Comparison of oxyfedrine and atenolol in angina pectoris--a double-blind study

Clinical pharmacokinetics of vasodilators. Part II

Stimulating cardiac beta 1-adrenoceptors with oxyfedrine causes dilatation of coronary vessels and positive inotropic effects on the myocardium. beta 1-adrenergic agonists increase coronary blood flow in nonstenotic and stenotic vessels. The main indication for the use of the phosphodiesterase inhibitors pamrinone, mirinone, enoximone and piroximone is acute treatment of severe congestive heart failure. Theophylline is indicated for the treatment of asthma, chronic obstructive pulmonary disease, apnea in preterm infants ans sleep apnea syndrome. Severe arterial occlusive disease associated with atherosclerosis can be beneficially affected by elcosanoids. These drugs must be administered parenterally and have a half-life of only a few minutes. Sublingual or buccal preparations of nitrates are the only prompt method (within 1 or 2 min) of terminating anginal pain, except for biting nifedipine capsules. The short half-life (about 2.5 min) of nitroglycerin (glyceryl trinitrate) makes long term therapy impossible. Tolerance is a problem encountered with longer-acting nitric oxide donors. Knowledge of the pharmacokinetic properties of vasodilating drugs can prevent a too sudden and severe blood pressure decrease in patients with chronic hypertension. In considering the administration of a second dose, or another drug, the time necessary for the initially administered drug to reach maximal efficacy should be taken into account. In hypertensive emergencies urapidil, sodium nitroprusside, nitroglycerin, hydralazine and phentolamine are the drugs of choice, with the addition of beta-blockers during catecholamine crisis or dissecting aortic aneurysm. Childhood hypertension is most often treated with angiotensin-converting enzyme (ACE) inhibitors or calcium antagonists, primarily nifedipine. Because of the teratogenic risk involved with ACE inhibitors, extreme caution must be exercised when prescribing for adolescent females. The propagation of health benefits to breast-fed infants, combined with more women delaying pregnancy until their fourth decade, has entailed an increase in the need for hypertension management during lactation. Low dose hydrochlorothiazide, propranolol, nifedipine and enalapril or captopril do not pose enough of a risk of preclude breastfeeding in this group. The most frequently used antihypertensive agents during pregnancy are methyldopa, labetalol and calcium channel antagonists. Methyldopa and beta-blockers are the drugs of choice for treating mild to moderate hypertension. Prazosin and hydralazine are used to treat moderate to severe hypertension and hydralazine, urapidil or labetalol are used to treat hypertensive emergencies. The use of overly aggressive antihypertensive therapy during pregnancy should be avoided so that adequate uteroplacental blood flow is maintained. Methyldopa is the only drug accepted for use during the first trimester of pregnancy.

Effects of oxyfedrine on regional myocardial blood flow in patients with coronary artery disease

Medical treatment of angina pectoris is largely based on the use of beta-blocking agents, calcium antagonists, and nitrates. Oxyfedrine, an amino ketone derivative and partial agonist at beta receptors, has been shown to have potent antianginal properties and to increase coronary blood flow in normal and ischemic myocardial regions in experimental studies. We assessed the effects of intravenous oxyfedrine on regional myocardial blood flow, using positron emission tomography (15-oxygen water), in six patients with chronic stable angina, positive exercise tests, and documented coronary artery disease. Myocardial blood flow was measured in all patients before (baseline) and 10 minutes after the intravenous administration of a single bolus (0.11-0.13 mg/kg) of oxyfedrine. Compared to baseline, heart rate and systolic blood pressure remained almost unchanged after the administration of oxyfedrine. Mean baseline myocardial blood flow was 0.90 +/- 0.15 ml/g/min in areas supplied by arteries with significant coronary stenosis and 1.08 +/- 0.19 ml/g/min in areas supplied by nonstenotic coronary vessels (p less than 0.05). After the administration of oxyfedrine, myocardial blood flow increased significantly in both the regions supplied by stenotic vessels (by 25%; from 0.90 +/- 0.15 to 1.20 +/- 0.31 ml/g/min; p = 0.002) and in areas supplied by angiographically normal coronary vessels (by 22%; from 1.08 +/- 0.19 to 1.38 +/- 0.49 ml/g/min; p less than 0.05). The results of this study indicate that in patients with coronary artery disease, intravenous oxyfedrine significantly increases regional myocardial blood flow, both in areas supplied by critically obstructed vessels and in areas supplied by normal or less severely narrowed coronary arteries.

Atenolol. A reappraisal of its pharmacological properties and therapeutic use in cardiovascular disorders

Atenolol is a selective beta 1-adrenoceptor antagonist with a duration of activity of at least 24 hours. The scope of therapeutic use of the drug has been expanded and become better defined since it was first reviewed in the Journal in 1979. Atenolol is effective and generally well tolerated in patients with all grades of hypertension. Data from comparative studies show that when administered orally, atenolol reduces blood pressure to a similar extent, and in a similar proportion of patients, as usual therapeutic doses of other beta-adrenoceptor antagonists (such as acebutolol, celiprolol, betaxolol, indenolol, metoprolol, nadolol, pindolol, propranolol, tertatolol), angiotensin converting enzyme (ACE) inhibitors (e.g. captopril, enalapril and lisinopril), calcium antagonists (e.g. amlodipine, diltiazem, felodipine, isradipine, nitrendipine, nifedipine, verapamil), doxazosin, ketanserin and alpha-methyldopa. Atenolol effectively lowers blood pressure in elderly patients with hypertension and in women with hypertension associated with pregnancy, and improves objective and subjective indices in patients with stable angina pectoris. Oral atenolol is used for preventing recurrence of supraventricular arrhythmias once control is achieved by intravenous administration of atenolol. Early intervention with intravenous atenolol followed by oral maintenance therapy reduces infarct recurrence and cardiovascular mortality in patients with known or suspected myocardial infarction. There is also encouraging evidence of reduced mortality from cardiovascular disease during long term therapy with atenolol in patients with hypertension. Atenolol is well tolerated in most patients. Increases in plasma levels of both total triglycerides and very low density lipoprotein (VLDL) triglycerides have accompanied atenolol therapy although the clinical relevance, if any, of longer term metabolic effects has yet to be determined. Its low lipid solubility and limited brain penetration results in a lower incidence of central nervous system effects than that associated with propranolol. After many years of clinical usage atenolol is a well established treatment option in several areas of cardiovascular medicine such as mild to moderate hypertension and stable angina pectoris. Furthermore, it has also shown potential in the treatment of some cardiac arrhythmias and has been associated with reduced cardiovascular mortality in patients with hypertension and in patients with myocardial infarction.

Atenolol and ischaemic heart disease: an overview

Data generated to date on the use of beta-blockers, especially atenolol, in ischaemic heart disease are reviewed and compared with the results available with the calcium antagonists. Atenolol appears to be effective as an anti-ischaemic agent in patients with obstructive coronary artery disease when reduction in myocardial oxygen supply (ischaemia not preceded by an increase in heart rate and due presumably to functional coronary stenosis) or increase in demand are the likely causes. Based on current concepts and available data, there is convincing evidence to support the use of atenolol across the spectrum of ischaemic heart disease. In contrast, results with the calcium antagonists have been disappointing and variable. Atenolol, to date, is the only beta-blocker which has been demonstrated to have a life-saving benefit in acute intervention (within 12 hours of onset) in myocardial infarction. This cardioprotective aspect of the drug is likely to be applicable to other areas of ischaemic heart disease, including silent ischaemia.