Terbinafine 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

Terbinafine Compounded Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled content of terbinafine (C₂₁H₂₅N). Prepare Terbinafine Compounded Oral Suspension containing 25 mg/mL of terbinafine as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

Calculate the required quantity of each ingredient for the total amount to be prepared. If using tablets, place the required number of tablets in a suitable mortar, and comminute the tablets to a fine powder or add Terbinafine Hydrochloride powder. Add the Vehicle in small portions, and triturate to make a smooth paste. Add increasing volumes of the Vehicle to make a terbinafine suspension 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

PROCEDURE

Mobile phase: Acetonitrile and water (2:3), with 0.15% triethylamine and 0.15% phosphoric acid. Make adjustments if necessary. Standard stock solution: 1.0 mg/mL of USP Terbinafine Hy drochloride RS in methanol

Standard solution: Transfer 0.5 mL of Standard stock solution to a 100-mL volumetric flask, dilute with Mobile phase to volume to obtain a solution containing 5 µg/mL of terbinafine, and pass through a suitable filter of 0.22-µm pore size.

Sample solution: Shake thoroughly by hand each bottle of Oral Suspension. Accurately pipet 1.0 mL to a 25-mL volumetric flask. Dilute with methanol to volume to obtain a nominal concentration of 1 mg/mL of terbinafine. Mix the sample again. Accurately pipet 0.5 mL of the diluted terbinafine solution to a 100-mL volumetric flask, and dilute with Mobile phase to volume to obtain a nominal concentration of 5 µg/mL of terbinafine.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 224 nm

Column: 4.6-mm × 15-cm; 3.5-µm packing L1

Flow rate: 0.4 mL/min

Injection volume: 10 µL

System suitability

Sample: Standard solution

[NOTE—The retention time of the terbinafine peak is 5.1 min.]

Suitability requirements

Relative standard deviation: NMT 5.8%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of terbinafine (C₂₁H₂₅N) in the volume of Oral Suspension taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

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

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

Acceptance criteria: 90.0%–110.0%

3 SPECIFIC TESTS

PH 〈791〉: 5.3–5.7

4 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Package in tight, light-resistant containers. Store at controlled room temperature or in a refrigerator.

BEYOND-USE DATE: NMT 30 days after the date on which it was compounded when stored at controlled room temperature or in a refrigerator

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

USP REFERENCE STANDARDS 〈11〉

USP Terbinafine Hydrochloride RS