Co-danthrusate Capsules
Action and use
Stimulant laxative.
Definition
Co-danthrusate Capsules contain Dantron and Docusate Sodium in the proportions, by weight, 5 parts to 6 parts.
Content of dantron, C14H8O4
90.0 to 110.0% of the stated amount.
Content of docusate sodium, C20H37NaO7S
90.0 to 110.0% of the stated amount.
Identification
15 volumes of methanol and 85 volumes of ethyl acetate.
The two principal spots in the chromatogram obtained with solution (1) correspond to the principal spots in the chromatograms obtained with solutions (2) and (3).
TEST
Related substances
Carry out the method for liquid chromatography, Appendix III D, using the following solutions.
2.5 volumes of glacial acetic acid, 40 volumes of tetrahydrofuran and 60 volumes of water.
The test is not valid unless, in the chromatogram obtained with solution (3):
a peak due to 1-hydroxyanthraquinone appears immediately before the principal peak, as indicated in the reference chromatogram supplied with dantron impurity standard BPCRS;
the height of the trough separating the two peaks is not greater than one third of the height of the peak due to 1-hydroxyanthraquinone.
In the chromatogram obtained with solution (1):
the area of any peak corresponding to 1-hydroxyanthraquinone is not greater than 2.5 times the area of the principal peak in the chromatogram obtained with solution (2) (3.3% taking into account the correction factor for the impurity);
the sum of the areas of any other secondary peaks is not greater than the area of the principal peak in the chromatogram obtained with solution (2) (2%).
Disregard any peak with a retention time less than one third of that of the principal peak.
Assay
For dantron
To a quantity of the mixed contents of 20 capsules containing 35 mg of Dantron add 50 mL of absolute ethanol, heat on a water bath for 30 minutes and cool. Add sufficient absolute ethanol to produce 100 mL and filter through glass-fibre paper (Whatman GF/C is suitable). Dilute 5 mL of the filtrate to 100 mL with absolute ethanol and measure the absorbance of the resulting solution at the maximum at 430 nm, Appendix II B. Calculate the content of C14H8O4 taking 458 as the value of A(1%, 1 cm) at the maximum at 430 nm.
For docusate sodium
To a quantity of the mixed contents of 20 capsules containing 0.3 g of Docusate Sodium add 25 mL of absolute ethanol, heat to 60° for 5 minutes and cool. Add sufficient water to produce 200 mL and filter through glass-fibre paper (Whatman GF/C is suitable). To 25 mL of the filtrate add 10 mL of water and 15 mL of chloroform and titrate with 0.004m benzethonium chloride VS, using dimidium bromide-sulfan blue mixed solution as indicator, to the first appearance of a green colour in the chloroform layer and shaking vigorously towards the end point. Each mL of 0.004m benzethonium chloride VS is equivalent to 1.778 mg of C20H37NaO7S.