Calcium channel blockers

Symposium on : Antihypertensive drugs..

Presented by :AASHNA DHINGRA

Roll no. 03Batch 2010

INTRODUCTION CLASSIFICATION

MECHANISM OF ACTION

PHARMACOLOGICAL ACTIONS

PHARMACOKINETICS

USES

ADVERSE EFECTS

CONTRAINDICATIONS

SUMMARY

Layout of the presentation :

INTRODUCTION..also known as calcium antagonists.

prevent calcium from infiltrating the cells of the heart and blood vessel walls.

relaxes and widens blood vessels of the heart within the arterial walls, promoting lowered blood pressure.

may also slow the heart rate, relieve chest pressure and control an irregular heartbeat.

they are first line antihypertensive drugs.

the onset of antihypertensive action is quick.

monotherapy with CCBs is effective in about 50% of the hypertensives.

can also be used for treating angina.

Classification of CCBs

PHENYLAKYLAMINES Verapamil

Very 1,4-DIHYDROPYRIDINES Nifedipine

Nice

BENZOTHIAZEPINES Diltiazem

Drugs

1,4 dihydopyrimidines are selective for the arteriolar beds.

The phenylalkylamines and benzothiazepines are selective for the atrioventricular node.

Short-acting• nifedipine, dilatiazem, verapamil

Long-acting• amlodipine, felodipine, isradipine,

nicardipine, nisoldipine,

Mechanism of action..o Calcium channels are of 5 subtypes- L, N, T, P, and R.

o L-type in cardiac and smooth muscle cells.

Moa : CCBs block voltage sensitive L- type Ca channels by binding to specific site on the α-1 subunit.

Prevent entry of Ca into cell.

No excitation-coupling reaction in heart and vascular smooth muscles.

Increase the time that Ca2+ channels are

closed.

Relaxation of the arterial smooth

muscle.

Significant reduction in afterload.

Coronary vasodilatation.

PHARMACOLOGICAL ACTIONS..

PHARMACOKINECTICS..

well absorbed through Git.

first pass metabolism.

highly bound to plasma proteins.

metabolised in liver.

excreted through urine.

USES OF CCBs..1. angina pectoris - Due to decrease in myocardial oxygen

consumption, and dilatation of coronary arteries.

2. supraventicular arrhythmias - because of its depressant action on S-A and A-V nodes.

3. hypertension - they control blood pressure by their vasodilatory effect.

4. Migraine

5. raynaud’s phenomenon - due to their vasodilatory property.

ADVERSE EFFECTS..

Postural hypotension palpitation reflex tachycardia edema dizziness constipation sedation A-V block headache fatigue lowered B.P.

CONTRAINDICATIONS

o Heart failure

o Bradycardia o Atrioventricular block. o Dihydropyridine calcium-channel blockers should not be used in people with uncontrolled heart failure.

SUMMARY..

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