Imidazoline receptor agonist drugs: a new approach to the treatment of systemic hypertension

The imidazoline receptors have recently been discovered to be involved in central nervous system control of blood pressure (I-1 receptor) and in neuroprotection for cerebral ischemia (I-2 receptor). A new class of central-acting antihypertensive agents has been developed, the imidazoline receptor agonists (rilmenidine and moxonidine), which control blood pressure effectively without the adverse effects of sedation and mental depression that are usually associated with central-acting antihypertensives. This new generation of central-acting antihypertensive agents are highly selective for the imidazoline receptor, while having a low affinity for alpha 2-adrenergic receptors.

beta-blockers. Drug interactions of clinical significance

The clinician prescribing beta-blockers for his or her patients is faced with an often difficult situation. There are many beta-blockers, each with its own pharmacological profile. Patients are often taking multiple medications, thus increasing the risk of both anticipated and unexpected drug interactions. Reports of drug interactions are frequently anecdotal. The prescriber may not be aware of the patient's other medications or lifestyle habits. Pharmacokinetic and pharmacodynamic drug interactions involving beta-blockers are documented in the literature, but these studies often examine small numbers of patients. For these reasons, it is difficult for the practitioner to distill guidelines for the administration of beta-blockers in conjunction with other medication. In general, beta-blockers are well tolerated, and symptomatic drug interactions are relatively infrequent. It is incumbent upon the clinical practitioner to have knowledge of his or her patient's drug profile and to be aware of the various drug interactions as well as each patient's unique pathophysiological profile when prescribing any medication, including beta-blockers. beta-Blockers may interact with a large number of commonly prescribed drugs, including antihypertensive and antianginal drugs, inotropic agents, anti-arrhythmics, NSAIDs, psychotropic drugs, anti-ulcer medications, anaesthetics, HMG-CoA reductase inhibitors, warfarin, oral hypoglycaemics and rifampicin (rifampin).

Comparison of amlodipine and benazepril monotherapy to amlodipine plus benazepril in patients with systemic hypertension: a randomized, double-blind, placebo-controlled, parallel-group study. The Benazepril/Amlodipine Study Group

A single-blind, run-in, randomized, double-blind, parallel-group, placebo-controlled comparison trial was conducted to assess the safety and efficacy of low-dose amlodipine 2.5 mg daily, low-dose benazepril 10 mg daily, and the combination of the two drugs at the same doses used once daily in patients (n = 401) with mild to moderate (stages I and II) systemic hypertension. Both monotherapy regimens were shown to significantly reduce both systolic and diastolic blood pressure compared with baseline placebo values, and the combination regimen was shown to be superior in lowering systolic and diastolic blood pressure when compared with either of the monotherapy regimens. The combination therapy also resulted in a greater percentage of patients having successful clinical response in mean sitting diastolic blood pressure. The amlodipine and benazepril regimen was also shown to be associated with a similar incidence of adverse experiences as the active monotherapy or placebo regimens, although the group given combination therapy appeared to have a lower incidence of edema than the group given amlodipine alone. Low-dose amlodipine (2.5 mg) plus benazepril (10 mg) provides greater blood-pressure-lowering efficacy than either monotherapy, and has an excellent safety profile.

Novel antiplatelet therapies for treatment of patients with ischemic heart disease: inhibitors of the platelet glycoprotein IIb/IIIa integrin receptor

Blood platelets play essential roles in normal coagulation and in coronary atherosclerotic disease and its complications. Various antiplatelet therapies, including aspirin, ticlopidine, and dipyridamole, have been developed for use in patients with known coronary artery artery disease to prevent ischemic complications. More recently a more complete anti-aggregation effect has been accomplished by the use of monoclonal antibodies and specific peptide and nonpeptide compounds that bind to the platelet GP IIb/IIIa surface receptor. This receptor becomes activated by platelet stimulation and binds fibrinogen molecules between platelets in the aggregation process. These new antiplatelet drugs are now being evaluated in clinical trials in patients undergoing balloon coronary angioplasty, in whom fewer ischemic events occur when the receptor blocker is used intravenously than with standard therapy, and in patients with stable and unstable angina. Excessive bleeding is an important problem with these agents, and efforts must be made to eliminate this side effect.

