability to tolerate prolonged periods of anoxia. A striking feature of turtle heart spectra is an extremely high concentration of NMR visible phosphodiesters (PDEs). Cardiac spectra from mammals, on the other hand, typically exhibit only a small resonance in the PDE region. Our aim in this study was to compare myocardial PDE profiles between the highly hypoxia tolerant western painted turtle (Chrysemys picta bellii) and the relatively hypoxia sensitive softshelled turtle (Trionyx spinifer) in order to begin to rest the hypothesis that high constitutive levels of cytosolic PDEs may play a role in conferring hypoxia and ischemia tolerance on the myocardium. We also collected 31P-NMR spectra of PCA extracts of tissue from these species and from Kemp's ridley sea turtles (Lepidochelys kempi), as well as spectra from isolated hearts and PCA extracts of red-eared sliders (Trachemys [formerly Pseudemys] scripta]). Total NMR visible phosphodiesters make up 24 +/- 8.6% of the total NMR visible phosphorus in Chrysemys hearts, 20.7 +/- 5.9% in Trachemys hearts, but only 12.2 +/- 5.1% in Trionyx hearts (P < 0.05). We have identified three distinct PDEs in turtle hearts: glycerophosphorylcholine (GPC); glycerophosphorylethanolamine (GPE); and serine ethanolamine phosphodiester (SEP). SEP is the dominant compound in Chrysemys and Trachemys (79.3 +/- 10.2% and 84.7 +/- 3.7% of total PDE, respectively), while GPC is most abundant in Trionyx (74.0 +/- 4.3% of total PDE) and Lepidochelys (not quantitated). The function of this class of compounds is unclear but it has been suggested that cytosolic PDEs may function as lysophospholipase inhibitors, a role that would decrease the rate of membrane phospholipid turnover. Our comparative data suggest that cytosolic PDEs could play a role in phospholipid sparing during anoxic or ischemic stress in turtles but a direct test of this hypothesis awaits future experimentation.

Bone mass, vitamin D deficiency, and hyperparathyroidism in congestive heart failure

PURPOSE

In contrast to renal and hepatic failure, congestive heart failure (CHF) has not been associated with a defined metabolic bone disorder. However, low bone mass has been reported in patients with CHF who receive a cardiac transplant. Both the pathophysiology and therapy of CHF may influence bone and mineral homeostasis and evidence that calciotropic hormones may affect cardiovascular function is accumulating. Therefore, we evaluated patients with severe CHF to determine the prevalence of osteoporosis and to characterize relationships between mineral homeostasis, bone turnover, bone mass, and severity of CHF.

PATIENTS AND METHODS

One hundred one patients (79 men and 22 women, aged 25 to 70 years) with severe CHF (New York Heart Association functional class III or IV) referred for consideration for cardiac transplantation were evaluated with measurements of serum 25-hydroxyvitamin D (25-OHD), 1,25 dihydroxyvitamin D [1,25(OH)2D], intact parathyroid hormone (PTH), markers of bone turnover (serum osteocalcin, urinary hydroxyproline, and pyridinium crosslinks); bone mineral density (BMD) by dual energy x-ray absorptiometry was measured in 91 patients. Left ventricular ejection fraction (LVEF) and resting cardiac output (CO) were determined in 88 and maximal treadmill exercise testing and peak oxygen consumption were performed in 45 patients.

RESULTS

Osteoporosis (T score < or = -2.5) was present in 7% at the lumbar spine, 6% at the total hip, and 19% at the femoral neck. Osteopenia (T scores between -1.0 and -2.5) was present in 43% at the lumbar spine, 47% at the total hip, and 42% at the femoral neck. Women were more severely affected (P = 0.007). Frankly low serum 25-OHD (< or = 9 pg/mL) and 1,25(OH)2D (< or = 15 pg/mL) levels were found in 17% and 26% of the patients, respectively, and elevated serum PTH (> or = 65 pg/mL) in 30%. Both low serum 1,25(OH)2D and increased serum PTH were associated with prerenal azotemia. Low serum vitamin D metabolites were associated with biochemical evidence of increased bone turnover, but BMD did not differ by vitamin D or PTH status. Patients with more severe CHF had significantly lower vitamin D metabolites and higher bone turnover, whereas elevated PTH was associated with better LVEF (21 +/- 1 versus 18 +/- 1%; P = 0.05) and correlated positively with resting CO (R = 0.220; P = 0.04).

