Cerebral ischaemia after nifedipine treatment

Calcium channel blockers: spectrum of side effects and drug interactions

Calcium antagonists are a chemically heterogenous group of agents with potent cardiovascular effects which are beneficial in the treatment of angina pectoris, arterial hypertension and cardiac arrhythmias. The main side effects for the group are dose-dependent and the result of the main action or actions of the calcium antagonists, i.e. vasodilatation, negative inotropic effects and antiarrhythmic effects. Pronounced hypotension is reported for the main calcium antagonist drugs; verapamil, diltiazem and nifedipine. While conduction disturbances and bradycardia are seen more often after verapamil and diltiazem, tachycardia, headache and flush are more frequent after nifedipine. Constipation is relatively frequent after verapamil while nifedipine is reported to induce diarrhea in som patients. Idiosyncratic side effects are rare but have been reported from the skin, mouth, musculoskeletal system, the liver and the central nervous system. These side effects include urticarial rashes, gingival hyperplasia, arthralgia, hepathotoxicity and transistory mental confusion or akathisia. Verapamil, diltiazem and possibly also nifedipine have been reported to increase serum digoxin concentrations but the clinical relevance of these drug interactions are not clear. Furthermore, verapamil and diltiazem may potentiate the effects of beta-adrenergic blocking drugs and verapamil may also potentiate the effects of neuromuscular blocking drugs. It is concluded that side effects after calcium antagonist drugs are mostly trivial and transient although they may sometimes be relatively common. Clinically relevant drug interactions are few. Judged from the point of efficacy and safety, calcium antagonists will have a major place in the future pharmacotherapy of several cardiovascular disorders.

A review of calcium channel antagonists in the treatment of pediatric hypertension

All children aged > or = 3 years should have an annual blood pressure (BP) measurement taken during a routine physical examination. Physicians should become familiar with recommended pediatric normative BP tables. BP above the 95th percentile may require drug therapy. There are several categories of antihypertensives available to the clinician. Calcium channel antagonists (CCAs) are a class of drugs that exert their antihypertensive effect by inhibiting the influx of calcium ions across the cell membranes. This results in dilatation of peripheral arterioles. When given orally, CCAs are metabolised in the liver by cytochrome P450 (CYP) enzyme CYP3A4; hence, some CCAs will affect the half-life of drugs that share this enzyme system for their metabolism. CCAs can be safely used in children with renal insufficiency or failure and as a general rule there is no need to modify drug dosage in this population. CCAs are generally well tolerated; most adverse effects appear to be dose related. Headache, flushing, gastrointestinal upset, and edema of the lower extremities are the most common symptoms reported with the use of CCAs. Pediatric data regarding safety and efficacy of CCAs have mostly been obtained from retrospective analyses. Extended-release nifedipine and amlodipine are the two most commonly used oral CCAs in the management of pediatric hypertension. These drugs can be given once a day, although many children require twice-daily administration. Extended-release nifedipine has to be swallowed whole; hence, its use in younger children who cannot swallow pills is limited. Amlodipine can be made into a solution without compromising its long duration of action; therefore, it is the CCA of choice for very young children. Oral short-acting nifedipine and intravenous nicardipine are safe and effective CCAs for the management of hypertensive crisis in children. Short-acting nifedipine can cause unpredictable changes in BP; hence, it should be used cautiously and in low doses. Intravenous nicardipine has a rapid onset of action and a short half-life. Intravenous infusion of nicardipine can be titrated for effective control of BP. Intravenous nicardipine has been used safely in hospitalized children and newborns for the management of hypertensive crisis, and for controlled hypotension during surgery. CCAs are a class of antihypertensives that are safe and effective in pediatric patients. They have relatively few adverse effects and are well tolerated by children. This article reviews CCAs as antihypertensives in the management of pediatric hypertension.

