Clonidine Hydrochloride Extended-Release 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

Clonidine Hydrochloride Extended-Release Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl).

2 IDENTIFICATION

2.1 A. THIN-LAYER CHROMATOGRAPHIC IDENTIFICATION TEST (201)

Standard solution: 10 mg/mL of USP Clonidine Hydrochloride RS in methanol. Sonicate to dissolve, if needed.

Sample solution: Powder NLT 20 Tablets and transfer a portion of the powder equivalent to 1 mg of clonidine hydrochloride to a separator containing 20 ml of water and 1 mL of 1 N sodium hydroxide. Swirl gently to dissolve the sample, and extract with 40 mL of chloroform. Allow the layers to separate for 15 min, and pass the chloroform layer through a suitable filter paper into a glass beaker. Repeat the extraction step and collect the filtrate in the same beaker. Evaporate the filtrate to dryness in a water bath, and dissolve the residue with 0.1 mL of methanol.

2.1.1 Chromatographic system

(See Chromatography (621), General Procedures, Thin-Layer Chromatography.)

Mode: TLC

Adsorbent: 0.25-mm layer of chromatographic silica gel mixture

Application volume: 5 µL

Developing solvent system: Methanol and ammonium hydroxide (200:3)

2.1.2 Analysis

Samples: Standard solution and Sample solution

Position the plate in a chromatographic chamber, and develop in Developing solvent system until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, mark the solvent front, and allow the solvent to evaporate for 2 min at 70°. Examine the plate under UV light at 254 nm.

Acceptance criteria: The R, value of the principal spot from the Sample solution corresponds to that from the Standard solution.

2.2 B.

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

3 ASSAY

3.1 PROCEDURE

Buffer: Dissolve 2.2 g of octanesulfonic acid sodium salt in 1000 mL of water.

Solution A: Methanol, Buffer, and phosphoric acid (50: 50:0.1). Adjust with 1 N sodium hydroxide to a pH of 3.0.

Solution B: Acetonitrile, methanol, and water (80:10:10)

Mobile phase: See Table 1.

   Table 1

Sample solution: Nominally 1 µg/mL of clonidine hydrochloride prepared as follows. Weigh and transfer 10 Tablets equivalent to 1 mg of clonidine hydrochloride to a 1000-mL volumetric flask. Add 50 mL of methanol and stir for 30 min. Add 700 mL of Solution A and stir for 15 min. Sonicate for 30 min with intermittent shaking every 5 min. Dilute with Solution A to volume. Pass through a suitable filter of 0.45-µm pore size. Discard the first few milliliters of the filtrate.

3.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 220 nm

Column: 4.6-mm x 15-cm; 5-µm packing 17

Flow rate: 1.5 mL/min

Injection volume: 50 µL

3.3 System suitability

Sample: Standard solution

3.4 Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

3.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) in the portion of Tablets taken:

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

r_U = peak response of clonidine from the Sample solution

r_S = peak response of clonidine from the Standard solution

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

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

Acceptance criteria: 90.0%-110.0%

Acceptance criteria: 90.0%-110.0%

4 PERFORMANCE TESTS

4.1 Change to read:

DISSOLUTION (711)

4.1.1 Test 1

Acid stage medium: 0.01 N bydrochloric acid: 500 mL

Buffer stage medium: pH 7.0 phosphate buffer (dissolve 6.8 g of monobasic potassium phosphate and 1.16 g of sodium hydroxide in 1000 mL of water. Adjust with 0.1 N sodium hydroxide to a pH of 7.0.); 500 mL

Apparatus 2: 50 rpm with a suitable sinker

4.1.1.1 Times

Acid stage: 2 h

Buffer stage: 1, 6, and 16 h. The time in the Buffer stage medium does not include the time in the Acid stage medium.

Buffer: 2.2 g/L of octanesulfonic acid sodium salt in water

Mobile phase: Methanol, Buffer, and phosphoric acid (50: 50: 0.1). Adjust with 1 N sodium hydroxide to a pH of 3.0.

Standard stock solution: 0.105 mg/mL of USP Clonidine Hydrochloride RS in the respective medium. Sonicate to dissolve, if needed.

