Finasteride 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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Finasteride Tablets contain not less than 95.0 percent and not more than 105.0 percent of finasteride (C₂₃H₃₆N₂O₂).

1 Packaging and storage

Preserve in tight, light-resistant containers, and store at controlled room temperature. USP Reference standards 〈11〉

USP Finasteride RS

2 Identification

The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

3 Dissolution 

Medium: water; 900 mL.

Apparatus 2: 50 rpm.

for products labeled as 5-mg tablets

Time: 45 minutes.

Determine the amount of C₂₃H₃₆N₂O₂ dissolved by employing the following method.

Mobile phase Prepare altered and degassed mixture of acetonitrile and water  fi(29:21). Make adjustments if necessary (see System

Suitability under Chromatography 〈621〉).

Diluting solution - Prepare a solution of acetonitrile and water (7:3).

Standard solution - Dissolve an accurately weighed quantity of USP Finasteride RS in Diluting solution, and dilute quantitatively, and stepwise if necessary, with Diluting solution to obtain a solution having a known concentration approximately equivalent to the sample under test.

Chromatographic system (see Chromatography 〈621〉) - The liquid chromatograph is equipped with a 220-nm detector and a 4.6-mm × 5-cm column that contains packing L1. The column temperature is maintained at 45°. The flow rate is about 2 mL per minute. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the capacity factor, k′, is not less than 2.0; the column efficiency is greater than 1000 theoretical plates; the tailing factor is less than 2; and the relative standard deviation for replicate injections is less than 2.0%.

Procedure - Separately inject equal volumes (about 200 μL) of the solution under test and the Standard solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity of C₂₃H₃₆N₂O₂ dissolved.

Tolerances - Not less than 75% (Q) of the labeled amount of C₂₃H₃₆N₂O₂ is dissolved in 45 minutes. for products labeled as 1-mg tablets

Time: 30 minutes.

Mobile phase - Prepare a degassed mixture of acetonitrile and water (11:9). Make adjustments if necessary (see System Suitability under Chromatography 〈621〉).

Diluting solution - Prepare a solution of water and acetonitrile (7:3).

Standard solution - Dissolve an accurately weighed quantity of USP Finasteride RS in Diluting solution, to obtain a solution having a known concentration of 0.1 mg per mL. Dilute this solution quantitatively, and stepwise if necessary, in 0.5% sodium lauryl sulfate to obtain a solution containing 0.001 mg of finasteride per mL.

Chromatographic system (see Chromatography 〈621〉) - The liquid chromatograph is equipped with a 220-nm detector and a 4.6-mm × 15-cm column that contains 5-μm packing L11. The column temperature is maintained at 45°. The flow rate is about 1.5 mL per minute.

Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the column efficiency is not less than 5000 theoretical plates; the tailing factor is not more than 2; and the relative standard deviation for replicate injections is not more than 2%.

Procedure - Separately inject equal volumes (about 100 μL) of the solution under test and the Standard solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity of finasteride (C₂₃H₃₆N₂O₂) dissolved.

Tolerances - Not less than 80% (Q) of the labeled amount of C₂₃H₃₆N₂O₂ is dissolved in 30 minutes.

Uniformity of dosage units 〈905〉: meet the requirements.

4 Assay

Mobile phase - Prepare a filtered and degassed mixture of 2.5 mM phosphoric acid and acetonitrile (1:1). Make adjustments if necessary (see

System Suitability under Chromatography 〈621〉).

Diluting solution - Prepare a solution of acetonitrile and water (7:3).

Standard preparation - Dissolve an accurately weighed quantity of USP Finasteride RS in Diluting solution, and dilute quantitatively, and stepwise if necessary, with Diluting solution to obtain a solution having a known concentration of about 100 μg per mL.

Assay preparation - Weigh and finely powder not fewer than 20 Tablets. Transfer an amount of powder equivalent to about 10 mg of finasteride, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Diluting solution to volume, and mix.

Chromatographic system (see Chromatography 〈621〉) - The liquid chromatograph is equipped with a 240-nm detector and a 4.6-mm × 10.0-cm column that contains packing L1. The column temperature is maintained at 45°. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the capacity factor, k′, is not less than 2.0; the column efficiency is not less than 1000 theoretical plates; the tailing factor is not more than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure - Separately inject equal volumes (about 20 μL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of finasteride (C₂₃H₃₆N₂O₂) in the portion of Tablets taken by the formula:

100C(r_U /r_S )

in which C is the concentration, in mg per mL, of USP Finasteride RS in the Standard preparation; and r and r are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.