Labetalol in severe and resistant hypertension

Labetalol in resistant hypertension

In 12 patients with resistant hypertension labetalol was added to existing therapy. The average dose was 1333 mg (range 400--3600). The subjects were followed up for three and a half years. Mean supine blood pressure (BP) was reduced from 202/123 to 163/103 mm Hg and mean standing BP from 193/127 to 144/100 mm Hg. Mean BP after exercise was 134/93 mm Hg. The main side-effect was postural hypotension during exercise, causing withdrawal of labetalol in two subjects. In patients with severe hypertension, resistant to several combinations of antihypertensive drugs, the addition of labetalol may lead to satisfactory BP reduction, especially when combined with a potent diuretic.

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.

Intravenous labetalol in the management of resistant hypertensive emergency

A case of intravenous labetalol in the treatment of a resistant hypertensive emergency is reported. Although there have been several reports of the use of oral labetalol in resistant hypertension, no intravenous administration in hypertensive emergency resistant to other drugs has been reported to date. A 36-year-old black female with BP of 270/160 mm Hg with complaints greater than one month's duration of dizziness, severe headaches, blurred vision, shortness of breath, vomiting, palpitations, flushing, agitation, diarrhea, weakness, and weight loss, was treated successfully with intravenous labetalol after she failed to respond to other established parenteral antihypertensive drugs. The patient received labetalol 20 mg iv bolus, and then 20 mg every ten minutes until a cumulative dose of 200 mg was attained. Labetalol produced a prompt but smooth reduction in BP without any reflex tachycardia or other adverse effects. Intravenous labetalol may be safe and effective for the management of rapid BP control in hypertensive emergencies resistant to other parenteral antihypertensive agents.

Short- and long-term (six-year) hemodynamic effects of labetalol in essential hypertension

The acute blood pressure lowering effect of intravenous labetalol (0.2 to 0.8 mg/kg) was studied in 11 patients with severe hypertension. The blood pressure was reduced by 22 percent partly due to a decrease in total peripheral resistance (-14 percent) and partly due to a reduction in cardiac output (-10 percent). Stroke volume was unchanged. Fifteen patients with moderate essential hypertension were studied at rest and during exercise before and after one and six years of labetalol therapy. Blood pressure was reduced approximately 22 percent at rest as well as during exercise, mainly due to a reduction in total peripheral resistance. However, after one year, cardiac index was reduced 10 to 14 percent (p less than 0.01) at rest (sitting) and during exercise due to a reduction in heart rate not compensated for by an increase in stroke volume. During the next five years, blood pressure control was maintained, but cardiac index tended to increase and was not significantly reduced in any situation six years after treatment was started. Total peripheral resistance decreased significantly and was reduced 15 to 20 percent (p less than 0.01) after six years. Stroke index increased about 10 to 15 percent (p less than 0.01). These alterations are the opposite of what is seen in untreated hypertensive patients restudied after 10 and 17 years. The normalization of central hemodynamics could reflect the regression of structural changes in the heart and in the resistance vessels.

Treatment of severe hypertension with labetalol compared with methyldopa and furosemide. Results of a long-term, double-blind, multicenter trial

Eighty-one severely hypertensive patients were enrolled in a multicenter, double-blind, parallel group study evaluating the efficacy and safety of labetalol alone or in combination with furosemide versus methyldopa in combination with furosemide. A one day to four week placebo lead-in phase was followed by a one- to six-week titration period and a one-year maintenance period. Treatment with labetalol alone or in combination with furosemide, as well as methyldopa plus furosemide, was associated with significant reductions in supine and standing blood pressure levels. Moreover, after six months and one year of treatment, respectively, labetalol caused a significantly (p less than 0.05) greater reduction in the systolic blood pressure than the methyldopa regimen. The antihypertensive effect of labetalol was associated with small, yet significant reductions in heart rate; in contrast, resting tachycardia was observed in methyldopa-treated patients. Side effect profiles of the two treatments were different, with nausea being the most commonly reported side effect during labetalol therapy, and asthenia, somnolence, and dry mouth during methyldopa therapy. Overall, 33 of 65 (53 percent) labetalol-treated and 28 of 60 (47 percent) methyldopa-treated patients had at least a good response (that is, standing diastolic blood pressure 90 to 94 mm Hg) to therapy, including 26 (40 percent) and 22 (37 percent) patients, respectively, who had standing diastolic blood pressure levels of less than 90 mm Hg. Thus, labetalol is a potentially safe and effective agent in the long-term management of the patient with severe hypertension.