Standard solution: 0.21 µg/mL of USP Clonidine Hydrochloride RS in the respective medium from the Standard stock solution

Sample solution: After 2 h in the Acid stage medium, withdraw an aliquot of the solution under test. Pass the solution through a suitable filter of 0.45-µm pore size and discard the first few milliliters of the filtrate. Carefully transfer the Tablet with sinker to a dissolution vessel containing the Buffer stage medium. At the times specified for the Buffer stage, withdraw an aliquot of the solution under test. Replace the aliquots withdrawn for analysis with equal volumes of fresh Buffer stage medium. Pass the solution through a suitable filter of 0.45-µm pore size and discard the first few milliliters of the filtrate.

4.1.1.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 220 nm

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

Flow rate: 1.5 mL/min

Injection volume: 100 µL

Run time: NLT 2.5 times the retention time of clonidine

4.1.1.3 System suitability

Sample: Standard solution

4.1.1.4 Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

4.1.1.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved in the Acid stage medium (Q):

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

r_U = peak response of clonidine from the Sample solution

r_S = peak response of clonidine from the Standard solution. s

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

L = label claim (mg/Tablet)

V = volume of Acid stage medium; 500 mL

Calculate the concentration (C) of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) in the sample withdrawn at each Buffer stage time point (1):

                      Result = (r_U/r_S) x C_S

r_U = peak response of clonidine from the Sample solution at each time point, i

r_S = peak response of clonidine from the Standard solution s

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

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved at each time point (i):

                       Result₁ = [C₁ x V x (1/L) x 100) + Q_A

                       Result₂ = {[(C₂ x V) + (C₁ x V_S)] x (1/L) x 100) + Q_A

                       Result₃ = ({(C₃ x V) + [(C₂+C₁) x V_S]) x (1/L) x 100) + Q_A

C_i = concentration of clonidine hydrochloride in the Sample solution withdrawn at the specified time point (mg/mL) C_{i} = 1

V = volume of Buffer stage medium, 500 mL

L = label claim (mg/Tablet)

Q_{A =} percentage of the labeled amount of clonidine hydrochloride dissolved in the Acid stage medium (%) 

V_S = volume of the Sample solution withdrawn at each time point (mL)

4.1.1.6 Tolerances

Acid stage: 30%-50% of the labeled amount of clonidine hydrochloride (C₂H₂CIN, HCI) is dissolved in 2 h.

Buffer stage: See Table 2.

Table 2

The percentages of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved at the times specified conform to

Dissolution (711), Acceptance Table 2.

4.1.2 Test 2

Acid stage medium: 0.01 N hydrochloric acid: 500 mL

Buffer stage medium: pH 7.0 phosphate buffer (dissolve 6.8 g of monobasic potassium phosphate and 1.1 g of sodium hydroxide in 1000 mL of water. Adjust with 1% hydrochloric acid or 1% sodium hydroxide to a pH of 7.0.); 500 mL

Apparatus 2: 50 rpm with a suitable sinker

4.1.2.1 Times

Acid stage: 2 h

Buffer stage: 2, 6, and 10 h. The time in the Buffer stage medium does not include the time in the Acid stage medium.

Buffer: 2.2 g/L of octanesulfonic acid sodium salt in water

Mobile phase: Methanol, Buffer, and phosphoric acid (50: 50: 0.1). Adjust with triethylamine to a pH of 3.0.

Standard solution acid stage: 0.2 µg/mL of USP Clonidine Hydrochloride RS in Acid stage medium

Standard solution buffer stage: 0.2 µg/mL of USP Clonidine Hydrochloride RS in Buffer stage medium

Sample solution: At the time specified for the Acid stage, withdraw an aliquot of the solution under test. Replace the aliquots withdrawn for analysis with equal volumes of fresh Acid stage medium. Pass the solution through a suitable filter of 0.45-µm pore size and discard the first few milliliters of the filtrate. Carefully transfer the Tablet to a dissolution vessel containing the Buffer stage medium. At the times specified for the Buffer stage, withdraw an aliquot of the solution under test. Replace the aliquots withdrawn for analysis with equal volumes of fresh Buffer stage medium. Pass the solution through a suitable filter of 0.45-µm pore size and discard the first few milliliters of the filtrate.

