Effects of treatment with nifedipine and metoprolol in essential hypertension

A Novel Composite Voltammetric Sensor Based on Yttria-Stabilized Zirconia Doped with Neodymium-Carbon Black-Nafion Glassy Carbon Electrode for Metoprolol Determination

For the first time, a new composite voltammetric sensor based on yttria-stabilized zirconia doped with neodymium-carbon black-Nafion glassy carbon electrode (YSZNd-CB-Nafion/GCE) for the determination of metoprolol (MET) has been developed. The instrumental parameters and supporting electrolyte were optimized. For 105 s accumulation time, linearity was achieved in the range of 0.01 to 0.2 µM. The limit of detection (for 105 s accumulation time) was equal to 2.9 nM (2 µg/L), and was the best result in comparison to other voltametric sensors. The reproducibility of the metoprolol signal presented as relative standard deviation (RSD) was equal to 1.9% (n = 7). Additionally, our electrode is characterized by high stability, is easy to use, and has a short preparation time. The proposed sensor was found useful for MET determination in plasma and urine, as well as for pharmaceutical samples, with a good recovery parameter (96-108%). Flow injection analysis (FIA) with amperometric detection was also performed for MET determination. The recovery was calculated and was in the range 101-103%, suggesting that the proposed material may be applied in flow injection analysis.

Regulatory mechanisms of cAMP levels as a multiple target for antiplatelet activity and less bleeding risk

Platelet activation is a critical component of atherothrombosis. The multiple pathways of platelet activation limit the effect of specific receptor/pathway inhibitors, resulting in limited clinical efficacy. Recent research has confirmed that combination therapy results in enhanced antithrombotic efficacy without increasing bleeding risk. In this way, the best-known inhibitor and turn off signaling in platelet activation is cAMP. In this article we discuss the mechanisms of regulation of intraplatelet cAMP levels, a) platelet-dependent pathway: Gi/Gs protein-coupled receptors, phosphodiesterase inhibition and activation of PPARs and b) platelet-independent pathway: inhibition of adenosine uptake by erythrocytes. With respect to the association between intraplatelet cAMP levels and bleeding risk it is possible to establish that compounds/drugs with pleitropic effect for increased intraplatelet cAMP level could have an antithrombotic activity with less risk of bleeding.

Poisoning caused by the combined ingestion of nifedipine and metoprolol

Poisonings due to ingestion of a calcium channel or beta-adrenergic blocker have been the subject of several previous reports, but reports of poisoning due to combined ingestion of these drugs are infrequent. This is a report of suicidal ingestion of nifedipine 600 mg, metoprolol 200 mg, and etizolam 20 mg. Intravenous dopamine, norepinephrine, and calcium chloride had little effect but the administration of methylprednisolone and glucagon were associated with an increase in systolic blood pressure above 100 mm Hg.

Calcium antagonists: an overview

Calcium antagonists reduce the influx of calcium ions through the calcium channels. This causes a reduction in myocardial contractility or a fall in vascular resistance because of a lowering of vascular smooth muscle tone. Therefore, the net effect is a fall in blood pressure. The three major classes of calcium antagonists, the dihydropyridines, papaverine derivatives, and benzothiazepines, differ in molecular structure and their binding characteristics to the calcium channels. Furthermore, newer antagonists, particularly the dihydropyridines such as nicardipine, have a high affinity for vascular tissue and are highly selective for vascular smooth muscle. These compounds also have a favorable effect on hypertension mainly because of lowering of vascular resistance. In addition, they do not cause potentially negative metabolic effects on glucose or lipid levels and are generally well tolerated. Based on these findings, the Joint National Committee in the United States and the World Health Organization/International Society of Hypertension Committee on the Management of Mild Hypertension recommended the use of calcium antagonists as first-line treatment in hypertension.

Nifedipine and hypertension: roles of vasodilation and sodium balance

Nifedipine reduces blood pressure predominantly by reducing systemic vascular resistance due to a direct vasodilating action on the arterioles. This peripheral vasodilation appears greater the more severe the hypertension. Nifedipine also causes a long-term loss of sodium, which may be an additive mechanism for the blood pressure fall. In patients who are not controlled on nifedipine alone, studies have demonstrated an additive effect of beta blockers and converting-enzyme inhibitors on blood pressure. There is controversy about whether diuretics have an additive effect on blood pressure in patients already on nifedipine.