Adverse events associated with aggressive treatment of increased blood pressure

Patients with severely increased blood pressure often present to the emergency department. Rapid lowering of blood pressure can precipitate or worsen end organ damage. We report two cases that developed cerebrovascular and cardiovascular adverse events associated with aggressive treatment of increased blood pressure by the use of sublingual nifedipine capsule. The first patient had developed ischaemic stroke; the second patient actually had acute left ventricular failure causing deteriorated, and required positive inotropic treatment for persistent hypotension. These cases emphasise that the pseudoemergency may rapidly progress into a real emergency when blood pressure is rapidly and aggressively reduced.

Adverse neurologic events associated with rebound hypertension after using short-acting nifedipine in childhood hypertension

INTRODUCTION

Short-acting nifedipine (SA-NIF) is widely prescribed for acute hypertension (HTN) in children despite reports of ischemic complications in adults. We describe two children with neurologic events caused by rebound hypertension following SA-NIF use.

CASES

Patient 1 is a 7-year-old with acute nephritis and blood pressure (BP) of 185/130. She received SA-NIF which decreased BP to 114/79. When BP rebounded to 160/103, she developed severe cortical visual impairment. Head CT demonstrated edema and petechial hemorrhages in the watershed region. Patient 2 is a 10-year-old renal transplant recipient who received SA-NIF for a BP of 155/98, which resulted in a prompt decrease to 114/74. Two hours later he developed aphasia and right-sided neglect. His BP increased to 168/88 and he developed partial complex seizures. Brain MRI showed high signal intensity in the watershed areas with early gadolinium enhancement.

DISCUSSION

The temporal association of the neurologic events with the rebound increase in BP suggests a possible role for the SA-NIF, consistent with its pharmacokinetic profile. Although the adult literature has focused on the unpredictable decline in BP after SA-NIF treatment, these cases suggest that rapid increases in BP following the maximal SA-NIF effect may be associated with impaired cerebral autoregulation and encephalopathy in children. These cases underscore the need for frequent blood pressure determinations and therapy to prevent rebound hypertension.

Stroke precipitated by moderate blood pressure reduction

Rapid lowering of blood pressure can precipitate or worsen ischemic strokes. This usually has been observed in the setting of profoundly lowered pressure and hypotension. We report on six patients in whom ischemic neurologic injury ensued or worsened after moderate reduction of blood pressure by pharmacological treatment. The 6 patients suffered new or worsened ischemic neurologic deficits after receiving oral or intravenous antihypertensive medications, mostly after relatively small doses. Mean arterial blood pressure in these patients was decreased by 25 +/- 7.7%, or 37 +/- 16 mm Hg (mean +/- SD) without resultant hypotension. These cases emphasize the potential hazards of moderate blood pressure reduction by antihypertensive medications in the setting of an acute ischemic stroke or transient ischemic attack (TIA), as well as rapidly treated hypertension even in those who have not yet manifested ischemic symptoms.

Intensive care unit management of the stroke patient

Although the majority of patients with acute stroke do not require intensive care, it is important to recognize when admission to an intensive care unit (ICU) is warranted. Patients undergoing thrombolytic therapy, those with brainstem infarcts referable to the basilar artery, those with large space occupying hemispheric infarcts, and those with fluctuating neurological examinations should be admitted to the ICU for monitoring and treatment.