Insulin resistance in systemic hypertension: pharmacotherapeutic implications

Systemic hypertension, a vascular disease with multiple origins, now is being linked to subtle abnormalities in glucose metabolism, which include insulin resistance and hyperinsulinemia. These conditions often occur together in patients with obesity, noninsulin-dependent diabetes, or both. Hyperinsulinemia and insulin resistance may cause systemic hypertension through multiple mechanisms. Insulin has a salt-retaining effect on the kidney. Also, insulin can augment catecholamine release, increase vascular sensitivity to vasoconstrictor substances, and decrease vascular sensitivity to vasodilator substances. In addition, insulin can increase production of tissue growth factors and help retain sodium and calcium in cells. Insulin resistance in patients can be treated with regular aerobic exercise, weight reduction, and a high-fiber diet. Pharmacologic approaches include hypoglycemic drugs, weight-reducing agents, and certain antihypertensive drugs that may have a favorable impact on both blood pressure and insulin resistance.

Endothelin and endothelin antagonism: roles in cardiovascular health and disease

Endothelin is the most potent mammalian vasoconstrictor yet discovered. Its three isoforms play leading roles in regulating vascular tone and causing mitogenesis. The isoforms bind to two major receptor subtypes (ETA and ETB), which mediate a wide variety of physiologic actions in several organ systems. Endothelin may also be a disease marker or an etiologic factor in ischemic heart disease, atherosclerosis, congestive heart failure, renal failure, myocardial and vascular wall hypertrophy, systemic hypertension, pulmonary hypertension, and subarachnoid hemorrhage. Specific and nonspecific receptor antagonists and ECE inhibitors that have been developed interfere with endothelin's function. Many available cardiovascular therapeutic agents, such as angiotensin-converting-enzyme inhibitors, calcium-entry blocking drugs, and nitroglycerin, also may interfere with endothelin release or may modify its activity. The endothelin antagonists have great potential as agents for use in the treatment of a wide spectrum of disease entities and as biologic probes for understanding the actions of endothelin in human beings.

Addition of zatebradine, a direct sinus node inhibitor, provides no greater exercise tolerance benefit in patients with angina taking extended-release nifedipine: results of a multicenter, randomized, double-blind, placebo-controlled, parallel-group study. The Zatebradine Study Group

OBJECTIVES

We examined the antianginal and anti-ischemic effects of oral zatebradine, a direct sinus node inhibitor that has no blood pressure-lowering or negative inotropic effects in patients with chronic stable angina pectoris taking extended-release nifedipine.

BACKGROUND

Heart rate reduction is considered an important pharmacologic mechanism for providing anginal pain relief and anti-ischemic action in patients with chronic stable angina, suggesting a benefit for sinus node-inhibiting drugs.

METHODS

In a single-blind placebo run-in, randomized double-blind, placebo-controlled, multicenter study, patients already receiving extended-release nifedipine (30 to 90 mg once a day) were randomized to receive zatebradine (5 mg twice a day [n = 64]) or placebo (n = 60). All subjects had reproducible treadmill exercise-induced angina at baseline, and after randomization they performed a serial exercise test 3 h after each dose for 4 weeks.

RESULTS

Zatebradine reduced rest heart rate both at 4 weeks ([mean +/- SEM] 12.9 +/- 1.23 vs. 2.3 +/- 1.6 [placebo] beats/min, p < 0.0001) and at the end of comparable stages of Bruce exercise (16.7 +/- 1.2 vs. 3.4 +/- 1.2 [placebo] beats/min, p < 0.0001). Despite the significant effects on heart rate at rest and exercise, there were no additional benefits of zatebradine from placebo baseline in measurements of total exercise duration, time to 1-mm ST segment depression or time to onset of angina. Subjects taking zatebradine also had more visual disturbances as adverse reactions.

CONCLUSIONS

Zatebradine seems to provide no additional antianginal benefit to patients already receiving nifedipine, and it raises questions regarding the benefit of heart rate reduction alone as an antianginal approach to patients with chronic stable angina.

