Diphenhydramine Hydrochloride and Ibuprofen Capsules

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

Diphenhydramine Hydrochloride and Ibuprofen Capsules contain NLT 95.0% and NMT 105.0% of the labeled amounts of diphenhydramine hydrochloride (C₁₇H₂₁NO · HCl) and ibuprofen (C₁₃H₁₈O₂).

2 IDENTIFICATION

A. The retention times of the diphenhydramine and ibuprofen peaks of the Sample solution correspond to those of the Standard solution, as obtained in the Assay.

B. The UV absorption spectra of the diphenhydramine and ibuprofen peaks of the Sample solution and those of the Standard solution exhibit maxima at the same wavelengths of 265 and 273 nm, as obtained in the Assay.

3 ASSAY

3.1 PROCEDURE

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

Mobile phase: Acetonitrile and Buffer (38:62)

Standard solution: 0.05 mg/mL of USP Diphenhydramine Hydrochloride RS and 0.4 mg/mL of USP Ibuprofen RS in Mobile phase

Sample stock solution: Nominally 0.25 mg/mL of diphenhydramine hydrochloride and 2.0 mg/mL of ibuprofen, prepared as follows. Transfer NLT 5 Capsules (including shells) to a suitable volumetric flask, add 4% of the final volume of water, and sonicate for 20 min. Dissolve and dilute with Mobile phase to volume. Pass a portion through a suitable filter of 0.45-µm pore size.

Sample solution: Nominally 0.05 mg/mL of diphenhydramine hydrochloride and 0.4 mg/mL of ibuprofen in Mobile phase from Sample stock solution

3.1.1 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

3.1.2 Detectors

Assay: UV 220 nm

Identification B: Diode array, UV 200-400 nm

Column: 4.6-mm x 10-cm; 3-µm packing L11

Column temperature: 25°

Flow rate: 1.0 mL/min

Injection volume: 5 µL

Run time: NLT 4 times the retention time of diphenhydramine

3.1.3 System suitability

Sample: Standard solution

3.1.4 Suitability requirements

Tailing factor: NMT 2.0 for both diphenhydramine and ibuprofen

Relative standard deviation: NMT 2.0% for both diphenhydramine and ibuprofen

3.1.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amounts of diphenhydramine hydrochloride (C₁₇H₂₁NO · HCl) and ibuprofen (C₁₃H₁₈O₂) in the portion of Capsules taken:

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

r_U = peak response of diphenhydramine or ibuprofen from the Sample solution

r_S = peak response of diphenhydramine or ibuprofen from the Standard solution r_{s} = 1

C_S = concentration of USP Diphenhydramine Hydrochloride RS or USP Ibuprofen RS in the Standard solution (mg/mL) C_{5} = 1

C_U = nominal concentration of diphenhydramine hydrochloride or ibuprofen in the Sample solution (mg/mL)

Acceptance criteria: 95.0%-105.0%

4 PERFORMANCE TESTS

Change to read:

4.1 DISSOLUTION (711)

4.1.1 Test 1 ▲(RB 1-May-2020)

Medium: Phosphate buffer, pH 7.2 (27.22 mg/mL of monobasic potassium phosphate in water and adjust with 100 mg/mL of sodium hydroxide to a pH of 7.2); 900 mL

Apparatus 1: 100 rpm

Time: 45 min

Buffer: 6.8 g/L of monobasic potassium phosphate in water. Adjust with 100 mg/mL of sodium hydroxide to a pH of 6.6.

Mobile phase: Methanol and Buffer (65:35)

Standard stock solution: 0.27 mg/mL of USP Diphenhydramine Hydrochloride RS and 2.2 mg/mL of USP Ibuprofen RS, prepared as follows. Transfer known amounts of USP Diphenhydramine Hydrochloride RS and USP Ibuprofen RS to a suitable volumetric flask. Add 5% of the final volume of methanol and sonicate to dissolve. Dilute with Medium to volume.

Standard solution: 0.027 mg/mL of USP Diphenhydramine Hydrochloride RS and 0.22 mg/mL of USP Ibuprofen RS in Medium from Standard stock solution

Sample solution: Pass a portion of the solution under test through a suitable filter of 0.45-µm pore size and discard the first few mL of the filtrate.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 220 nm

Column: 4.6-mm x 15-cm; 5-µm packing L7

Column temperature: 35°

Flow rate: 1.0 mL/min

Injection volume: 5 µL

Run time: NLT 2.3 times the retention time of ibuprofen

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0 for both diphenhydramine and ibuprofen

Relative standard deviation: NMT 2.0% for both diphenhydramine and ibuprofen

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amounts of diphenhydramine hydrochloride (C₁₇H₂₁NO · HCl) and ibuprofen (C₁₃H₁₈O₂) dissolved:

                Result = (r_U/r_S) x C_S x V x (1/L) x 100

r_U = peak response of diphenhydramine or ibuprofen from the Sample solution

r_S = peak response of diphenhydramine or ibuprofen from the Standard solution

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

V = volume of Medium, 900 mL

L = label claim of diphenhydramine or ibuprofen (mg/Capsule)

Tolerances: NLT 75% (Q) of the labeled amounts of diphenhydramine hydrochloride (C₁₇H₂₁NO · HCl) and ibuprofen (C₁₃H₁₈O₂) is dissolved. 

