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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calcium antagonists are potent vasodilators and are widely used in the treatment of hypertension and angina pectoris. The currently available compounds belong to three classes: (1) dihydropyridines (e.g. nifedipine, amlodipine and felodipine), (2) phenylalkylamines (e.g. verapamil) and (3) benzothiazepines (e.g. diltiazem). The three classes differ in their pharmacological profile and safety. For example, verapamil and diltiazem lower heart rate, while dihydropyridines increase it or leave it unchanged. With most of the latter compounds, a marked activation of the sympathetic nervous system has been noted. Most compounds exhibit negative inotropic effects, particularly the first-generation molecules, which is disadvantageous in patients with impaired left-ventricular function. The most common side effects of these drugs are flushing, headache and edema. With verapamil, constipation may represent a problem in certain patients. Hence, in spite of a large number of calcium antagonists available, there remains a need for new compounds with enhanced efficacy and improved tolerability. A new compound should lack any negative inotropism, avoid any increase in sympathetic outflow or heart rate and exhibit a high degree of vascular selectivity. Furthermore, a low incidence of side effects, particularly ankle edema and optimal pharmacokinetics allowing once-daily dosing would be desirable. Mibefradil is a new calcium antagonist with promising pharmacological and clinical properties. The compound has a high bioavailability, lacks negative inotropic effects at therapeutic concentrations, does not exhibit reflex tachycardia during vasodilation and actually slightly decreases heart rate. It is a potent direct vasodilator efficacious in hypertension and chronic angina pectoris, elicits endothelium-dependent relaxations and facilitates the effects of nitric oxide in vascular smooth muscle. The drug is a particularly efficacious vasodilator in intramyocardial coronary arteries which may be important for its anti-ischemic effects and the lack of steal in the coronary circulation. Furthermore, mibefradil has antiproliferative properties in human vascular smooth muscle cells in culture. As a unique property, mibefradil blocks T-type calcium channels and hence represents a new class of calcium channel blockers. In patients with hypertension, mibefradil has a high efficacy in controlling blood pressure. The drug does not cause constipation and has a low incidence of ankle edema. A large trial is under way to further delineate the properties of this new calcium antagonist in patients with heart failure.
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PMID:Comparative pharmacological properties among calcium channel blockers: T-channel versus L-channel blockade. 957 Apr 24

During the last 2 decades, remarkable progress has been made in the treatment of hypertension with the discovery of new drugs lowering blood pressure by various mechanisms, e.g. calcium channel blockers, angiotensin-converting enzyme inhibitors and angiotensin II antagonists. These antihypertensive agents are now widely used as first-line therapy although there is still no definite proof that they have a cardioprotective effect and reduce the mortality rate in patients with coronary heart disease. Mibefradil is a new calcium antagonist with a novel mechanism of action since it is the only drug available so far able to block T channels. This compound might be particularly effective in preventing cardiac morbidity and mortality. It reduces heart rate when lowering blood pressure, has no negative inotropic effect, allows regression of cardiac hypertrophy and is effective in the treatment of angina. Mibefradil produces a sustained blood pressure reduction with a close to optimal trough:peak ratio. A major advantage of this novel compound is its excellent tolerability over the dose range recommended (50-100 mg/day). In particular, leg edema is seen clearly less often during mibefradil treatment than during therapy with dihydropyridines. Mibefradil has therefore an attractive profile in terms of both efficacy and safety and represents a promising first-line option to treat hypertensive patients.
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PMID:Potential cardioprotective effect of mibefradil in the long-term treatment of hypertension. 957 Apr 25

Mibefradil, a tetralol derivative, is the first representative of a new class of calcium antagonists. It selectively blocks entry of calcium into cells through T-type channels. The efficacy and tolerability of mibefradil in the treatment of mild-to-moderate essential hypertension were evaluated in four placebo-controlled, double-blind, dose-finding studies involving over 1000 patients. Two trials involved patients from the general population, one examined a subpopulation of elderly patients, and one evaluated patients receiving chronic hydrochlorothiazide (HCTZ) treatment. Based on these studies, the recommended doses of mibefradil are 50 mg and 100 mg. Doses >100 mg/day were associated with small gains in efficacy and an increased incidence of adverse effects. Response (sitting diastolic blood pressure normalization to < or =90 mm Hg or reduction by > or =10 mm Hg) rates to mibefradil ranged from 46.0% to 68.6% with 50 mg, and from 60.0% to 93.2% with 100 mg. Normalization rates paralleled the response rates, ranging from 34.0% to 62.9% with 50 mg, and from 42.5% to 81.8% with 100 mg. The effects on sitting systolic blood pressure were similar. Treatment was associated with a slight, potentially beneficial reduction in heart rate. Results were similar across all populations, indicating that no dose adjustment is required for elderly and for HCTZ-treated patients. The frequency of adverse events was similar to that reported for placebo groups, with headache being the most common complaint. In comparative trials, mibefradil was more effective than nifedipine SR and diltiazem CD, and at least as effective as amlodipine and nifedipine GITS. Overall, mibefradil was better tolerated than the comparison drugs. Mibefradil, at the recommended doses of 50 to 100 mg/day, is safe and effective for the treatment of mild-to-moderate hypertension.
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PMID:Mibefradil, a T-channel-selective calcium antagonist: clinical trials in hypertension. 960 72

