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Amlodipine Besylate

Pharmacology: Amlodipine is a calcium ion influx inhibitor (calcium entry blocker or calcium ion antagonist). Amlodipine is a member of the dihydropyridine class of calcium antagonists. rx canada pharmacy

Mechanism of Action: The therapeutic effect of this group of drugs is believed to be related to their specific cellular action of selectively inhibiting transmembrane influx of calcium ions into vascular smooth muscle and cardiac muscle. The contractile processes of these tissues are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels. Amlodipine inhibits calcium ion influx across cell membranes selectively, with a greater effect on vascular smooth muscle cells than on cardiac muscle cells. Serum calcium concentration is not affected by amlodipine. Within the physiologic pH range, amlodipine is an ionized compound and its kinetic interaction with the calcium channel receptor is characterized by the gradual association and dissociation with the receptor binding site. Experimental data suggest that amlodipine binds to both dihydropyridine and nondihydropyridine binding sites. rx canada pharmacy

Hypertension: The mechanism by which amlodipine reduces arterial blood pressure involves direct peripheral arterial vasodilation and reduction in peripheral vascular resistance. rx canada pharmacy

Angina: The precise mechanism by which amlodipine relieves angina has not been fully delineated. Amlodipine is a dilator of peripheral arteries and arterioles which reduces the total peripheral resistance and, therefore, reduces the workload of the heart (afterload). The unloading of the heart is thought to decrease ischemia and relieve effort angina by reducing myocardial energy oxygen consumption and oxygen requirements. rx canada pharmacy

Pharmacokinetics: After oral administration of therapeutic doses of amlodipine, absorption occurs gradually with peak plasma concentration reached between 6 and 12 hours. Absolute bioavailability has been estimated to be between 64 and 90%. The bioavailability of amlodipine is not altered by the presence of food. rx canada pharmacy

Amlodipine is metabolized through the cytochrome P450 system, mainly via CYP3A4 isoenzyme. rx canada pharmacy

Amlodipine is extensively (about 90%) converted to inactive metabolites (via hepatic metabolism) with 10% of the parent compound and 60% of the metabolites excreted in the urine. Ex vivo studies have shown that approximately 93% of the circulating drug is bound to plasma proteins in hypertensive patients. Elimination from the plasma is biphasic with a terminal elimination half-life of about 35 to 50 hours. Steady-state plasma levels of amlodipine are reached after 7 to 8 days of consecutive daily dosing. rx canada pharmacy

The pharmacokinetics of amlodipine are not significantly influenced by renal impairment. Plasma concentrations in the patients with moderate to severe renal failure were higher than in the normal subjects. Accumulation and mean elimination half-life in all patients were within the range of those observed in other pharmacokinetic studies with amlodipine in normal subjects. rx canada pharmacy

In elderly hypertensive patients (mean age 69 years) there was a decrease in clearance of amlodipine from plasma as compared to young volunteers (mean age 36 years) with a resulting increase in the area under the curve (AUC) of about 60%. rx canada pharmacy

Following single oral administration of 5 mg of amlodipine, patients with chronic mild-moderate hepatic insufficiency showed about 40% increase in AUC of amlodipine as compared to normal volunteers. This was presumably due to a reduction in clearance of amlodipine as the terminal elimination half-life was prolonged from 34 hours in young normal subjects to 56 hours in the elderly patients with hepatic insufficiency.. rx canada pharmacy

Following oral administration of 10 mg amlodipine to 20 male volunteers, pharmacokinetics of amlodipine were similar when amlodipine was administered with and without grapefruit juice. Geometric mean C _max of amlodipine was 6.2 ng/mL when the drug was administered with grapefruit juice and 5.8 ng/mL when administered with water. Mean T _max of amlodipine was 7.6 hours with grapefruit juice and 7.9 hours with water. Geometric mean AUC _0Ã¥ was 315 ng/h/mL with grapefruit juice and 293 ng/h/mL with water. Geometric mean bioavailability of amlodipine was 85% when administered with grapefruit juice and 81% when administered with water. rx canada pharmacy

Pharmacodynamics: Hemodynamics: Following administration of recommended doses to patients with hypertension, amlodipine produces vasodilation resulting in a reduction of supine and standing blood pressures. These decreases in blood pressure are not accompanied by any significant change in heart rate or plasma catecholamine levels with chronic dosing. With chronic once daily oral administration (5 and 10 mg once daily), antihypertensive effectiveness is maintained throughout the 24-hour dose interval with minimal peak to trough differences in blood pressure reduction. Since the vasodilation induced by amlodipine is gradual in onset, acute hypotension has rarely been reported after oral administration of amlodipine. In normotensive patients with angina amlodipine has not been associated with any clinically significant reductions in blood pressure or changes in heart rate. rx canada pharmacy

