Prostaglandin biosynthesis by rabbit renomedullary interstitial cells in tissue culture. Stimulation by angiotensin II, bradykinin, and arginine vasopressin.

Rabbit renomedullary interstitial cells were isolated and grown in tissue culture. These cells synthesize 0.8 ng of prostaglandin E2 (PGE2) per microgram cellular protein per hour in monolayer tissue culture; prostaglandins A2 and F2alpha (PGA2 and PGF2alpha) biosynthesis was 10 and 5% of PGE2 biosynthesis, respectively. Arachidonic acid markedly stimulated the production of PGE2 and PGF2alpha, with conversion rates of 0.24 and 0.02%/h, respectively. Angiotensin II, hyperosmolality, bradykinin, and arginine vasopressin each stimulated PGE2 biosynthesis; maximum stimulation was 20, 3.7, 3.6, and 3.2 times basal production, respectively. PGE2 biosynthesis by the renomedullary interstitial cells was inhibited by isoproterenol, potassium, nonsteroidal anti-inflammatory agents (indomethacin, naproxen, ibuprofen, suprofen, meclofenamate, and acetylsalicylic acid), mepacrine (a phospholipase inhibitor), hydrocortisone, and cortisone. The rabbit renomedullary interstitial cell in tissue culture is a model system for the study of hormonal regulation of PGE2 biosynthesis.

Vasopressin-stimulated prostaglandin E biosynthesis in the toad urinary bladder. Effect of water flow.

Prostaglandin E biosynthesis and its effect on water permeability were investigated in the toad urinary bladder. Arginine vasopressin (1 mU/ml) increased prostaglandin E (PGE) biosynthesis from 0.5+/-0.1 to 5.0+/-0.4 pmol/min per hemibladder (mean +/-SEM, n= 8, P less than 0.001). Maximal vasopressin-stimulated PGE biosynthesis, 6.4+/-0.2 pmol/min per hemibladder, occurred at vasopressin concentrations in excess of 3 mU/ml. Half-maximal stimulation of PGE biosynthesis occurred at a vasopressin concentration of approximately 0.7 mU/ml, whereas half-maximal stimulation of water flow occurred at a vasopressin concentration of approximately 5 mU/ml. Vasopressin-stimulated PGE biosynthesis did not depend on water flow along an osmotic gradient or upon sodium transport. Thin-layer chromatographic analysis of the lipids released from hemibladders labeled with tritium-arachidonic acid revealed that vasopressin stimulates the release of arachidonic acid from intracellular lipid stores without affecting the percentage of free arachidonic acid converted to PGE. Neither cyclic AMP nor theophylline stimulated PGE biosynthesis although they mimic arginine vasopressin (AVP) in stimulating water permeability. Biosynthesis of PGE was inhibited by mepacrine, a phospholipase inhibitor, and by agents that inhibit arachidonic acid oxygenase. The inhibition of PGE biosynthesis resulted in augmented vasopressin- and theophylline-stimulated water flow, but had no effect on cyclic AMP-stimulated water flow. We interpret these results to mean that endogenous PGE inhibits basal and vasopressin-stimulated adenylate cyclase activity. In contrast to the effects of AVP on permeability and transport, AVP stimulates PGE biosynthesis by a mechanism that does not depend on an increase in cellular cyclic AMP levels. The water permeability response of the toad urinary bladder to vasopressin is inhibited by PGE synthesized by the bladder in response to vasopressin.

Inhibition of vasopressin-stimulated prostaglandin E biosynthesis by chlorpropamide in the toad urinary bladder. Mechanism of enhancement of vasopressin-stimulated water flow.

Chlorpropamide is known to enhance the water permeability response of the toad urinary bladder to vasopressin and to theophylline. In other studies, we have shown that prostaglandin E synthesis by the toad bladder inhibits the water permeability response to arginine vasopressin and to theophylline. In this study, the effect of chlorpropamide on vasopressin-, theophylline-, and cyclic AMP-stimulated water flow and on prostaglandin E biosynthesis was investigated in the toad urinary bladder in vitro. Chlorpropamide inhibited prostaglandin E biosynthesis during vasopressin-, theophylline- and cyclic AMP-stimulated water flow. Tolbutamide and glyburide, two other sulfonylurea compounds, also enhanced vasopressin-stimulated water flow and inhibited vasopressin-stimulated prostaglandin E biosynthesis. We conclude that the mechanism of enhancement on vasopressin-stimulated water flow by the sulfonylureas is the inhibition of prostaglandin E biosynthesis.