4.1.2.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 210 nm

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

4.1.2.3 Temperatures

Autosampler: 10"

Column: 30*

Flow rate: 1 mL/min

Injection volume: 100 µL

Run time: NLT 2 times the retention time of clonidine

4.1.2.4 System suitability

Samples: Standard solution acid stage and Standard solution buffer stage

4.1.2.5 Suitability requirements

Tailing factor: NMT 2.0, Standard solution acid stage and Standard solution buffer stage

Relative standard deviation: NMT 5.0%, Standard solution acid stage and Standard solution buffer stage

4.1.2.6 Analysis

Samples: Standard solution acid stage, Standard solution buffer stage, and Sample solution

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved in the Acid stage medium (Q):

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

r_U = peak response of clonidine from the Sample solution

r_S = peak response of clonidine from the Standard solution acid stage s

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

L = label claim (mg/Tablet)

V = volume of Acid stage medium; 500 mL

Calculate the concentration (C) of clonidine hydrochloride (C,H,CI,N, HCI) in the sample withdrawn at each Buffer stage time point (i):

                         Result = (r_U/r_S) x C_S

r_U = peak response of clonidine from the Sample solution at each time point, i

r_S = peak response of clonidine from the Standard solution buffer stage r_{s} = 1

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

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₂H₂CIN, HCI) dissolved at each time point (i):

                       Result₁ = [C₁ x V x (1/L) x 100) + Q_A

                       Result₂ = {[(C₂ x V) + (C₁ x V_S)] x (1/L) x 100) + Q_A

                       Result₃ = ({(C₃ x V) + [(C₂+C₁) x V_S]) x (1/L) x 100) + Q_A

C_i = concentration of clonidine hydrochloride in the Sample solution withdrawn at the specified time point (mg/mL)

V = volume of Buffer stage medium, 500 mL

L = label claim (mg/Tablet)

Q_A = percentage of the labeled amount of clonidine hydrochloride dissolved in the Acid stage medium (%)

V_S = volume of the Sample solution withdrawn at each time point (mL)

4.1.2.7 Tolerances

Acid stage: NMT 37% of the labeled amount of clonidine hydrochloride (CH,CIN, HCI) is dissolved in 2 h.

Buffer stage: See Table 3.

Table 3

The percentages of the labeled amount of clonidine hydrochloride (CH,CIN, HCI) dissolved at the times specified conform to Dissolution (711), Acceptance Table 2.

4.1.3 Test 3

Acid stage medium: 0.01 N hydrochloric acid: 500 ml.

Buffer stage medium: pH 7.0 phosphate buffer (dissolve 6.8 g of monobasic potassium phosphate and 1.16 g of sodium hydroxide in 1000 mL of water. Adjust with 1 N phosphoric acid TS or 1 N sodium hydroxide to a pH of 7.0.); 500 mL

Apparatus 2: 50 rpm

4.1.3.1 Times

Acid stage: 2 h

Buffer stage: 2, 6, and 14 h. The time in the Buffer stage medium does not include the time in the Acid stage medium.

Buffer: 1.8 g/L of octanesulfonic acid sodium salt in water

Mobile phase: Methanol and Buffer (40:60). Add 1 mL of phosphoric acid into each liter of the mixture. Adjust with 1 N sodium hydroxide to a pH of 3.0.

Standard solution: 0.2 µg/ml. of USP Clonidine Hydrochloride RS in Acid stage medium

Sample solution: After 2 h in the Acid stage medium, withdraw an aliquot of the solution under test. Pass the solution through a suitable filter of 0.45-µm pore size and discard the first few milliliters of the filtrate. Carefully, replace the Acid stage medium with Buffer stage medium pre-equilibrated to the appropriate temperature. At the times specified for the Buffer stage, withdraw an aliquot of the solution under test. Pass the solution through a suitable filter of 0.45-um pore size and discard the first few milliliters of the filtrate.

