ISOPTIN ® SR (verapamil hydrochloride) is a calcium ion influx inhibitor (slow channel blocker or calcium ion antagonist). Verapamil belongs to the class of medications called calcium channel blockers. The sustained release (SR) form of this medication is used for the treatment of mild-to-moderate high blood pressure, when beta-blockers or diuretics (water pills) are not recommended or have caused unacceptable side effects. The immediate-release form of verapamil may be used to treat certain abnormal heart rhythms, angina (chest pain) and certain conditions where the heart muscle is enlarged, as well as blood pressure. It works to control blood pressure and reduce the number of angina attacks by relaxing blood vessels. It also helps to normalize heart rhythms. Each light-green, scored, oblong, film-coated tablet with 2 triangles embossed on one side contains 240 mg of verapamil HCl. Nonmedicinal ingredients: hydroxypropyl methylcellulose, indigo carmine, macrogol 400, macrogol 6000, magnesium stearate, microcrystalline cellulose, montan glycol wax, povidone, purified water, quinoline yellow, sodium alginate, talc, and titanium dioxide.