Amiloride Tablets

General Notices

Action and use

Sodium channel blocker; potassium-sparing diuretic.

Definition

Amiloride Tablets contain Amiloride Hydrochloride Dihydrate.

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

Content of anhydrous amiloride hydrochloride, C6H8ClN7O,HCl

90.0 to 110.0% of the stated amount.

Identification

A. Extract a quantity of the powdered tablets containing the equivalent of 0.5 mg of anhydrous amiloride hydrochloride with 100 mL of 0.1m hydrochloric acid and filter. The light absorption of the filtrate, Appendix II B, in the range 230 to 380 nm exhibits two maxima, at 285 nm and at 361 nm.
B. In the test for Related substances, the principal peak in the chromatogram obtained with solution (1) has the same retention time as the principal peak in the chromatogram obtained with solution (5).

TEST

Related substances

Carry out the method for liquid chromatography, Appendix III D, using the following solutions in a mixture of 1 volume of acetonitrile and 3 volumes of water.

(1) Shake a quantity of the powdered tablets containing the equivalent of 17.5 mg of anhydrous amiloride hydrochloride with 10 mL of a mixture of 1 volume of acetonitrile and 3 volumes of water, disperse with the aid of ultrasound for 5 minutes and centrifuge.
(2) Dilute 1 volume of solution (1) to 100 volumes.
(3) Dilute 1 volume of solution (2) to 10 volumes.
(4) 0.0010% w/v of methyl 3,5-diamino-6-chloropyrazine-2-carboxylate BPCRS.
(5) 0.175% w/v of amiloride hydrochloride BPCRS.
chromatographic conditions
(a) Use a stainless steel column (25 cm × 4.6 mm) packed with end-capped octadecylsilyl silica gel for chromatography (5 µm) (Nucleosil C18 is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 1 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 254 nm.
(f) Inject 20 µL of each solution.
(g) Allow the chromatography to proceed for 5 times the retention time of the peak due to amiloride.
mobile phase

5 volumes of tetramethylammonium hydroxide solution, 250 volumes of acetonitrile and 745 volumes of water, the pH of the mixture being adjusted to 7.0 using a mixture of 1 volume of orthophosphoric acid and 9 volumes of water.

Adjust the concentration of acetonitrile so that, in the chromatogram obtained with solution (4), the retention time of methyl 3,5-diamino-6-chloropyrazine-2-carboxylate is 5 to 6 minutes (an increase in the concentration of acetonitrile reduces the retention time). Adjust the concentrations of tetramethylammonium hydroxide and orthophosphoric acid so that, in the chromatogram obtained with solution (2), the retention time of amiloride is 9 to 12 minutes keeping the pH at 7.0 (an increase in the concentrations reduces the retention time).

system suitability

The test is not valid unless, in the chromatogram obtained with solution (3), the signal-to-noise ratio of the peak due to amiloride in the chromatogram obtained is at least 5.0.

limits

In the chromatogram obtained with solution (1):

the sum of the areas of any secondary peaks is not greater than the area of the peak due to methyl 3,5-diamino-6-chloropyrazine-2-carboxylate in the chromatogram obtained with solution (4) (0.6%).

Disregard any peak with an area less than 0.1 times the area of the peak due to methyl 3,5-diamino-6-chloropyrazine-2-carboxylate in the chromatogram obtained with solution (4) (0.06%).

Assay

Weigh and powder 20 tablets. To a quantity of the powder containing the equivalent of 10 mg of anhydrous amiloride hydrochloride add 10 mL of methanol and shake for 10 minutes. Add 60 mL of 0.1m sodium hydroxide, shake for 30 minutes and dilute to 100 mL with 0.1m sodium hydroxide. Immediately transfer 4 mL of the resulting solution to a stoppered centrifuge tube and add 10 mL of 0.1m sodium hydroxide and 20 mL of tributyl orthophosphate that has been washed with water before use. Shake vigorously for 2 minutes and centrifuge for 5 minutes. Remove the upper layer and repeat the extraction with a further 20 mL of the water-washed tributyl orthophosphate. To the combined extracts add 2 mL of methanol and sufficient of the water-washed tributyl orthophosphate to produce 50 mL and centrifuge to remove traces of water. Measure the absorbance of the resulting solution at the maximum at 363 nm, Appendix II B, using in the reference cell a mixture of 48 volumes of the water-washed tributyl orthophosphate and 2 volumes of methanol. Calculate the content of C6H8ClN7O,HCl taking 692 as the value of A(1%, 1 cm) at the maximum at 363 nm.

Labelling

The quantity of active ingredient is stated in terms of the equivalent amount of anhydrousamiloride hydrochloride.