Serotonin and serotonin antagonism in cardiovascular and non-cardiovascular disease

Serotonin, or 5-hydroxytryptamine, is a naturally-occurring vasoactive substance found primarily in the brain, enterochromaffin tissue, and blood platelets. It has diffuse cardiophysiologic effects. The multiple effects of serotonin on blood vessels can be explained by the existence of 2 serotonergic receptor subtypes (the S1 receptor mediates vasodilation, and the S2 receptor vasoconstriction). Serotonin via the S2 receptor also augments the actions of several other vasoconstricting substances. Serotonin may be responsible for causing, or at least perpetuating, some forms of systemic hypertension through peripheral and central nervous system (CNS) actions. Ketanserin is a highly selective S2-serotonergic antagonist with additional alpha-adrenergic blocking activity, which has been proposed as a therapy for various cardiovascular diseases including hypertension. It has been shown to be more effective than placebo in treating hypertension and comparable in effectiveness to other antihypertensive drugs. Its major side effects relate to the CNS, and prolongation of the electrocardiogram QT interval has been described. Caution must be used when using ketanserin in patients receiving potassium- and magnesium-losing agents, because of the risk of torsades de pointes. Ketanserin has potential utility in the treatment of eclampsia, peripheral vascular disease, carcinoid syndrome, and "shock lung." The drug is not yet approved for clinical use in the United States.

Vesnarinone: a new inotropic agent for treating congestive heart failure

Vesnarinone is a new and novel inotropic drug that has unique and complex mechanisms of action. It inhibits phosphodiesterase, thereby leading to increased intracellular calcium, and also affects numerous myocardial ion channels, resulting in the prolongation of the opening time of sodium channels and the decrease in the delayed outward and inward rectifying potassium current. In vitro, it has also demonstrated significant effects on cytokine production, which may account for some of its observed clinical benefits. Hemodynamic studies in humans with congestive heart failure reveal that vesnarinone can improve ventricular function. Placebo-controlled studies in large numbers of patients with heart failure have suggested a morbidity and mortality benefit with a 60 mg daily dose. There is increased mortality with vesnarinone at the 120 mg daily dose, however, suggesting a narrow therapeutic window for the drug. Its predominant toxic side effect is a 2% incidence of reversible neutropenia.

Sotalol: a new beta-adrenergic blocker for ventricular arrhythmias

Sotalol is a water-soluble, nonselective, beta-adrenergic blocker that was recently approved in oral form in the United States for the treatment of ventricular arrhythmias that are judged to be life-threatening. As a beta-blocker, sotalol is unique in having additional class-III antiarrhythmic activity. It is still not resolved whether sotalol is more effective than other beta-blockers in managing arrhythmias, but there are suggestions that it might possess greater antiarrhythmic and life-protecting activities than other types of antiarrhythmic drugs. The drug is well tolerated, but, because of its electrophysiologic activity, there is a small risk of proarrhythmia, specifically the development of polymorphic ventricular tachycardia and torsade de pointes.

Drug utilization in the old old and how it relates to self-perceived health and all-cause mortality: results from the Bronx Aging Study

OBJECTIVE

To characterize medication use in a "well" very old population and relate the quantity and type of medication use to 10-year mortality.

DESIGN AND SUBJECTS

A longitudinal, 10-year, follow-up study involving 488 healthy, community-dwelling volunteers aged 75 to 85 years. The subjects underwent a detailed baseline evaluation and annual assessments that included comprehensive physical exams, laboratory and diagnostic tests, and related interviews. Prescription and nonprescription drug use was determined by self report, confirmation through hospital records, and reports by subjects and significant others.

RESULTS

At study baseline, the mean number of prescription and nonprescription medications used was 2.3 and 1.5, respectively. Female subjects (n = 315), those older than 80 years, or those who reported themselves to be in fair or poor health on initial health self-report were found to show significantly increased use of prescription medications. The most commonly used classes of medications were cardiovascular drugs and analgesics. Subjects who were consuming a greater number of prescription and nonprescription medications did not have higher mortality rates. After correcting for differences in cardiovascular health status between users and nonusers, only digoxin approached significance as an independent predictor of death (P < .08).

