Thioridazine 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

Thioridazine Hydrochloride Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of thioridazine hydrochloride.

Throughout the following procedures, protect samples, the Reference Standard, and the solutions containing them by conducting the procedures without delay, under subdued light, or by using low-actinic glassware.

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.

3 ASSAY

Procedure

Mobile phase: Acetonitrile, water, and triethylamine (850:150:1)

System suitability solution: 0.1 mg/mL of USP Mesoridazine Besylate RS and 0.11 mg/mL of USP Thioridazine Hydrochloride RS in methanol

Standard solution: 125 μg/mL of USP Thioridazine Hydrochloride RS in methanol. Sonication may be used to aid dissolution.

Sample stock solution: Nominally 1.0 mg/mL prepared as follows. Weigh and finely powder NLT 20 Tablets. Transfer a weighed portion of the powder, equivalent to 100 mg of thioridazine hydrochloride, to a 100-mL volumetric flask. Add 80 mL of methanol, and shake by mechanical means for 30 min. Dilute with methanol to volume, and sonicate for 45 min with intermittent shaking. Allow the undissolved solids to settle, and filter, discarding the first 20 mL of the ltrate.

Sample solution: 125 μg/mL in methanol from a portion of filtrate from the Sample stock solution. Pass through a suitable filter of 0.45-μm pore size.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 265 nm

Column: 4.6-mm × 25-cm; packing L1

Flow rate: 2.5 mL/min

Injection volume: 10 μL

System suitability

Samples: System suitability solution and Standard solution

[Note—The relative retention times for mesoridazine and thioridazine are 0.44 and 1.0, respectively.]

Suitability requirements

Resolution: NLT 1.0 between mesoridazine and thioridazine, System suitability solution

Relative standard deviation: NMT 2.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of thioridazine hydrochloride in the portion of Tablets taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of thioridazine from the Sample solution

r_S = peak response of thioridazine from the Standard solution

C_S = concentration of USP Thioridazine Hydrochloride RS in the Standard solution (μg/mL)

C_U = nominal concentration of thioridazine hydrochloride in the Sample solution (μg/mL)

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Dissolution 〈711〉

Medium: 0.01 N hydrochloric acid; 1000 mL

Apparatus 2: 75 rpm

Time: 60 min

Sample solution: Pass a portion of the solution under test through a suitable filter. Dilute with Medium, if necessary, to a concentration similar to that of the Standard solution.

Standard solution: USP Thioridazine Hydrochloride RS in Medium at a known concentration

Instrumental conditions

(See Ultraviolet-Visible Spectroscopy 〈857〉.)

Mode: UV

Analytical wavelength: 262 nm

Blank: Medium

Tolerances: NLT 75% (Q) of the labeled amount of thioridazine hydrochloride is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers.

USP Reference Standards 〈11〉

USP Mesoridazine Besylate RS

USP Thioridazine Hydrochloride RS