Pioglitazone and Metformin Hydrochloride 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

Pioglitazone and Metformin Hydrochloride Tablets contain an amount of pioglitazone hydrochloride (C₁₉H₂₀N₂O₃S·HCI) equivalent to NLT 95.0% and NMT 105.0% of the labeled amount of pioglitazone (C₁₉H₂₀N₂O₃S), and NLT 95.0% and NMT 105.0% of the labeled amount of metformin hydrochloride (C₄H₁₁N₅·HCI).

2 IDENTIFICATION

Change to read:

A. SPECTROSCOPIC IDENTIFICATION TESTS (197), Ultraviolet-Visible Spectroscopy: 1970 (CN 1-MAY-2020)

[NOTE-The UV spectra of the major peaks of the Sample solution and the Standard solution as obtained in the Assay may also be used to meet the Acceptance criteria.]

Pioglitazone

Sample solution: Transfer a quantity of finely powdered Tablets to a suitable container, and add water to obtain a final concentration of about 0.03 mg/mL of pioglitazone. Sonicate for about 30 s. Pass through a 5-mL portion of the resulting suspension using a suitable filter of 0.45-µm pore size, then wash the filter with 10 mL of water, and discard the filtrate. Wash the filter with 5 mL of 0.1 N hydrochloric acid, and use the filtrate.

Acceptance criteria: The UV absorption spectrum exhibits a maximum between 265 and 271 nm.

Metformin hydrochloride

Sample solution: Transfer a quantity of finely powdered Tablets to a suitable container, and add a suitable quantity of water, based on the labeled amount of metformin hydrochloride in the sample, to obtain a final concentration of about 0.4 mg/mL of metformin hydrochloride. Sonicate for about 30 s, and pass through a suitable filter of 0.45-µm pore size, discarding the first few mL of filtrate. Dilute a portion of the filtrate with water to obtain a solution containing about 8 µg/mL of metformin hydrochloride.

Acceptance criteria: The UV absorption spectrum exhibits a maximum between 230 and 235 nm.

B. The retention times of the pioglitazone and metformin peaks of the Sample solution correspond to those of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 PROCEDURE

Mobile phase: 7.2 g/L of sodium dodecyl sulfate in a mixture of 0.05 M monobasic ammonium phosphate and acetonitrile (1:1)

Diluent: Methanol and 0.1 N hydrochloric acid (1:1)

System suitability stock solution: 0.5 mg/mL of p-methoxyacetophenone and 0.4 mg/mL of butylparaben in Diluent

Pioglitazone standard stock solution: 0.84 mg/mL of USP Pioglitazone Hydrochloride RS in Diluent

Mixed standard stock solution: 2.5 mg/mL of USP Metformin Hydrochloride RS and 0.084 mg/mL of USP Pioglitazone Hydrochloride RS in 0.1 N hydrochloric acid from the Pioglitazone standard stock solution

System suitability solution: Transfer 10.0 mL of the Mixed standard stock solution and 5.0 mL of the System suitability stock solution to a 50-mL volumetric flask, and dilute with 0.1 N hydrochloric acid to volume.

Standard solution: 16.8 µg/mL of USP Pioglitazone Hydrochloride RS and 0.5 mg/mL of USP Metformin Hydrochloride RS in 0.1 N hydrochloric acid from the Mixed standard stock solution

Sample stock solution: Weigh and finely powder NLT 10 Tablets. Transfer an amount of powdered Tablets, equivalent to about 15 mg of pioglitazone, to a 200-mL volumetric flask. Add 120 mL of 0.1 N hydrochloric acid, shake for about 30 min, and then sonicate for about 5 min. Dilute with 0.1 N hydrochloric acid to volume, and mix well. Pass through a suitable filter of 0.45-µm pore size, discarding the first few mL of filtrate.

Sample solution: Transfer a suitable volume of the Sample stock solution (see Table 1) to a 50-mL volumetric flask, and dilute with 0.1 N hydrochloric acid to volume.

