Terbinafine 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

Terbinafine Tablets contain Terbinafine Hydrochloride equivalent to NLT 90.0% and NMT 110.0% of the labeled amount of terbinafine (C₂₁H₂₅N).

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.

B. The UV spectrum of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

PROCEDURE

Buffer solution: 0.85 g/L of monobasic potassium phosphate in water. Add 1 g of sodium 1-decanesulfonate and adjust with dilute phosphoric acid to a pH of 3.0.

Mobile phase: Acetonitrile and Buffer solution (2:3)

Standard solution: 0.2 mg/mL of USP Terbinafine Hy drochloride RS in Mobile phase (equivalent to 0.19 mg/mL of terbinafine)

Sample stock solution: Nominally equivalent to 0.5 mg/mL of terbinafine in Mobile phase, from crushed, finely powdered Tablets. [NOTE— Sonicate for 20 min with intermittent shaking.]

Sample solution: Nominally equivalent to 0.2 mg/mL of terbinafine in Mobile phase, from the Sample stock solution

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 220 nm. For Identification B, use a diode array detector in the range of 200–400 nm.

Column: 3.9-mm × 15-cm; 5-µm packing L7

Flow rate: 1.8 mL/min Injection volume: 5 µL

Run time: 1.5 times the retention time of the terbinafine peak

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of terbinafine (C₂₁H₂₅N) in the portion of Tablets taken:

Result = (r_U/r_S) × (C_S/C_U) × (M_r1/M_r2) × 100

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

C_S = concentration of USP Terbinafine Hydrochloride RS in the Standard solution (mg/mL)

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

M_r1 = molecular weight of terbinafine, 291.44

M_r2 = molecular weight of terbinafine hydrochloride, 327.90

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

DISSOLUTION 〈711〉

Medium: pH 3.0 citrate buffer; 500 mL

Apparatus 2: 50 rpm

Time: 30 min

Standard solution: 32 µg/mL of USP Terbinafine Hydrochloride RS in Medium

Sample solution: Pass a portion of the solution under test through a suitable filter of 0.45-µm pore size. Dilute with Medium, if necessary.

Instrumental conditions

(See Ultraviolet-Visible Spectroscopy 〈857〉.)

Mode: UV

Analytical wavelength: 283 nm Cell: 1 cm

Blank: Medium Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of terbinafine (C₂₁H₂₅N) dissolved:

Result = (A_U/A_S) × (C_S/L) × (M_r1/M_r2) × V × D × 100

A_U = absorbance of the Sample solution

A_S = absorbance of the Standard solution

C_S = concentration of USP Terbinafine Hy drochloride RS in the Standard solution (mg/mL)

L = label claim (mg/Tablet)

M_r1 = molecular weight of terbinafine, 291.44

M_r2 = molecular weight of terbinafine hydrochloride, 327.90

V = volume of Medium, 500 mL

D = dilution factor for the Sample solution

Tolerances: NLT 80% (Q ) of the labeled amount of terbinafine (C₂₁H₂₅N) is dissolved.

UNIFORMITY OF DOSAGE UNITS 〈905〉: Meet the requirements

5 IMPURITIES

5.1 ORGANIC IMPURITIES

Buffer solution, Mobile phase, and Sample solution: Proceed as directed in the Assay.

Standard solution: 0.7 µg/mL of USP Terbinafine Hydrochloride RS in Mobile phase (equivalent to 0.6 µg/mL of terbinafine)

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 220 nm

Column: 3.9-mm × 15-cm; 5-µm packing L7

Flow rate: 1.8 mL/min

Injection volume: 50 µL

Run time: 4 times the retention time of the terbinafine peak

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 10.0%

Analysis

Samples: Sample solution and Standard solution

Calculate the percentage of any individual impurity in the portion of Tablets taken:

Result = (r_U/r_S) × (C_S/C_U) × (1/F) × (M_r1/M_r2) × 100

r_U = peak response of each individual impurity from the Sample solution

r_S = peak response of terbinafine from the Standard solution

C_S = concentration of USP Terbinafine Hydrochloride RS in the Standard solution (mg/mL)

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

F = relative response factor (see Table 1)

M_r1 = molecular weight of terbinafine, 291.44

M_r2 = molecular weight of terbinafine hydrochloride, 327.90

Acceptance criteria: See Table 1.

Table 1

5.2 LIMIT OF TERBINAFINE DIMER

Diluent: Acetonitrile and water (4:1)

Solution A: 1 mL/L of triethylamine in water

Solution B: 1 mL/L of triethylamine in a mixture of acetonitrile and water (19:1)

Mobile phase: See Table 2.

Table 2

Standard solution: 1.4 µg/mL of USP Terbinafine Hy drochloride RS in Diluent (equivalent to 1.2 µg/mL of terbinafine)

Sample solution: Nominally equivalent to 2.5 mg/mL of terbinafine in Diluent, from crushed, finely powdered Tablets. [NOTE—Sonicate for 20 min with intermittent shaking.]

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 280 nm

Column: 4.6-mm × 15-cm; 5-µm packing L1

Column temperature: 52°

Flow rate: 1 mL/min

Injection volume: 100 µL

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 10.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the terbinafine dimer in the portion of Tablets taken:

Result = (r_U/r_S) × (C_S/C_U) × (1/F) × (M_r1/M_r2) × 100

r_U = peak response of the terbinafine dimer from the Sample solution

r_S = peak response of terbinafine from the Standard solution

C_S = concentration of USP Terbinafine Hy drochloride RS in the Standard solution (mg/mL)

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

F = relative response factor for the terbinafine dimer

M_r1 = molecular weight of terbinafine, 291.44

M_r2 = molecular weight of terbinafine hydrochloride, 327.90

Acceptance criteria: See Table 3.

Table 3

^a  (2E,4E)-4-(4,4-Dimethylpent-2-ynylidene)-N1,N5-dimethyl-N1,N5-bis(naphthalen-1-ylmethyl)pent-2-ene-1,5-diamine.

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in well-closed containers, protected from light. Store at controlled room temperature.

USP REFERENCE STANDARDS 〈11〉

USP Terbinafine Hydrochloride RS