4.1.3.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 220 nm

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

Flow rate: 1.5 mL/min

Injection volume: 100 µL

Run time: NLT 3 times the retention time of clonidine

4.1.3.3 System suitability

Sample: Standard solution

4.1.3.4 Suitability requirements

Relative standard deviation: NMT 2.0%

4.1.3.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved in the Acid stage medium (Q):

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

r_U = peak response of clonidine from the Sample solution 

r_S = peak response of clonidine from the Standard solution

C_S = concentration of USP Clonidine Hydrochloride RS in the Standard solution 

L = label claim (mg/Tablet)

V = volume of Acid stage medium; 500 mL

Calculate the concentration (C) of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) in the sample withdrawn at each Buffer stage time point (7):

                        Result = (r_U/r_S) x C_S

r_U = peak response of clonidine from the Sample solution at each time point, i

r_S = peak response of clonidine from the Standard solution

C = concentration of USP Clonidine Hydrochloride RS in the Standard solution (mg/mL)

Calculate the percentage of the labeled amount of clonidine hydrochloride (C,H,CIN, HCI) dissolved at each time point (i):

                       Result₁ = [C₁ x V x (1/L) x 100) + Q_A

                       Result₂ = {[(C₂ x (V - V_S) + (C₁ x V_S)} x (1/L) x 100) + Q_A

                       Result₃ = [({C₃ x [V - (2 x V_S)] + [(C₂ + C₁) x V_S) x (1/L) x 100] + Q_A

C_i = concentration of clonidine hydrochloride in the Sample solution withdrawn at the specified time point (mg/mL) 

V = volume of Buffer stage medium, 500 mL

L = label claim (mg/Tablet)

Q_A  = percentage of the labeled amount of clonidine hydrochloride dissolved in the Acid stage medium (%)

V_S = volume of the Sample solution withdrawn at each time point (mL)

4.1.3.6 Tolerances

Acid stage: 23%-43% of the labeled amount of clonidine hydrochloride (C₂H₂CIN, HCI) is dissolved in 2 h.

Buffer stage: See Table 4.

    Table 4

The percentages of the labeled amount of clonidine hydrochloride (C,H,CIN, HCI) dissolved at the times specified conform to Dissolution (711), Acceptance Table 2

4.1.4 Test 4

Acid stage medium: 0.01 N hydrochloric acid: 500 mL, deaerated

Buffer stage medium: pH 7.0 phosphate buffer (dissolve 6.8 g of monobasic potassium phosphate and 1.16 g of sodium hydroxide in 1000 mL of water. Adjust with 1 N phosphoric acid TS or 1 N sodium hydroxide to a pH of 7.0.); 500 mL

Apparatus 2: 50 rpm with a suitable sinker

4.1.4.1 Times

Acid stage: 2 h

Buffer stage: 2, 6, and 14 h. The time in the Buffer stage medium does not include the time in the Acid stage medium.

Buffer: 6.8 g/L of monobasic potassium phosphate in water. Adjust with phosphoric acid to a pH of 3.0.

Mobile phase: Methanol and Buffer (30:70)

Standard solution: 0.4 µg/mL of USP Clonidine Hydrochloride RS in Acid stage medium

Sample solution: After 2 h in the Acid stage medium, withdraw an aliquot of the solution under test. Pass the solution through a suitable filter of 0.45-µm pore size and discard the first few milliliters of the filtrate. Carefully transfer the Tablet with sinker to a dissolution vessel containing the Buffer stage medium. At the times specified for the Buffer stage, withdraw an aliquot of the solution under test. Pass the solution through a suitable filter of 0.45-um pore size and discard the first few milliliters of the filtrate.

4.1.4.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 214 nm

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

Flow rate: 1 mL/min

Injection volume: 80 µL

Run time: NLT 2 times the retention time of clonidine

4.1.4.3 System suitability

Sample: Standard solution

4.1.4.4 Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

4.1.4.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved in the Acid stage medium (Q):

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

r_U = peak response of clonidine from the Sample solution

r_S = peak response of clonidine from the Standard solution s

C_S = concentration of USP Clonidine Hydrochloride RS in the Standard solution (mg/mL) C_{g} = 1

L = label claim (mg/Tablet)

V = volume of Acid stage medium; 500 mL

Calculate the concentration (C) of clonidine hydrochloride (C,H,CIN, HCI) in the sample withdrawn at each Buffer stage time point (1):

                        Result = (r_U/r_S) x C_S

r_U = peak response of clonidine from the Sample solution at each time point, i

r_S = peak response of clonidine from the Standard solution s

C_S = concentration of USP Clonidine Hydrochloride RS in the Standard solution (mg/mL) C_{s} = 1

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved at each time point (1):

