Norfan

Uses

Patients with mild to moderate hypertension (alone or in combination with other antihypertensives).

The treatment of chronic stable and vasospastic angina.

Raynaud\'s disease.

Norfan is also used to associated treatment for these conditions: Anginal Pain, Cardiovascular Events, Chronic Stable Angina Pectoris, Coronary Artery Disease (CAD), High Blood Pressure (Hypertension), Homozygous Familial Hypercholesterolemia, Hypertension,Essential, Mixed Dyslipidemias, Primary Hypercholesterolemia, Vasospastic Angina

How Norfan works

Mechanism of action on blood pressure

Norfan is considered a peripheral arterial vasodilator that exerts its action directly on vascular smooth muscle to lead to a reduction in peripheral vascular resistance, causing a decrease in blood pressure. Norfan is a dihydropyridine calcium antagonist (calcium ion antagonist or slow-channel blocker) that inhibits the influx of calcium ions into both vascular smooth muscle and cardiac muscle. Experimental studies imply that amlodipine binds to both dihydropyridine and nondihydropyridine binding sites, located on cell membranes. The contraction of cardiac muscle and vascular smooth muscle are dependent on the movement of extracellular calcium ions into these cells by specific ion channels. Norfan blocks calcium ion influx across cell membranes with selectivity. A stronger effect of amlodipine is exerted on vascular smooth muscle cells than on cardiac muscle cells . Direct actions of amlodipine on vascular smooth muscle result in reduced blood pressure .

Mechanism of action in angina

The exact mechanism by which amlodipine relieves the symptoms of angina have not been fully elucidated to this date, however, the mechanism of action is likely twofold:

Norfan has a dilating effect on peripheral arterioles, reducing the total peripheral resistance (afterload) against which the cardiac muscle functions. Since the heart rate remains stable during amlodipine administration, the reduced work of the heart reduces both myocardial energy use and oxygen requirements .

Dilatation of the main coronary arteries and coronary arterioles, both in healthy and ischemic areas, is another possible mechanism of amlodipine reduction of blood pressure. The dilatation causes an increase in myocardial oxygen delivery in patients experiencing coronary artery spasm (Prinzmetal's or variant angina) and reduces coronary vasoconstriction caused by smoking .

Dosage

Norfan dosage

For treatment of both hypertension and angina pectoris, the usual initial dose is 5 mg once daily. If the desired therapeutic effect cannot be achieved within 2-4 weeks, the dose may be increased to a maximum dose of 10 mg once daily. Norfan 10 mg once daily provides symptomatic improvement in patients with Raynaud's disease.

Use in children: Use of Norfan in children (under 12 years of age) is not recommended.

Side Effects

Norfan is generally well tolerated. The most commonly observed side effects are headache, peripheral oedema, palpitations, flushing, dizziness, nausea, abdominal pain.

Toxicity

Acute oral toxicity (LD50): 37 mg/kg (mouse) .

Overdose

An overdose of amlodipine could result in a high degree of peripheral vasodilatation with a possibility of reflex tachycardia. Significant and prolonged hypotension leading to shock and fatal outcomes have been reported .

Carcinogenesis, mutagenesis, impairment of fertility

Rats and mice treated with amlodipine maleate in the diet on a long-term basis for up to 2 years demonstrated no evidence of a carcinogenic effect of the drug. For the mouse, the highest dose was comparable to the maximum recommended human dose of 10 mg amlodipine per day. For the rat, the highest dose was measured to be about twice the maximum recommended human dose .

Mutagenicity studies using amlodipine maleate showed no drug-related gene or chromosomal effects .

There was no impact on the fertility of rats given oral amlodipine maleate (males for 64 days and females for 14 days before mating) at doses up to 10 mg amlodipine/kg/day (8 times the maximum recommended human dose) .

Use in pregnancy

The safety of amlodipine in human pregnancy or lactation has not been proven. Norfan is therefore considered a pregnancy category C drug . Use amlodipine only if the potential benefit justifies the potential risk .

Use in nursing

Discontinue when administering amlodipine .

Precaution

Hypotension: Since the vasodilUse in renal failure

Although Norfan is excreted primarily via kidney, mild renal impairment does not appear to have an effect on the plasma concentrations. Severe renal impairment may however require a dosage reduction. Norfan is not dialyzable.

Use in patients with impaired hepatic function

Norfan half-life is prolonged in patient with impaired hepatic function. Norfan should therefore be administered at lower (5mg) initial dose in these patients.

Use in heart failure

An increased number of pulmonary oedema has been reported.atation induced by Norfan is gradual in onset, acute hypotension has rarely been reported after oral administration of Norfan. Nonetheless, caution should be exercised when administering the drug with any other peripheral vasodilator particularly in patients with severe aortic stenosis.

Cardiac failure: Patients with heart failure should be treated with caution. Calcium channel blockers, including Norfan, should be usedwith caution in patients with congestive heart failure, as they may increase the risk of future cardiovascular events and mortality.

Beta blocker withdrawal: Norfan gives no protection against the danger of abrupt beta blocker withdrawal; any such withdrawal should be gradualreduction of the dose of beta blocker.