The effect of chronic sodium loading and sodium restriction on plasma prostaglandin A, E, and F concentrations in normal humans.

It has been suggested that prostaglandins may be involved in the control of sodium homeostasis. Prostaglandin A and prostaglandin E have been shown to increase renal blood flow and urinary sodium excretion and prostaglandin A has been shown to stimulate aldosterone release. The purpose of this study was to determine the effect of chronic sodium loading and sodium restriction on plasma prostaglandin A, E, and F concentrations. SEVEN NORMAL HUMAN VOLUNTEERS WERE PLACED ON THREE SODIUM INTAKE DIETS: (a) ad lib. sodium intake, (b) high sodium intake, and (c) low sodium intake. Plasma prostaglandin A, E, and F concentrations were measured by radioimmunoassay. Mean prostaglandin A levels on the ad lib. diet were 1.60 ng/ml. Prostaglandin A levels decreased 49% to 0.82 ng/ml on the high sodium intake and increased 34% to 2.14 ng/ml on the low sodium intake. Prostaglandin A levels increased 161% on the low sodium diet in comparison with levels on the high sodium diet. Plasma prostaglandin E and F concentrations did not change significantly during variation in sodium intake. These results show that dietary sodium content markedly effects plasma prostaglandin A levels and that prostaglandins may play a role in the physiologic mechanism of sodium homeostasis.

The kallikrein-kinin system in Bartter's syndrome and its response to prostaglandin synthetase inhibition.

The kallikrein-kinin system was characterized in seven patients with Bartter's syndrome on constant metabolic regimens before, during, and after treatment with prostaglandin synthetase inhibitors. Patients with Bartter's syndrome had high values for plasma bradykinin, plasma renin activity (PRA), urinary kallikrein, urinary immunoreactive prostaglandin E excretion, and urinary aldosterone; urinary kinins were subnormal and plasma prekallikrein was normal. Treatment with indomethacin or ibuprofen which decreased urinary immunoreactive prostaglandin E excretion by 67%, decreased mean PRA (patients recumbent) from 17.3+/-5.3 (S.E.M.) ng/ml per h to 3.3+/-1.1 ng/ml per h, mean plasma bradykinin (patients recumbent) from 15.4+/-4.4 ng/ml to 3.9+/-0.9 ng/ml, mean urinary kallikrein excretion from 24.8+/-3.2 tosyl-arginine-methyl ester units (TU)/day to 12.4+/-2.0 TU/day, but increased mean urinary kinin excretion from 3.8+/-1.3 mug/day to 8.5+/-2.5 mug/day. Plasma prekallikrein remained unchanged at 1.4 TU/ml. Thus, with prostaglandin synthetase inhibition, values for urinary kallikrein and kinin and plasma bradykinin returned to normal pari passu with changes in PRA, in aldosterone, and in prostaglandin E. The results suggest that, in Bartter's syndrome, prostaglandins mediate the low urinary kinins and the high plasma bradykinin, and that urinary kallikrein, which is aldosterone dependent, does not control kinin excretion. The high plasma bradykinin may be a cause of the pressor hyporesponsiveness to angiotensin II which characterizes the syndrome.

Effect of prostacyclin on vascular capacity in the dog.

