Treatment of hypertensive emergencies with the calcium channel blocker nifedipine

Management of eclampsia at Assiut University Hospital, Egypt

OBJECTIVE

To evaluate the protocol used for management of eclampsia at Assiut University Hospital, Assiut, Egypt.

METHODS

In a prospective cross-sectional study, data were collected from 1998 women treated for eclampsia at Assiut University Hospital between January 1990 and January 2010, including 1594 cases of prepartum eclampsia, 75 of intrapartum eclampsia, 16 of intercurrent eclampsia, and 313 of postpartum eclampsia. The treatment regimen included use of nifedipine as an antihypertensive, magnesium sulfate as an anticonvulsant, rapid interruption of pregnancy, and admission to the ICU. Data were evaluated for control of blood pressure, prevention and control of convulsions, and maternal and perinatal outcomes.

RESULTS

Magnesium sulfate was effective in controlling convulsions in 98.1% of women. Nifedipine initiated a smooth decline in blood pressure (P>0.0001). There were 79 maternal deaths (3.95%). Maternal morbidity occurred in 439 (22%) women. Twenty-seven percent of women delivered vaginally (most of these women were admitted postpartum). Perinatal mortality occurred in 7.9% of cases.

CONCLUSION

A combination of nifedipine as an antihypertensive drug, magnesium sulfate as an anticonvulsant, rapid interruption of pregnancy, and managing the patients in the ICU resulted in a marked improvement in the outcome for both mother and fetus at Assiut University Hospital.

Acute hypertensive emergencies in pregnancy

OBJECTIVE

Obstetrical hypertensive emergencies are life-threatening conditions involving significant risk to both the mother and fetus. Aggressive treatment of the maternal hypertensive state requires an initial consideration of the effect of treatment on the fetus, via changes to the uteroplacental circulation with treatment. The challenge then is to correct blood pressure using appropriate, safe pharmacologic agents to prevent catastrophic maternal consequences, while minimizing acute changes to placental perfusion and any corresponding fetal ill effects. Hypertension in pregnancy may be one manifestation of a multiple-system pathologic process, as is the case in preeclampsia. Blood pressure control, along with delivery, will be the first step in treating the renal, hematologic, hepatic, and cardiac dysfunction that can be seen in preeclampsia.

DESIGN

A review of medications most commonly used for hypertensive emergencies in pregnancy.

CONCLUSIONS

Hypertensive emergencies in pregnancy require prompt evaluation and treatment in an intensive care setting to prevent untoward effects to both the fetus and mother.

Management of acute severe hypertension and encephalopathy

We still do not have an ideal drug to treat acute severe hypertension in pregnancy. Hydralazine and labetalol are the safest agents, but they are inadequate to control blood pressure in some women. Both hypertensive encephalopathy and eclampsia now appear to be forms of an acute process known as reversible posterior leukoencephalopathy syndrome.

A new preparation of nifedipine for sublingual application in hypertensive urgencies

A new preparation of nifedipine for sublingual application in hypertensive urgencies was investigated in a prospective study. Patients admitted to the Emergency Department with a persistent elevation of systolic blood pressure (SBP) greater than 190 mmHg and/or a diastolic blood pressure (DBP) greater than 100 mmHg received nifedipine 10 mg sublingual with a sprayer. A second dose was administrated fifteen minutes later if an adequate response defined as a stable reduction of SBP below 180 mmHg and DBP below 100 mmHg had not occurred. Of 30 patients, 21 (70%) responded to the first nifedipine application, 7 responded to the second dose, and 2 nonresponders had to be treated with urapidil. Overall mean SBP was 206 +/- 19 mmHg and mean DBP was 113 +/- 15 mmHg before treatment, and a significant antihypertensive effect was noted within fifteen minutes after nifedipine spray (p < 0.05). The maximum antihypertensive effect was for SBP in sixty minutes (146 +/- 19 mmHg) and for DBP after one hundred twenty minutes (78 +/- 18 mmHg). The average reduction in SBP was 29% and in DBP 31%. In first-dose responders (n = 21) a significant antihypertensive effect was noted within fifteen minutes. SBP declined from 205 +/- 21 to a minimum of 142 +/- 15 mmHg (22.3%) after sixty minutes and DBP from 113 +/- 13 to a minimum of 77 +/- 11 mmHg (22.2%) after one hundred twenty minutes. In second-dose responders (n = 7) a significant antihypertensive effect was noted within thirty minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Intravenous nicardipine in hypertensive children

