Flashcards
Calcium Channel Blockers
Flashcards do conjunto (4)
- 1Give eg's of & indications for calcium channel blockers.eg's: amlodipine, nifedipine, diltiazem, verapamil
Indications:
• Amlodipine, & to a lesser extent nifedipine, for 1st or 2nd line Rx of HT
• Stable angina - β-blockers are the main alternative
• Supraventricular arrhythmias - inc SVT, atrial flutter, AF - 2MOA of calcium channel blockers.Calcium channel blockers decrease Ca2+ entry into vascular & cardiac cells, reducing intracellular calcium concentration. This causes relaxation & vasodilation in arterial smooth muscle, lowering arterial pressure. In the HT, calcium channel blockers reduce myocardial contractility. They suppress cardiac conduction, particularly across the AV node, slowing ventricular rate. Reduced cardiac rate, contractility & afterload reduce myocardial oxygen demand, preventing angina. Calcium channel blockers can broadly be divided into two classes. Dihydropyridines, including amlodipine & nifedipine, are relatively selective for the vasculature, whereas non-dihydropyridines are more selective for the HT. Of the non-dihydropyridines, verapamil is the most cardioselective, whereas diltiazem also has some effects on the vessels.
- 3SE 's of calcium channel blockers.Amlodipine, diltiazem, nifedipine:
• Ankle swelling
• Flushing
• Headache
• Palpitations
Verapimil, diltiazem:
• Constipation
• Bradycardia
• HT block
• Cardiac failure - 4CI's, cautions, and important interactions of calcium channel blockers.CI's:
Amlodipine, nifedipine -
• Unstable angina
• Severe aortic stenosis
Cautions:
Verapimil, diltiazem -
• Poor L ventricular function
• AV nodal conduction delay
Important interactions:
Non-dihydropyridine calcium channel blockers (verapamil and diltiazem) should not be prescribed with β-blockers except under close specialist supervision. Both drug classes are negatively inotropic & chronotropic, & together may cause HF, bradycardia, & even asystole.