Table 1

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 255 nm for metformin and p-methoxyacetophenone; UV 225 nm for pioglitazone and butylparaben. If this procedure is used for Identification A, use a diode-array detector set at 200-400 nm.

Column: 6.0-mm x 15-cm; 5-µm packing L7

Column temperature: 25 ± 5°

Flow rate: 1 mL/min. [NOTE-The flow rate may be adjusted to achieve the retention time of the metformin peak of about 5 min.]

Injection volume: 10 µL

System suitability

Samples: System suitability solution and Standard solution

[NOTE-See Table 2 for the approximate relative retention times.]

Table 2

Suitability requirements

Resolution: NLT 2.5 between metformin and p-methoxyacetophenone; NLT 2.5 between pioglitazone and butylparaben, System suitability solution

Relative standard deviation: NMT 1.0% for the metformin peak; NMT 1.0% for pioglitazone peak, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of pioglitazone (C₁₉H₂₀N₂O₃S) in the portion of Tablets taken:

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

r_U = peak response of pioglitazone from the Sample solution

r_S = peak response of pioglitazone from the Standard solution

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

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

M_r1 = molecular weight of pioglitazone, 356.44

M_r2 = molecular weight of pioglitazone hydrochloride, 392.90

Calculate the percentage of the labeled amount of metformin hydrochloride (C₄H₁₁N₅·HCI) in the portion of Tablets taken:

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

r_U = peak response of metformin from the Sample solution

r_S = peak response of metformin from the Standard solution

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

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

Acceptance criteria: 95.0%-105.0% for each of the labeled amounts of pioglitazone and metformin hydrochloride

4 PERFORMANCE TESTS

4.1 DISSOLUTION (711)

4.1.1 Test 1

Medium: pH 2.5 Mcllvaine buffer (could be prepared by adjusting 0.1 M citric acid with 0.2 M dibasic sodium phosphate to a pH of 2.5); 900 mL

Apparatus 2: 50 rpm

Time: 30 min

Diluent and Mobile phase: Proceed as directed in the Assay.

Pioglitazone standard stock solution: 0.37 mg/mL of USP Pioglitazone Hydrochloride RS in Diluent

Standard solution: 0.0185 mg/mL of USP Pioglitazone Hydrochloride RS from the Pioglitazone standard stock solution and (L/900) mg/mL of USP Metformin Hydrochloride RS in Medium, where L is the label claim, in mg/Tablet, of metformin hydrochloride

Sample solution: Pass a portion of the solution under test through a suitable filter of 0.45-µm pore size.

Chromatographic system: Proceed as directed in the Assay, except use an Injection volume of 5 µL.

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.5 for the metformin peak; NMT 2.0 for the pioglitazone peak

Relative standard deviation: NMT 2.0% for the metformin peak; NMT 2.0% for the pioglitazone peak

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of pioglitazone (C₁₉H₂₀N₂O₃S) dissolved:

Result = (r_U/r_S) x (C_S/L) x V x (M_r1/M_r2) x 100

r_U = peak response of pioglitazone from the Sample solution

r_S = peak response of pioglitazone from the Standard solution

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

L = label claim of pioglitazone (mg/Tablet)

V = volume of Medium, 900 mL

M_r1 = molecular weight of pioglitazone, 356.44

M_r2 = molecular weight of pioglitazone hydrochloride, 392.90

Calculate the percentage of the labeled amount of metformin hydrochloride (C₄H₁₁N₅·HCI) dissolved:

Result = (r_U/r_S) x (C_S/L) x V x 100

r_U = peak response of metformin hydrochloride from the Sample solution

r_S = peak response of metformin hydrochloride from the Standard solution

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

L = label claim of metformin hydrochloride (mg/Tablet)

V = volume of Medium, 900 mL

Tolerances: NLT 80% (Q) of the labeled amount of pioglitazone (C₁₉H₂₀N₂O₃S) is dissolved; NLT 80% (Q) of the labeled amount of metformin hydrochloride (C₄H₁₁N₅·HCI) is dissolved.