Negative inotropic effects have not been observed when amlodipine was administered at the recommended doses to man, but has been demonstrated in animal models. Hemodynamic measurements of cardiac function at rest and during exercise (or pacing) in angina patients with normal ventricular function have generally demonstrated a small increase in cardiac index without significant influence on dP/dt or on left ventricular end diastolic pressure or volume. rx canada pharmacy

In hypertensive patients with normal renal function, therapeutic doses of amlodipine resulted in a decrease in renal vascular resistance and an increase in glomerular filtration rate and effective renal plasma flow without change in filtration fraction. rx canada pharmacy

Electrophysiologic Effects: Amlodipine does not change sinoatrial nodal function or atrioventricular conduction in intact animals, or man. In patients with chronic stable angina, i.v. administration of 10 mg of amlodipine and a further 10 mg of amlodipine after a 30-minute interval produced peripheral vasodilation and afterload reduction, but did not significantly alter A-H and H-V conduction and sinus node recovery time after pacing. Similar results were obtained in patients receiving amlodipine and concomitant beta-blockers. In clinical studies in which amlodipine was administered in combination with beta-blockers to patients with either hypertension or angina, no adverse effects on electrocardiographic parameters were observed. In clinical trials with angina patients, amlodipine as monotherapy did not alter electrocardiographic intervals. rx canada pharmacy


Indications: Hypertension: For the treatment of mild to moderate essential hypertension. Amlodipine should normally be used in those patients in whom treatment with diuretics or beta-blockers was found ineffective or has been associated with unacceptable adverse effects. rx canada pharmacy

Amlodipine can be tried as an initial agent in those patients in whom the use of diuretics and/or beta-blockers is contraindicated or in patients with medical conditions in which these drugs frequently cause serious adverse effects. rx canada pharmacy

Combination of amlodipine with a diuretic, a beta-blocking agent or an angiotensin converting enzyme inhibitor has been found to be compatible and showed additive antihypertensive effect. rx canada pharmacy

Chronic Stable Angina: For the management of chronic stable angina (effort-associated angina) in patients who remain symptomatic despite adequate doses of beta-blockers and/or organic nitrates or who cannot tolerate those agents. rx canada pharmacy

Amlodipine may be tried in combination with beta-blockers in chronic stable angina in patients with normal ventricular function. When such concomitant therapy is introduced, care must be taken to monitor blood pressure closely since hypotension can occur from the combined effects of the drugs. rx canada pharmacy

Contraindications: Patients with hypersensitivity to the drug or other dihydropyridines and in patients with severe hypotension (less than 90 mmHg systolic). rx canada pharmacy


Warnings: Increased Angina and/or Myocardial Infarction: Rarely, patients, particularly those with severe obstructive coronary artery disease, have developed documented increased frequency, duration and/or severity of angina or acute myocardial infarction on starting calcium channel blocker therapy or at the time of dosage increase. The mechanism of this effect has not been elucidated. rx canada pharmacy

Outflow Obstruction (Aortic Stenosis): Amlodipine should be used with caution in a presence of fixed left ventricular outflow obstruction (aortic stenosis). rx canada pharmacy

Patients with Impaired Hepatic Function: There are no adequate studies in patients with liver dysfunction and dosage recommendations have not been established. In a small number of patients with mild to moderate hepatic impairment given single dose of 5 mg, amlodipine half-life has been prolonged (see Pharmacology, Pharmacokinetics). Amlodipine should, therefore, be administered with caution in these patients and careful monitoring should be performed. A lower starting dose may be required (see Dosage). rx canada pharmacy

Beta-blocker Withdrawal: Amlodipine gives no protection against the dangers of abrupt beta-blocker withdrawal and such withdrawal should be done by the gradual reduction of the dose of beta-blocker. rx canada pharmacy

Precautions: Patients With Congestive Heart Failure: Although generally calcium channel blockers should only be used with caution in patients with heart failure, it has been observed that amlodipine had no overall deleterious effect on survival and cardiovascular morbidity in both short-term and long-term clinical trials in these patients. While a significant proportion of the patients in these studies had a history of ischemic heart disease, angina or hypertension, the studies were not designed to evaluate the treatment of angina or hypertension in patients with concomitant heart failure. rx canada pharmacy

Hypotension: Amlodipine may occasionally precipitate symptomatic hypotension. Careful monitoring of blood pressure is recommended, especially in patients with a history of cerebrovascular insufficiency, and those taking medications known to lower blood pressure. rx canada pharmacy

