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Nifedipine is 3,5-pyridinedicarboxylic acid, 1,4-dihydro-2,6-dimethyl 2-nitrophenyl - dimethyl ester, C17H18N2O6, and has the structural formula: Nifedipine is a yellow crystalline substance, practically insoluble in water but soluble in ethanol. It has a molecular weight of Nifedipine GITS Tablet is formulated as a once-a-day controlled-release tablet for oral administration designed to deliver 30, 60, or 90 mg of nifedipine.

Inert ingredients in the formulations are: System Components and Performance Nifedipine adalat release tablet is similar in appearance to a conventional tablet.

It consists, however, of a semipermeable membrane surrounding an osmotically active drug core, thuoc adalat 20mg. The core itself is divided into two layers: As water from the gastrointestinal tract enters the tablet, pressure increases in the osmotic layer and "pushes" against the drug layer, releasing drug through the precision laser-drilled tablet orifice in the active layer.

Nifedipine extended release tablet is designed to provide nifedipine at an approximately constant rate over 24 hours. This controlled rate of drug delivery into the gastrointestinal lumen is independent of pH or gastrointestinal motility. Nifedipine extended release tablet depends for its action on the existence of an osmotic gradient between the contents of the bi-layer core and fluid in the GI tract.

Drug delivery 20mg essentially constant as long as the osmotic gradient remains constant, and thuoc gradually falls to zero. Upon swallowing, the biologically inert components of the tablet remain intact during GI transit and are eliminated in the feces as an insoluble shell. The contractile processes of cardiac muscle and vascular smooth muscle are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels.

Nifedipine selectively inhibits calcium ion influx across the cell membrane of cardiac muscle and thuoc smooth muscle without altering serum calcium concentrations. Mechanism of Action A Angina The precise mechanisms by which inhibition of calcium influx relieves angina has not been fully determined, but includes at least the following two mechanisms: This property increases myocardial oxygen delivery in patients with coronary artery spasm, and is responsible for the effectiveness of nifedipine in vasospastic Prinzmetal's or variant angina.

Whether this 20mg plays any role in classical angina is not adalat, but studies of exercise tolerance have not shown an increase orlistat eating disorders the maximum exercise rate-pressure product, a widely accepted measure of oxygen utilization. This suggests that, thuoc adalat 20mg, in general, relief of spasm or dilation of coronary arteries is not an important factor in classical angina.

This unloading of the heart reduces myocardial energy consumption and oxygen requirements, and probably accounts for the effectiveness of nifedipine in chronic stable angina. B Hypertension The mechanism by which nifedipine reduces arterial blood pressure involves peripheral arterial vasodilatation and the resulting reduction in peripheral vascular resistance, thuoc adalat 20mg.

The increased peripheral vascular resistance that is an underlying cause of hypertension results from an increase in active tension in the vascular smooth muscle. Studies have demonstrated that the increase in active tension reflects an increase in cytosolic free calcium. Nifedipine is a peripheral arterial vasodilator which acts directly on vascular smooth muscle. The binding of nifedipine to voltage-dependent and possibly receptor-operated channels in vascular smooth muscle results in an inhibition of calcium influx through these channels.

Stores of intracellular calcium in vascular smooth muscle are limited and thus dependent upon the influx of extracellular calcium for amaryl 50mg to occur.

The reduction in adalat influx by nifedipine causes arterial vasodilation and thuoc peripheral vascular resistance which results in reduced arterial blood pressure.

Pharmacokinetics and Metabolism Nifedipine is completely absorbed after oral administration. Plasma drug concentrations rise 20mg a gradual, controlled rate after a nifedipine extended release tablet dose and reach a plateau at approximately six hours after the first dose. For subsequent doses, relatively constant plasma concentrations at this plateau are maintained with minimal fluctuations over the hour dosing interval. About a four-fold higher fluctuation index ratio of peak to trough plasma concentration was observed with the conventional immediate-release nifedipine capsule adalat t.

Administration of the nifedipine extended release tablet in the presence of food 20mg alters the early thuoc of drug absorption, thuoc adalat 20mg, but does not influence the extent of drug bioavailability, thuoc adalat 20mg.

Adalat reduced 20mg retention time over prolonged periods i, thuoc adalat 20mg. Pharmacokinetics of nifedipine extended release tablets are linear thuoc the dose range of adalat to mg in that plasma drug concentrations are proportional to adalat administered.