Since the discovery of prostacyclin (PGI2) in 1976, there has been great interest in its vascular effects and potential clinical applications. High infusion rates of PGI2 markedly depress arterial blood pressure both in animal studies and in clinical trials. This fall in pressure may result entirely from a decrease in arterial resistance. However, it is possible that the administration of PGI2 may decrease ventricular filling due to an increase in vascular capacity. To investigate whether or not PGI2 affects vascular capacity, we infused PGI2 intraarterially at both 10 and 25 micrograms/min into 15 dogs on total cardiopulmonary bypass. These infusions were associated with a 25 +/- 3 mmHg decrease in arterial pressure and an increase in vascular capacity of 155 +/- 29 ml (SE, P less than 0.005). This increase in capacity was greater (P less than 0.02) than the increase of 23 +/- 42 ml resulting from infusions of nitroglycerin into eight dogs at 2 mg/min, which produced a decrease in arterial pressure of 23 +/- 4 mmHg, which was the maximal effect that could be achieved. Neither bilateral cervical vagotomy nor beta adrenergic blockade with propranolol significantly diminished the increase in vascular capacity associated with infusions of PGI2. The results from studies in four eviscerated dogs indicated that PGI2 acts on both splanchnic and extrasplanchnic capacity vasculature. To compare the direct effects of PGI2 with those of nitroglycerin and nitroprusside on venous tone, we used an isolated canine spleen preparation. Infusions of PGI2 (100 mcg/min) increased spleen weight in this preparation by 9.0 +/- 2.4% (n = 10, P less than 0.001); this increase was significantly greater than increases of 3.6 +/- 2.2% (P less than 0.001) and 3.5 +/- 2.3% (P less than 0.001) caused by high dose infusions of nitroglycerin (1 mg/min) and nitroprusside (400 micrograms/min), respectively. Thus, PGI2 substantially increases vascular capacity by a mechanism that appears to involve a direct action on vascular smooth muscle. Furthermore, these results suggest that PGI2 might be useful in clinical conditions in which an increase in vascular capacity is indicated.

Alternatives to traditional first-line antihypertensive treatment: unresolved questions and therapeutic dilemmas. A personal approach.

The best antihypertensive regimen for use in patients with mild-to-moderate hypertension has not been determined. When nonpharmacological treatment of hypertension fails, initial drug treatment with diuretic drugs, sympatholytic agents (including beta-adrenergic receptor blockers), or vasodilators will result in satisfactory blood pressure control. However, each of these therapies has effects that are independent of their antihypertensive activity and that should be considered before a selection is made for initial therapy. The adverse effects of diuretic agents and beta-adrenergic receptor-blocking drugs on plasma lipid profiles may diminish the beneficial effects of blood pressure reduction. On the other hand, the hypocholesterolemic effect of alpha-adrenergic receptor antagonists, the potential cardioprotective effect of angiotensin converting enzyme inhibitors, and the salutary effects of calcium channel blockers on left ventricular function are responses that would support the use of vasodilatory therapy. Vasodilating antihypertensive drugs may be more beneficial than "standard" therapy and should be considered for the initial treatment of newly diagnosed hypertensive patients.

Benign breast dysplasia causing hypercalcemia.

An adolescent female had hypercalcemia and massive, bilateral breast enlargement. At neck and mediastinal explorations three parathyroid glands were removed and found to be histologically normal. Following bilateral mastectomy the hypercalcemia resolved within two days and did not recur during a six-year period of followup. Microscopic examination of the excised breast tissue revealed marked dysplasia but no cancer. Those findings suggest that benign, dysplastic breast tissue can release humoral mediators of hypercalcemia.

Age, race, diagnosis, and sodium effects on the pressor response to infused norepinephrine.

We studied the blood pressure responses to infused norepinephrine in 34 normotensive and 21 unmedicated subjects with essential hypertension. The two groups were similar in age, relative body weight, and urinary electrolyte excretion. Patients were studied on two extremes of dietary salt (200 mEq Na and 10 mEq Na per day). The dose-response curves were highly linear (p less than 0.00001) for both systolic and diastolic blood pressures. There was no evidence for an increased sensitivity to infused norepinephrine among the hypertensive subjects. On the other hand, older subjects had steeper slopes (p less than 0.005). Subjects on a high salt diet had steeper slopes than those on low salt diets (p less than 0.0025); this trend was especially apparent among blacks (p less than 0.005). Black and white hypertensive subjects responded to the high salt diet in opposite fashion: The blacks showed an increased pressor sensitivity (p less than 0.05), whereas the whites demonstrated a nonsignificant decreased pressor sensitivity. These results indicate that age, race, and salt effects must be meticulously controlled in studies of sympathetic nervous system physiology.

Is renin a factor in the etiology of essential hypertension?

