Propylthiouracil Tablets

General Notices

Action and use

Thiourea antithyroid drug.

Definition

Propylthiouracil Tablets contain Propylthiouracil.

The tablets comply with the requirements stated under Tablets and with the following requirements.

Content of propylthiouracil, C7H10N2OS

92.5 to 107.5% of the stated amount.

Identification

A. Shake a quantity of the powdered tablets containing 50 mg of Propylthiouracil with 20 mL of methanol for 10 minutes, filter and evaporate to dryness. The infrared absorption spectrum of the residue, Appendix II A, is concordant with the reference spectrum of propylthiouracil (RS 300).
B. Shake a quantity of the powdered tablets containing 50 mg of Propylthiouracil with 60 mL of methanol for 20 minutes, dilute to 100 mL with methanol and filter. Dilute 5 mL of this solution to 250 mL with methanol. The light absorption of the resulting solution, Appendix II B, in the range 230 to 350 nm exhibits a maximum only at 274 nm.
C. Extract a quantity of the powdered tablets in a continuous extraction apparatus with ether and evaporate the solution to dryness. The melting point of the residue, after drying at 105°, is about 219°, Appendix V A.

Related substances

Carry out the method for thin-layer chromatography, Appendix III A, using silica gel GF254 as the coating substance and a mixture of 0.2 volume of glacial acetic acid, 12 volumes of propan-2-ol and 100 volumes of chloroform as the mobile phase. Apply separately to the plate 10 µL of each of the following solutions. For solution (1) shake a quantity of the powdered tablets containing 50 mg of Propylthiouracil with 5 mL of methanol for 15 minutes, filter and use the filtrate. For solution (2) dilute 1 volume of solution (1) to 100 volumes with methanol. Solution (3) contains 0.0010% w/v of thiourea in methanol. After removal of the plate, allow it to dry in air, examine under ultraviolet light (254 nm) and expose to iodine vapour for 10 minutes. Any spot corresponding to thiourea in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (3) (0.1%) and any other secondary spot is not more intense than the spot in the chromatogram obtained with solution (2) (1%). Disregard any spot remaining on the line of application.

Assay

Weigh and powder 20 tablets. Dissolve a quantity of the powder containing 0.15 g of Propylthiouracil in a mixture of 20 mL of 0.1m sodium hydroxide VS and 75 mL of water with the aid of gentle heat. Cool, add 4 g of sodium acetate, just acidify the solution to litmus paper with 6m acetic acid, add 0.5 mL of a freshly prepared 0.5% w/v solution of 1,5-diphenylcarbazone in ethanol (96%) and titrate with 0.02m mercury nitrate VS until a pinkish violet colour persists for 2 to 3 minutes. Each mL of 0.02m mercury nitrate VS is equivalent to 6.808 mg of C7H10N2OS.