CONCLUSION

This study confirmed that medication use in an ambulatory, old old population is not excessive. The oldest subjects in the cohort consumed more medications than did the younger subjects. Women used more prescription drugs than men. Increased medication use was associated with worse ratings on health self report. Medication use alone, however, was not a predictor of 10-year mortality in this population. Questions are raised about the inappropriate prescription of digoxin in older subjects.

Nitric oxide donors in the treatment of cardiovascular and pulmonary diseases

NO has been shown to be a biologic substance important to normal physiologic functioning. It appears to be an endogenous vasodilator and is involved in hemostasis and inflammation. Endothelial cell dysfunction often leads to diminished NO production; this reduction in NO concentrations may be an etiologic factor in systemic hypertension, myocardial and splanchnic ischemia, atherosclerosis, CHF, and pulmonary vascular disease. A new class of drugs, NO donors, have potential utility in the treatment of coronary and pulmonary arterial diseases. Their major advantage over nitrates and nitroprusside is a lack of pharmacologic tolerance. Clinical trials with drugs of this class are now in progress.

Controlled-release drug delivery systems in cardiovascular medicine

Controlled-release drug delivery technology has had a significant effect on the pharmacotherapy of cardiovascular diseases. Oral and transcutaneous controlled-release systems allow relatively short-acting drugs to be administered once or twice daily with comparable therapeutic efficacy and fewer adverse reactions compared with standard formulations. They can provide decreased fluctuations in drug concentrations in plasma while possibly reducing the total amount of drug necessary for a clinical response. Techniques include the diffusion, bioerosion or degradation, and generation of osmotic pressure in orally active and transcutaneous drug delivery systems. Calcium-channel blocking agents, nitrates, beta-blocking agents, antiarrhythmic agents, clonidine, and nicotinic acid can be administered by these techniques, which have greatly influenced the application of these drugs in clinical practice.

First-line therapy option with low-dose bisoprolol fumarate and low-dose hydrochlorothiazide in patients with stage I and stage II systemic hypertension

This 30-center, randomized, double-blind, placebo-controlled, parallel-group study was designed to (1) establish that 6.25 mg of hydrochlorothiazide (HCTZ) given once daily with 5 mg of bisoprolol fumarate can contribute to antihypertensive effectiveness in patients with stage I and stage II (mild to moderate) systemic hypertension; and (2) assess whether this formulation was more effective or possessed a safety advantage over standard monotherapy with bisoprolol or 25 mg of HCTZ. Results showed that HCTZ 6.25 mg contributed significantly to the antihypertensive effectiveness of bisoprolol 5 mg. Bisoprolol 5 mg/HCTZ 6.25 mg (B5/H6.25) produced significantly greater mean reductions from baseline in sitting systolic and diastolic blood pressure (-15.8 mm Hg/-12.6 mm Hg) than bisoprolol 5 mg alone (-10.0 mm Hg/-10.5 mm Hg) and HCTZ 25 mg alone (-10.2 mm Hg/-8.5 mm Hg). A 73% response rate was achieved with the low-dose formulation compared with 61% for the bisoprolol 5 mg (B5) group and 47% for the HCTZ 25 mg (H25) group. B5/H6.25 was found to be significantly more effective than B5 or H25 in all subgroups of patients, regardless of gender, race, age, or smoking history. Antihypertensive effects were maintained during the 24-hour dosing interval. The incremental effectiveness of B5/H6.25 was not accompanied by an increase in the frequency or severity of adverse experiences; the incidence of adverse experiences in the B5/H6.25 group was comparable to that in the placebo group. B5/H6.25 was shown to provide safety advantages over H25, as shown by less hypokalemia (< 1% with B5/H6.25 versus 6.5% with H25).(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium-channel entry blocker therapy for hypertensive patients with concomitant renal impairment: a focus on isradipine