                       Result₁ = [C₁ x V x (1/L) x 100) + Q_A

                       Result₂ = {[(C₂ x (V - V_S) + (C₁ x V_S)} x (1/L) x 100) + Q_A

                       Result₃ = [({C₃ x [V - (2 x V_S)] + [(C₂ + C₁) x V_S) x (1/L) x 100] + Q_A

C_i = concentration of clonidine hydrochloride in the Sample solution withdrawn at the specified time point (mg/mL) 

V = volume of Buffer stage medium, 500 mL

L = label claim (mg/Tablet)

Q_A = 1 percentage of the labeled amount of clonidine hydrochloride dissolved in the Acid stage medium (%)

V = volume of the Sample solution withdrawn at each time point (mL)

4.1.4.6 Tolerances

Acid stage: 18%-38% of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) is dissolved in 2 h.

Buffer stage: See Table 5

   Table 5

The percentages of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved at the times specified conform to Dissolution (711). Acceptance Table 2.

4.1.5 Test 5

Acid stage medium: 0.01 N hydrochloric acid; 500 mL

Buffer stage medium: pH 7.0 phosphate buffer (dissolve 6.8 g of monobasic potassium phosphate in water and add 7.0 mL of 5 N sodium hydroxide. Dilute to 1000 mL with water. Adjust with dilute phosphoric acid or dilute sodium hydroxide to a pH of 7.0.); 500 mL

Apparatus 2: 50 rpm with a suitable sinker

4.1.5.1 Times

Acid stage: 2 h

Buffer stage: 2, 6, and 16 h. The time in the Buffer stage medium does not include the time in the Acid stage medium.

Buffer: 6.9 g/L of monobasic sodium phosphate in water. Adjust with phosphoric acid to a pH of 3.0.

Mobile phase: Acetonitrile and Buffer (60:40)

Standard solution: 0.4 µg/mL of USP Clonidine Hydrochloride RS in Buffer stage medium

Sample solution: After 2 h in the Acid stage medium, withdraw an aliquot of the solution under test. Pass the solution through a suitable filter of 0.45-µm pore size and discard the first few milliliters of the filtrate. Carefully transfer the Tablet with sinker to a dissolution vessel containing the Buffer stage medium. At the times specified for the Buffer stage, withdraw an aliquot of the solution under test. Pass the solution through a suitable filter of 2.7-um pore size and discard the first few milliliters of the filtrate.

4.1.5.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 210 nm

Column: 4.6-mm x 10-cm; 5-µm packing 19

Column temperature: 30°

Flow rate: 1 mL/min.

Injection volume: 100 µL

Run time: NLT 1.5 times the retention time of clonidine

4.1.5.3 System suitability

Sample: Standard solution

4.1.5.4 Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

4.1.5.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved in the Acid stage medium (Q):

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

r_U = peak response of clonidine from the Sample solution

r_S = peak response of clonidine from the Standard solution

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

L = label claim (mg/Tablet)

V = volume of Acid stage medium; 500 mL 

Calculate the concentration (C) of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) in the sample withdrawn at each Buffer stage time point (1):

                        Result = (r_U/r_S) x C_S

r_U = peak response of clonidine from the Sample solution at each time point, /

r_S = peak response of clonidine from the Standard solution

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

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved at each time point (1):

                       Result₁ = [C₁ x V x (1/L) x 100) + Q_A

                       Result₂ = {[(C₂ x (V - V_S) + (C₁ x V_S)} x (1/L) x 100) + Q_A

                       Result₃ = [({C₃ x [V - (2 x V_S)] + [(C₂ + C₁) x V_S) x (1/L) x 100] + Q_A

C_i = concentration of clonidine hydrochloride in the Sample solution withdrawn at the specified time point (mg/mL)

V = volume of Buffer stage medium, 500 mL

L = label claim (mg/Tablet)

Q_A = percentage of the labeled amount of clonidine hydrochloride dissolved in the Acid stage medium (%)

V_S = volume of the Sample solution withdrawn at each time point (mL)

4.1.5.6 Tolerances

Acid stage: 8%-28% of the labeled amount of clonidine hydrochloride (C₂H₂CI,N, HCI) is dissolved in 2 h.

Buffer stage: See Table 6.

    Table 6

The percentages of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved at the times specified conform to Dissolution (711), Acceptance Table 2.

4.1.6 Test 6:

If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 6.