Fourteen hypertensive patients hospitalized in a paediatric intensive care unit were studied to evaluate safety and hypotensive efficacy of intravenous nicardipine. Systolic and diastolic blood pressure significantly decreased 1 h after the beginning of the treatment (1 microgram/kg per minute). Mean decrease in systolic blood pressure during the first 24 h was between 9.9% and 13.4% of the initial value. Mean lowering of diastolic blood pressure was between 16.7% and 25.6%. Nicardipine did not significantly affect heart rate with dose of 1 microgram/kg per minute. No clinical side-effects were observed. Nicardipine could be a first line drug for the treatment of hypertension in paediatric intensive care units.

Evolution of the treatment of hypertension: what really matters in the 1990s?

Over the past decade we have seen a shift in the strategy for the treatment of hypertension, from stepped therapy--involving a highly structured, unvarying series of steps--to recommendations for more individualized treatment. How shall we accomplish that goal? Severe hypertension provides a clear indication to bypass earlier recommendations. Demographic data such as age, gender, and race, often cited, have proved less helpful. Concomitant medical problems, which are found in greater than 50% of hypertensive patients, are most often the crucial determinants in the selection of antihypertensive therapy. Concurrent coronary artery disease, diabetes mellitus, heart failure, azotemia, asthma, chronic obstructive pulmonary disease, borderline cognitive dysfunction, anxiety, and depression are all common. Each has implications for antihypertensive therapy. Moreover, blood pressure reduction is a surrogate for our real goal, which is reduction of cardiovascular risk. Thus, consideration of concomitant medical problems has extended to left ventricular hypertrophy, obesity, hyperlipidemia, and insulin resistance as additional risk factors in hypertension. Consideration of all of these factors makes it possible to individualize antihypertensive therapy in most patients.

Oral nifedipine in the treatment of hypertensive crises in patients with hypertensive encephalopathy

Hypertensive emergencies, including hypertensive encephalopathy represents an acute threat to vital organ functions and call for urgent treatment. The intravenous medications currently available for the management of hypertensive emergencies, have significant potential for serious side effects and acute lowering of blood pressure has often been the cause of considerable morbidity and mortality. Nifedipine is known to be effective as an antihypertensive agent and it is widely used in hypertensive emergencies. We studied the efficacy and effective dose of nifedipine in 22 patients (9 females and 13 males; mean age 51) with hypertensive encephalopathy. Nifedipine (20 mg by oral drop) caused a significant fall in diastolic an systolic blood pressure in all patients from 236/121 to 172/96 mmHg after 30 minutes (P less than 0.005, P less than 0.001). Continuous therapy with nifedipine (2-5 mg every 2-3 hours, mean total dose 52 mg/24 h) gave successful control of blood pressure. These data prove that nifedipine can be used as the first-line drug for the treatment of hypertensive crises in patients with hypertensive encephalopathy.

Single-dose sublingual nifedipine as the only treatment in hypertensive urgencies and emergencies

One hundred and eighteen patients with hypertensive urgencies and emergencies and diastolic blood pressure (DBP) at least 120 mm Hg by the cuff method were seen at the Emergency Care Department; none had received calcium channel blockers during the previous twelve hours. Patients with DBP of 120 to 139 mm Hg received 10 mg of sublingual nifedipine; patients with left ventricular hypertrophy or failure, renal disease, hypertensive encephalopathy, angina, papilledema, or a DBP over 140 mm Hg received 20 mg of the drug. The criterion for control was the achievement of a DBP of 100 mm Hg or less within sixty minutes of receiving sublingual nifedipine and maintenance of the effect until discharge. Control was achieved in all patients; a sixty-three-year-old man died of a brain hemorrhage after pulmonary edema and a DBP of 210 had been controlled; the other 117 were discharged to their attending physicians, either as outpatients or to a hospital ward. No patient developed hypotension, clinical or electrocardiographic signs of myocardial ischemia, or clinical signs of neurologic dysfunction. Practical, fast, safe, and dependable control of hypertensive urgencies and emergencies has made sublingual nifedipine the treatment of choice of such patients in the Emergency Care Department.