Comparative tolerability profile of hypertensive crisis treatments

Hypertensive crisis is defined as a severe elevation in BP and is classified as either urgency or emergency. In hypertensive urgency there is no end-organ injury and no evidence that acute BP lowering is beneficial. Indeed, rapid uncontrolled pressure reduction may be harmful. Therefore, in hypertensive urgencies BP should be lowered gradually over 24 to 48 hours using oral antihypertensives. When the cause of transient BP elevations is easily identified, appropriate treatment should be given. When the cause is unknown, an oral antihypertensive should be given. The efficacy of available treatments appear similar; however, the underlying pathophysiological and clinical findings, mechanism of action and potential for adverse effects should guide choice. Captopril should be avoided in patients with bilateral renal artery stenosis or unilateral renal artery stenosis in patients with a solitary kidney. Nifedipine and other dihydropyridines increase heart rate whereas clonidine, beta-blockers and labetalol tend to decrease it. This is particularly important in patients with ischaemic heart disease. Labetalol and beta-blockers are contraindicated in patients with bronchospasm and bradycardia or heart blocks. Clonidine should be avoided if mental acuity is desired. In hypertensive emergency there is an immediate threat to the integrity of the cardiovascular system. BP should be immediately reduced to avoid further end organ damage. Sodium nitroprusside is the most popular agent. Nitroglycerin (glyceryl trinitrate) is preferred when there is acute coronary insufficiency. A beta-blocker may be added in some patients. Loop diuretics, nitroglycerin and sodium nitroprusside are effective in patients with concomitant pulmonary oedema. Enalaprilat is also theoretically helpful, especially when the renin system might be activated. Initial treatment of aortic dissection involves rapid, controlled titration of arterial pressure to normal levels using intravenous sodium nitroprusside and a beta-blocker. If beta-blockers are contraindicated, urapidil or trimetaphan camsilate are alternatives. Hydralazine is the drug of choice for patients with eclampsia. Labetalol, urapidil or calcium antagonists are possible alternatives if hydralazine fails or is contraindicated. For patients with catecholamine-induced crises, an alpha-blocker such as phentolamine should be given; labetalol or sodium nitroprusside with beta-blockers are alternatives. There are few, if any, comparative or randomised trials providing definitive conclusions about the efficacy and safety of comparative agents. Some investigators recommend decreasing the diastolic BP to no less than 100 to 110 mm Hg. A reasonable approach for most patients with hypertensive emergencies is to lower the mean arterial pressure by 25% over the initial 2 to 4 hours with the most specific antihypertensive regimen.

Evaluation of the efficacy and safety of oral nicardipine in treatment of urgent hypertension: a multicenter, randomized, double-blind, parallel, placebo-controlled clinical trial

This study was a prospective, randomized, double-blind, placebo-controlled clinical trial designed to evaluate the safety and efficacy of oral nicardipine for the treatment of urgent hypertension in the emergency department. Of 57 patients with urgent hypertension 53 patients were enrolled: 36 men and 17 women, 43 black and 10 white, age range 48 +/- 11 years, and diastolic blood pressure 128 +/- 7 mm Hg. Patients were randomly assigned to receive 30 mg nicardipine or placebo in blind fashion followed by 30 mg open-label nicardipine in nonresponders. Responders to one or two doses of nicardipine received 30 or 40 mg nicardipine three times a day for 1 week after discharge from the emergency department. Adequate blood pressure reduction, defined as a reduction of diastolic blood pressure to less than 100 mm Hg or by at least 20 mm Hg, was achieved in 65% and 22% of patients who received 30 mg nicardipine or placebo (p = 0.002). Adequate blood pressure reduction after administration of open-label nicardipine occurred in 76% of the nonresponders to placebo. Blood pressure reductions were maintained at 1 week after discharge. The drug was well tolerated, and no significant adverse events occurred. We conclude that oral nicardipine is a safe and effective drug for the initial treatment of urgent hypertension.

Advances in pharmacotherapy: treatment of hypertensive crisis

A hypertensive crisis can be caused by many factors. Frequently, the mechanism involved is complex and highly variable among patients. Without drug therapy, this condition is associated with very high mortality and morbidity. There are a number of oral and intravenous hypotensive agents available, which can effectively control blood pressure in a hypertensive crisis. The relative advantages and disadvantages of each treatment option is discussed.

Sustained release nifedipine formulations. An appraisal of their current uses and prospective roles in the treatment of hypertension, ischaemic heart disease and peripheral vascular disorders