Calcium channel blockers. Potential medical benefits and side effects

Calcium channel blockers are recently developed antihypertensive drugs. In terms of mechanisms of action, their specificity is not so well established as that of angiotensin converting enzyme inhibitors but is better understood than that for diuretics or adrenergic-inhibiting drugs. Calcium channel blockers were originally developed for treatment of angina but were found to lower arterial pressure as well. Three of them are now in wide use in the United States; their therapeutic spectrum in regard to type of hypertension is broad. Sublingual nifedipine has replaced intravenously administered vasodilators as immediate treatment of severe hypertension, and all three drugs, given orally, have been shown to be effective in mild, moderate, and severe hypertension. The three drugs available in this country are verapamil, diltiazem, and nifedipine. Pharmacological studies have shown that verapamil has the most negative chronotropic and inotropic effects of the three, with nifedipine producing the most vasodilation and having the potential for causing reflex tachycardia. Actually in practice, these various pharmacological differences have proved to have less significance than previously thought, and the drugs seem to have about equal antihypertensive effectiveness. Comparisons of calcium entry blockers with other drugs have shown them to be equally effective in whites as propranolol but more effective in blacks. Responsiveness appears to be related, as well, to pretreatment plasma renin activity and age. Thus, the antihypertensive effect is directly related to age and inversely related to plasma renin activity. The side effects mostly relate to vasodilation, reflex tachycardia, palpitations, headache, and edema; they are not frequent, and the drugs are well tolerated.

Calcium channel antagonists. Part III: Use and comparative efficacy in hypertension and supraventricular arrhythmias. Minor indications

The major antihypertensive mechanism of calcium antagonists is by decreasing the systemic vascular resistance, modified by the counter-regulatory responses of the baroreflexes and the renin-angiotensin-aldosterone system. In severe hypertension, the concept that calcium overload of the vascular myocyte could precipitate or aggravate peripheral vasoconstriction provides a logical basis for the use of these agents as first choice therapy; nifedipine, especially, has been well tested. As monotherapy for mild to moderate hypertension each of the three first-generation agents compares well with beta-blockers. Calcium antagonists may have a special role in the therapy of certain patient groups (elderly, black) or in those subjects whose life style involves intense physical or mental exertion (hemodynamics better maintained than with beta-blockade) or in patients with early end-organ damage such as left ventricular hypertrophy or renal insufficiency. However, the goal blood pressure may not be reached during monotherapy so that drug combinations may be required. Further indications for these compounds are as follows. Verapamil and diltiazem are frequently used in supraventricular tachycardias including acute and chronic atrial fibrillation. In the arrhythmias of the Wolff-Parkinson-White syndrome, there is the potential danger of provocation of anterograde conduction. Further indications for calcium antagonists, still under evaluation, include congestive heart failure (controversial), hypertrophic cardiomyopathy (verapamil), primary pulmonary hypertension (high doses required), Raynaud's phenomenon (nifedipine and diltiazem effective), peripheral vascular disease (proof not yet documented), cerebral insufficiency and subarachnoid hemorrhage (nimodipine promising), migraine, exertional bronchospasm, renal disease, atherosclerosis (experimental), and primary aldosteronism (nifedipine inhibits aldosterone release). Second-generation agents include dihydropyridines, such as nitrendipine, nicardipine, felodipine, amlodipine, nisoldipine, nimodipine, and isradipine. From these will be selected agents that are longer acting and provide higher vascular selectivity. New preparations of existing agents include slow-release formulations of nifedipine, verapamil, and diltiazem. 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 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. Yet caution is required when 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.(ABSTRACT TRUNCATED AT 400 WORDS)

Drug treatment of hypertension

There are several first choices for the treatment of mild and moderate hypertension. The selection of a drug may be influenced by concomitant pathology, with positive indications for particular drugs, e.g. coexistent angina, indicating use of a beta-receptor blocking drug or calcium antagonist; fluid retention indicating a diuretic; or contraindication e.g. asthma, and beta-adrenoceptor blocking drugs. beta-Adrenoceptor blocking drugs have the advantage of a long history and of possibly being cardioprotective following myocardial infarction, but they have not yet been established as primary preventive agents in hypertensive patients. The alpha-receptor blocking drugs have the advantage of favourably affecting lipid profile and blood pressure. Therefore, there may be advantages in the use of combined alpha- and beta-blockade. The diuretics, which have the advantage of being inexpensive, are widely used but long term metabolic effects, particularly hypokalaemia, cause concern. This is correctable by co-administration of a potassium sparing diuretic and often preventable by using low doses of the diuretic. Diet may be important as hypokalaemia appears to be less of a problem where potassium intake is high. Experience with calcium antagonists is widening but the use of converting enzyme inhibitors is more limited, and some physicians are less ready to use them as first choice in mild hypertension at present. Drugs like methyldopa, clonidine, the adrenergic neurone inhibitory drugs are now used more as reserve agents. More severe cases of hypertension may require drugs from 2 of the 3 major groups: beta-blocking drugs, vasodilators and diuretics. In some cases, drugs from each of these 3 groups will be required.

