Aggravation of myocardial ischaemia by nifedipine

Nifedipine--a survey of adverse effects. Four years' reporting in Sweden

During the period February 1983 to December 1984 the Swedish Adverse Drug Reactions Advisory Committee received 80 reports describing 116 adverse reactions with a possible or probable connection to nifedipine. The most frequently reported reactions are oedema, tachycardia, headache and rash. Confusion and sleep disorders constitute 8 cases. Impaired angina is a potentially serious reaction and one patient developed myocardial infarction.

Blood pressure management during acute ischaemic stroke

Control of hypertension is a well-established goal of primary stroke prevention. Management of blood pressure in patients during acute ischaemic stroke, however, is complicated by the need to maintain brain perfusion. Lowering blood pressure in the acute setting may avoid the deleterious effects of high blood pressure but may also lead to cerebral hypoperfusion and worsening of the ischaemic stroke. Little information is available from clinical trials concerning optimal blood pressure management in acute stroke. Current protocols of thrombolytic therapy require strict blood pressure control below certain prescribed limits; however, in most acute stroke patients not treated with thrombolysis, blood pressure reduction is not routinely recommended and guidelines for target blood pressures are difficult to justify. Preliminary studies, in fact, suggest that there may be a role for blood pressure elevation in the treatment of some patients with acute ischaemic stroke.

Cardiac effects of calcium antagonists in systemic hypertension

The calcium antagonists are a class of heterogeneous drugs, with a wide spectrum of direct and indirect cardiac effects that vary a great deal from one drug to another and depend upon formulation and duration of action. Calcium antagonists act by decreasing total peripheral resistance to lower arterial pressure. As a consequence, reflex tachycardia, increased cardiac output, and increased plasma catecholamine and plasma renin activity are commonly seen, particularly with the initial dose and with short-acting dihydropyridines. The abrupt vasodilation can paradoxically elicit angina and even acute myocardial infarction. These hemodynamic and neuroendocrine changes are less pronounced with the long-acting formulations. Most calcium antagonists diminish automaticity of the sinus node, slow conduction in the atrioventricular node, and have little, if any, effect on the automaticity of the myocytes. The dihydropyridines generally have less effect on automaticity and cardiac conduction than nondihydropyridines. The negative inotropic effect is most profound with nondihydropyridines and is greatly reduced or absent with newer dihydropyridines, such as isradipine, felodipine, amlodipine, and nisoldipine. Long-acting calcium antagonists generally improve myocardial oxygenation by unloading the heart, increasing coronary blood flow, and reducing myocardial oxygen consumption. Thus, calcium antagonists have a variety of beneficial effects in patients with hypertensive heart disease: they reduce left ventricular hypertrophy and its sequelae, such as ventricular dysrhythmias, impaired filling and contractility, and myocardial ischemia. Ongoing studies should provide a more conclusive answer regarding the efficacy and safety of calcium antagonists.

Calcium channel antagonists in the management of anginal syndromes: changing concepts in relation to the role of coronary vasospasm

Despite the increasing evidence that alterations in coronary vascular tone can and do occur in patients with anginal syndromes, only in a minority of such patients with Prinzmetal's angina is there decisive evidence that the coronary vasodilation induced by calcium channel antagonists (CCAs) plays a specific therapeutic role. CCAs may also give therapeutic benefit in a number of conditions in which coronary vasoconstriction may contribute to ischemia, such as hyperventilation, cold-induced angina, or silent ischemia not caused by an increase in heart rate. Thus, the decision of whether or not to use CCAs in angina syndromes will often have to be made on grounds other than what appears to be a minor role of vasospasm in the overall spectrum of angina. There are preliminary indications that the long-term prognosis may be different among different categories of CCAs.

Atenolol or nicardipine alone is as efficacious in stable angina as their combination: a double blind randomised trial

BACKGROUND

Beta blockers and calcium antagonists are widely used in the management of angina pectoris in the belief that the combination is more efficacious than either drug alone.

METHODS

This double blind randomised crossover placebo controlled study compares the effects of nicardipine, atenolol and their combination in 30 patients with chronic stable angina. Each treatment period lasted 6 weeks with dose titration after 3 weeks. Symptom limited treadmill exercise testing and radionuclide ventriculography at rest was carried out at the end of each treatment period.

RESULTS

Total exercise duration and time to 1-mm ST-segment depression was significantly prolonged by nicardipine and atenolol when compared to placebo, the combination offered no additional benefit. Time to onset of angina was significantly prolonged by nicardipine and the combination but not by atenolol. Indices of left ventricular function were not significantly affected by any treatment other than an increase in left ventricular end diastolic volume on atenolol and the combination.

CONCLUSIONS

Nicardipine and atenolol are equally effective in prolonging exercise duration and time to onset of ischemia in patients with chronic stable angina while the combination appeared to offer no additional benefit. Nicardipine prolonged the time to onset of angina significantly; again there was no further improvement with the combination. Neither drug appears to have an important effect on the parameters of diastolic function studied in patients with chronic stable angina.