Mibefradil is the prototype of a new class of calcium antagonists that selectively block T-type voltage-gated plasma membrane calcium channels in vascular smooth muscle. The drug is structurally and pharmacologically different from traditional calcium antagonists. It does not have negative inotropism at therapeutic concentrations, and is not associated with reflex activation of neurohormonal and sympathetic systems. In clinical studies of hypertension, mibefradil 50 and 100 mg/day reduced trough sitting diastolic and systolic blood pressures in a dose-related manner. Dosages exceeding 100 mg/day generally did not result in significantly greater efficacy, but were associated with a higher frequency of adverse events. No first-dose hypotensive phenomenon was observed. Mibefradil has antiischemic properties resulting from dilation of coronary and peripheral vascular smooth muscle, and a slight reduction in heart rate. In clinical studies of chronic stable angina pectoris, dose-related increases in exercise duration, time to onset of angina, and time to 1-mm ST-segment depression during exercise tolerance tests occurred. Mibefradil reduced the number and duration of ischemic events recorded by 48-hour ambulatory electrocardiograph (ECG) monitoring, as well as number of anginal episodes and nitroglycerin consumption. Favorable hemodynamic and clinical profiles are reported, including high trough:peak ratios (> 80%), high oral bioavailability, and long elimination half-life (17-25 hrs) permitting once/day dosing. Dizziness, headache, leg edema, and lightheadedness are frequently reported, but overall the agent is well tolerated. First-degree atrioventricular block and sinus bradycardia are the most frequent ECG changes caused by the drug. In vitro studies indicate mibefradil inhibits cytochrome P450 1A2, 2D6, and 3A4, resulting in elevated plasma concentrations of drugs metabolized by those isoenzymes. Therefore, it is contraindicated in patients receiving terfenadine, astemizole, cisapride, lovastatin, or simvastatin.
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PMID:Mibefradil, a pharmacologically distinct calcium antagonist. 962 98

Mibefradil, the first member of the tetralol derivatives, a new class of calcium antagonists, is used for the treatment of hypertension and angina pectoris. This study was designed to investigate the effect of varying degrees of chronic renal impairment on mibefradil pharmacokinetics and pharmacodynamics. Neither pharmacokinetic nor pharmacodynamic parameters varied as a function of renal status. Additionally, hemodialysis removed only a relatively small fraction of drug from the body. It was concluded that the majority of renal-failure patients will not require a change in mibefradil dosage relative to patients with normal renal function. Following hemodialysis, supplemental mibefradil treatment should not be necessary.
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PMID:Pharmacokinetics and pharmacodynamics of mibefradil in hypertensive patients with varying degrees of renal insufficiency. 965 16

Mibefradil is a T-type and L-type calcium channel blocker (CCB) released in the United States in 1997 for management of hypertension and chronic stable angina. Postmarketing surveillance revealed a potential serious interaction between mibefradil and beta-blockers, digoxin, verapamil, and diltiazem, especially in elderly patients. The manufacturer voluntarily withdrew mibefradil on June 8, 1998. We describe 4 cases of cardiogenic shock in patients taking mibefradil and beta-blockers who began taking dihydropyridine CCBs. One case resulted in death; the other 3 survived episodes of cardiogenic shock with intensive support of heart rate and blood pressure. Physicians who are preparing to switch patients' medications from mibefradil to other antihypertensive agents should be aware of these potentially life-threatening drug-drug interactions.
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PMID:Life-threatening interaction of mibefradil and beta-blockers with dihydropyridine calcium channel blockers. 966 89

Mibefradil is a new T-channel selective calcium antagonist effective in the treatment of hypertension and chronic stable angina pectoris. In this study steady-state plasma mibefradil concentrations and pharmacodynamic measurements were obtained from American and European clinical studies and analyzed using NONMEM. Doses ranged from 12.5-200 mg orally once-daily. A linear one-compartment pharmacokinetic model with first-order absorption was employed. Best parameter estimates were as follows: absorption rate-constant = 2.7 hours-1, clearance = 5.7 L/hour, volume of distribution = 179 L. The bioavailability of the 25 mg oral dose relative to higher doses was 0.83. Conclusions based on the Emax model equations were that at average plasma concentrations achieved clinically (approximately 300 ng/ml and approximately 600 ng/ml for 50 and 100 mg/day, respectively) the effect on heart rate is near maximum, the effect on blood pressure is about 50% of maximum, and the effect on PQ interval is small. The model also predicts that diastolic blood pressure and heart rate reductions will tend to be greater in patients with higher baseline values and with increasing mibefradil plasma concentrations. The increase in PQ interval is strongly related to plasma mibefradil concentration. The population analysis shows that mibefradil pharmacokinetics and pharmacodynamics were not affected in a clinically relevant manner by demographic characteristics.
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PMID:Mibefradil pharmacokinetic and pharmacodynamic population analysis. 967 23

