Amiloride Hydrochloride Tablets

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Amiloride Hydrochloride Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of amiloride hydrochloride (C₆H₈ClN₇O · HCl).

2 IDENTIFICATION

A. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

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B. The UV spectrum of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay. (USP 1-Dec-2022)

3 ASSAY

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3.1 Procedure

Buffer: Dissolve 136 g of monobasic potassium phosphate in 800 mL of water. Adjust with phosphoric acid to a pH of 3.0. Dilute with water to 1000 mL.

Mobile phase: Methanol, water, and Buffer (25:71:4)

Standard stock solution: 1.0 mg/mL of USP Amiloride Hydrochloride RS in methanol

Standard solution: 0.1 mg/mL of USP Amiloride Hydrochloride RS from the Standard stock solution, prepared as follows. Transfer 5.0 mL of the Standard stock solution to a 50-mL volumetric flask. Add 10.0 mL of methanol and 2.0 mL of 0.1 N hydrochloric acid. Dilute with water to volume.

Sample solution: Nominally 0.1 mg/mL of amiloride hydrochloride prepared as follows. (USP 1-Dec-2022) Transfer an amount equivalent to 5mg of amiloride hydrochloride, from finely powdered Tablets (NLT 20), to a 50-mL volumetric flask containing 15.0 mL of methanol and 2.0mL of 0.1 N hydrochloric acid. Sonicate for 10 min, dilute with water to volume, sonicate for an additional 10 min, and filter.

3.2 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 286 nm. For Identification B, use a diode array detector in the range of 190–400 nm. (USP 1-Dec-2022)

Column: 3.9-mm × 30-cm; 10-μm (USP 1-Dec-2022) packing L1

Flow rate: 1 mL/min

Injection volume: 10 μL

3.3 System suitability

3.4 Sample: Standard solution

3.5 Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

3.6 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of amiloride hydrochloride (C₆H₈ClN₇O · HCl) in the portion of Tablets taken:

Result = (r_u/r_s) × (C_s/C_u)   × 100

r_u = peak response of amiloride from the Sample solution

r_s = peak response of amiloride from the Standard solution

C_s = concentration of USP Amiloride Hydrochloride RS in the Standard solution (mg/mL)

C_u = nominal concentration of amiloride hydrochloride in the Sample solution (mg/mL)

Acceptance criteria: 90.0%-110.0%

4 PERFORMANCE TESTS

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Dissolution 〈711〉

Medium: 0.1 N hydrochloric acid; 900 mL

Apparatus 2: 50 rpm

Time: 30 min

4.1 Instrumental conditions

Mode: UV

Analytical wavelength: 363 nm

Standard solution: A known concentration of USP Amiloride Hydrochloride RS in Medium. [Note-An amount of methanol not to exceed 2% of the total volume of the Standard solution may be used to dissolve the amiloride hydrochloride.]

Sample solution: Sample per Dissolution 〈711〉. Dilute with Medium as necessary.

4.2 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of amiloride hydrochloride (C₆H₈ClN₇O · HCl) dissolved:

Result = (A_u/A_s) × C_s× V × D × (1/L) × 100

A_u = absorbance of the Sample solution

A_s = absorbance of the Standard solution

C_s = concentration of USP Amiloride Hydrochloride RS in the Standard solution (mg/mL)

V = volume of Medium, 900 mL

D = dilution factor, if needed

L = label claim of amiloride hydrochloride (mg/Tablet) (USP 1-Dec-2022)

Tolerances: NLT 80% (Q) of the labeled amount of amiloride hydrochloride (C₆H₈ClN₇O · HCl) is dissolved.

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Uniformity of Dosage Units 〈905〉: Meet the requirements (USP 1-Dec-2022)

5 IMPURITIES

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5.1 Organic Impurities

Diluent: Methanol, 1 N hydrochloric acid, and water (40:4:56)

Buffer: 0.9 g/L of sodium 1-hexanesulfonate in water. Initially add water to about 90% of the volume of the flask, adjust with diluted phosphoric acid to a pH of 3.0 ± 0.1, and dilute with water to volume.

Mobile phase: Acetonitrile and Buffer (10:90)

Standard solution: 0.01 mg/mL of USP Amiloride Hydrochloride RS in Diluent

Sensitivity solution: 0.001 mg/mL of USP Amiloride Hydrochloride RS in Diluent, from the Standard solution (USP 1-Dec-2022)

Sample solution: Nominally 2 mg/mL of amiloride hydrochloride in Diluent from powdered Tablets (NLT 20). Initially add methanol to fill about 40% of the volume of the flask and 1 N hydrochloric acid to about 4% of the volume of the flask. Sonicate for 10 min, dilute with water to volume, and sonicate for another 10 min. Pass through a suitable filter of 0.45-μm pore size.

5.2 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 350 nm

Column: 4.6-mm × 15-cm; 4-μm packing L1

Flow rate: 2 mL/min

Injection volume: 10 μL

5.3 System suitability

Samples: Standard solution and Sensitivity solution (USP 1-Dec-2022)

5.4 Suitability requirements

Relative standard deviation: NMT 3.0%, Standard solution

Signal-to-noise ratio: NLT 10, Sensitivity solution (USP 1-Dec-2022)

5.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each individual impurity in the portion of Tablets taken:

Result = (r_u/r_s) × (C_s/C_u) × (1/F) × 100

r_u = peak response of each impurity from the Sample solution

r_s = peak response of amiloride from the Standard solution

C_s = concentration of USP Amiloride Hydrochloride RS in the Standard solution (mg/mL)

C_u = nominal concentration of amiloride hydrochloride in the Sample solution (mg/mL)

F = relative response factor (see Table 1) (USP 1-Dec-2022)

Acceptance criteria: See Table 1. The reporting threshold is 0.05%. (USP 1-Dec-2022)

Table 1

^a 3,5-Diamino-6-chloropyrazine-2-carboxylic acid. (USP 1-Dec-2022)

^b Methyl 3,5-diamino-6-chloropyrazine-2-carboxylate. (USP 1-Dec-2022)

^c 3-Amino-N-carbamimidoyl-6-chloro-5-hydroxypyrazine-2-carboxamide hydrochloride. (USP 1-Dec-2022)

^d Total impurities is the sum of all the impurities including process-related ones.  (USP 1-Dec-2022)

6 ADDITIONAL REQUIREMENTS

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Packaging and Storage: Preserve in well-closed containers at controlled room temperature. (USP 1-Dec-2022)

USP Reference Standards 〈11〉

USP Amiloride Hydrochloride RS