Nifedipine pharmacokinetics and pharmacodynamics during the immediate postpartum period in patients with preeclampsia

Pharmacokinetic and pharmacodynamic parameters of oral nifedipine were studied in the immediate postpartum period in eight women with preeclampsia. Peak serum concentrations of 18 +/- 2.1 micrograms/L occurred 40 minutes after ingestion of nifedipine (10 mg). The terminal elimination half-life (mean = 1.35 +/- 0.3 hours) was found to be shorter than that reported for normotensive volunteers or nonpregnant hypertensive women (mean, 3.4 +/- 0.4 hours). A mean apparent oral elimination clearance of 3.3 +/- 1.3 L/hr/kg was more rapid than that found in normal volunteers (mean, 0.49 +/- 0.09 L/hr/kg) or in women with pregnancy-induced hypertension in the third trimester (mean, 2.0 +/- 0.8 L/hr/kg). Initial nadirs in mean arterial pressure were noted at 50 minutes after ingestion of nifedipine, with an average reduction in mean arterial pressure of 13.8 mm Hg. A dosing interval of every 3 to 4 hours is suggested when rapid-release nifedipine is used in the postpartum patient with preeclampsia.

Treatment of hypertensive urgencies with oral nifedipine, nicardipine, and captopril

Sixty-five patients with uncomplicated hypertensive urgencies were treated in the emergency and cardiology departments with 20 mg nifedipine, 20 mg nicardipine, or 25 mg captopril in a randomized study. The study population consisted of 65 patients ranging in age from forty-one to seventy-one. Blood pressure and heart rate were assessed for six hours after intake of the antihypertensive agents. Within sixty minutes nifedipine reduced blood pressure by an average of 74.7 mmHg for the systolic and 35.4 mmHg for the diastolic. Average heart rate increased significantly by 11.6 beats/min at within thirty minutes. Nicardipine and captopril produced equivalent falls in systolic (-81.6 and -79.4 mmHg) and diastolic (-37.3 and -33 mmHg) blood pressure respectively, but did not increase heart rate significantly. The antihypertensive effect of each drug was maintained until six hours after medication. In conclusion, nifedipine, nicardipine, and captopril show similar efficacy in the treatment of hypertensive urgencies. The authors believe that these drugs can be used as first-line therapy in the treatment of hypertensive urgencies safely and effectively.

Prehospital use of nifedipine for severe hypertension

The prehospital management of severe hypertension is limited by a paucity of pharmacologic agents suitable for field use. This prospective study was designed to test the safety and efficacy of intraoral nifedipine therapy in 50 patients with severe hypertension being transported by an urban emergency medical service system. Ten milligrams of nifedipine were administered. Serial blood pressure determinations were obtained at 3, 5, 10, and 15 minutes and patients were observed for possible side effects. A marked effect on systolic blood pressure (SP), diastolic blood pressure (DP), and mean arterial pressure (MAP) was evident and was statistically significant in all three categories by 3 minutes. MAP decreased from 169 to 129 mm Hg (delta MAP of 40 mm Hg) at 15 minutes with parallel changes in the SP (55 mm Hg) and delta DP (32 mm Hg). These changes were highly significant (P less than .01) when compared with those of 50 historical controls. No evidence of severe adverse effects were noted. Nifedipine appears to be a promising agent for the prehospital treatment of severe hypertension, but its proper role is not yet defined.

