Four simple procedures for the assay of methdilazine in bulk drug and in tablets and syrup using potassium iodate.

Four simple, selective, accurate and reproducible procedures are described for the assay of methdilazine in bulk form and in formulations. One titrimetric and three spectrophotometric methods are based on the oxidation of the drug with potassium iodate, and determination of either excess iodate or iodine released in the reaction. In the titrimetric method (Method A) the drug is reacted with a known excess of iodate in sulphuric acid medium followed by the iodometric determination of residual oxidant. The residual oxidant is determined by reacting it with variamine blue and measuring the absorbance of the oxidised dye at 540 nm (Method B). The second spectrophotometric method (Method C) is based on the oxidation of the drug in sulphuric acid medium in the presence of chloride ions by a large excess of iodate and the iodate being reduced to iodine. The ICl(2)(-) generated in this reaction is used to iodinate 2',7'-dichlorofluorescein dye, and the red colour of the iodinated dye is measured at 525 nm. The other spectrophotometric method (Method D) also involves the oxidation of the drug in acid medium by a large excess of iodate with the liberation of iodine and its subsequent extraction with carbon tetrachloride followed by measuring the absorbance 520 nm. The methods were successfully applied to the determination of methdilazine in tablets and syrup and the results obtained in agreement with the label claim.