Phenobarbital Compounded Oral Suspension

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

Phenobarbital Compounded Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of phenobarbital (C₁₂H₁₂N₂O₃).

Prepare Phenobarbital Compounded Oral Suspension 10 mg/mL as follows (see Pharmaceutical Compounding-Nonsterile Preparations (795)).

^a Phenobarbital 60-mg tablets, Excellium Pharmaceutical, Inc., Fairfield, NJ.

^b Paddock Laboratories, Minneapolis, MN.

Calculate the required quantity of each ingredient for the total amount to be prepared. Place the required number of Phenobarbital tablets in a suitable mortar, and comminute to a fine powder with a pestle. Add the Vehicle in small portions, and triturate to make a smooth paste. Add increasing volumes of the Vehicle to make a phenobarbital liquid that is pourable. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add enough of the Vehicle to bring to final volume, and mix well.

2 ASSAY

2.1 PROCEDURE

Mobile phase: Acetonitrile and water (30:70). Adjust with dilute sulfuric acid to a pH of 3.0.

Standard stock solution: 0.4 mg/mL of USP Phenobarbital RS in Mobile phase

Standard solution: 20 µg/mL of phenobarbital prepared from Standard stock solution and Mobile phase

Sample solution: Shake thoroughly by hand each bottle of Oral Suspension. Prepare 20 µg/mL of phenobarbital from Oral Suspension and Mobile phase, and centrifuge.

2.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 235 nm

Column: 4.6-mm x 25-cm; 5-µm packing L1

Column temperature: 60°

Flow rate: 1.0 mL/min

Injection volume: 5 µL

2.3 System suitability

Sample: Standard solution

[NOTE-The retention time for phenobarbital is about 6.8 min.]

Suitability requirements

Relative standard deviation: NMT 2.0% for replicate injections

2.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of phenobarbital (C₁₂H₁₂N₂O₃) in the portion of Oral Suspension taken:

Result = (r_U/r_S) x (C_S/C_U) x 100

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

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

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

Acceptance criteria: 90.0%-110.0%

3 SPECIFIC TESTS

PH (791): 3.8-4.8

4 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE

Package in tight, light-resistant containers. Store at controlled room temperature.

4.1 BEYOND-USE DATE

NMT 115 days after the date on which it was compounded, when stored at controlled room temperature

4.2 LABELING

Label it to indicate that it is to be well shaken before use, and to state the Beyond-Use Date.

4.3 USP REFERENCE STANDARDS (11)

USP Phenobarbital RS