Oral clonidine for rapid control of accelerated hypertension

Oral antihypertensives for hypertensive urgencies

OBJECTIVE

To review the data describing the use of oral antihypertensive agents in the treatment of hypertensive urgencies (HU).

DATA SOURCES

A MEDLINE search of the English-language literature and fan searches of papers evaluating oral antihypertensives in HUs and emergencies were conducted.

STUDY SELECTION

Controlled and uncontrolled studies in humans are reviewed. Emphasis was placed on recent trials evaluating individual agents and comparative trials.

DATA SYNTHESIS

Comparative trials have demonstrated that four currently available oral agents can lower blood pressure rapidly and predictably. Nifedipine, the most extensively studied, and clonidine have served traditionally as the oral agents of choice for the treatment of HUs. All the agents can lower blood pressure effectively within the first few hours after dosing, but their use also has been associated with adverse effects. Nifedipine and captopril are the two agents with the most rapid onset, within 0.5-1 hour, and may treat hypertensive emergencies as well as urgencies. Clonidine and labetalol have maximal blood pressure lowering effects at 2-4 hours.

CONCLUSIONS

Captopril, clonidine, labetalol, and nifedipine are all effective agents for the treatment of HUs. Agent selection should be based on the perceived need for urgent blood pressure control, the cause of HU, and concomitant conditions. A definite benefit from acute blood pressure lowering in HUs has yet to be demonstrated, especially in asymptomatic patients. More controlled trials with less aggressive dosing regimens and placebo controls need to be performed to assess the most appropriate treatment for HUs with the fewest adverse effects.

The USA experience with the clonidine transdermal therapeutic system

Cardiovascular diseases are the leading causes of death in the United States, with hypertension being amongst the most prevalent of the cardiovascular risk factors. Improvement of hypertension management has, in consequence, received much attention. Extensive pre- and post-marketing experience with the transdermal formulation of clonidine marketed in the USA in the mid-1980s has now been accumulated. Transdermal clonidine is effective as monotherapy in mild-moderate hypertension, and in combination with diuretics, calcium antagonists and ACE inhibitors in more resistant cases. It controls blood pressure throughout the 24-h circadian cycle. It is effective and generally well-tolerated in adolescents, the elderly, blacks, diabetics, and subjects with chronic renal insufficiency. It has been used perioperatively and for suppression of adrenergic symptoms in subjects withdrawing from addicting substances. In comparison with oral clonidine, transdermal clonidine reduces the incidence and severity of such symptomatic side-effects as dry mouth, drowsiness, and sexual dysfunction. Minor skin reactions occur at the site of application of the transdermal patch with moderate frequency. Adherence to transdermal clonidine therapy is high, and patients commonly prefer it to oral therapy. Transdermal administration of clonidine is a useful therapeutic advance in the long-term management of hypertension.

Oral labetalol versus oral clonidine in the emergency treatment of severe hypertension

This study was designed to compare the clinical efficacy and safety of oral clonidine and oral labetalol in the treatment of severe hypertension in an emergency department setting. Thirty-six patients with severely elevated blood pressure (mean baseline blood pressure 199/132 mm Hg) without acute end-organ dysfunction were treated with either oral labetalol or oral clonidine in a randomized double-blind prospective study. Labetalol was administered as an initial dose of 200 mg, followed by hourly 200 mg doses up to 1,200 mg. Clonidine was administered as an initial dose of 0.2 mg, followed by hourly 0.1 mg doses up to 0.7 mg. Labetalol reduced diastolic blood pressure in 94% of the patients within 6 hours, with a mean reduction in blood pressure of 54/37 mm Hg. Clonidine reduced diastolic blood pressure in 83% of the patients within 6 hours, with a mean reduction in blood pressure of 57/32 mm Hg. The authors conclude that oral labetalol was comparable to clonidine in efficacy, had a similar incidence of side effects, and offered the clinician a useful alternative for the treatment of severe hypertension in an emergency department setting. Further studies are indicated to determine appropriate dosing regimens for oral labetalol in the acute treatment of severe hypertension.