4.1.2 Test 2: If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 2.

Medium: pH 2.5 Mcllvaine buffer (could be prepared by adjusting 0.1 M citric acid with 0.2 M dibasic sodium phosphate to a pH of 2.5); 900 mL

Apparatus 2: 50 rpm

Time: 45 min

Solution A: 1.4 g/L of dibasic sodium phosphate anhydrous and 1.4 g/L of sodium dodecyl sulfate in water

Solution B: Phosphoric acid and water (50:50)

Mobile phase: Acetonitrile and Solution A (34:66). Adjust with Solution B to a pH of 7.1.

Diluent A: Acetonitrile and Medium (50:50)

Diluent B: Acetonitrile and water (70:30)

Pioglitazone standard stock solution: 0.019 mg/mL of USP Pioglitazone Hydrochloride RS in Diluent B. Sonicate as needed to dissolve.

Metformin standard stock solution: 0.92 mg/mL of USP Metformin Hydrochloride RS in Medium. Sonicate as needed to dissolve.

Standard solution: 0.003 mg/mL of USP Pioglitazone Hydrochloride RS from the Pioglitazone standard stock solution and 0.11 mg/mL of USP Metformin Hydrochloride RS from the Metformin standard stock solution in Diluent A

Sample solution: Pass a portion of the solution under test through a suitable filter and dilute with Diluent A to a metformin concentration that is similar to the Standard solution.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 225 nm

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

Temperatures

Autosampler: 5°

Column: 40°

Flow rate: 1 mL/min

Injection volume: 15 µL

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: 0.8-2.0 for the metformin peak; 0.8-2.0 for the pioglitazone peak

Relative standard deviation: NMT 2.0% for the metformin peak; NMT 2.5% for the pioglitazone peak

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of pioglitazone (C₁₉H₂₀N₂O₃S) dissolved:

Result = (r_U/r_S) x (C_S/L) x V x D x (M_r1/M_r2) x 100

r_U = peak response of pioglitazone from the Sample solution

r_S = peak response of pioglitazone from the Standard solution

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

L = label claim of pioglitazone (mg/Tablet)

V = volume of Medium, 900 mL

D = dilution factor of the Sample solution

M_r1 = molecular weight of pioglitazone, 356.44

M_r2 = molecular weight of pioglitazone hydrochloride, 392.90

Calculate the percentage of the labeled amount of metformin hydrochloride (C₄H₁₁N₅·HCI) dissolved:

Result = (r_U/r_S) x (C_S/L) x V x D x 100

r_U = peak response of metformin hydrochloride from the Sample solution

r_S = peak response of metformin hydrochloride from the Standard solution

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

L = label claim of metformin hydrochloride (mg/Tablet)

V = volume of Medium, 900 mL

D = dilution factor of the Sample solution

Tolerances: NLT 80% (Q) of the labeled amount of pioglitazone (C₁₉H₂₀N₂O₃S) is dissolved; NLT 80% (Q) of the labeled amount of metformin hydrochloride (C₄H₁₁N₅·HCI) is dissolved.

4.2 UNIFORMITY OF DOSAGE UNITS (905), Content Uniformity

Meet the requirements for pioglitazone and metformin hydrochloride

5 IMPURITIES

5.1 ORGANIC IMPURITIES: PIOGLITAZONE

Mobile phase: Acetonitrile, 0.1 M ammonium acetate, and glacial acetic acid (25:25:1)

Diluent: Methanol and 0.1 N hydrochloric acid (1:1)

Standard stock solution: 0.2 mg/mL of USP Pioglitazone Hydrochloride RS, dissolved first in methanol using 20% of the final volume, then diluted with Mobile phase to volume

System suitability solution: Prepare a solution containing 0.3 mg/mL of benzophenone in methanol. Transfer 1.0 mL of this solution to a 50-mL volumetric flask, add 5.0 mL of the Standard stock solution, and dilute with Mobile phase to volume. This solution contains 20 µg/mL of USP Pioglitazone Hydrochloride RS and 6 µg/mL of benzophenone.

