Thiopental Sodium for Injection

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

Thiopental Sodium for Injection is a sterile mixture of Thiopental Sodium and anhydrous Sodium Carbonate as a buffer. It contains NLT 93.0% and NMT 107.0% of the labeled amount of thiopental sodium.

2 IDENTIFICATION

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A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020)

Sample: Nominally 500 mg of thiopental sodium from Thiopental Sodium for Injection

Analysis: Dissolve the Sample in 10 mL of water in a separator, add 10 mL of 3 N hydrochloric acid, and extract the liberated thiopental with two 25-mL portions of chloroform. Evaporate the combined chloroform extracts to dryness. Add 10 mL of ether, evaporate again, and dry at 105° for 2 h.

Acceptance criteria: The IR absorption spectrum of a potassium bromide dispersion of the residue so obtained exhibits maxima only at the same wavelengths as those of a similar preparation of USP Thiopental RS.

B. Identification Tests—General, Sodium〈191〉

Sample: Nominally 500 mg of thiopental sodium from Thiopental Sodium for Injection

Analysis: Ignite the Sample.

Acceptance criteria: The residue meets the requirements.

3 ASSAY

Procedure

Diluent: 4 g/L of sodium hydroxide in water

Standard solution: 5 μg/mL of USP Thiopental RS in Diluent

Sample stock solution: Nominally 50 mg/mL of thiopental sodium from the contents of 10 containers of Thiopental Sodium for Injection dissolved in a sufficient volume of water

Sample solution: Nominally 5 μg/mL of thiopental sodium in Diluent from the Sample stock solution

Instrumental conditions

(See Ultraviolet-Visible Spectroscopy 〈857〉.)

Mode: UV

Analytical wavelength: 304 nm

Cell: 1 cm

Blank: Diluent

Analysis

Samples: Standard solution, Sample solution, and Blank

Calculate the percentage of the labeled amount of thiopental sodium in the portion of Thiopental Sodium for Injection taken:

Result = (A_U/A_S) × (C_S/C_U) × (M_r1/M_r2) × 100

A_U = absorbance of the Sample solution

A_S = absorbance of the Standard solution

C_S = concentration of the Standard solution (μg/mL)

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

M_r1 = molecular weight of thiopental sodium, 264.32

M_r2 = molecular weight of thiopental, 242.34

Acceptance criteria: 93.0%–107.0%

4 PERFORMANCE TESTS

Uniformity of Dosage Units 〈905〉: Meets the requirements

5 SPECIFIC TESTS

Completeness of Solution 〈641〉

Sample solution: Mix 800 mg of Thiopental Sodium for Injection with 10 mL of carbon dioxide-free water.

Acceptance criteria: After 1 min, the solution is clear and free from undissolved solid.

Constituted Solution: At the time of use, it meets the requirements in Injections and Implanted Drug Products 〈1〉, Specific Tests, Completeness and clarity of solutions.

Bacterial Endotoxins Test 〈85〉: It contains NMT 1.0 USP Endotoxin Unit/mg of thiopental sodium.

pH 〈791〉

Sample solution: Use the Sample solution prepared in the test for Completeness of Solution.

Acceptance criteria: 10.2–11.2

Sterility Tests 〈71〉: Meets the requirements

Other Requirements: Meets the requirements in Labeling 〈7〉, Labels and Labeling for Injectable Products

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve as described in Packaging and Storage Requirements 〈659〉, Injection Packaging, Packaging for constitution.

USP Reference Standards 〈11〉

USP Thiopental RS