Phenobarbital Tablets

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

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

DOWNLOAD PDF HERE

>> Phenobarbital Tablets contain not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C₁₂H₁₂N₂O₃.

1 Packaging and storage

Preserve in well-closed containers.

2 USP REFERENCE STANDARDS (11)

USP Phenobarbital RS

3 Identification

A: Triturate a quantity of finely powdered Tablets, equivalent to about 60 mg of phenobarbital, with 50 mL of chloroform, and filter. Evaporate the clear filtrate to dryness, and dry at 105° for 2 hours: the residue so obtained responds to Identification test A under Phenobarbital.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation, both relative to the internal standard, as obtained in the Assay.

3.1 DISSOLUTION (711)

Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Procedure-Determine the amount of C₁₂H₁₂N₂O₃ dissolved from UV absorbances at the wavelength of maximum absorbance at about 240 nm on filtered portions of the solution under test, suitably diluted with pH 9.6 alkaline borate buffer (see Buffer Solutions in the section Reagents, Indicators, and Solutions), in comparison with a Standard solution having a known concentration of USP Phenobarbital RS in the same Medium.

Tolerances-Not less than 75% (Q) of the labeled amount of C₁₂H₂N₂O₃ is dissolved in 45 minutes. 3

3.2 UNIFORMITY OF DOSAGE UNITS (905)

Meet the requirements.

4 Assay

4.1 pH 4.5 Buffer solution, Mobile phase, Internal standard solution, Standard preparation, and Chromatographic system

Prepare as directed in the Assay under Phenobarbital.

4.2 Assay preparation

Weigh and finely powder not fewer than 20 Tablets. Weigh accurately a portion of the powder, equivalent to about 20 mg of phenobarbital, add 15.0 mL of Internal standard solution, mix, and sonicate for 15 minutes. Filter through a membrane filter having a 0.5-µm or finer porosity before use.

4.3 Procedure

Proceed as directed for Procedure in the Assay under Phenobarbital. Calculate the quantity, in mg, of C₁₂H₁₂N₂O₃ in the portion of Tablets taken by the formula:

(W)(R_U/R_S)

in which the terms are as defined therein.