The widespread clinical study of converting-enzyme inhibitors has shown that they are effective antihypertensive drugs even in patients who may manifest either normal or decreased plasma renin activity. This suggests either that renin in a site other than plasma may play a contributory role in essential hypertension or that the hypotensive effect is caused by increased concentrations of kinins and prostaglandins, both demonstrated consequences of converting-enzyme inhibitor administration. Specific renin inhibitors appropriate for studies in humans would aid in the resolution of this question. Four classes of compounds have been demonstrated to be renin inhibitors of high potency: specific antibody, general peptide inhibitors of acid proteases, analogs of angiotensinogens, and peptides that are related to the amino-terminal sequence of prorenin. With the purification of renin, specific polyclonal or monoclonal antibodies have become available. The former have already been used extensively in physiologic studies in intact animals. Pepstatin is an inhibitor of many acid proteases. Its in vivo application has been retarded by its relative insolubility, but recent chemical modifications, particularly the addition of charged amino acids at the carboxy terminus, have rendered it more useful. The minimal substrate for renin is an octapeptide segment of the protein substrate: His-Pro-Phe-His-Leu-Leu-Val-Tyr. Variants of this sequence have resulted in competitive inhibitors that are useful in vivo. Recently, remarkably active inhibitors have been synthesized by reducing the peptide bond that is cleaved by renin, producing what may be a transition state inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Once-daily fosinopril in the treatment of hypertension.

This multicenter, dose-ranging study evaluated the antihypertensive effectiveness of once-daily administration of fosinopril sodium in 220 patients with supine diastolic blood pressure of 95-115 mm Hg. After a 4-week placebo period, patients were randomly assigned to double-blind therapy with either placebo or 10, 40, or 80 mg fosinopril once daily for 4 weeks. If treatment goals were not met, chlorthalidone 25 mg/day was added for weeks 5 to 8. Thereafter, patients could enter the long-term, open-label phase and receive 10-80 mg/day fosinopril plus chlorthalidone, if needed. After 4 weeks of monotherapy, the average decreases in supine diastolic blood pressure were 9% (10 mg), 11.5% (40 mg), and 12.5% (80 mg) compared with 6% in the placebo group. After 8 weeks, the average decreases, with or without diuretic therapy, were 12.5-18.2%, compared with 10.8% with placebo. Blood pressure continued to be well controlled, and the patients showed no evidence of tachyphylaxis or tolerance through 12-15 months of treatment. Fosinopril was well tolerated. During the short-term phase, no patient withdrew because of adverse events possibly related to fosinopril; during the long-term phase, nine of 148 patients (6.1%) withdrew for that reason. In patients with mild-to-moderate hypertension, once-daily fosinopril (40 and 80 mg) provided significant antihypertensive effects with or without diuretic therapy. The 10 mg dose was effective in some patients and may be considered a starting dose.

Effects of prostacyclin infusion in uremic patients: hematologic and hemodynamic responses.

The effects of sequential prostacyclin infusions at 2, 4, and 8 ng/kg/min for 1 hr were determined in six patients with chronic renal failure. Diastolic blood pressure decreased in a dose-dependent fashion from 74 +/- 4 mm Hg (mean +/- SEM) to 70 +/- 4, 66 +/- 5, and 55 +/- 5 during the 2, 4, and 8 ng/kg/min infusions, respectively; systolic blood pressure was not affected by prostacyclin. The fall in diastolic blood pressure was associated with a progressive rise in heart rate from 77 +/- 3 to 91 +/- 4 bpm and lowering of body temperature from 36.7 +/- 0.1 to 36 +/- 0.2 degrees. The threshold concentration of adenosine diphosphate that evoked reversible and irreversible platelet aggregation increased progressively from 1.2 to 2.8 and from 2.8 to 6 microM, respectively, during the prostacyclin infusions. Prostacyclin infusions had no effect on prothrombin time, activated partial thromboplastin time, or platelet count, but template bleeding time increased (not statistically significantly) from 5.8 to 12.3 min. In three of six patients, the 8 ng/kg/min infusion was terminated prematurely due to nausea, vomiting, and/or hypotension. We conclude that platelet aggregability can be inhibited in patients with chronic uremia by infusing 4 ng/kg/min prostacyclin without causing untoward side effects. When infused at hemodynamically tolerable doses, prostacyclin might serve as an in vivo inhibitor of platelet aggregation during hemodialysis or cardiopulmonary bypass.

Comparison of nifedipine and propranolol used in combination with diuretics for the treatment of hypertension.