CONCLUSIONS

Osteopenia or osteoporosis were observed in approximately half of these patients with severe CHF. Abnormal calciotropic hormone concentrations, also common, were associated with evidence of increased bone resorption but were not related to BMD in this cross-sectional study. Abnormal concentrations of calciotropic hormones were related to the severity of cardiovascular compromise. Because both low BMD and low serum concentrations of 25-OHD in patients with CHF are associated with higher rates of bone loss and fracture after cardiac transplantation, patients should be evaluated for and receive appropriate therapy for these disorders.

Differing mechanisms of action of angiotensin-converting enzyme inhibition in black and white hypertensive patients. The Trandolapril Multicenter Study Group

The antihypertensive effect of the angiotensin-converting enzyme inhibitor trandolapril administered in doses of 1, 2, and 4 mg/d was compared in 207 white patients and 91 black patients with mild to moderate hypertension following a double-blind, randomized, placebo-controlled, parallel study design. Trandolapril is a prodrug that is rapidly hydrolyzed to its active diacid metabolite, trandolaprilat. After 6 weeks of double-blind treatment, trandolapril lowered baseline sitting diastolic pressure in both white and black patients. A comparison of the antihypertensive response of the two populations revealed that the black patients required between two and four times the dose of trandolapril to obtain a response similar to that observed in the white patients. A dose of 1 mg/d trandolapril resulted in a 6.1 mm Hg mean decrease in baseline sitting diastolic pressure for white patients; a similar response (-6.5 mm Hg) was observed in the black patients at 4 mg/d. In contrast to the population differences in blood pressure, the decreases in angiotensin-converting enzyme activity were similar for both populations. An evaluation of trandolaprilat levels revealed that there were no racial differences in the trandolaprilat concentrations required to achieve a given degree of angiotensin-converting enzyme inhibition. Therefore, it appears that the antihypertensive response of black patients is not completely explained by a reduction in angiotensin-converting enzyme activity. The lack of response at a lower dose but increasing response at a higher dose could reflect another vasodepressor activity of trandolapril or just be evidence of reduced sensitivity of high blood pressure in blacks to angiotensin-converting enzyme inhibition.

Glycerol phosphorylcholine (GPC) and serine ethanolamine phosphodiester (SEP): evolutionary mirrored metabolites and their potential metabolic roles

Water-soluble phosphodiesters (WSPDE) are a prominent feature of many 31P-NMR spectra; however, their role has remained somewhat of a mystery. What has been missed in almost all previous studies is the fact that two classes of WSPDE exist in vertebrates: those in mammals and those in the other (reptile-avian) line. The first is represented by glycerol phosphorylcholine and the second by serine ethanolamine phosphodiester. A further examination of the literature suggests a common role for all WSPDE as lysophospholipase inhibitors and therefore net sparers of phospholipids by decreasing phospholipid metabolic throughput.

Changes in pulmonary hemodynamics predict benefits in exercise capacity after ACE inhibition in patients with mild to moderate congestive heart failure

