Selective spectrophotometric determination of diltiazem hydrochloride in tablets.

Diltiazem hydrochloride (Ia) is an important coronary vasodilator drug of the calcium channel-blocker type, used in therapy of heart disease and hypertension. The compound is (+)-5-[2-(dimethylamino)ethyl]-c&, 2,3dihydro3-hydroxy-2-(p-methoxyphenyl)-1,5-benzothiazepin-4(5H)-one acetate monohydrochloride. The drug and its tablet formulations are official in the USP [l] wherein they are estimated by an HPLC method. The other methods for its estimation include GC [2, 31 HPLC [4, 51 and titrimetry [6]. The ferric hydroxamate method is one of the most widely used methods in spectrophotometric analysis of drugs with an ester functionality [7-l 11. Diltiazem hydrochloride contains an acetate moiety and hence is amenable to quantification by the above method. The present work describes the optimization of conditions for the determination of diltiazem in its tablet formulation by the ferric hydroxamate method.