Standard solution: 1 µg/mL of USP Pioglitazone Hydrochloride RS in Mobile phase from the Standard stock solution

Sample solution: Weigh and finely powder 10 Tablets. Transfer an amount of powdered Tablets, equivalent to about 18 mg of pioglitazone, to a 100-mL volumetric flask, and add 50 mL of Diluent. Shake for 30 min, and dilute with Mobile phase to volume. Pass through a suitable filter of 0.45-um pore size, discarding the first few mL of filtrate.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 269 nm

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

Column temperature: 25 ± 5°

Flow rate: 0.8 mL/min. [NOTE-The flow rate may be adjusted to achieve the retention time of the pioglitazone peak of about 7 min.]

Injection volume: 40 µL

Run time: At least 4 times the retention time of the pioglitazone peak

System suitability

Samples: System suitability solution and Standard solution

[NOTE-Elution order is the pioglitazone peak followed by benzophenone.]

Suitability requirements

Resolution: NLT 10 between pioglitazone and benzophenone, System suitability solution

Tailing factor: NMT 1.5 for the pioglitazone peak, System suitability solution

Relative standard deviation: NMT 5.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each pioglitazone related impurity in the portion of Tablets taken:

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

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

r_S = peak response of pioglitazone from the Standard solution

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

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

M_r1 = molecular weight of pioglitazone, 356.44

M_r2 = molecular weight of pioglitazone hydrochloride, 392.90

Acceptance criteria

Any individual pioglitazone related impurity: NMT 0.2%

Total pioglitazone related impurities: NMT 0.6%

[NOTE-Disregard the peaks due to metformin and its impurities that elute before 4.5 min, corresponding to the relative retention time of the pioglitazone peak of about 0.64.]

5.2 ORGANIC IMPURITIES: METFORMIN

Solution A: 1.74 g of sodium 1-pentanesulfonate and 1.15 g of monobasic ammonium phosphate in 1000 mL of water

Solution B: Acetonitrile and water (7:3)

Mobile phase: See Table 3.

Table 3

System suitability solution: 5 µg/mL of USP Metformin Hydrochloride RS and 2 µg/mL of melamine in water

Standard solution: 5 µg/mL of USP Metformin Hydrochloride RS in water

Sample solution: Accurately weigh 10 Tablets, and finely powder. Transfer an amount of powdered Tablets, equivalent to about 100 mg of metformin hydrochloride, to a 100-mL volumetric flask, and add 50 mL of water. Shake for 30 min. Dilute with water to volume, and pass through a suitable filter of 0.45-um pore size, discarding the first few mL of filtrate.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 215 nm

Column: 4.6-mm x 15-cm; 5-µm packing L62

Column temperature: 25 ± 5°

Flow rate: 1.0 mL/min. [NOTE-The flow rate may be adjusted to achieve the retention time of the metformin peak of about 8 min.]

Run time: 15 min

Injection volume: 20 µL

System suitability

Samples: System suitability solution and Standard solution

[NOTE-The relative retention times for melamine and metformin are about 0.9 and 1.0, respectively.]

Suitability requirements

Resolution: NLT 4 between melamine and metformin hydrochloride, System suitability solution

Tailing factor: NMT 1.5 for the metformin hydrochloride peak, System suitability solution

Relative standard deviation: NMT 5.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each metformin hydrochloride related impurity in the portion of Tablets taken:

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

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

r_S = peak response of metformin hydrochloride from the Standard solution

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

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

Acceptance criteria

Any individual impurity: NMT 0.1%

Total impurities: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

6.1 PACKAGING AND STORAGE

Preserve in tight containers, and store at controlled room temperature.

6.2 LABELING

When more than one Dissolution test is given, the labeling states the Dissolution test used only if Test 1 is not used.

6.3 USP REFERENCE STANDARDS (11)

USP Metformin Hydrochloride RS

USP Pioglitazone Hydrochloride RS