The use of nifedipine during the postpartum period in patients with severe preeclampsia

Nifedipine is a calcium channel blocker that reduces blood pressure and increases renal blood flow. This double-blind investigation evaluated the effect of nifedipine in postpartum patients with severe preeclampsia. Thirty-one patients were randomized to receive either nifedipine (10 mg) or placebo every 4 hours beginning immediately after delivery. Data analysis revealed a significantly higher urine output in the nifedipine group during the first 24 hours after delivery (3834 versus 2057 ml; p less than 0.05). A significant reduction in mean arterial pressure was also noted in the nifedipine group between 18 and 24 hours postpartum (93.9 versus 100.2 mm Hg; p less than 0.05). There were no significant differences in the systolic or diastolic blood pressures, pulse, laboratory study results, or the need to administer hydralazine to control blood pressure. Nifedipine appears to have a beneficial effect on urinary output and mean arterial pressure during the first 24 hours post partum in patients with severe preeclampsia.

Nicardipine versus placebo for the treatment of postoperative hypertension

Postoperative hypertension can cause serious complications, including bleeding from fresh anastomoses, cardiovascular accident, and myocardial ischemia. Therefore rapid control of blood pressure is essential to prevent poor outcome. In this study, 30 American Society of Anesthesiologists class I and II patients who did not have cardiac surgery and subsequently developed postoperative hypertension were randomly assigned to receive either nicardipine, a new dihydropyridine calcium channel blocker, or placebo. Intravenous nicardipine was given as a loading bolus of 10 mg/hr for 5 minutes and was titrated to 15 mg/hr if needed to achieve a therapeutic response. After therapeutic response, intravenous nicardipine was decreased to 3 mg/hr and subsequently titrated in increments of 1.0 to 2.5 mg/hr to maintain blood pressure control. Systolic and diastolic blood pressures during titration and maintenance did not differ significantly from preoperative levels in patients treated with nicardipine. The mean time to therapeutic response for the nicardipine-treated group was 8.67 +/- 1.46 minutes, and the median time to offset of action was 15 minutes. Eleven of the 12 patients who received placebo were crossed over to antihypertensive therapy, and of these, 10 received intravenous nicardipine. In this group all achieved therapeutic response in 7.3 +/- 1.18 minutes. The usefulness of intravenous nicardipine for postoperative hypertension was demonstrated in this study by: (1) the rapid control of blood pressure, (2) its continued efficacy during maintenance, and (3) little need to adjust dosage to control blood pressure.

Risk of cerebral hypoperfusion with antihypertensive therapy

The effective treatment of hypertension is a major factor in the declining incidence of stroke in North America. There are subsets of patients, however, in which antihypertensive therapy may actually cause cerebral ischemia and infarction. Elderly patients and those with malignant hypertension, acute stroke, and occlusive cerebrovascular disease appear to be the populations at greatest risk of iatrogenic stroke. This article reviews the effect of beta-blockers, angiotensin-converting enzyme inhibitors, direct vasodilators, and calcium-channel blockers on cerebral blood flow in various populations. Although many investigations have been performed, it remains difficult to predict the risk of cerebral hypoperfusion due to antihypertensive medication in an individual patient. It is best for practitioners to be aware of the patient populations at risk and treat high blood pressure cautiously in these patients.

Intravenous nicardipine in severe systemic hypertension

Sixty-six patients with severe hypertension were treated with intravenous nicardipine in 3 separate protocols. Each protocol had a common end point: Diastolic blood pressure would either reduce 25 mm Hg or measure below 95 mm Hg. Each of the 66 patients studied attained the desired clinical response end point. Intravenous nicardipine produced a gradual reduction in blood pressure, was effective in maintaining blood pressure control during constant infusion and had few undesirable effects. These observations suggest that intravenous nicardipine maybe a useful addition to a limited number of therapeutic agents currently available to the physician for treatment of hypertensive urgencies.