Nifedipine antagonises influx of calcium through cell membrane slow channels, and sustained release formulations of the calcium channel blocker have been shown to be effective in the treatment of mild to moderate hypertension and both stable and variant angina pectoris. Preliminary findings also indicate that these formulations are effective in the treatment of Raynaud's phenomenon and hypertension in pregnancy, and that they reduce the frequency of ischaemic episodes in some patients with silent myocardial ischaemia. The exact mechanism of action of nifedipine in all of these disorders has not been defined. However, its potent peripheral and coronary arterial dilator properties, together with improvements in oxygen supply/demand, are of particular importance. A major goal of sustained release therapy is to permit reductions in the frequency of nifedipine administration, preferably to once daily, and thus improve patient compliance. Two new once-daily formulations--the nifedipine gastrointestinal therapeutic system (GITS) and a fixed combination capsule comprising sustained release nifedipine 20 mg and atenolol 50 mg--have exhibited marked antihypertensive efficacy. The GITS preparation has also been used effectively in the treatment of stable angina pectoris, and both formulations appear to be well tolerated. Sustained release nifedipine formulations are generally better tolerated than their conventionally formulated counterparts, particularly with regard to reflex tachycardia. Adverse effects seem to be dose related, are mainly associated with the drug's potent vasodilatory action, and include headache, flushing and dizziness. Generally, these effects are mild to moderate in severity and transient, usually diminishing with continued treatment. Thus, sustained release nifedipine formulations are useful and established cardiovascular therapeutic agents which have demonstrable efficacy in various forms of angina, mild to moderate hypertension and Raynaud's phenomenon. Further, promising results shown by the nifedipine GITS formulation, with its advantage of once daily administration suggest that it is likely to become one of the preferred nifedipine formulations for the treatment of hypertension and the various forms of angina.

Cerebral blood flow during the acute therapy of severe hypertension with oral clonidine

A major risk associated with the acute treatment of severe hypertension is a reduction in cerebral blood flow (CBF) with ischemic injury to the central nervous system. The authors studied CBF before and after the acute treatment of severe hypertension (diastolic blood pressure greater than 115 mm Hg) with clonidine in 13 patients. One patient did not reach goal blood pressure (diastolic blood pressure 105 mm Hg or a decrease by 30 mm Hg) after clonidine alone. In the remaining 12 patients, oral clonidine reduced supine blood pressure from 201.7 +/- 5.0/126.3 +/- 2.1 mm Hg to 149.4 +/- 5.3/96.8 +/- 1.7 mm Hg over an average time period of 85 +/- 7 minutes. Although mean CBF for the group did not change (72.6 +/- 4.2 v 73.7 +/- 3.5 mL/100 mg/min), a significant (greater than 10%) change occurred in 9 of the 12 patients (5 increases and 4 reductions). The magnitude and direction of the change were dependent upon initial CBF (r = -0.65, P less than .05); patients with low pretreatment CBF experienced an increase, whereas those with high initial flow exhibited a decrease. No significant adverse effects were observed. These data confirm previous reports that clonidine is effective in the acute treatment of severe hypertension and demonstrate that its effects on CBF are determined by the pretreatment levels of flow.

Nifedipine overdose accompanied by ethanol intoxication in a patient with congenital heart disease

A 34-year-old female was brought to the emergency department after taking 200 to 250 mg of nifedipine and drinking an unknown amount of ethanol in a suicide attempt. She was hypotensive, acidotic, mildly hyperglycemic, and exhibited a conduction abnormality on the ECG. The patient was treated with IV fluids, thiamine, and calcium infusion. The patient was later found to have an endocardial cushion defect with a patched ventricular septal defect and an atrial septal defect of the ostium primum type. We did not observe any untoward effects due to the combination of drugs and congenital abnormalities that could be explained on an individual basis. Nifedipine overdose associated with alcohol intoxication, to our knowledge, has not been previously reported.

Role of calcium channel blockade in chronic hypertension following successful management of hypertensive emergency

Nifedipine is known to reduce blood pressure for both short- and long-term periods. We have shown that nifedipine can be given safely for a short-term period to patients with severe hypertension in an outpatient setting, that its efficacy can be retained with long-term follow-up therapy, and that nifedipine is safe in the presence of cardiomegaly, acting without precipitating a decrease in ejection fraction when used for short-term blood pressure reduction. The acute hypotensive effect of sublingual nifedipine can predict the efficacy of subsequent follow-up therapy with oral nifedipine, so that there is a sustained long-term hypotensive effect.

Rupture of a cerebral aneurysm associated with nifedipine treatment

We describe rupture of a cerebral arterial aneurysm in a 32 year old hypertensive woman following the introduction of nifedipine treatment. It is suggested this relationship is causal rather than coincidental and mediated through cerebral arterial vasodilatation.