Peripheral Edema: Mild to moderate peripheral edema was the most common adverse event in the clinical trials (see Adverse Effects). The incidence of peripheral edema was dose-dependent and ranged in frequency from 3.0 to 10.8% in 5 to 10 mg dose range. Care should be taken to differentiate this peripheral edema from the effects of increasing left ventricular dysfunction. rx canada pharmacy

Pregnancy: Although amlodipine was not teratogenic in the rat and rabbit, some dihydropyridine compounds have been found to be teratogenic in animals. In rats, amlodipine has been shown to prolong both the gestation period and the duration of labor. There is no clinical experience with amlodipine in pregnant women. Amlodipine should be used during pregnancy only if the potential benefit outweighs the potential risk to the mother and fetus. rx canada pharmacy

Lactation: It is not known whether amlodipine is excreted in human milk. Since amlodipine safety in newborns has not been established, amlodipine should not be given to nursing mothers. rx canada pharmacy

Children: The use of amlodipine is not recommended in children since safety and efficacy have not been established in that population. rx canada pharmacy

Geriatrics: In elderly patients (³ 65 years) clearance of amlodipine is decreased with a resulting increase in AUC (see Pharmacology, Pharmacokinetics). In clinical trials the incidence of adverse reactions in elderly patients was approximately 6% higher than that of younger population (<65 years). Adverse reactions include edema, muscle cramps and dizziness. Amlodipine should be used cautiously in elderly patients. Dosage adjustment is advisable (see Dosage). rx canada pharmacy

Interaction With Grapefruit Juice: Published data indicate that through inhibition of the cytochrome P450 system, grapefruit juice can increase plasma levels and augment pharmacodynamic effects of some dihydropyridine calcium channel blockers. Following oral administration of 10 mg amlodipine to 20 male volunteers, pharmacokinetics of amlodipine were similar when amlodipine was administered with and without grapefruit juice (see Pharmacology, Pharmacokinetics). rx canada pharmacy

Drug Interactions : As with all drugs, care should be exercised when treating patients with multiple medications. Dihydropyridine calcium channel blockers undergo biotransformation by the cytochrome P450 system, mainly via CYP3A4 isoenzyme. Coadministration of amlodipine with other drugs which follow the same route of biotransformation may result in altered bioavailability of amlodipine or these drugs. Dosages of similarly metabolized drugs, particularly those of low therapeutic ratio, and especially in patients with renal and/or hepatic impairment, may require adjustment when starting or stopping concomitantly administered amlodipine to maintain optimum therapeutic blood levels. rx canada pharmacy

Drugs known to be inhibitors of the cytochrome P450 system include: azole antifungals, cimetidine, cyclosporine, erythromycin, quinidine, terfenadine, warfarin. rx canada pharmacy

Drugs known to be inducers of the cytochrome P450 system include: phenobarbital, phenytoin, rifampin. rx canada pharmacy

Drugs known to be biotransformed via P450 include: benzodiazepines, flecainide, imipramine, propafenone, theophylline. rx canada pharmacy

Amlodipine has a low (rate of first-pass) hepatic clearance and consequent high bioavailability and, thus, may be expected to have a low potential for clinically relevant effects associated with elevation of amlodipine plasma levels when used concomitantly with drugs that compete for or inhibit the cytochrome P450 system. rx canada pharmacy

Cimetidine, Warfarin, Cyclosporin, Digoxin: Pharmacokinetic interaction studies with amlodipine in healthy volunteers have indicated: cimetidine did not alter the pharmacokinetics of amlodipine; amlodipine did not change warfarin-induced prothrombin response time; amlodipine does not significantly alter the pharmacokinetics of cyclosporin; amlodipine did not change serum digoxin levels or digoxin renal clearance. rx canada pharmacy

Antacids: Concomitant administration of Maalox had no effect on the disposition of a single 5 mg dose of amlodipine in 24 subjects. rx canada pharmacy

Beta-blockers: When beta-adrenergic receptor blocking drugs are administered concomitantly with amlodipine, patients should be carefully monitored since blood pressure lowering effect of beta-blockers may be augmented by amlodipine's reduction in peripheral vascular resistance. rx canada pharmacy

Sildenafil: A single 100 mg dose of sildenafil in subjects with essential hypertension had no effect on AUC _t or C _max of amlodipine. When sildenafil (100 mg) was coadministered with amlodipine, 5 or 10 mg in hypertensive patients, the mean additional reduction of supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic. rx canada pharmacy