Hepatic failure: The half-life of amlodipine is prolonged and AUC values are higher in patients with impaired liver function. Norfan should therefore be initiated at the lower end of the dosing range and caution should be used, both on initial treatment and when increasing the dose. Slow dose titration and careful monitoring may be required in patients with severe hepatic impairment.

Interaction

Use of Norfan together with thiazide diuretics or angiotensin-converting-enzyme inhibitors in the treatment of hypertension is additive. There are no hazardous interaction of Norfan with Digoxin, Cimetidine, Warfarin and food.

Food Interaction

• Avoid grapefruit products.
• Avoid natural licorice.
• Take with or without food. The absorption is unaffected by food.

[Minor] The consumption of grapefruit juice may slightly increase plasma concentrations of amlodipine.

The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

Data have been conflicting and the clinical significance is unknown.

Monitoring for calcium channel blocker adverse effects (e.g., headache, hypotension, syncope, tachycardia, edema) is recommended.

Norfan multivitamins interaction

[Moderate] Calcium-containing products may decrease the effectiveness of calcium channel blockers by saturating calcium channels with calcium.

Calcium chloride has been used to manage acute severe verapamil toxicity.

Management consists of monitoring the effectiveness of calcium channel blocker therapy during coadministration with calcium products.

Norfan Drug Interaction

Moderate: aspirin, aspirin, aspirin, aspirin, atorvastatin, atorvastatin, metoprolol, metoprolol, metoprolol, metoprololUnknown: rosuvastatin, rosuvastatin, omega-3 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acids, cyanocobalamin, cyanocobalamin, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol

Norfan Disease Interaction

Major: cardiogenic shock/hypotension, coronary artery disease, liver diseaseModerate: CHF/AMI

Volume of Distribution

21 L/kg , .

Elimination Route

Norfan absorbed slowly and almost completely from the gastrointestinal tract. Peak plasma concentrations are achieved 6-12 hours after oral administration. The estimated bioavailability of amlodipine is 64-90%. Steady-state plasma amlodipine levels are achieved after 7-8 days of consecutive daily dosing. Absorption is not affected by food .

Half Life

The terminal elimination half-life of about 30–50 hours .

Plasma elimination half-life is 56 hours in patients with impaired hepatic function, titrate slowly when administering this drug to patients with severe hepatic impairment .

Clearance

Total body clearance (CL) has been calculated as 7 ± 1.3 ml/min/kg (0.42 ± 0.078 L/ h/kg) in healthy volunteers , .

Elderly patients show a reduced clearance of amlodipine with an AUC (area under the curve) increase of about 40–60%, and a lower initial dose may be required .

Elimination Route

Elimination from the plasma occurs in a biphasic with a terminal elimination half-life of about 30–50 hours. Steady-state plasma levels of amlodipine are reached after 7-8 days of consecutive daily dosing . Norfan is 10% excreted as unchanged drug in the urine. Norfan can be initiated at normal doses in patients diagnosed with renal failure , .

Pregnancy & Breastfeeding use

Pregnancy: Safety in pregnancy has not been established.

Lactation: It is not known whether Norfan is excreted in breast milk. It is advised to stop breastfeeding during treatment with Norfan.

Contraindication

Norfan is contraindicated in patients with-

• Hypersensitivity to amlodipine, dihydropyridine derivatives or any of the excipients
• Shock (including cardiogenic shock)
• Obstruction of the outflow-tract of the left ventricle (e.g. high grade aortic stenosis)
• Unstable angina
• Hemodynamically unstable heart failure after acute myocardial infarction (during the first 28 days)
• Severe hypotension

Special Warning

Children with hypertension from 6 years to 17 years of age: 2.5 mg once daily as a starting dose, up-titrated to 5 mg once daily if blood pressure goal is not achieved after 4 weeks. Doses in excess of 5 mg daily have not been studied in pediatric patients.

Children under 6 years old: The effect of amlodipine on blood pressure in patients less than 6 years of age is not known.

Elderly: Norfan used at similar doses in elderly or younger patients is equally well tolerated. Normal dosage regimens are recommended in the elderly, but increase of the dosage should take place with care.

Renal impairment: Changes in amlodipine plasma concentrations are not correlated with degree of renal impairment, therefore the normal dosage is recommended. Norfan is not dialysable.

Hepatic impairment: Dosage recommendations have not been established in patients with mild to moderate hepatic impairment; therefore dose selection should be cautions and should start at the lower end of the dosing range. The pharmacokinetics of Norfan have not been studied in severe hepatic impairment. Norfan should be initiated at the lowest dose (2.5 mg once daily) and titrated slowly in patients with severe hepatic impairment.

Acute Overdose

There is no well documented experience with Norfan overdosage. In case of clinically significant hypotension due to Norfan over dosage, calls for active cardiovascular support including monitoring of cardiac and respiratory function, elevation of extremities and attention to circulating fluid volume and urine output. Since Norfan is highly protein-bound, dialysis is unlikely to be of benefit.

Storage Condition

Keep out of the reach of children. Store below 30° C. Keep in the original package in a cool & dry place in order to protect from light and moisture.

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