Several causes may affect the efficacy of angiotensin-converting enzyme (ACE) inhibitors in congestive heart failure (CHF). The present study was undertaken to identify what factors might predict benefits in exercise capacity after ACE inhibition in 22 patients with mild to moderate CHF. All patients underwent hemodynamic evaluation before and following an oral dose of quinapril (20 mg). They were then treated daily with 20 mg of quinapril and underwent exercise stress test off-drugs 1 day and 6 months later. Patients were grouped according to their relative changes in vascular resistances after quinapril: Group A (n = 15) showed a greater decrease in pulmonary vascular resistance (PVR) than in systemic vascular resistance (SVR) (% delta PVR/% delta SVR > 1). The opposite occurred in Group B (n = 7). Comparison of pretreatment baseline features revealed that the two groups had similar biochemical and hormonal variables, cardiac index, and SVR. Conversely, Group A patients had higher (p < 0.05) pulmonary artery pressure and PVR compared with Group B patients. Following quinapril, Group A patients showed a greater (p < 0.05) increase in cardiac index than Group B patients, despite a similar reduction in SVR. Accordingly, 1-day drug treatment significantly (p < 0.001) increased exercise duration in Group A (+29%), but not in Group B patients (+7%). Benefits in exercise capacity were still significant (p < 0.001) 6 months later.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy and safety of quinapril in the elderly hypertensive patient

The efficacy and safety of once-daily administration of the new angiotensin-converting enzyme inhibitor quinapril or quinapril plus hydrochlorothiazide (HCTZ) were assessed in 64 older (greater than 65 years) patients with mild to moderate hypertension in an uncontrolled, open-label study. Treatment was initiated with 20 mg of quinapril once daily and titrated upward to 40 mg of quinapril or 40 mg of quinapril combined with 25 mg of HCTZ according to efficacy. At the end of the 12-week active-treatment phase, 43 patients received 20 mg of quinapril once daily, 12 patients received 40 mg of quinapril once daily, and 4 patients received 40 mg of quinapril combined with 25 mg of HCTZ once daily. Of 48 patients evaluable for efficacy, the mean decrease from baseline in sitting diastolic blood pressure (DBP) was 12.8 mm Hg; 96% of the patients had a blood pressure reduction of greater than or equal to 10 mm Hg, and 98% had a sitting DBP of less than or equal to 90 mm Hg 20 to 28 hours after administration. The decrease in sitting DBP was significant after 1 week and continued for the entire study, as did corresponding changes in sitting systolic blood pressure. We conclude that quinapril administered once daily is well tolerated and effective for the treatment of mild to moderate hypertension in elderly patients.

Comparative pharmacokinetics of captopril, enalapril, and quinapril

This review compares the metabolism and pharmacokinetic profiles of captopril, the first orally active angiotensin-converting enzyme (ACE) inhibitor, and 2 newer ACE inhibitors, enalapril and quinapril. Captopril differs from both enalapril and quinapril in that its chemical structure contains a sulfhydryl group, the presence of which may be important in the development of adverse reactions. Captopril also differs from enalapril and quinapril in its ability to be metabolized in plasma. Enalapril and quinapril are both de-esterified, most likely in the liver, to their active metabolites, enalaprilat and quinaprilat. All 3 ACE inhibitors are eliminated primarily via renal excretion, and renal dysfunction markedly increases the area under the time versus plasma concentration curves. Hepatic dysfunction also slows the conversion of enalapril and quinapril to their active metabolites. There is evidence that both captopril and enalapril, but not quinapril, may accumulate with repeated dosing. The pharmacokinetics of these agents are not significantly modified by co-administration of other drugs. However, captopril does cause marked increases in trough plasma levels of digoxin. Overall, the pharmacokinetic profiles of captopril, enalapril, and quinapril make them suitable for a wide range of patients with hypertension or congestive heart failure.

Angiotensin-converting enzyme in renal and cerebral tissue and implications for successful blood pressure management

In addition to the classic circulating renin-angiotensin system, increasing evidence supports the existence of local tissue renin-angiotensin systems (vascular, cardiac, kidney, and brain) that appear to participate in cardiovascular homeostasis and in the pathogenesis of cardiovascular disorders via multiple autocrine and paracrine functions. Components of local systems have been detected in cardiovascular tissues. Studies with angiotensin-converting enzyme (ACE) inhibitors provide further evidence of the existence and importance of tissue renin-angiotensin systems. The blood pressure-lowering effect of quinapril, for example, correlated better with inhibition of tissue ACE (aorta) than with inhibition of plasma ACE. The effects of ACE inhibitors on local tissue renin-angiotensin systems (vascular in particular) may be the crucial determinant of response to treatment. Newer ACE inhibitors, such as quinapril, have favorable side effect profiles as well as apparent tissue specificity for the vascular renin-angiotensin system (and possibly other relevant cardiovascular tissue). Differentiation among ACE inhibitors should play an even more important role in the future for individualization of therapy.