Nicardipine in the treatment of essential hypertension controlled 6-month-study comparing nicardipine with propranolol at rest and during exercise

Thirty patients with mild to moderate essential hypertension entered a randomised double-blind parallel group study for 6 months to compare the effects of the new calcium channel blocker nicardipine 90 mg/day and propranolol 240 mg/day. Both drugs reduced systolic and diastolic blood pressures significantly in the supine and in standing positions. After 6 months of treatment, nicardipine had reduced the supine systolic and diastolic blood pressures by 16 and 17 mm Hg, respectively, and propranolol by 15 and 12 mm Hg. While propranolol treatment led to a marked decline in heart rate, nicardipine caused a small but statistically significant increase in heart rate throughout the study. Both drugs reduced blood pressure during maximal exercise, but propranolol had a greater effect. During exercise nicardipine did not affect the heart rate, whereas propranolol dramatically reduced it. Nicardipine did not produce any ECG changes at rest or during exercise. The side-effects for nicardipine were mild and were related to the vasodilatation induced by the drug. No abnormalities in routine blood chemical tests were found for either of the drugs. Nicardipine appears to be an effective single drug treatment for mild to moderate hypertension.

Metoprolol. An updated review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy, in hypertension, ischaemic heart disease and related cardiovascular disorders

During the intervening years since metoprolol was first reviewed in the Journal (1977), it has become widely used in the treatment of mild to moderate hypertension and angina pectoris. Although much data have accumulated, its precise mechanisms of action in these diseases remain largely uncertain. Optimum treatment of hypertension and angina pectoris with metoprolol is achieved through dose titration within the therapeutic range. It has been clearly demonstrated that metoprolol is at least as effective as other beta-blockers, diuretics and certain calcium antagonists in the majority of patients. Although a twice daily dosage regimen is normally used, satisfactory control can be maintained in many patients with single daily doses of conventional or, more frequently, slow release formulations. Addition of a diuretic may improve the overall response rate in hypertension. Several controlled trials have studied the effects of metoprolol administered during the acute phase and after myocardial infarction. In early intervention trials a reduction in total mortality was achieved in one moderately large trial of prolonged treatment, but in another, which excluded patients already being treated with beta-blockers or certain calcium antagonists and where treatment was only short term, mortality was significantly reduced only in 'high risk' patients. Overall results with metoprolol have not demonstrated that early intervention treatment in all patients produces clinically important improvement in short term mortality. Thus, the use of metoprolol during the early stages of myocardial infarction is controversial, largely because of the requirement to treat all patients to save a small number at 'high risk'. This blanket coverage approach to treatment may be more justified during the post-infarction follow-up phase since it has been shown that metoprolol slightly, but significantly, reduces the mortality rate for periods of up to 3 years. Metoprolol is generally well tolerated and its beta 1-selectivity may facilitate its administration to certain patients (e.g. asthmatics and diabetics) in whom non-selective beta-blockers are contraindicated. Temporary fatigue, dizziness and headache are among the most frequently reported side effects. After a decade of use, metoprolol is well established as a first choice drug in mild to moderate hypertension and stable angina, and is beneficial in post-infarction patients. Further study is needed in less well established areas of treatment such as cardiac arrhythmias, idiopathic dilated cardiomyopathy and hypertensive cardiomegaly.

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.

Calcium channel blockers and treatment of hypertension

Over the past years, research efforts have been focused on the pathophysiologic role of calcium ions, and the implication for the potential role of calcium channel blockers in the management of essential hypertension. Numerous studies have shown that nifedipine and verapamil are effective antihypertensive agents, initial experience with diltiazem is also encouraging. The magnitude of blood pressure reduction with these drugs is related to the pre-treatment blood pressure. In refractory hypertension, combination with other antihypertensive agents provide additive effect. In the elderly population and in patients with ischemic heart disease, supraventricular arrhythmia, bronchospastic disease, peripheral vascular disease or diabetes mellitus, the calcium channel blockers offer potential advantages over other antihypertensive agents. Experimental studies also suggest that these drugs may reverse ventricular hypertrophy. When long-term safety with these drugs is documented from well-controlled clinical trials, the calcium channel blockers may be our first line of therapy for the management of hypertension.