Mibefradil is a single-enantiomer calcium antagonist belonging to a new class, the tetralol derivatives. The recommended doses for treatment of hypertension and chronic stable angina pectoris are 50 or 100 mg. Mibefradil is metabolized via parallel pathways of esterase-catalysed hydrolysis and cytochrome P450 3A4-mediated oxidation. Mibefradil also inhibits cytochrome P450 3A4 and consequently inhibits its own metabolism, a property illustrated by three studies performed early in the drug's development. After single intravenous doses of 2.5 to 80 mg to healthy male subjects, pharmacokinetics are linear. At the representative 40 mg intravenous dose mean pharmacokinetic parameters were clearance 241 +/- 76 mL min(-1), terminal exponential half-life 15.0 h and volume of distribution at steady state 213 L. After single oral doses of 10 to 320 mg, reduced first-pass metabolism occurs with increasing dose. This effect is accompanied by increasing absolute bioavailability as the dose is increased. In an oral multiple-dose study of healthy male volunteers mibefradil doses of 100, 150 or 250 mg (from tablets) were administered once daily for 28 days. Reduction of the first-pass effect was noted, although the data suggested that a maximum was reached for doses of 150 mg or more. In a study of the effect of hypertension on mibefradil pharmacokinetics, 12 patients received oral mibefradil once daily at doses of 50, 100, 150, or 200 mg in 100 mL orange juice for 8 days. Steady state was reached within 3 days and accumulation generally ranged from three- to sevenfold. Single-dose non-linearity was observed in the first-pass effect, although for multiple dosing oral clearance values were dose-independent and lower than for single doses. After multiple dosing at the recommended dosage of 50 and 100 mg once daily, oral clearance of mibefradil stabilizes to approximately the same value for both doses. Hence, the single-dose non-linearity has little clinical relevance but demonstrates the self-inhibition of metabolism seen with mibefradil. Studies so far suggest that self-inhibition of its oxidative metabolic pathway leads to a low clearance and long half-life, enabling once-daily dosing and conferring low intra- and inter-patient variability in pharmacokinetics.
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PMID:Single- and multiple-dose mibefradil pharmacokinetics in normal and hypertensive subjects. 981 Nov 58

Mibefradil is a calcium antagonist approved for the treatment of hypertension and chronic stable angina pectoris. To investigate the relationship between steady state, trough plasma concentrations and blood pressure response in patients with renal dysfunction, data from a multicenter, multiple-dose mibefradil study were analyzed. Changes in sitting diastolic blood pressure from baseline were linearly related to trough plasma mibefradil concentrations. Renal function did not affect plasma mibefradil concentrations. Consequently, mibefradil dosage adjustment is not required for patients with renal impairment.
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PMID:Steady-state trough plasma mibefradil concentrations and correlation to blood pressure response in hypertensive patients with chronic renal disease. 982 66

Mibefradil is a new cardiovascular drug with peculiar Ca++ antagonistic properties. The most remarkable feature of mibefradil is its unique relative selectivity for T type calcium channels, a property that has been proposed to explain in part the beneficial pharmacological and clinical profiles of this drug. In adrenal glomerulosa cells, aldosterone biosynthesis and secretion in response to angiotensin II or extracellular potassium is dependent on a sustained influx of Ca++ through T type Ca++ channels. The effect of mibefradil on the steroidogenic function of glomerulosa cells was therefore investigated. Using the patch clamp technique, we found that mibefradil inhibits selectively and in a concentration-dependent manner (IC50 = 3 microM)++ T type currents in bovine glomerulosa cells. In addition to this tonic (voltage independent) inhibition, the drug also induced a shift of the steady-state inactivation curve of these channels toward hyperpolarized voltages, contributing to its efficacy to prevent Ca++ influx into the cell through T type channels. Concomitantly, mibefradil reduced the cytosolic calcium responses to potassium and angiotensin II (as assessed with fluorescent probes), without affecting the capacitative Ca++ influx, and inhibited pregnenolone and aldosterone formation. This inhibition of steroidogenesis was not exclusively due to mibefradil action on voltage-operated Ca++ channels, because this agent also partially reduced steroid synthesis induced by adrenocorticotropic hormone or forskolin, two activators of the cyclic AMP pathway. In conclusion, mibefradil is highly effective in adrenal glomerulosa cells in reducing T type channel activity and aldosterone biosynthesis, two actions that should contribute to the beneficial effect of the drug in the treatment of hypertension.
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PMID:Inhibitory action of mibefradil on calcium signaling and aldosterone synthesis in bovine adrenal glomerulosa cells. 986 60


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