Angiotensin-converting enzyme in cardiovascular and adrenal tissues and implications for successful blood pressure management

Components of the renin-angiotensin system, and the ability to synthesize these components locally, have been demonstrated in cardiovascular tissues. Locally generated angiotensin II may affect vascular tone, regional blood flow, cardiac contractility, and vascular and cardiac growth. Local renin-angiotensin systems may exert autocrine and paracrine functions, whereas the circulating system serves an endocrine function. Use of angiotensin-converting enzyme (ACE) inhibitors has provided further clarification of the activities of local renin-angiotensin systems. Tissue and systemic effects of these agents may prove equally important in determining their clinical efficacy. Experiments with quinapril demonstrated that inhibition of vascular ACE was a significant component of the antihypertensive effect of the drug. Differences at the tissue level may have implications for the efficacy and tolerability of a particular agent. Improved individualization of therapy may be accomplished by the use of newer ACE inhibitors with very favorable side effects profiles and tissue specificity. The newest agent, quinapril, appears to exert an important effect on vascular converting enzyme.

Effects of antihypertensive agents on coronary artery disease risk factors

The adverse effects of certain antihypertensive medications, most notably diuretics and beta blockers, on serum lipids, glucose, and potassium may explain why control of hypertension has not been accompanied by declines in coronary artery disease. Evidence indicates that angiotensin-converting enzyme (ACE) inhibitors, including quinapril, the newest member of this class of drugs, have no deleterious effects on these coronary risk factors. In addition to differences in chemical structure, the unique activity of quinapril at the local tissue level might to some degree explain its comparatively favorable clinical profile. Consequently, ACE inhibiting agents may be better choices for the management of patients with mild-to-moderately elevated blood pressure. However, controlled clinical trials with these drugs are needed to determine their impact on events related to coronary artery disease.

Adverse effects of angiotensin-converting enzyme inhibitors in antihypertensive therapy with focus on quinapril

Angiotensin-converting enzyme (ACE) inhibitors are useful first-line drugs in the therapy of mild and moderate hypertension. Adverse reactions to this drug class are rarely serious. Hypotension, cough, rash, and taste disturbance are uncommon; reduced glomerular filtration and hyperkalemia occur infrequently; angioedema is rare and neutropenia is extremely rare. Quinapril is a new ACE inhibitor that is converted to biologically active quinaprilat in the liver. This ACE inhibitor has a rapid onset of action and inhibits local tissue converting enzyme systems in kidney, heart, and brain, as well as in the circulating renin-angiotensin system. Clinically significant adverse effects of quinapril occur at low rates. In 1,771 patients receiving quinapril, the reported incidence of the first occurrence of orthostatic hypotension was comparable to that seen in patients receiving placebo. In other studies, headache was reported by up to 4.7% of patients receiving quinapril, which is comparable to reported incidences of headache in patients receiving other ACE inhibitors. Other adverse events reported at rates greater than 1% include cough with associated rhinitis and bronchitis, dizziness, and somnolence. Such adverse events have only rarely led to the withdrawal of patients from clinical studies of quinapril.

