DESCRIPTION ISOPTIN SR (verapamil hydrochloride) is a calcium ion influx inhibitor (slow channel blocker or calcium ion antagonist). ISOPTIN SR is available for oral administration as light green, capsule shaped, scored, film-coated tablets containing 240 mg verapamil hydrochloride, as light pink, oval shaped, scored, film-coated tablets containing 180 mg verapamil hydrochloride, and as light v...