Pharmacodynamics of intravenous labetalol and follow-up therapy with oral labetalol

Pharmacologic management of childhood hypertension

Antihypertensive drug therapy is used in children primarily to treat secondary forms of hypertension, because the prevalence of essential hypertension in the first decade of life is considerably less than 1% of the childhood population. This prevalence increases during the second decade of life, but the percentage of teenagers with essential hypertension continues to be low. Pharmaceutical companies have been able to target drug development to specific physiologic and biochemical systems. The converting enzyme inhibitors and calcium-channel blockers have greatly improved the success of therapy concomitant with a reduction in the incidence of adverse effects. The result has been a major change during the past decade in the recommendations for antihypertensive drug therapy.

Clinical experience with dual-acting drugs in hypertension

There are now several antihypertensive agents with dual actions. Among these, labetalol has been studied most extensively. The drug has a place in the chronic treatment of hypertension and in the therapy of hypertensive emergencies. Carvedilol, now available in Germany, has been shown to be effective in different forms of hypertension. Celiprolol binds to beta 1- and beta 2-receptors. This drug also binds to alpha 2-receptors. It is not clear, at present, whether or not this binding property contributes to its antihypertensive effect.

The use of oral labetalol in the treatment of arrhythmias associated with the long QT syndrome

A 7-year-old white boy with the long QT syndrome began to experience recurrent syncope associated with torsade de pointes ventricular tachycardia in spite of beta-blocker therapy. The patient was therefore given a combined alpha- and beta-blocking agent (labetalol) with complete suppression of the syncopal episodes. This suggests a role for combined alpha- and beta-blocking agents in the therapy of arrhythmias associated with the long QT syndrome.

Intravenous esmolol in acute aortic dissection

Acute aortic dissection is a devastating condition requiring prompt intensive pharmacologic management geared toward control of blood pressure and reduction in myocardial contractility (change in velocity/change in time). The treatment of choice currently is sodium nitroprusside and intravenous propranolol hydrochloride. During acute aortic dissection, hemorrhage may spread into the interatrial septum, extending to the atrioventricular junctional tissues, thus causing conduction abnormalities. Adverse effects of long-acting beta-blockers, including bradycardia, heart failure, and bronchospasm, may limit their usefulness because these effects persist for a long time after discontinuation. This may be detrimental, especially in patients with compromised cardiac function, bronchospastic disease, or both. We report a case of a 64-year-old woman with compromised cardiac function and aortic dissection who was successfully treated with esmolol hydrochloride (an ultrashort-acting beta-blocker) and sodium nitroprusside.

Labetalol and MRI as initial medical and diagnostic modalities in a marfanoid patient with expanding ascending aortic aneurysm

Marfan syndrome is a hereditable disorder of connective tissue that causes several distinct cardiovascular abnormalities, including aortic regurgitation, dissection, and aneurysm. These cardiac manifestations can be identified with echocardiography, computer tomography, and angiography. Standard treatment of an acute hypertensive crisis in Marfan syndrome uses propranolol and sodium nitroprusside. This patient with Marfan syndrome whose case is reported herein presented with chest pain, hypertensive crisis, and aortic insufficiency; labetalol was used successfully to treat the acute hypertensive crisis and magnetic resonance imaging (MRI) was used to differentiate between aortic dissection and an expanding aortic aneurysm. This report is unique in that labetalol was used to control the hypertensive crisis in Marfan syndrome and MRI was used as the initial diagnostic modality in an emergency setting.

Prolonged labetalol infusion for management of severe hypertension and tachycardia in a critically ill trauma patient

A trauma victim sustained multiple injuries including cervical spine injuries, splenic laceration, and left kidney fracture. His recovery was complicated by acute renal failure, resistant hypertension, and tachycardia refractory to multiple therapies. The patient was ultimately managed with continuous infusions of labetalol 2-3 mg/min for 14 days, with adequate control of both blood pressure and heart rate. The sustained labetalol infusion was not associated with clinically significant adverse effects although a progressive decrease in heart rate was noted near the end of therapy. This downward trend in heart rate was not associated with hemodynamic compromise and returned to pretreatment baseline of 90-110 beats/min upon discontinuation of parenteral therapy and initiation of oral labetalol. The prolonged use of labetalol infusions may be beneficial in certain patients. Further work needs to be done to identify the safety and efficacy of labetalol infusions.

Intravenous labetalol for the control of hypertension following repair of coarctation of the aorta

Paradoxical hypertension is a relatively common complication of surgical repair of coarctation of the aorta. An early phase of systolic hypertension has been ascribed to elevated levels of norepinephrine. Activation of the renin-angiotensin system from sympathetic stimulation has been implicated in a later phase of systolic and diastolic hypertension that can result in mesenteric arteritis. The use of a rapidly acting, titratable intravenous alpha- and beta-adrenergic blocker, such as labetalol hydrochloride, addresses both of these neurohormonal mechanisms. In the intravenous form, it would appear to be an excellent choice for the management of early postoperative hypertension and it can be converted to the oral form in cases of persistent hypertension. We report for the first time the use of labetalol in two young patients for the control of paradoxical hypertension following coarctation repair.

Clinical experience with labetalol and enalapril in combination in patients with severe essential and renovascular hypertension

Severe hypertension may be a difficult management issue, and it often requires therapy with multiple drugs at frequent dosing intervals. We report on the antihypertensive effects of the alpha-beta adrenergic blocking agent, labetalol, in combination with enalapril, a long-acting angiotensin-converting enzyme inhibitor, administered to 14 patients with severe hypertension (nine of whom had nephrosclerosis or renal artery stenosis) on other antihypertensive drug therapies. Blood pressure (BP), heart rate (HR), hematologic and blood chemistry values, and adverse side effects were monitored at 24 hours, 1 week, and 4 weeks of therapy. Rapid titration of the drugs was performed in the hospital in 10 patients; four were managed closely as outpatients. Following one month of combination therapy blood pressure decreased from 212 +/- 31/120 +/- 16 mm Hg at baseline to 155 +/- 19/86 +/- 12 mm Hg, and heart rate declined from 86 +/- 18 bpm to 70 +/- 16 bpm. Ten of the 14 patients (71%) maintained good BP control (BP less than 140/90 mm Hg) with no additional treatment. Serum potassium, creatinine, blood urea nitrogen concentrations, and hematologic parameters did not significantly change in 13 of 14 patients. Three patients developed symptomatic postural hypotension; in one patient this side effect resulted in discontinuation from the study. These data suggest that combination therapy with labetalol and enalapril is effective in lowering BP in patients with severe essential or renovascular hypertension. An additional advantage of this regimen is the twice-daily dosing interval, which may promote better long-term compliance.