Amlodipine

Amlodipine (as besylate, mesylate or maleate) is a long-acting calcium channel blocker (dihydropyridine) used as an anti-hypertensive and in the treatment of angina. As other calcium channel blockers, amlodipine acts by relaxing the smooth muscle in the arterial wall, decreasing peripheral resistance and hence reducing blood pressure; in angina it increases blood flow to the heart muscle.

Amlodipine is marketed as Norvasc® in North America and as Istin® in the United Kingdom by Pfizer as well as under various other names.

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Indications

• hypertension
• prophylaxis of angina

Cautions

• hepatic impairment
• pregnancy

Contra-indications

• cardiogenic shock
• unstable angina
• significant aortic stenosis
• breast feeding

Side effects

Some side effects^[1] of the use of amlodipine may be:

• Very often: peripheral edema (feet and ankles) - in 1 of 10 users
• Often: dizziness, palpitations, muscle, stomach or headache, dyspepsia, nausea - in 1 in 100 users
• Sometimes: blood disorders, development of breasts in men (gynecomastia), impotence, depression, insomnia, tachycardia - in 1 in 1,000 users
• Rarely: erratic behavior, hepatitis, jaundice - in 1 in 10,000 users
• Very rarely: hyperglycemia, tremor, Stevens-Johnson syndrome - in 1 in 100,000 users

Dose

• Hypertension or angina: 5 or 10 mg once daily.

Salts

In the United Kingdom tablets of amlodipine from different suppliers may contain different salts. The strength of the tablets is expressed in terms of amlodipine base. i.e. without the salt. Tablets containing different salts are therefore considered interchangeable.

Drug Metabolism and Excretion

Amlodipine is almost entirely metabolised to inactive metabolites. Ten per cent of the parent substance and 60% of the metabolites are excreted in urine.

Patent loss

Pfizer patent protection on Norvasc lasts until 2007. A number of generic versions are now available. Total patent expiration will occur later in 2007. ^[2]

References

1. ^ Source: Sandoz product information sheet
2. ^ okpatents.com/.../patent_loss_res