Verapamil (VRP)

Verapamil is an L-type calcium channel blocker of the phenylalkylamine class. It has been used in the treatment of hypertension, angina pectoris, cardiac arrhythmia, and most recently, cluster headaches. It is also an effective preventive medication for migraine. Verapamil has also been used as a vasodilator during cryopreservation of blood vessels. Verapamil's mechanism in all cases is to block voltage-dependent calcium channels. In cardiac pharmacology, calcium channel blockers are considered class IV antiarrhythmic agents. Since calcium channels are especially concentrated in the sinoatrial and atrio-ventricular nodes, these agents can be used to decrease impulse conduction through the AV node, thus protecting the ventricles from atrial tachyarrhythmias. Calcium channels are also present in the smooth muscle that lines blood vessels.