Chlortalidone Tablets

Action and use

Thiazide-like diuretic.

Definition

Chlortalidone Tablets contain Chlortalidone.

Content of chlortalidone, C₁₄H₁₁ClN₂O₄S

92.5 to 107.5% of the stated amount.

Identification

Heat a quantity of the powdered tablets containing 0.2 g of Chlortalidone with 20 mL of acetone on a water bath for 10 minutes, cool and filter. Add 40 mL of water to the filtrate and heat on a water bath for 20 minutes using a gentle current of air to remove the acetone. Cool the solution to room temperature, allow to stand, filter and dry the crystals at 105° for 4 hours. The infrared spectrum of the crystals, Appendix II A, is concordant with the reference spectrum of chlortalidone (RS 058).

Related substances

Carry out the method for thin-layer chromatography, Appendix III A, using a silica gel F₂₅₄ precoated plate (Merck silica gel 60 F₂₅₄ plates are suitable) and a mixture of 5 volumes of toluene, 10 volumes of xylene, 20 volumes of 18m ammonia, 30 volumes of 1,4-dioxan and 30 volumes of propan-2-ol as the mobile phase. Apply separately to the plate 5 µL of each of the following solutions. For solution (1) add a quantity of the powdered tablets containing 0.1 g of Chlortalidone to 5 mL of ethanol (96%), mix with the aid of ultrasound for 15 minutes, centrifuge and use the supernatant liquid. For solution (2) dilute 1 volume of solution (1) to 200 volumes with ethanol (96%). Solution (3) contains 0.020% w/v of 2-(4-chloro-3-sulfamoylbenzoyl)benzoic acid BPCRS in ethanol (96%). After removal of the plate, allow it to dry in air and examine under ultraviolet light (254 nm). Any spot corresponding to 2-(4-chloro-3-sulfamoylbenzoyl)benzoic acid in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (3) (1%) and any other secondary spot is not more intense than the spot in the chromatogram obtained with solution (2) (0.5%).

Assay

Weigh and powder 20 tablets. Boil a quantity of the powder containing 0.1 g of Chlortalidone under a reflux condenser with 30 mL of methanol for 5 minutes, shake vigorously for 15 minutes, cool and filter. Wash the residue and filter with methanol and dilute the combined filtrate and washings to 100 mL with methanol. To 5 mL add 2 mL of 1m hydrochloric acid and sufficient methanol to produce 50 mL and measure the absorbance of the resulting solution at the maximum at 275 nm, Appendix II B. Calculate the content of C₁₄H₁₁ClN₂O₄S taking 57.4 as the value of A(1%, 1 cm) at the maximum at 275 nm.