Cerebrovascular aspects of antihypertensive treatment

Although the treatment of hypertension clearly benefits the brain in most patients, there are, however, unfortunate exceptions. Overzealous blood pressure lowering especially, and sometimes conservative blood pressure lowering, occasionally compromise the supply of blood to the brain to such an extent that neurological dysfunction or death results. Despite an awareness of this problem for more than a decade, the number of reports of such cases is increasing. An understanding of the problem requires detailed knowledge of both the pathophysiology of the cerebral circulation in hypertension and the cerebrovascular effects of antihypertensive drugs. If antihypertensive treatment, in particular emergency blood pressure lowering, is to always be safe, thought must be given to the cerebrovascular effects of the drugs to be used. This topic is discussed in relation to the observed (i.e., experimentally determined) and inferred (i.e., from clinical observation) effects of antihypertensive drugs and treatment on the cerebral circulation, especially with regard to autoregulation of cerebral blood flow.

Intravenous nicardipine for the treatment of severe hypertension

PURPOSE

Severe hypertension responds to treatment with nifedipine given orally or sublingually. Nicardipine hydrochloride, a water soluble dihydropyridine analogue similar to nifedipine, has less of a negative ionotropic effect and produces less reflex tachycardia than nifedipine. Our purpose was to assess the antihypertensive efficacy and safety of intravenous nicardipine in a group of patients with severe hypertension (defined as a supine diastolic blood pressure of more than 120 mm Hg).

PATIENTS AND METHODS

Eighteen patients with severe hypertension received treatment with intravenous nicardipine. Nicardipine titration was performed using doses of 4 to 15 mg/hour to achieve therapeutic goal (diastolic blood pressure 95 mm Hg or less or decrease in diastolic blood pressure of more than 25 mm Hg). After this therapeutic end-point was reached, patients received maintainance therapy with nicardipine for varying lengths of time: one hour (Group I), six hours (Group II), or 24 hours. When blood pressure control was lost, patients in Groups I and II entered a second maintenance period lasting a maximum of 24 hours. Onset and offset of action of nicardipine at various infusion rates and times of infusion were measured.

RESULTS

Onset time to achieve therapeutic response was rapid at 15 mg/hour (0.31 +/- 0.13 hours) when compared with lower doses (1.11 +/- 0.36 hours at 4 mg/hour; 0.54 +/- 0.09 hours at 5 mg/hour; 0.52 +/- 0.09 hours at 7 to 7.5 mg/hour). Those who showed a therapeutic response received maintenance infusions with nicardipine for one (n = 7), six (n = 6), or 24 (n = 5) hours. Sustained blood pressure control at a constant rate of nicardipine infusion was seen in all patients during the maintenance period. After discontinuation of nicardipine, the time for offset of action (increase in diastolic blood pressure of 10 mm Hg or more) was independent of duration of infusion. Decreases in both systolic and diastolic pressures correlated well with plasma nicardipine levels. Heart rate increased by about 10 beats/minute, but this increase did not correlate with plasma nicardipine levels. Side effects were minimal, consisting of headache and flushing. In seven patients, local phlebitis developed at the site of infusion. This occurred after at least 14 hours of infusion at a single site, and the incidence can probably be reduced by shortening the infusion time at a single site.

CONCLUSION

Nicardipine appears to be a safe and effective drug for intravenous use in the treatment of severe hypertension.

Systemic and regional haemodynamic profile of diuretics and alpha- and beta-blockers. A review comparing acute and chronic effects

The influence of the acute and chronic administration of antihypertensive agents on blood flow to various organs which are known targets of hypertension is important in the determination of drug therapy for this disorder. In association with the frequently observed fall in cardiac output and increase in total peripheral resistance in response to acute administration, beta-blockers may induce a decrease in blood flow to the brain and kidney. However, during chronic treatment it has been widely shown that total peripheral resistance returns to pretreatment levels (except for labetalol, a beta-blocker with alpha-blocking properties) whilst renal and cerebral blood flows are unaffected. Although alpha-blockers acutely lower blood pressure and induce a baroreflex-mediated increase in heart rate and cardiac output while not affecting cerebral blood flow, during chronic treatment no change in systemic or cerebral or renal blood flow is observed. Diuretics and dietary sodium restriction, which are the most widely used therapeutic interventions, are usually well tolerated; however, in aged patients in whom renal adaptation to sodium depletion is impaired, deterioration of renal function may be observed.

