Spectrophotometric determination of ritodrine and isoxsuprine hydrochlorides using 4-aminoantipyrine.

A simple, accurate, and rapid method for the quantitative determination of ritodrine hydrochloride (RTH) and isoxsuprine hydrochloride (ISH) in both pure and dosage forms, is described. The method is based on the development of pink colored product as a result of the condensation of 4-aminoantipyrine with phenols in the presence of an alkaline oxidizing agent. The resulting products are measured at 510 nm for both drugs, with molar absorptivities of 0.98 x 10(4) and 1.20 x 10(4) L/mol x cm for RTH and ISH, respectively. A study of the effect of commonly associated excipients revealed that they did not cause interference.