Oral nifedipine for the treatment of patients with severe hypertension

Ten mg of nifedipine was administered to 19 patients with severe hypertension (mean blood pressure 187 +/- 17/122 +/- 12 mm Hg) without intensive care monitoring. Patients were instructed to bite and swallow the contents of the capsule. Blood pressure declined significantly to a mean of 149 +/- 17/92 +/- 10 mm Hg. No adverse side effects or hypotension occurred. Ten patients required an additional dose 30 to 60 minutes after the initial dose. Mean heart rate increased from 79 to 95 beats per minute without symptomatic consequences. Laboratory parameters measured before and after the four-hour study did not change significantly, although peripheral renin activity rose transiently. Urinary sodium excretion increased 43 percent over four hours after therapy in three patients in whom it was measured. Cardiac output, which was measured noninvasively in seven patients, rose nonsignificantly whereas systemic vascular resistance declined from 2,070 dynes/second/cm-5 to 1,271 dynes/second/cm-5 (statistically significant difference) in 20 minutes. These results indicate that oral nifedipine, when bitten and swallowed, effectively lowers blood pressure in patients with severe hypertension without the occurrence of adverse side effects or hypotension. Oral nifedipine may be used safely in an outpatient setting when urgent intervention is required.

Long-acting nifedipine in moderate and severe hypertensive patients with serious concomitant diseases

Long-acting nifedipine tablets were given to 47 severely and moderately hypertensive patients with renal insufficiency, cardiovascular, cerebrovascular, and peripheral vascular disease, diabetes mellitus, asthma, and systemic lupus erythematosus. Nifedipine substituted vasodilators (n = 22), was added to beta blockers and thiazides (n = 14), and was used alone (n = 11). In all three groups blood pressure was significantly reduced without aggravation of angina pectoris, intermittent claudication, cerebrovascular disease, or renal failure. Side effects were mild and transient. We found nifedipine tablets convenient and safe, as well as efficacious in patients with serious conditions.

Slow-release nifedipine as a single or additional agent in the treatment of essential hypertension--a placebo-controlled crossover study

The efficacy and safety of a new slow-release formulation of nifedipine ("Adalat Retard") were assessed in a double-blind cross-over trial in 19 subjects with essential hypertension (14 male, 5 female--ages: 34-72 years), 14 of whom continued previous antihypertensive medication. There were two 6 week treatment phases in which nifedipine 20 mg twice daily and placebo tablets twice daily were administered in random order. Supine mean blood pressure was 115 +/- 2 mm Hg during the placebo phase and 105 +/- 2 mm Hg during the nifedipine phase (p less than 0.001); and standing mean blood pressure was 121 +/- 2 mm Hg after placebo and 110 +/- 2 mm Hg after nifedipine (p less than 0.001). The magnitude of the blood pressure difference between the two phases was not related either to age or to the placebo phase blood pressure. The hypotensive effect of nifedipine was observed when administered as a single agent or in combination with diuretic and/or beta blocker. Heart rate was increased after nifedipine--75 +/- 2 beats/minute compared with 71 +/- 2 beats/minute after placebo (p less than 0.01). In this dose nifedipine (as "Adalat Retard") is an effective hypotensive agent which is a useful addition to presently available therapy.

Lack of a pharmacokinetic interaction between nifedipine and the beta-adrenoceptor blockers metoprolol and atenolol

Nifedipine, metoprolol and atenolol were administered orally to young, healthy volunteers. Each drug was given alone and nifedipine was also given with both beta-adrenoceptor blockers. Each drug was given for 3 days immediately before the study days. Plasma and urine drug concentrations were measured and the relevant pharmacokinetic parameters calculated. No pharmacokinetic interaction between nifedipine and the beta-adrenoceptor blockers was revealed.

Felodipine--a new vasodilator, in addition to beta-receptor blockade in hypertension

In a double-blind, cross-over trial, 10 men with primary hypertension, not adequately controlled with a beta-blocker alone, were also given felodipine or placebo for periods of one week. Placebo was administered single-blind for 2 weeks and 1 week, respectively, before randomization and between treatments. The dose of felodipine ranged from 6.25 mg to 25 mg. The addition of felodipine resulted in a pronounced (20%), statistically significant reduction in blood pressure (BP) and a small but significant increase in heart rate (HR). The effects were seen within 1-2 h and were maximal after 3-4 h. During steady state treatment the duration of BP reduction was at least 12 h. No orthostatic reaction was seen. There was a significant correlation between the plasma concentration of felodipine and change in BP. The most frequently reported side-effects were headache and ankle oedema, the latter probably being due to pronounced pre-capillary vasodilatation. There was no weight increase and thus no indication of general water retention. No clinically significant change in laboratory variables and no influence on the P-Q time were seen. Thus, felodipine in combination with a beta-blocker seems to be a useful addition to the treatment of hypertensive patients whose BP is not adequately controlled with a beta-blocker alone.