Nifedipine in hypertensive emergencies: a prospective study

Hypertensive emergencies usually present to the emergency department. Nifedipine was administered to 15 patients presenting to the emergency department with a diastolic blood pressure greater than 120 mm Hg with chest pain, shortness of breath, or focal neurological symptoms. Average blood pressure on entry was 215/134.9 mm Hg and decreased to 158/88 mm Hg over a two-hour period. No patient had any worsening of symptoms or suffered deleterious effects. All patients with pulmonary edema or chest pain noted prompt improvement in symptoms. One patient became hypotensive without clinical significance. Two patients failed to respond to nifedipine and were treated with nitroprusside. Nifedipine appears to be safe and effective in the management of hypertensive crises.

Current management of hypertensive emergencies

A number of potent and rapidly acting pharmacological agents are available to achieve safe, rapid, and controlled blood pressure reduction in most hypertensive crises. While sodium nitroprusside remains the drug of choice in many hypertensive emergencies, several newer agents are now available that may prove to be acceptable alternatives in the management of certain cases. Glyceryl trinitrate (nitroglycerin) and labetalol may be advantageous in patients with significant coronary artery disease. When adequate facilities to monitor continuous infusion of sodium nitroprusside are not immediately available, the intermittent minibolus administration of diazoxide or labetalol or the use of sublingual or oral nifedipine prove useful. A thorough knowledge of the pharmacological properties and proper indications of the currently used agents is essential for optimum management of the critically ill hypertensive patient.

Calcium channel blockers and cardiac surgery

Calcium channel blockers have an important role in the pharmacotherapy of cardiovascular disorders. These agents act by inhibiting the slow inward current into excitable cells, exert direct negative inotropic, chronotropic, and dromotropic activity, and are potent vasodilators. These direct effects are modified by reflex autonomic stimulation and by pathologic states. Serious adverse effects of the calcium channel blockers are most frequently observed in patients with ventricular dysfunction, conduction system disease, or concomitant beta blockade. Calcium channel blockers are indicated in the treatment of angina pectoris, supraventricular arrhythmias, and hypertension. The use of these agents in patients with hypertrophic cardiomyopathy, congestive heart failure, and pulmonary hypertension is investigational. The calcium channel blockers are gaining increased importance in the management of patients undergoing cardiac surgery. Verapamil is indicated for the treatment of post-cardiac-surgical atrial flutter and fibrillation; however, the calcium antagonists are not effective as prophylaxis against postoperative supraventricular arrhythmias. Laboratory studies have shown that drug interactions exist between calcium channel blockers and inhalational anesthetics and nondepolarizing neuromuscular blocking agents; clinical studies have demonstrated that these interactions are rarely significant. Perioperative coronary spasm can be effectively treated with the calcium channel blockers. The timing of calcium antagonist withdrawal prior to surgery is controversial, but continuation of therapy until surgery is usually safe. The clinical significance of platelet function inhibition by the calcium antagonists is unknown. Protection of ischemic myocardium by calcium channel blockers has been demonstrated. Important interactions between the calcium antagonists, hypothermia, and the ionic constituents of cardioplegia require further study before the role of these agents as adjuncts to clinical cardioplegia is defined. Expanded indications and the introduction of new calcium channel blockers will result in increased use of these agents in the future.

A randomized comparison of nifedipine and sodium nitroprusside in severe hypertension

We randomized patients with severe hypertension in the Medical Intensive Care Unit to a treatment regimen of oral nifedipine or intravenous nitroprusside. Patients treated with nifedipine achieved a sustained reduction in diastolic blood pressure to less than or equal to 120 mm Hg in an average of less than five hours. Patients treated with nitroprusside achieved a similar reduction in 14 hours (p less than 0.05). Treatment with nifedipine was less expensive and required less time in the ICU than treatment with nitroprusside and was accompanied by no associated increase in morbidity or mortality. Oral nifedipine can be used as an alternative to intravenous nitroprusside in severe uncomplicated hypertension.