An audit of nifedipine in a hypertension clinic

The results of treating 235 hypertensive patients who had been prescribed nifedipine in a hypertension clinic were examined for factors affecting blood pressure response and the frequency of side-effects. Pretreatment systolic and diastolic blood pressure correlated significantly with the decrease in blood pressure but this effect was lost following statistical correction. No relation was found between response and age or race nor did any biochemical or haematological parameter predict the antihypertensive effect. Fifty-nine (25%) patients complained of side-effects which were dose related; the drug had to be discontinued in 30 patients (13%) but the remaining 29 continued at the same or reduced dosage. Small, but statistically significant, elevations were seen in serum albumin, alkaline phosphatase and bilirubin as well as a rise in average blood glucose levels. Although side-effects are fairly common nifedipine is an effective antihypertensive drug when given alone or in combination with other therapies.

Acute effect of nifedipine on blood pressure and left ventricular ejection fraction in severely hypertensive outpatients: predictive effects of acute therapy and prolonged efficacy when added to existing therapy

Nifedipine is known to reduce blood pressure both acutely and chronically. However, the following questions remain to be answered: can nifedipine be given acutely and safety to patients with severe hypertension in an outpatient setting, would its efficacy be retained with long-term therapy, and is nifedipine safe in the presence of cardiomegaly? Nifedipine (10 mg capsule sublingually) was given to 46 outpatients with severe or apparently refractory hypertension; 19 were followed-up for 18 months and 18 for 24 months. Nifedipine reduced blood pressure acutely and safely in 43 of 46 outpatients (mean control diastolic pressure 137 mm Hg), irrespective of prior treatment regimen. Blood pressure levels after 2 to 24 months of twice daily oral nifedipine (10 mg) were similar to 20-minutes levels, showing that tolerance did not occur. In a separate series of 37 patients, who had radiologic cardiomegaly in addition to hypertension, the control ejection fraction was 62%. Nifedipine, when used acutely, slightly increased the ejection fraction to 65% (p less than 0.005). Our studies show that in outpatients with severe hypertension, sublingual nifedipine is an antihypertensive agent which acts swiftly and safely, without causing a decrease in the ejection fraction when it is used for acute blood pressure reduction, and that subsequent therapy with oral nifedipine results in a predictive long-term hypotensive effect.

Treatment of hypertensive emergencies with the calcium channel blocker nifedipine

The severe elevations in blood pressure that occur in hypertensive emergencies pose a serious threat to life or vital organ functions. However, use of antihypertensive agents to acutely reduce blood pressure during hypertensive emergencies may cause deficits in the perfusion of the central nervous system or the heart. Therefore, a knowledge of cerebral blood flow regulation during acute treatment of hypertensive emergencies is indispensable. Experience with the calcium channel blocker nifedipine in the acute treatment of patients with hypertensive emergencies has shown that this agent has a pronounced vasodilatory effect, especially in vessels with a high vasoconstrictor tone, and that it does not reduce cardiac output or cerebral blood flow. The drug is highly efficacious and safe, and reports of serious side effects are rare. However, nifedipine should be used with caution in patients with suspected or proved critical arteriosclerotic stenosis of the cerebral arteries, because a reduction in perfusion pressure with any drug places these patients at risk for development of ischemic symptoms. Nifedipine can be used as a first-line drug for acute reduction of blood pressure in patients with hypertensive emergencies.

Aggravation of myocardial ischaemia by nifedipine

Three cases in which myocardial ischaemia was possibly precipitated by the administration of nifedipine are reported. It is suggested that the initial administration of nifedipine should be undertaken with caution in patients with unstable ischaemic heart disease.

Cerebral blood flow autoregulation and hypertension

Hypertension and antihypertensive therapy have clinically important effects on cerebral blood flow. The autoregulatory changes that occur with chronic arterial hypertension should influence the clinician's choice of antihypertensive agents and the rapidity with which the blood pressure is lowered in order to avoid symptoms of focal or global cerebral hypoperfusion.