One hundred patients participated in a double-blind, randomized study to compare the antihypertensive efficacy of sustained-release nifedipine and propranolol in hypertensive patients whose diastolic blood pressure exceeded 95 mm Hg while receiving diuretic therapy. Nifedipine (mean dose, 79.6 mg per day) decreased blood pressure by 11.4/10.5 mm Hg; propranolol (mean dose, 198.4 mg per day) decreased blood pressure by 13.5/10.3 mm Hg. Reduction of diastolic blood pressure to below 90 mm Hg was achieved in 63 percent of nifedipine-treated patients and in 57 percent of propranolol-treated patients. Nifedipine therapy was associated with an increase in high-density lipoprotein cholesterol levels and a decrease in serum triglyceride levels. In contrast, propranolol therapy was associated with a decrease in high-density lipoprotein cholesterol levels and an increase in serum triglyceride levels. Nifedipine is as effective as propranolol in the treatment of patients with mild to moderate hypertension whose blood pressure is inadequately controlled by diuretic therapy.

Effect of sildenafil citrate on blood pressure and heart rate in men with erectile dysfunction taking concomitant antihypertensive medication. Sildenafil Study Group.

OBJECTIVES: To assess the acute effect of sildenafil citrate on blood pressure and heart rate in men with erectile dysfunction taking concomitant antihypertensive medication. DESIGN: Post-hoc subanalysis of five, 12- or 24-week, prospective, randomized, double-blind, placebo-controlled studies. SETTING: Private-practice and academic urology clinics. PATIENTS: A total of 1685 men with erectile dysfunction of > or = 6 months duration, of whom 667 (sildenafil n = 406, placebo n = 261) were taking antihypertensive medication (diuretic, beta-blocker, alpha-blocker, angiotensin converting enzyme inhibitor, and/or calcium antagonist). Of the patients taking antihypertensive medication, 608 (91%) completed the studies (374 of 406 receiving sildenafil, 234 of 261 receiving placebo). INTERVENTIONS: The last dose of oral sildenafil (25-200 mg) or placebo was taken at home on the morning of the final clinic visit. Patients taking antihypertensive medication maintained usual dosing schedules. MAIN OUTCOME MEASUREMENTS: Sitting systolic (SBP)/diastolic blood pressure (DBP) and heart rate at baseline and after dosing with sildenafil or placebo (end-of-treatment visit). RESULTS: Mean changes from baseline in SBP/DBP for men taking antihypertensive medication were -3.6/-1.9 mmHg for those receiving sildenafil and -0.8/-0.1 mmHg for those receiving placebo compared with -2.2/-2.0 mmHg and -0.1/0.4 mmHg, respectively, for men not taking antihypertensive medication. Mean changes from baseline in heart rate for men taking antihypertensive medication were -0.6 beats/min after sildenafil and 0.9 beats/min after placebo compared with 0.4 beats/min and -0.6 beats/min, respectively, for patients not taking antihypertensive medication. Differences in SBP, DBP, and heart rate between the patients taking and those not taking antihypertensive medication were small. CONCLUSIONS: The acute, short-term effects of oral sildenafil on blood pressure and heart rate in men with erectile dysfunction were small and not likely to be clinically significant in those taking concomitant antihypertensive medication.

Angiotensin-converting enzyme inhibitors: more different than alike? Focus on cardiac performance.

Development of an increased systemic vascular resistance and the concomitant increase in blood pressure are associated with significant changes in left ventricular structure and function. The plasma and tissue renin-angiotensin systems play an important, but variable, role in the regulation of blood pressure and systemic vascular resistance in normotensive and hypertensive patients. Non-angiotensin-mediated effects of angiotensin-converting enzyme (ACE) inhibitors and/or differential tissue specificities may result in a variable hemodynamic response to individual therapies. Using first-pass radionuclide cineangiography, the hemodynamic effects of captopril, lisinopril, and fosinopril were compared. Fosinopril induced a greater reduction in systemic vascular resistance than did equipotent hypotensive doses of captopril or lisinopril and was associated with an increase in cardiac output, left ventricular peak ejection rate, and left ventricular peak filling rate. Along with previously accumulated data, these results suggest that structural differences among ACE inhibitors may result in unique physiologic effects. Fosinopril appears to have a cardiotropic effect that causes improved left ventricular diastolic performance; this effect is unique among currently available ACE inhibitors. The clinical significance of the unique profiles of individual ACE inhibitors awaits assessment via comparative clinical investigations.