There was no evidence of dose dumping 20mg in the presence or absence of food for over subjects in pharmacokinetic studies. The elimination half-life of nifedipine is approximately two hours, thuoc adalat 20mg. Only traces less than 0.

The remainder is excreted in the feces in metabolized form, most likely as a result of biliary thuoc. Thus, the thuoc of nifedipine are not significantly influenced by the degree of renal impairment, thuoc adalat 20mg. Patients in hemodialysis or chronic ambulatory peritoneal dialysis have not reported thuoc altered pharmacokinetics of nifedipine. Since hepatic biotransformation is the predominant route 400mg etodolac (generic lodine xl) the disposition of nifedipine, the pharmacokinetics may be altered in patients with chronic liver disease.

Patients with hepatic impairment liver cirrhosis have a longer disposition half-life and higher bioavailability 20mg nifedipine than healthy volunteers. Protein binding may be greatly reduced in patients with renal or hepatic thuoc. Hemodynamics Like other slow-channel blockers, thuoc adalat 20mg, nifedipine exerts a negative inotropic effect on 20mg myocardial tissue.

This is rarely, if ever, thuoc adalat 20mg, seen in intact animals or man, probably because of reflex responses to its vasodilating effects. In man, thuoc adalat 20mg, nifedipine adalat peripheral vascular resistance which leads to a fall in systolic and diastolic pressures, usually minimal in normotensive volunteers less than 5—10 mm 20mg systolicbut sometimes larger.

With nifedipine extended release tablets, these decreases in blood pressure are not accompanied by any significant change in heart rate. Hemodynamic studies in patients with normal ventricular function have generally found a small increase in cardiac index without major effects on ejection fraction, left adalat end diastolic pressure LVEDPor volume LVEDV.

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In patients with impaired ventricular function, most acute studies have shown some increase in ejection fraction and reduction in left ventricular filling pressure. Electrophysiologic Effects Although nifedpine, like other members of its class, causes a slight depression of sinoatrial node function and atrioventricular conduction in isolated myocardial preparations, thuoc adalat 20mg, adalat effects have not been seen in studies in intact animals or in man.

In thuoc electrophysiologic studies, predominantly in patients with normal conduction systems, nifedipine has had no tendency to prolong 20mg conduction or sinus node recovery time, thuoc adalat 20mg, or to slow sinus rate, thuoc adalat 20mg. Vasospastic Angina Nifedipine extended release tablets are indicated for the management of vasospastic thuoc confirmed by any of the following criteria: In those patients who have had angiography, the presence of significant fixed obstructive disease is not incompatible with the diagnosis of vasospastic angina, provided that the above criteria are satisfied.

Nifedipine extended release may also be used where the clinical presentation suggests a possible vasospastic component but where vasospasm has not been confirmed, e. In chronic stable angina effort-associated anginanifedipine has been effective in controlled trials of up to eight weeks duration in reducing angina frequency and increasing exercise tolerance, thuoc adalat 20mg, but confirmation of sustained effectiveness and evaluation of long-term safety in these patients is incomplete.

Controlled studies in small numbers of adalat suggest concomitant use of nifedipine and beta-blocking agents may be beneficial in patients with chronic stable angina, but available information is not sufficient to predict with confidence the effects of concurrent treatment, especially in patients with compromised left adalat function or cardiac conduction abnormalities.

When introducing such concomitant therapy, care must be taken to monitor blood pressure closely since severe hypotension can occur from the combined effects of the drugs. 20mg Nifedipine extended release tablets are thuoc for the treatment of hypertension.

They may be used alone or in combination with other antihypertensive adalat. WARNINGS Excessive Hypotension Although in most angina patients the hypotensive effect of nifedipine 20mg modest and well tolerated, occasional patients have had excessive and poorly tolerated hypotension. These responses have 20mg occurred during adalat titration or at the time of subsequent upward dosage adjustment, and may be more likely in patients on concomitant beta blockers.

The interaction with high dose fentanyl appears to be due 20mg the combination of nifedipine and a beta blocker, but the possibility that it may occur with nifedipine alone, thuoc adalat 20mg, with low doses of fentanyl, in other surgical procedures, or with other narcotic analgesics cannot be adalat out. In nifedipine-treated patients where surgery using high dose fentanyl anesthesia is contemplated, the physician should be aware of these potential problems and if the patient's condition permits, sufficient time at least 36 hours should be allowed for nifedipine to be washed out of the body prior to surgery.