Calcium channel blockers in emergency medicine

Diltiazem, nifedipine, and verapamil inhibit calcium entry into cells via different mechanisms with different pharmacologies. They display different relative effects on different cardiovascular functions, a complex interplay of direct actions and adrenergic reflexes. Peripheral arterial vasorelaxation causes adrenergic reflex activity which opposes their direct negative chronotropic, dromotropic, inotropic, and hypotensive actions. Verapamil's most potent activity is electrophysiologic, and nifedipine's effects are hemodynamic; diltiazem acts like a less-potent combination of verapamil and nifedipine. All three drugs are efficacious in angina. These three drugs may not be interchangeable in all patients, but individualization of therapy is possible. Future indications for calcium channel blocker therapy may include hypertrophic cardiomyopathy, cerebral vasospasm, migraine headaches, pulmonary hypertension, asthma, esophageal spasm, intestinal ischemia, Raynaud's phenomenon, dysmenorrhea, and premature labor.

[Calcium antagonists in the therapy of hypertension]

Calcium antagonists (nifedipine, verapamil, diltiazem) are potent vascular smooth muscle relaxants. Experimental and clinical investigations provide growing evidence that they are effective in acute and (sub)chronic therapy of arterial hypertension by lowering peripheral vascular resistance and improvement of altered hemodynamics--independent from pathogenesis of hypertension. Due to its prompt and profound hypotensive action, sublingual or oral nifedipine has been used successfully in hypertensive crises. The hypotensive effect usually correlated closely with the severity of hypertension and is nearly absent in normotensive controls. Since the blood pressure drop may occasionally results in absolute or relative hypotension, the initial dose should be as low as possible. The activation of the adrenergic and renin angiotension systems seen after nifedipine administration is less pronounced after chronic administration of the drug and is nearly absent after verapamil and diltiazem. Plasma aldosterone concentrations remain constant or are slightly decreased. In contrast to classic vasodilators, the long-term administration of calcium antagonists usually does not result in tachycardia (nifedipine), but slight sinus bradycardia (verapamil, diltiazem). Peripheral edema may occasionally occur after nifedipine. A tolerance has been observed during long-term treatment of hypertension. Combining these drugs (verapamil, diltiazem) with betablockers is not recommended due to the negative inotropic and bathmotropic effects. Simultaneous administration of nifedipine and beta-blockers enhances the hypotensive action, but favours the development of peripheral edema and in rare cases (especially in severe coronary heart disease) results in a dramatic drop in blood pressure and/or congestive heart failure. Further clinical evaluation and long-term trials of calcium antagonists as antihypertensive agents will be needed before definite conclusions can be drawn.

Nifedipine in hypertensive emergencies

The effects and safety of using oral nifedipine 10-20 mg as acute antihypertensive treatment were studied in a single-blind placebo-controlled study of 25 consecutive patients with very high blood pressure requiring emergency reduction. In addition the effect of this treatment on cerebral blood flow was investigated using xenon-133 in 10 patients randomly allocated to receive oral nifedipine or intravenous clonidine. Whereas placebo did not alter the blood pressure, oral nifedipine significantly reduced the systolic and diastolic blood pressures in all 25 patients (from 221 +/- 22/126 +/- 14 mm Hg to 152 +/- 20/89 +/- 12 mm Hg after 30 minutes, p less than 0.001). Heart rate increased from 74 +/- 11 to 84 +/- 11 beats/minute (p less than 0.01); this effect was inversely related to age (r = -0.65, p less than 0.01). The falls in systolic and diastolic blood pressures were closely related to the blood pressures before treatment ) r = 0.67, p less than 0.001 for systolic, and r = -0.58, p less than 0.01 for diastolic values). No serious unwanted effects were observed. Measurement of cerebral blood flow after nifedipine showed an increase in flow in four out of five patients. Clonidine, by contrast, reduced cerebral blood flow in all patients by up to 28%. Nifedipine is a simple, effective, and safe alternative drug for managing hypertensive emergencies, especially when continuous monitoring of the patient cannot be guaranteed.