Cardiovascular effects of sildenafil citrate and recommendations for its use.

Sildenafil citrate is the first orally active therapy proved to be effective and safe treatment for erectile dysfunction (ED). Because men with cardiovascular disease are at increased risk of developing ED, and because ED and cardiovascular disease share important risk factors, attention has focused recently on the use of sildenafil in these men. When used in combination with nitroglycerin and other nitric oxide (NO) donors, sildenafil may potentiate major drops in blood pressure. Use of nitrate antianginal agents are an absolute contraindication to sildenafil use. In normotensive men and in men receiving antihypertensive medications evaluated in Phase II/III clinical trials, sildenafil use at the recommended doses (25-100 mg 1 hour before sexual intercourse and no more than once daily) was associated with modest, transient reductions in blood pressure and negligible effects on heart rate. In a more recent study, sildenafil was well tolerated in patients receiving antihypertensive medications and was not associated with major decreases in blood pressure. From the time of its approval in the United States in March 1998 through mid-November 1998, with approximately 6 million prescriptions written, 130 deaths were reported by the US Food and Drug Administration (FDA). Seventy-seven of the men who died had documented cardiovascular events. Sixteen men took or were administered nitroglycerin or an organic nitrate; 3 others had nitroglycerin in their possession. Physician prescribing guidelines issued by the American College of Cardiology/American Heart Association (ACC/AHA) recommend caution when prescribing sildenafil to men with certain cardiovascular conditions, liver or kidney disease, and to those taking medications that may prolong sildenafil's half-life (e.g., erythromycin or cimetidine). Those with known or suspected coronary artery disease may benefit from an exercise test to determine whether resumption of sexual activity with use of sildenafil is likely to be associated with an increased risk of myocardial ischemia.

Diltiazem and captopril alone or in combination for treatment of mild to moderate systemic hypertension.

The efficacy and safety of sustained-release diltiazem, 60 to 180 mg twice daily, was compared with that of captopril, 25 to 75 mg twice daily, alone and in combination, in 132 patients with mild to moderate essential hypertension (supine diastolic blood pressure [BP] 95 to 114 mm Hg). All patients received placebo for 4 to 6 weeks, followed by randomization to diltiazem or captopril during the double-blind monotherapy phase. Either study drug was titrated over 6 weeks to achieve a goal supine diastolic BP reduction of at least 10 mm Hg and a diastolic BP of less than 90 mm Hg. Patients achieving the goal BP reduction were maintained on monotherapy for an additional 8 weeks. Patients not achieving the treatment goal after 8 weeks with either drug alone received the other drug in combination, titrated to achieve goal BP response. Both drugs lowered BP significantly and, at the doses used, diltiazem had a greater effect on diastolic BP than did captopril. The mean changes from baseline at week 8 were -10.6 and -7.3 mm Hg, respectively, (p = 0.01). Goal BP was achieved in 38% of patients taking diltiazem monotherapy and in 34% of patients taking captopril monotherapy. There were no significant differences between diltiazem and captopril in diastolic or systolic BP reductions by race or age. The addition of alternate therapy for non-goal achievers at week 8 resulted in significant reductions in diastolic and systolic BP by week 16.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of antianginal therapy on left ventricular systolic and diastolic performance: comparison of the response to bepridil, propranolol, and diltiazem.

Abnormalities of left ventricular (LV) systolic performance develop during exercise in patients with coronary artery disease (CAD) as a result of ischemia-induced regional wall motion abnormalities. Like patients with hypertension and those with hypertrophic cardiomyopathy, patients with CAD display abnormalities of LV diastolic performance under basal conditions in the absence of ischemia. The purpose of these studies was to compare the effects of bepridil versus those of propranolol or diltiazem in patients with exertional angina pectoris. LV systolic and diastolic performance were assessed at rest and during peak upright bicycle exercise by first-pass radionuclide ventriculography. Compared with propranolol, bepridil increased exercise capacity, cardiac output, and stroke volume and decreased systemic vascular resistance. Compared with diltiazem, bepridil increased exercise capacity, peak filling rate, and early diastolic filling fraction and decreased systemic vascular resistance, heart rate, time to peak filling rate, and atrial filling volume. Bepridil therapy is associated with improved exercise capacity and decreased anginal frequency and nitroglycerin consumption. In addition, its use is accompanied by favorable changes in LV systolic and diastolic function at rest and during exercise. These changes are consistent with benefits resulting from resolution of myocardial ischemia as well as from positive lusitropic effects of bepridil on the ventricular myocardium.