In the treatment of hypertension in renally impaired patients, normalization of blood pressure alone may not be sufficient to prevent significant morbidity to the kidneys. Treatment must reduce pressure in the renal vasculature, otherwise glomerular filtration rate and renal plasma flow will continue to deteriorate. Isradipine a dihydropyridine calcium-channel blocker, has been investigated as a suitable treatment in this setting. Isradipine maintains glomerular filtration rate, preserves or enhances renal plasma flow, decreases renal vascular resistance, maintains or reduces filtration fraction, and exerts a sustained natriuretic effect, all of which may enable isradipine to slow the rate of progression of renal deterioration. In addition, isradipine may decrease proteinuria and may decrease glomerular capillary pressure by dilating both the efferent and afferent arterioles. Unlike older calcium-channel blockers, isradipine exhibits minimal cardiodepressant activity and is not associated with any negative inotropic effects. It is metabolized in the liver and dosage adjustments may not be necessary when administered to patients with renal insufficiency. Isradipine has a favorable renal effect profile and also has several properties that meet the requirements of other patient populations where an extra measure of antihypertensive safety is required, such as diabetics, dialysis patients, and transplant recipients. Side effects with isradipine are usually mild and transient, occurring in a dose-dependent manner.

Atrial natriuretic peptide and its potential role in pharmacotherapy

Atrial natriuretic peptide (ANP) is a 28 amino-acid polypeptide secreted into the blood by atrial myocytes after atrial pressure and distension. Although its role in humans is not clear, it can produce a variety of physiologic effects including vasodilatation, natriuresis, and suppression of the renin-angiotensin-aldosterone axis. These actions are potentially useful in a variety of pathologic states such as hypertension and congestive heart failure, and diverse methods to augment the effects of ANP in these states have been devised. The results are exciting and, despite some problems, may lead to the pharmacologic use of enhancement of ANP actions in several clinical disorders.

Serum vitamin B12 levels and incidence of dementia in a healthy elderly population: a report from the Bronx Longitudinal Aging Study

OBJECTIVE

To determine whether low serum B12 levels are associated with an increased incidence of dementing illness.

DESIGN

Longitudinal cohort study, 5-year follow-up.

PARTICIPANTS

Volunteer cohort of 410 nondemented ambulatory subjects aged 75 to 85 years.

MEASUREMENTS

Annual serum B12 determinations and neuropsychological assessments including the Blessed Test of Information, Memory and Concentration (BIMC) and the Fuld Object Memory Evaluation (FOME). If subject met criteria for a major cognitive change (as defined by an increase of 4 or more points on the BIMC), a work-up that included CT, EEG, and neurologic assessment was performed. Clinical diagnoses were made according to established criteria.

RESULTS

Mean serum B12 level of entire sample was 558 pg/mL. Twenty-two subjects had low B12 levels defined as values < 150 pg/mL. Three of these 22 subjects (13.6%) became demented, compared with 57 of 388 subjects (14.7%) with higher levels. The incidence of Alzheimer disease among the low B12 group was 4.5% compared with 7.5% in the higher B12 group. The mean B12 level at time of diagnosis in subjects who did develop Alzheimer disease was 551 pg/mL. There was no evidence of hematologic disorder among the 22 subjects with low B12. Of the 3 low B12 subjects who did become demented, none responded to monthly B12 injections.

CONCLUSION

A low B12 level may not be a risk factor for dementia in general or Alzheimer disease in particular.

Renin inhibition: a new approach to cardiovascular therapy

The renin-angiotensin system (RAS) functions as a primary regulator in the short-term and long-term control of blood pressure. Pharmacologic inhibition of the RAS with angiotensin-converting enzyme (ACE) inhibition is effective for treating systemic hypertension and congestive heart failure. As a more specific therapy, the development of renin inhibitors has evolved through various approaches: specific renin antibodies, peptides developed from prosegments of renin precursor, oligopeptides related to pepstatin a universal inhibitor of aspartyl proteinase enzyme, and analogs of angiotensinogen (the renin substrate). Angiotensinogen analogs are promising as therapeutic agents because of high potency, metabolic stability, and good oral bioavailability. Ongoing research is directed towards the application of renin inhibition, the treatment of various cardiovascular disorders, and as a biological probe for understanding the role of the RAS in control of blood pressure and blood volume.