Special Studies: Effect of amlodipine on other agents. rx canada pharmacy

Atorvastatin: In healthy volunteers, coadministration of multiple 10 mg doses of amlodipine with 80 mg of atorvastatin resulted in no significant change in the AUC _t or C _max or T _max of atorvastatin. rx canada pharmacy

Adverse Effects: Amlodipine has been administered to 1714 patients (805 hypertensive and 909 angina patients) in controlled clinical trials (vs placebo alone and with active comparative agents). Most adverse reactions reported during therapy were of mild to moderate severity. rx canada pharmacy

Hypertension: In the 805 hypertensive patients treated with amlodipine in controlled clinical trials, adverse effects were reported in 29.9% of patients and required discontinuation of therapy due to side effects in 1.9% of patients. The most common adverse reactions in controlled clinical trials were: edema (8.9%) and headache (8.3%). rx canada pharmacy

The following adverse reactions were reported with an incidence of ³ 0.5% in the controlled clinical trials program (n=805). rx canada pharmacy

Cardiovascular: edema (8.9%), palpitations (2.0%), tachycardia (0.7%), postural dizziness (0.5%). rx canada pharmacy

Skin and Appendages: pruritus (0.7%). rx canada pharmacy

Musculoskeletal: muscle cramps (0.5%). rx canada pharmacy

Central and Peripheral Nervous System: headache (8.3%), dizziness (3.0%), paresthesia (0.5%). rx canada pharmacy

Autonomic Nervous System: flushing (3.1%), increased sweating (0.9%), dry mouth (0.7%). rx canada pharmacy

Psychiatric: somnolence (1.4%). rx canada pharmacy

Gastrointestinal: nausea (2.4%), abdominal pain (1.1%), dyspepsia (0.6%), constipation (0.5%). rx canada pharmacy

General: fatigue (4.1%), pain (0.5%). rx canada pharmacy

Angina: In the controlled clinical trials in 909 angina patients treated with amlodipine, adverse effects were reported in 30.5% of patients and required discontinuation of therapy due to side effects in 0.6% of patients. The most common adverse reactions reported in controlled clinical trials were: edema (9.9%) and headache (7.8%). rx canada pharmacy

The following adverse reactions occurred at an incidence of ³ 0.5% in the controlled clinical trials program (n=909). rx canada pharmacy

Cardiovascular: edema (9.9%), palpitations (2.0%), postural dizziness (0.6%). rx canada pharmacy

Skin and Appendages: rash (1.0%), pruritus (0.8%). rx canada pharmacy

Musculoskeletal: muscle cramps (1.0%). rx canada pharmacy

Central and Peripheral Nervous System: headache (7.8%), dizziness (4.5%), paresthesia (1.0%), hypoesthesia (0.9%). rx canada pharmacy

Autonomic Nervous System: flushing (1.9%). rx canada pharmacy

Psychiatric: somnolence (1.2%), insomnia (0.9%), nervousness (0.7%). rx canada pharmacy

Gastrointestinal: nausea (4.2%), abdominal pain (2.2%), dyspepsia (1.4%), diarrhea (1.1%), flatulence (1.0%), constipation (0.9%). rx canada pharmacy

Respiratory: dyspnea (1.1%). rx canada pharmacy

Special Senses: vision abnormal (1.3%), tinnitus (0.6%). rx canada pharmacy

General: fatigue (4.8%), pain (1.0%), asthenia (1.0%). rx canada pharmacy

Amlodipine has been evaluated for safety in about 11 000 patients with hypertension and angina. The following events occurred in <1% but >0.1% of patients in comparative clinical trials (double-blind comparative vs placebo or active agents; n=2615) or under conditions of open trials or marketing experience where a causal relationship is uncertain. rx canada pharmacy

Cardiovascular: arrhythmia (including ventricular tachycardia and atrial fibrillation), bradycardia, hypotension, peripheral ischemia, syncope, tachycardia, postural dizziness, postural hypotension, vasculitis. rx canada pharmacy

Central and Peripheral Nervous System: hypoesthesia, peripheral neuropathy, tremor, vertigo. rx canada pharmacy

Gastrointestinal: anorexia, constipation, dysphagia, vomiting, gingival hyperplasia. rx canada pharmacy

General: allergic reaction, asthenia ⁺, back pain, hot flushes, malaise, rigors, weight gain. rx canada pharmacy

Musculoskeletal: arthralgia, arthrosis, myalgia. rx canada pharmacy

Psychiatric: sexual dysfunction (male ⁺ and female), insomnia, nervousness, depression, abnormal dreams, anxiety, depersonalization. rx canada pharmacy

