CALAN SR (verapamil hydrochloride) is a calcium ion influx inhibitor (slow-channel blocker or calcium ion antagonist). CALAN SR is available for oral administration as light green, capsule-shaped, scored, film-coated tablets (caplets) containing 240 mg of verapamil hydrochloride; as light pink, oval, scored, film-coated tablets (caplets) containing 180 mg of verapamil hydrochloride; and as light violet, oval, film-coated tablets (caplets) containing 120 mg of verapamil hydrochloride. The caplets are designed for sustained release of the drug in the gastrointestinal tract; sustained-release characteristics are not altered when the caplet is divided in half.
The structural formula of verapamil HCl is:
Benzeneacetonitrile, α-[3-[[2-(3,4-dimethoxyphenyl)ethyl]methylamino]propyl]-3,4-dimethoxy-α-(1-methylethyl) hydrochloride
Verapamil HCl is an almost white, crystalline powder, practically free of odor, with a bitter taste. It is soluble in water, chloroform, and methanol. Verapamil HCl is not chemically related to other cardioactive drugs.
Inactive ingredients include alginate, carnauba wax, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polyvinyl pyrrolidone, talc, titanium dioxide, and coloring agents: 240 mg—D&C Yellow No. 10 Lake and FD&C Blue No. 2 Lake; 120 and 180 mg—iron oxide.