Quinapril: a new second-generation ACE inhibitor

Quinapril is a new non-sulfhydryl angiotensin-converting enzyme (ACE) inhibitor. The drug undergoes hepatic hydrolysis into its major active diacid metabolite, quinaprilat, and two minor inactive metabolites. On a weight basis quinaprilat is three times as potent an ACE inhibitor as quinapril. Approximately 60 percent of an oral dose of quinapril is absorbed. In contrast with captopril, the absorption of quinapril is unaffected by food. Peak serum concentrations of quinapril and quinaprilat are achieved within one and two hours, respectively. Approximately 61 percent of an orally administered dose is excreted in the urine, principally as quinaprilat. The elimination half-life of quinaprilat is three hours, but is prolonged up to 11 hours in patients with renal dysfunction. Quinapril dose reduction is recommended in patients with a creatinine clearance of 0.50 mL/sec or less. In the elderly the elimination of quinaprilat is reduced and correlates well with renal function. In patients with cirrhosis the hydrolysis of quinapril to quinaprilat is impaired resulting in lower plasma quinaprilat concentrations and up to a two-fold increase in quinapril half-life. Quinaprilat has a strong binding capacity to tissue ACE allowing for once-daily dosing. The recommended starting dose for quinapril is 20 mg/d. The nature and incidence of adverse reactions to quinapril are similar to those of enalapril and captopril. Quinapril's antihypertensive efficacy is equal to that of captopril and enalapril. A small number of patients with congestive heart failure (CHF) have been treated with quinapril. Preliminary data indicate that quinapril is an equally effective therapeutic alternative to presently available ACE inhibitors in the treatment of CHF.(ABSTRACT TRUNCATED AT 250 WORDS)

Overview of the clinical development of quinapril

Quinapril hydrochloride is the newest member of a family of angiotensin-converting enzyme (ACE) inhibitors. On completion of laboratory and animal studies, a clinical program was initiated to evaluate the antihypertensive and other properties of the drug in human subjects. The initial phase of clinical development was concerned with the pharmacokinetics and pharmacology of quinapril. The latter studies established a dose range for the drug and explored its effect on human hemodynamics and blood pressure. Safety and interactions with other drugs were also examined. Subsequent studies explored the safety and efficacy of quinapril in patients with mild to moderate hypertension and, later, in patients with more severe hypertension. Results of these studies supported the recommendation of a once daily dosage of quinapril, 10-40 mg, as first-line therapy in the management of hypertension, with diuretics as concomitant therapy as required in patients with severe hypertension. Quinapril has also been found to be the most potent of all available ACE inhibitors in binding to tissue ACE, which may contribute to its potent and sustained duration of action. Clinical evaluation of quinapril has also been undertaken in patients with congestive heart failure. Initial findings indicate that doses of 10-20 mg/day, given twice daily, are therapeutic when administered with diuretic or digitalis. Safety of the drug has been established in 2700 patients.

The safety profile of quinapril: is there a difference among ACE inhibitors?

The safety of quinapril hydrochloride, a new nonsulfhydryl angiotensin-converting enzyme (ACE) inhibitor with an intermediate duration of action, has been evaluated in 3,031 patients with hypertension and congestive heart failure (CHF) and has been compared with other ACE inhibitors. A comparison of double-blind studies showed quinapril to have a lower incidence of adverse effects and withdrawals than reported for captopril or enalapril. Analysis of onset of adverse events or withdrawals did not show either a time-dependent or dose-dependent relationship with quinapril. The proportion of patients who experienced orthostatic hypotension was less than that of patients on captopril or enalapril. Double-blind, long-term, and open-label studies with quinapril showed no increase in the incidence of events reported in patients with CHF compared with hypertensive patients. Quinapril produced minimal adverse effects on renal function in both patients with normal renal function and in those with pre-existing renal impairment. Age analysis of data from all studies showed no increase in total reporting of adverse events in older patients who did not take concomitant diuretics.

Ultrastructural juxtaglomerular cell changes in normotensive rats treated with quinapril, an inhibitor of angiotensin-converting enzyme