Acid stage medium: 0.01 N hydrochloric acid; 500 mL

Buffer stage stock solution: Dissolve 13.61 g of monobasic potassium phosphate in 400 mL of 0.19 N sodium hydroxide. Adjust the concentration of 0.19 N sodium hydroxide, if necessary, so that a mixture of 10 mL of the solution with 40 mL of Acid stage medium has a pH of 7.0.

Buffer stage medium: pH 7.0 phosphate buffer (To 400 mL of Acid stage medium add 100 mL of pre-warmed Buffer stage stock solution.); 500 ml

Apparatus 2: 50 rpm with wire sinker

4.1.6.1 Times

Acid stage: 1 and 2 h

[NOTE-The result calculated in Acid stage for 2 h is only used for cummulative calculation and not reported.]

Buffer stage: 2, 6, and 14 h. The time in the Buffer stage medium does not include the time in the Acid stage medium.

Solution A: Transfer 1 mL of triethylamine to 1 L of water. Adjust with phosphoric acid to a pH of 6.9.

Mobile phase: Acetonitrile and Solution A (16:84)

Standard stock solution: 4 µg/ml, of USP Clonidine Hydrochloride RS in methanol. Sonicate to dissolve, if necessary.

Acid stage standard solution: 0.08 µg/mL of USP Clonidine Hydrochloride RS from Standard stock solution in Acid stage medium

Buffer stage standard solution: 0.2 µg/mL of USP Clonidine Hydrochloride RS from Standard stock solution in Buffer stage medium

Acid stage sample solution: At the times specified, withdraw 10 mL of the solution under test. Pass through a suitable filter of 0.45-µm pore size, discarding an appropriate volume of filtrate so that a consistent result can be obtained. After 2 h, withdraw 90 mL of the solution under test and proceed to Buffer stage.

Buffer stage sample solution: At the times specified, withdraw 10 mL of the solution under test and replace with same volume of the Buffer stage medium maintained at 37°. Pass through a suitable filter of 0.45-µm pore size, discarding an appropriate volume of filtrate so that a consistent result can be obtained.

4.1.6.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 210 nm

Column: 4.6-mm x 10-cm; 5-µm packing Li

Column temperature: 35°

Flow rate: 1 mL/min

Injection volume: 100 µL

Run time: NLT 1.4 times the retention time of clonidine

4.1.6.3 System suitability

Samples: Acid stage standard solution and Buffer stage standard solution

4.1.6.4 Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 3.0%

4.1.6.5 Analysis

Samples: Acid stage standard solution, Buffer stage standard solution, Acid stage sample solution, and Buffer stage sample solution

Acid stage

Calculate the concentration (C) of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) in the portion of sample withdrawn in Acid stage from the vessel at each time point (1):

                            Result = (r_i/r_S) x C_SA

r_i = peak response of clonidine from the Acid stage sample solution at time point /

r_S = peak response of clonidine from the Acid stage standard solution r_{s} = 1

C_SA = concentration of USP Clonidine Hydrochloride RS in the Acid stage standard solution (mg/mL)

[NOTE-The result calculated in Acid stage for 2 h is only used for cummulative calculation and not reported.]

Calculate the percentage of the labeled amount of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) dissolved at 1 h in the Acid stage:

                          Result = C x V x (1/L) x 100

C = concentration of clonidine hydrochloride in the portion of the sample withdrawn at 1 h in the Acid stage (mg/mL) 

V = volume of Acid stage medium (500 mL)

L = label claim (mg/Tablet)

Buffer stage

Calculate the concentration (C) of clonidine hydrochloride (C₉H₉Cl₂N₃ · HCl) in the portion of sample withdrawn in Buffer stage from the vessel at each time point (/):

                         Result_i = (r_i/r_S) x C_SB

r_i = peak response of clonidine from the Buffer stage sample solution at time point i 5

r_S = peak response of clonidine from the Buffer stage standard solution

C_SB = concentration of USP Clonidine Hydrochloride RS in the Buffer stage standard solution (mg/mL)

Calculate the percentage of the labeled amount of clonidine hydrochloride (C,H,CI,N, HCI) dissolved in Buffer stage at each time point (0):