Respiratory: epistaxis. rx canada pharmacy

Skin and Appendages: pruritus ⁺, rash erythematous, rash maculopapular, erythema multiforme. rx canada pharmacy

Special Senses: conjunctivitis, diplopia, eye pain, tinnitus. rx canada pharmacy

Urinary: micturition frequency, micturition disorder, nocturia. rx canada pharmacy

Autonomic Nervous System: dry mouth, sweating increased. rx canada pharmacy

Metabolic and Nutritional: hyperglycemia, thirst. rx canada pharmacy

Hemopoietic: leukopenia, purpura, thrombocytopenia. rx canada pharmacy

⁺These events occurred in less than 1% of patients in placebo controlled trials, but the incidence of these side effects was between 1 and 2% in all multiple dose studies. rx canada pharmacy

The following events occurred in £ 0.1% of patients: cardiac failure, skin discoloration, urticaria, skin dryness, Stevens-Johnson syndrome, alopecia, twitching, ataxia, hypertonia, migraine, apathy, amnesia, gastritis, pancreatitis, increased appetite, coughing, rhinitis, parosmia, taste perversion, and xerophthalmia. rx canada pharmacy

Isolated cases of angioedema have been reported. Angioedema may be accompanied by breathing difficulty. rx canada pharmacy

In postmarketing experience, jaundice and hepatic enzyme elevations (mostly consistent with cholestasis or hepatitis), in some cases severe enough to require hospitalization, have been reported in association with use of amlodipine. rx canada pharmacy

Overdose: Symptoms: Overdosage can cause excessive peripheral vasodilation with marked and probably prolonged hypotension and possibly a reflex tachycardia. In humans, experience with overdosage of amlodipine is limited. When amlodipine was ingested at doses of 105 to 250 mg some patients remained normotensive with or without gastric lavage while another patient experienced hypotension (90/50 mmHg) which normalized following plasma expansion. A patient who took 70 mg of amlodipine with benzodiazepine developed shock which was refractory to treatment and died. In a 19-month-old child who ingested 30 mg of amlodipine (about 2 mg/kg) there was no evidence of hypotension but tachycardia (180 bpm) was observed. Ipecac was administered 3.5 hours after ingestion and on subsequent observation (overnight) no sequelae were noted. rx canada pharmacy



Treatment: Clinically significant hypotension due to overdosage requires active cardiovascular support including monitoring of cardiac and respiratory function, elevation of extremities, and attention to circulating fluid volume and urine output. A vasoconstrictor (such as norepinephrine) may be helpful in restoring vascular tone and blood pressure, provided that there is no contraindication to its use. As amlodipine is highly protein bound, hemodialysis is not likely to be of benefit. I.V. calcium gluconate may be beneficial in reversing the effects of calcium channel blockade. Clearance of amlodipine is prolonged in elderly patients and in patients with impaired liver function. Since amlodipine absorption is slow, gastric lavage may be worthwhile in some cases. rx canada pharmacy


Dosage: Dosage should be individualized depending on patient's tolerance and responsiveness. rx canada pharmacy

For both hypertension and angina, the recommended initial dose is 5 mg once daily. If necessary, dose can be increased after 1 to 2 weeks to a maximum dose of 10 mg once daily. rx canada pharmacy

Geriatrics or Patients with Impaired Renal Function: The recommended initial dose in patients over 65 years of age or patients with impaired renal function is 5 mg once daily. If required, increasing the dose should be done gradually and with caution (see Precautions). rx canada pharmacy

Patients with Impaired Hepatic Function: Dosage requirements have not been established in patients with impaired hepatic function. When amlodipine is used in these patients, the dosage should be carefully and gradually adjusted depending on patient's tolerance and response. A lower starting dose of 2.5 mg once daily should be considered (see Warnings). rx canada pharmacy


Supplied: 5 mg: Each white, octagonal tablet, scored, debossed on one face as NRV 5 with Pfizer on the opposite face, contains: amlodipine besylate equivalent to amlodipine 5 mg. Nonmedicinal ingredients: dibasic calcium phosphate anhydrous, magnesium stearate, microcrystalline cellulose and sodium starch glycolate. White plastic (high density polyethylene) bottles of 100 and 250. rx canada pharmacy

10 mg: Each white, octagonal tablet, debossed on one face as NRV 10 with Pfizer on the opposite face, contains: amlodipine besylate equivalent to amlodipine 10 mg. Nonmedicinal ingredients: dibasic calcium phosphate anhydrous, magnesium stearate, microcrystalline cellulose and sodium starch glycolate. White plastic (high density polyethylene) bottles of 100 and 250. rx canada pharmacy


Store at 15 to 30°C. Protect from light.

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