Antihypertensive effectiveness of intravenous labetalol in accelerated hypertension

Labetalol, an antihypertensive agent that blocks both beta- and alpha-adrenergic receptors, was administered intravenously to 19 patients with accelerated hypertension who required rapid lowering of blood pressure. Systolic blood pressure was lowered from 209 +/- 4 to 143 +/- 2 mm Hg; diastolic blood pressure was reduced from 140 +/- 2 to 93 +/- 2 mm Hg. Side-effects were minimal and included nausea, epigastric burning, rhinorrhea, and premature ventricular contractions. One patient became hypotensive and required treatment. Overall, the study demonstrates labetalol to be a safe and effective agent for the emergency lowering of blood pressure, with demonstrated results comparable to other parenteral agents.

Labetalol: a review of its pharmacology, pharmacokinetics, clinical uses and adverse effects

Labetalol is a combined alpha- and beta-adrenoceptor blocking agent for oral and intravenous use in the treatment of hypertension. It is a nonselective antagonist at beta-adrenoceptors and a competitive antagonist of postsynaptic alpha 1-adrenoceptors. Labetalol is more potent at beta that at alpha 1 adrenoceptors in man; the ratio of beta-alpha antagonism is 3:1 after oral and 6.9:1 after intravenous administration. Labetalol is readily absorbed in man after oral administration, but the drug, which is lipid soluble, undergoes considerable hepatic first-pass metabolism and has an absolute bioavailability of approximately 25%. There are no active metabolites, and the elimination half-life of the drug is approximately 6 hours. Unlike conventional beta-adrenoceptor blocking drugs without intrinsic sympathomimetic activity, labetalol, when given acutely, produces a decrease in peripheral vascular resistance and blood pressure with little alteration in heart rate or cardiac output. However, like conventional beta-blockers, labetalol may influence the renin-angiotensin-aldosterone system and respiratory function. Clinical studies have shown that the antihypertensive efficacy of labetalol is superior to placebo and to diuretic therapy and is at least comparable to that of conventional beta-blockers, methyldopa, clonidine and various adrenergic neuronal blockers. Labetalol administered alone or with a diuretic is often effective when other antihypertensive regimens have failed. Studies have shown that labetalol is effective in the treatment of essential hypertension, renal hypertension, pheochromocytoma, pregnancy hypertension and hypertensive emergencies. In addition, preliminary studies indicate that labetalol may be of value in the management of ischemic heart disease. The most troublesome side effect of labetalol therapy is posture-related dizziness. Other reported side effects of the drug include gastrointestinal disturbances, tiredness, headache, scalp tingling, skin rashes, urinary retention and impotence. Side effects related to the beta-adrenoceptor blocking effect of labetalol, including asthma, heart failure and Raynaud's phenomenon, have been reported in rare instances.

Magnitude and mechanisms of the antihypertensive action of labetalol, including ambulatory assessment

The blood pressure (BP) effect and modes of action of a twice daily regimen of labetalol (mean 450 mg/day) were assessed in ten mild to moderate hypertensives using continuous ambulatory BP monitoring. The reflex control of BP during physiological interventions was examined just prior to the next dose of medication to estimate the residual alpha- and beta-adrenoceptor blockade. Global 24 h BP was reduced by 15/9 mm Hg, and home pressures by 13/11 mm Hg. The predominant antihypertensive effect was noted during the waking hours. During dynamic exercise significant inhibition of the heart rate and blood pressure rise occurred. Coupled with a reduction of the post-release BP 'overshoot' in Valsalva's manoeuvre, the response resembles that seen with beta-adrenoceptor blockade. A small alpha-adrenoceptor blocking action was evident in one patient's response to the Valsalva manoeuvre.

Anti-hypertensive action of labetalol: a detailed profile

Continuous, ambulatory blood pressure (BP) and self measured home recordings were used to study the response of ten mild to moderate hypertensives taking a twice daily labetalol dosage. Testing of cardiovascular reflexes was carried out 12 hours after a dose of drug. The mean 24 hour BP was reduced from 145/80 +/- 14/7 (SD) mmHg to 130/71 +/- 11/6 (p less than 0.001) and home BP from 147/96 +/- 15/9 to 134/84 +/- 10/9 (p less than 0.01). The predominant effect of labetalol was evident during the waking hours. A residual 9.5% BP reduction was seen 12 hours after a dose compared to an 11% lowering effect over the entire 24 hours (NS). No symptomatic hypotensive episodes were noted. Significant inhibition of heart rate and BP rise during dynamic exercise (p less than 0.01) and reduction of post-release BP "overshoot" (p less than 0.01) in Valsalva's manoeuvre indicated a beta adrenoceptor blocking effect. There was however a reduction in the rate of rise of BP during static handgrip (p less than 0.01) indicating a small alpha adrenoceptor blocking component. This study has demonstrated the efficacy of a twice daily regimen of labetalol in continuously lowering BP. The mode of action of the drug during exercise (static and dynamic) and Valsalva's manoeuvre would indicate a predominant beta adrenoceptor blocking action.