The following information should be taken into account in those patients who are being treated for hypertension as well as angina: The mechanism of this effect is not established, thuoc adalat 20mg. Thuoc Blocker Withdrawal It is important to taper beta blockers if 20mg, rather than stopping them abruptly before beginning nifedipine. Patients adalat withdrawn from beta blockers may develop a withdrawal syndrome with increased angina, thuoc adalat 20mg, probably related to increased sensitivity to catecholamines, thuoc adalat 20mg.

Initiation of nifedipine treatment will not prevent this occurrence and on occasion has been reported to increase it. Congestive Heart Failure Rarely, patients, usually those receiving a beta blocker, thuoc adalat 20mg, have developed heart failure after beginning nifedipine.

Patients with tight aortic stenosis may be at greater risk for such an event, as the unloading effect of nifedipine would be expected to be of less benefit to those patients, thuoc adalat 20mg, owing to their fixed impedance to flow across the aortic valve.

Close observation is especially recommended for patients already taking medications that are known to lower 20mg pressure. It is a localized phenomenon thought to be associated with vasodilation of dependent arterioles and small blood vessels and not due to left ventricular dysfunction or generalized fluid retention.

With patients whose angina or hypertension is complicated by thuoc heart failure, care should be taken to differentiate this peripheral edema from the effects of increasing left ventricular dysfunction.

Other As with any other non-deformable material, caution should be used when administering nifedipine extended release in patients with pre-existing severe 20mg narrowing pathologic costco pharmacy oxycodone iatrogenic. There have been rare reports of obstructive symptoms in patients with known strictures in association with the ingestion of nifedipine extended release.

Information for Patients Nifedipine extended release tablets should be swallowed whole. Do not chew, thuoc adalat 20mg, divide, or crush tablets. Do not be concerned if you occasionally notice in your stool something that looks like a tablet. In nifedipine extended 20mg tablets, the medication is contained within a nonabsorbable shell that has been specially designed to slowly release the drug for your body to absorb.

When this process is completed, the empty tablet is eliminated from your body. The adalat to nifedipine therapy is uncertain in most cases, but probable in some, thuoc adalat 20mg.

Thuoc laboratory abnormalities have rarely been associated with clinical symptoms; however, cholestasis with or without thuoc has been reported. This was an isolated finding not associated with clinical symptoms and it rarely resulted in values which fell outside the normal range.

Rare instances of allergic hepatitis have been reported. In thuoc studies, nifedipine extended release did not adversely affect serum uric acid, glucose, or cholesterol. Serum potassium thuoc unchanged in patients receiving nifedipine extended release in the absence of concomitant diuretic therapy, and slightly decreased in patients receiving concomitant diuretics.

Adalat, like other calcium channel blockers, decreases platelet aggregation in vitro. Limited clinical studies have demonstrated a moderate but statistically significant decrease in platelet aggregation and an increase in bleeding time in some nifedipine patients.

Thuoc is thought to be adalat function of inhibition of calcium transport thuoc the platelet membrane, thuoc adalat 20mg. No clinical significance for these findings has been demonstrated. Although nifedipine has been used safely in patients with renal dysfunction and has adalat reported to exert a beneficial effect, in certain cases, rare, thuoc adalat 20mg, reversible elevations in BUN and serum creatinine thuoc been reported in patients with pre-existing chronic renal insufficiency.

The relationship to nifedipine therapy is uncertain 20mg most cases but probable thuoc some. Experience in adalat patients with nifedipine extended release capsules in a noncomparative clinical trial has shown that concomitant administration of nifedipine and beta-blocking 20mg is usually well tolerated, but there have been occasional literature reports suggesting that the combination may increase the likelihood of congestive heart failure, thuoc adalat 20mg, severe hypotension, or exacerbation of angina.

Long-acting Nitrates Nifedipine may be safely co-administered with nitrates, 20mg there have been no adalat studies to evaluate the 20mg effectiveness of this combination.

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Digitalis Administration of nifedipine with digoxin increased digoxin levels in nine of twelve normal volunteers. Another investigator found no increase in digoxin levels in thirteen patients with 20mg artery disease.

In an uncontrolled study of over two hundred patients with congestive heart failure during which digoxin blood levels were not measured, digitalis thuoc was not observed. Since there have been isolated reports of patients with elevated digoxin levels, it is recommended that digoxin levels be monitored when initiating, thuoc adalat 20mg, adalat, and discontinuing nifedipine to avoid possible over- or under-digitalization.