                       Result₁ = [(C₁ x V) x (C_A2 x V_A2) x (C_A1 x V_A1)] x (1/L) x 100

                       Result₂ = [(C₂ x V) x (C₁ x V_S) x (C_A2 x V_A2)] x (1/L) x 100) 

                       Result₃ = {(C₃ x V) x (C₂ x C₁) x  V_S)] + [(C_A1 + V_A1)} x (1/L) x 100

C_i = concentration of clonidine hydrochloride in the portion of the sample withdrawn in Buffer stage at time point i (mg/mL)

V = volume of Buffer stage medium (500 mL)

C_A2 = concentration of clonidine hydrochloride in the portion of the sample withdrawn in Acid stage at 2 h (mg/mL)

V_A2 = volume of Acid stage sample solution withdrawn at 2 h (90 mL)

C_A1 = concentration of clonidine hydrochloride in the portion of the sample withdrawn in Acid stage at 1 h (mg/mL)

V_A1 = volume of Acid stage sample solution withdrawn at 1 h (10 mL)

L = label claim (mg/Tablet)

V_S = volume of Buffer stage sample solution withdrawn (10 mL) V_{s} = 1

4.1.6.6 Tolerances

Acid stage: NMT 20% of the labeled amount of clonidine hydrochloride (C H Cl N · HCl) is dissolved in 1 h.

Buffer stage: See Table 7.

   Table 7 

The percentages of the labeled amount of clonidine hydrochloride (C₂H₂CIN HCI) dissolved at the times specified conform to Dissolution (711), Acceptance Table 2. (RB 1-Sep-2024)

UNIFORMITY OF DOSAGE UNITS (905): Meet the requirements

5 IMPURITIES

Change to read:

5.1 ORGANIC IMPURITIES

Buffer: Dissolve 4 g of octanesulfonic acid sodium salt in 1000 mL of water.

Solution A: Methanol, Buffer, and phosphoric acid (45: 55:0.1). Adjust with phosphoric acid to a pH of 2.5.

Solution B: Acetonitrile, methanol, and water (65:5:30)

Mobile phase: See ^▲Table 8.

Table 8▲_{(RB 1-Sep-2024)}

Diluent 1: 4 g of octanesulfonic acid sodium salt in 1 L of water. Add 1 mL of phosphoric acid. Adjust with triethylamine to a pH of 2.5.

Diluent 2: Methanol and Diluent 1 (50:50)

Standard stock solution: 0.25 mg/mL of USP Clonidine Hydrochloride RS in methanol. Sonicate to dissolve, if needed.

Standard solution: 0.125 µg/mL of USP Clonidine Hydrochloride RS in Diluent 2 from the Standard stock solution

Sensitivity solution: 0.025 µg/mL of USP Clonidine Hydrochloride RS in Diluent 2 from the Standard solution

Sample stock solution: Nominally 0.05 mg/mL of clonidine hydrochloride prepared as follows. Weigh and finely powder NLT 20 Tablets.

Transfer a portion of the powder equivalent to 1 mg of clonidine hydrochloride to a 20-mL volumetric flask. Add 15 mL of methanol Sonicate for 15 min with intermittent shaking every 2 min at 10". Dilute with methanol to volume. Centrifuge for 10 min and use the supernatant.

Sample solution: Nominally 25 µg/mL of clonidine hydrochloride in Diluent 1 from the Sample stock solution. Pass through a suitable filter of 0.45-µm pore size. Discard the first few milliliters of the filtrate.

5.1.1 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: 220 nm

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

Autosampler temperature: 10°

Flow rate: 1 mL/min

Injection volume: 100 µL

5.1.2 System suitability

Samples: Standard solution and Sensitivity solution

5.1.3 Suitability requirements

Tailing factor: NMT 2.0, Standard solution

Relative standard deviation: NMT 5.0%, Standard solution

Signal-to-noise ratio: NLT 10, Sensitivity solution

5.1.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of any unspecified degradation product in the portion of Tablets taken:

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

r_U = peak response of any unspecified degradation product from the Sample solution

r_S = peak response of clonidine from the Standard solution

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

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

5.1.5 Acceptance criteria

Any unspecified degradation product: NMT 1.0%

Total degradation products: NMT 3.0%

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight, light-resistant containers, and store at controlled room temperature.

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

USP REFERENCE STANDARDS (11)

LISP Clonidine Hydrochloride RS