Topical ophthalmic beta-adrenergic blockade for the treatment of glaucoma and ocular hypertension

Since the late 1970s, topical beta-adrenergic blockers have been the drugs of choice in treating ocular hypertension and associated glaucoma. The currently available drugs are timolol, betaxolol, levobunolol, metipranolol, and carteolol. All reduce intraocular pressure by decreasing the production of aqueous humor. Although these drugs are applied locally in the eye, they may enter the general circulation and reach concentrations high enough to cause systemic effects, including alterations in heart rate and rhythm, bronchoconstriction, dyslipidemia, and central nervous system abnormalities. Interactions with other drugs may also occur. Ocular beta- blockers differ in beta 1-selectivity (betaxolol is beta 1-selective, whereas the other drugs are nonselective) and in intrinsic sympathomimetic activity (ISA) or partial agonist properties (only carteolol possesses ISA). These differences give betaxolol and carteolol potential advantages in minimizing certain side effects. The advantage of betaxolol vis-à-vis systemic side effects is more clearly established than that of carteolol. Further systematic study is needed to determine what advantages, if any, are conferred by the presence of ISA.

A multifactorial trial design to assess combination therapy in hypertension. Treatment with bisoprolol and hydrochlorothiazide

BACKGROUND

The safety and effectiveness of different dosages and combinations of antihypertensive agents can be efficiently studied using a multifactorial trial design. In consultation with the Cardio-Renal Division of the Food and Drug Administration, we conducted a randomized, double-blind, placebo-controlled, 3 x 4 factorial trial of bisoprolol, a beta 1-selective adrenergic blocking agent, and hydrochlorothiazide.

METHODS

A total of 512 patients with mild to moderate essential hypertension were randomized to once-daily treatment with bisoprolol (0, 2.5, 10, or 40 mg), hydrochlorothiazide (0, 6.25, or 25 mg), and all possible combinations. Diastolic and systolic blood pressures were monitored during this 12-week trial.

RESULTS

The effects of bisoprolol and hydrochlorothiazide were additive with respect to reductions in diastolic and systolic blood pressures over the dosage ranges studied. The addition of hydrochlorothiazide (or bisoprolol) to therapy with bisoprolol (or hydrochlorothiazide) produced an incremental reduction in blood pressure. Dosages of hydrochlorothiazide as low as 6.25 mg/d contributed a significant antihypertensive effect. A hydrochlorothiazide dosage of 6.25 mg/d produced significantly less hypokalemia and less of an increase in uric acid levels than a dosage of 25 mg/d. The low-dose combination of bisoprolol, 2.5 mg/d, and hydrochlorothiazide, 6.25 mg/d, reduced diastolic blood pressure to lower than 90 mm Hg in 61% of patients and demonstrated a safety profile that compared favorably with that of placebo.

CONCLUSIONS

The utility of factorial design trials to characterize dose-response relationships and to test the potential interactions between various antihypertensive agents has been demonstrated. The combination of low dosages of bisoprolol and hydrochlorothiazide may be a rational alternative to conventional stepped-care therapy for the initial treatment of patients with mild to moderate hypertension.

Intranasal delivery of cardiovascular agents: an innovative approach to cardiovascular pharmacotherapy

The intranasal administration of drugs has long been used for the topical treatment of various nasal disorders. Many features of the intranasal mucosa also make it useful for delivery of systemically active agents. It has been shown that intranasal drug administration can provide plasma drug levels similar to those observed with comparable doses of parenteral drugs. The feasibility of intranasal administration of propranolol, nifedipine, and nitroglycerin has been investigated in several small clinical studies. Intranasal propranolol has been shown to improve exercise tolerance in patients with angina pectoris. Intranasal nifedipine has been used to treat patients with perioperative hypertension and hypertensive crisis. Intranasal administration of nitroglycerin was shown to blunt the hypertensive response to endotracheal intubation. These studies and others suggest that intranasal delivery of cardiovascular drug treatment could be used in those clinical situations where a rapid or intermittent drug effect is desired and can potentially serve as an alternative to parenteral drug administration.