Verapamil

Verapamil:
• blocks calcium channels in heart and arteries
• in peripheral vessels  dilation  reduction in arterial pressure
• in heart  increased coronary perfusion (dilation of arterioles), blockage at SA node (reduces heart rate), blockage at AV node (decreases conduction), blockage at myocardium (decrease contractile force)
• but, lowering of blood pressure  activation of baroceptor reflex  sympathetic nerves to heart are activated  increase in heart rate, increase in AV node conduction and force of contraction  negates the direct effects of verapamil on the heart  no or minimal affect on cardiac function  main effect of verapamil is peripheral vasodilation
• indicated for essential hypertension (first line drug), angina pectoris (commonly used) and dysrhythmias
• adverse effects – constipation, dizziness, facial flushing, headache, ankle oedema

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