Dose-response evaluation of oral labetalol in patients presenting to the emergency department with accelerated hypertension

STUDY OBJECTIVE

Dose-response evaluation of oral labetalol (100, 200, or 300 mg) on heart rate and systemic blood pressure in emergency department patients with hypertensive urgency (diastolic blood pressure, 110 to 140 mm Hg, and no end-organ evidence of hypertensive emergency).

METHODS

This acute-treatment, dose-ranging study used a randomized, double-blind, parallel design. Patients with supine diastolic blood pressure of 110 to 140 mm Hg after 30 minutes of bedrest received an oral dose of labetalol. Supine blood pressure and heart rate were measured manually and recorded hourly for four hours after dose. Diastolic blood pressure of 100 mm Hg or less or a 30-mm Hg reduction in diastolic blood pressure was considered a treatment success.

RESULTS

Two hundred fifty-five patients were evaluated for inclusion, and 36 patients (19 women and 17 men; mean age, 44 years; age range, 23 to 67 years) were studied. The most frequent reason for exclusion was a spontaneous decrease in diastolic blood pressure to less than 110 mm Hg (31%) with bedrest. There were 12 patients in each treatment group. Compared with baseline, the 100-mg dose significantly (P less than .05) reduced heart rate at three and four hours after dose, and the 300-mg dose significantly (P less than .05) reduced heart rate at one, two, and three hours after dose; the 200-mg dose did not significantly affect heart rate. All doses produced a significant decrease in systolic and diastolic blood pressures at one, two, three, and four hours after dose compared with baseline. There were no statistically significant differences between treatment groups with regard to systolic or diastolic blood pressure or heart rate at baseline or one, two, three, or four hours after dose. At two hours after dose, diastolic blood pressure control was observed in 75%, 58%, and 67% of patients receiving 100, 200, and 300 mg, respectively (P = .903). At four hours after dose, diastolic blood pressure control was observed in 50%, 64%, and 67% of patients receiving 100, 200, and 300 mg, respectively (P = .755). A comparison of treatment success rates between the two time periods showed a waning of response with the 100-mg dose of labetalol at hour 4 compared with hour 2 (P less than .05). No adverse effects were observed.

CONCLUSION

Labetalol provides safe and effective treatment for hypertensive urgencies when administered orally in doses of 100 to 300 mg.

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.

Calcium channel antagonists. Part IV: Side effects and contraindications drug interactions and combinations

With the correct selection of drug and patient, the calcium antagonists as a group can be remarkably effective at relatively low cost of serious side effects. Almost all side effects are dose related. Minor side effects include those caused by vasodilation (flushing and headaches), constipation (verapamil), and ankle edema. Serious side effects are rare and result from improper use of these agents, as when intravenous verapamil (or diltiazem) is given to patients with sinus or atrioventricular nodal depression from drugs or disease, or nifedipine to patients with aortic stenosis. The potential of a marked negative inotropic effect is usually offset by afterload reduction, especially in the case of nifedipine which actually has the most marked negative inotropic effect. Yet caution is required when even calcium antagonists, especially verapamil, are given to patients with myocardial failure unless caused by hypertensive heart disease. Drug interactions of calcium antagonists occur with other cardiovascular agents such as alpha-adrenergic blockers, beta-adrenergic blockers, digoxin, quinidine, and disopyramide. The most marked interaction with digoxin is that with verapamil, which may raise digoxin levels by over 50%. Combination therapy of calcium antagonists with beta-blockers is increasingly common, and is probably safest in the case of dihydropyridines. Other combinations being explored are those with angiotensin-converting enzyme inhibitors and diuretics.

Calcium channel antagonists. Part II: Use and comparative properties of the three prototypical calcium antagonists in ischemic heart disease, including recommendations based on an analysis of 41 trials

An analysis of 41 trials of angina of all varieties confirms that calcium antagonists are an important advance and are now established therapy for these syndromes. In effort angina, verapamil in a dose of 360-480 mg daily is better than propranolol in standard doses. Although nifedipine is highly effective against vasospastic angina, its use in threatened myocardial infarction or severe unstable angina is not supported by recent studies, unless combined with a beta-blocker. Diltiazem has recently been tested with apparent benefit in non-Q-wave myocardial infarction. Otherwise, these calcium antagonist agents all seem to have approximate equipotency in clinical ischemic syndromes including effort and vasospastic angina. Subjective side effects seem most troublesome in the case of nifedipine. All three calcium antagonists, especially nifedipine, have been successfully combined with beta-blocker therapy, yet occasional additive negative inotropic or chronotropic or dromotropic interactions may occur when verapamil or diltiazem is added to beta-blockade, and occasionally the direct negative inotropic potential of nifedipine may become evident. The choice between the calcium antagonists is determined not only by the clinical picture but also by the anticipated side effects in a given patient and by the overall cardiovascular status. In patients with supraventricular tachycardias or sinus tachycardia, verapamil or diltiazem is preferred, whereas in patients with a resting bradycardia or borderline heart failure nifedipine is likely to be chosen.