Sequential histologic and ultrastructural changes in juxtaglomerular apparatus (JGA) were defined in male rats treated with quinapril, an inhibitor of angiotensin-converting enzyme (ACE). Doses of 0, 10, 100, and 400 mg/kg were administered daily by gavage for up to 4 weeks. Granular juxtaglomerular (JG) cells were normal or hypogranular on Day 1 at all doses and were hypergranular by Day 7 in rats given 100 and 400 mg/kg relative to age-matched controls. Histologically, JGA hypertrophy was apparent by Day 7 at all doses and was most pronounced by Day 14 in intermediate and deep cortical zones of rats given 100 and 400 mg/kg. Ultrastructurally, hypertrophic JG cells had abundant rough endoplasmic reticulum and free ribosomes, and prominent Golgi complexes associated with numerous cytoplasmic coated vesicles. Dose-dependent increases in numbers of protogranules, altered granules, and cytoplasmic vacuoles occurred in association with decreased size and increased pleomorphism of mature secretory granules. Granule alterations included vesicular to lamellar membranous matrical inclusions, irregular patterns of osmiophilia, matrical vacuolation, and flocculent to coarsely granular matrix of greater density than mature granules. We concluded that JG cell hypertrophy and hyperplasia occurred rapidly in response to subchronic ACE inhibition. Further, ultrastructural changes in JG cells were indicative of stimulated renin synthesis by a regulated pathway, renin secretion by exocytosis and cytoplasmic solubilization of granules, and autophagy of granules as a mechanism whereby JG cells regulate levels of stored renin under conditions of excessive stimulation.

Preliminary hemodynamic report of the efficacy and safety of quinapril in acute and chronic treatment of patients with congestive heart failure

A two-part hemodynamic trial of the efficacy and safety of quinapril hydrochloride was conducted in 26 patients with congestive heart failure (NYHA Class III or IV) who had not optimally responded to treatment with diuretics and digitalis. A total of 25 patients had evaluable data after receiving single doses (2.5, 5, or 10 mg) of quinapril. Following acute dosing, favorable hemodynamic changes began within thirty minutes to one hour and usually reached a maximum within four hours post-dose. Nineteen evaluable patients who had responded to acute therapy received an additional sixteen weeks of chronic treatment with quinapril in individualized dosage regimens. Hemodynamic responses did not differ markedly between acute and chronic therapy. Favorable hemodynamic responses were maintained or enhanced following chronic doses of 5 to 30 mg/day (given either once daily or in divided doses). The most frequent doses were 10-15 mg/day in divided doses. The mean maximum percent changes in four primary hemodynamic parameters after chronic dosing (compared with baseline) were: mean arterial blood pressure, -3.9%; pulmonary capillary wedge pressure, -39.7%; cardiac output, +31.7%; and systemic vascular resistance, -25.2%. Changes in heart rate and mean arterial blood pressure did not result in clinically significant bradycardia or hypotention. Overall, quinapril produced both acute and sustained beneficial hemodynamic effects in patients whose congestive heart failure was not clinically controlled with diuretics and digitalis.

The clinical pharmacokinetics of quinapril

Quinapril (Q) and quinaprilat (QT) pharmacokinetics are dose proportional following single oral 2.5- to 80-mg Q doses. Q absorption and hydrolysis to QT is rapid with peak Q and QT concentrations occurring one and two hours postdose, respectively. Peak plasma QT concentrations were approximately fourfold higher than those of Q (923 vs 207 ng/mL following 40-mg Q). Dose-proportional QT area under the curve and dose-independent percent of dose excreted in urine as QT demonstrate that the extent of Q conversion to QT is constant over the dose range studied. Q and QT were eliminated from plasma with apparent half-lives of 0.8 and 1.9 hours and apparent plasma clearances of 1,850 and 220 mL/min, respectively, over the 2.5- to 80-mg dose range. Following oral 14C-Q, 61% and 37% of radiolabel was recovered in urine and feces, respectively. Q plus QT accounted for 46% of radioactivity circulating in plasma and 56% of that excreted in urine. Metabolism to compounds other than QT is not extensive. Two diketopiperazine metabolites of Q have been identified in plasma and urine, with approximately 6% of an administered dose excreted in urine as each of these metabolites. Peak plasma concentrations of these metabolites are similar to that of Q, and each is eliminated rapidly with a half-life of approximately one hour. Urinary excretion profiles indicate the presence of other minor metabolites. In summary, the absorption of Q and conversion to QT is rapid and dose-proportional, subsequent clearance of both Q and QT is independent of dose, and metabolism to compounds other than QT is not extensive.