Overall cardiovascular profile of sildenafil citrate.

Sildenafil, a selective inhibitor of phosphodiesterase type 5 (PDE5), is the first in a new class of orally effective treatments for erectile dysfunction. During sexual stimulation, the cavernous nerves release nitric oxide (NO), which induces cyclic guanosine monophosphate (cGMP) formation and smooth muscle relaxation in the corpus cavernosum. Sildenafil facilitates the erectile process during sexual stimulation by inhibiting PDE5 and thus blocking the breakdown of cGMP. Sildenafil alone can cause mean peak reductions in systolic/diastolic blood pressure of 10/7 mm Hg that are not dose related, whereas the heart rate is unchanged. Sildenafil and nitrates both increase cGMP levels in the systemic circulation but at different points along the NO-cGMP pathway. The combination is contraindicated because they synergistically potentiate vasodilation and may cause excessive reductions in blood pressure. Erectile dysfunction is a significant medical condition that shares numerous risk factors with ischemic heart disease, and hence a substantial overlap exists between these patient groups. From extensive clinical trials, the most commonly reported cardiovascular adverse events in patients treated with sildenafil were headache (16%), flushing (10%), and dizziness (2%). The incidences of hypotension, orthostatic hypotension, and syncope and the rate of discontinuation of treatment due to adverse events were <2% and were the same in patients taking sildenafil and those taking placebo. Retrospective analysis of the concomitant use of antihypertensive medications (beta blockers, alpha blockers, diuretics, angiotensin-converting enzyme inhibitors, and calcium antagonists) in patients taking sildenafil did not indicate an increase in the reports of adverse events or significant episodes of hypotension compared with patients treated with sildenafil alone. In clinical trials, the incidence of serious cardiovascular adverse events, including stroke and myocardial infarction, was the same for patients treated with sildenafil or placebo. Concurrent disease states, such as renal or hepatic impairment, or concomitant use of inhibitors of the cytochrome P450 isozyme CYP3A4 could increase systemic exposure to sildenafil. Since the US market launch in April 1998, monitoring of spontaneous adverse event reports in association with sildenafil has demonstrated a pattern that is generally consistent with the experience observed during clinical development, with the exception of infrequent reports of priapism. In conclusion, extensive clinical testing has shown that overall treatment with sildenafil for up to 1 year is well tolerated and is associated with a low incidence of adverse events that result in discontinuation of treatment in <3% of patients.

Evaluation of bepridil for the treatment of angina pectoris: evidence for preservation of left ventricular function.

The efficacy of bepridil (400 mg once a day) was assessed in 15 patients with exertional angina pectoris. All 15 patients reported substantial clinical improvement during bepridil treatment compared with placebo treatment. Episodes of angina were 11.8 +/- 4.1 (mean +/- standard error of the mean)/week with placebo and 3.8 +/- 1.6 with bepridil (p less than 0.05); nitroglycerin use was 9.1 +/- 3.3 tablets/week with placebo and 3.5 +/- 1.7 with bepridil (p less than 0.05). Five of 15 patients receiving bepridil did not experience angina during treadmill exercise; in the remaining 10 patients, time to onset of angina during exercise was 5.7 +/- 0.9 minutes with bepridil as opposed to 4.5 +/- 0.8 minutes with placebo (p less than 0.05). Left ventricular (LV) performance at peak exercise as measured by first-pass radionuclide angiography revealed the ejection fraction to be 38 +/- 3% during placebo therapy and 47 +/- 4% during bepridil therapy (p less than 0.0025). End-diastolic LV volume was unchanged, but end-systolic volume was 136 +/- 11 and 117 +/- 13 ml (p less than 0.05) and stroke volume was 82 +/- 6 and 97 +/- 9 ml (p less than 0.05) during placebo and bepridil therapy, respectively. Heart rate at peak exercise was 136 +/- 3 beats/min with placebo and 128 +/- 3 beats/min with bepridil; however, blood pressure was unchanged. These studies demonstrate that bepridil results in significant clinical improvement and enhanced LV performance in patients with angina pectoris.