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

4.1.2.1 Tier 1

0.2 M phosphate buffer pH 7.2: Dissolve 27.22 g/L of potassium phosphate, monobasic in water and add 5.52 g/L of sodium hydroxide pellets, and mix. Adjust with 0.2 N sodium hydroxide or 0.2 N hydrochloric acid to a pH of 7.2

Medium: 0.2 M phosphate buffer pH 7.2, 900 mL

Apparatus 1: 100 rpm

Time: 30 min

4.1.2.2 Tier 2

0.2 M phosphate buffer pH 7.2 with pancreatin: 160 mg/L of pancreatin in 0.2 M phosphate buffer pH 7.2

Medium A: 0.2 M phosphate buffer pH 7.2 with pancreatin; 450 mL

Medium B: 0.2 M phosphate buffer pH 7.2; 450 mL

Apparatus 1: 10 mesh, 100 rpm

Times

Medium A: 20 min

Medium A and Medium B (see Procedure): 10 min

Procedure: Perform the test using the conditions under Tier 1. In the presence of cross-linking, repeat the test with new capsules using the conditions under Tier 2 as follows. After 20 min with 450-mL of Medium A, stop the dissolution bath and timer and carefully add 450-mL of Medium B, pre-equilibrated at 37°. Restart the bath and timer, and continue the dissolution for an additional 10 min.

Solution A: 2.72 g/L of potassium phosphate, monobasic in water, adjusted with 10% phosphoric acid to a pH of 3.0

Solution B: Acetonitrile

Mobile phase: See Table 1.

Table 1 

Diluent: 0.2 M phosphate buffer pH 7.2 and 0.2 M phosphate buffer pH 7.2 with pancreatin (50:50)

Standard stock solution A: 0.7 mg/mL of USP Diphenhydramine Hydrochloride RS in Medium for Tier 1, or in Diluent for Tier 2. Sonicate to dissolve.

Standard stock solution B: 1.1 mg/mL of USP Ibuprofen RS. Transfer a suitable quantity of USP Ibuprofen RS to a suitable volumetric flask.

Add about 10% of the flask volume of acetonitrile and sonicate to dissolve. Dilute with Medium for Tier 1, or Diluent for Tier 2, to volume.

Standard solution: 0.028 mg/mL of USP Diphenhydramine Hydrochloride RS and 0.22 mg/mL of USP Ibuprofen RS in Medium for Tier 1, or Diluent for Tier 2

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

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 220 nm

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

Column temperature: 40°

Flow rate: 1.2 mL/min

Injection volume: 20 µL

System suitability

Sample: Standard solution

[NOTE-The relative retention times for diphenhydramine and ibuprofen are 0.3 and 1.0 respectively.]

Suitability requirements

Tailing factor: NMT 2.0 for both diphenhydramine and ibuprofen

Relative standard deviation: NMT 2.0% for diphenhydramine and ibuprofen

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amounts of diphenhydramine hydrochloride (C₁₇H₂₁NO · HCl) and ibuprofen (C₁₃H₁₈O₂) dissolved:

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

r_U = peak response of diphenhydramine or ibuprofen from the Sample solution

r_S = peak response of diphenhydramine or ibuprofen from the Standard solution

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

L = label claim of diphenhydramine hydrochloride or ibuprofen (mg/Capsule)

V = volume of appropriate Medium (Tier 1 or Tier 2), 900 mL.

Tolerances:

NLT 80% (Q) of the labeled amount of diphenhydramine hydrochloride (C₁₇H₂₁NO · HCl) is dissolved; NLT 80% (Q) of the labeled amount of ibuprofen (C₁₃H₁₈O₂) is dissolved. _{▲(RB 1-May-2020)} 

UNIFORMITY OF DOSAGE UNITS (905): Meet the requirements

5 IMPURITIES

Change to read:

5.1 ORGANIC IMPURITIES

Buffer: Proceed as directed in the Assay.

Mobile phase: Acetonitrile and Buffer (32:68)

Diluent: Acetonitrile and Buffer (40:60)

System suitability solution: 0.0005 mg/mL of USP Diphenhydramine Related Compound A RS and 0.25 mg/mL of USP Diphenhydramine Hydrochloride RS in Diluent. Sonicate if necessary to dissolve.

Standard solution: 0.00125 mg/mL of USP Diphenhydramine Hydrochloride RS and 0.01 mg/mL of USP Ibuprofen RS in Diluent. Sonicate to dissolve.

Sample solution: Nominally 0.25 mg/mL of diphenhydramine hydrochloride and 2 mg/mL of ibuprofen, prepared as follows. Transfer a suitable amount of Capsule contents from NLT 10 Capsules to a dry volumetric flask. Add about 60% of the final volume of Diluent and dissolve the contents completely by using a vortex. Dilute with Diluent to volume. Pass a portion through a suitable filter of 0.45-µm pore size.

5.1.1 Chromatographic system

(See Chromatograpby (621), System Suitability.)

Mode: LC

Detector: UV 220 nm

Column: 4.6-mm x 10-cm; 3-µm packing L11

Column temperature: 25°

Flow rate: 1.0 mL/min

Injection volume: 20 µL

Run time: NLT 20 times the retention time of diphenhydramine

5.1.2 System suitability

Samples: System suitability solution and Standard solution

5.1.3 Suitability requirements

Resolution: NLT 1.5 between diphenhydramine related compound A and diphenhydramine, System suitability solution

Relative standard deviation: NMT 5.0% for both diphenhydramine and ibuprofen, Standard solution

5.1.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each individual impurity in the portion of Capsules taken:

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

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

r_S = peak response of diphenhydramine from the Standard solution

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

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

F = relative response factor of each individual impurity (see Table ^▲2_{▲(R8-1-May-2020)})

Acceptance criteria: See Table ^▲2_{▲(RB-1-May-2020)}

Table 2 _{▲(RB 1-May-2020)} 

^a N,N-Dimethyl-2-[phenyl(p-tolyl)methoxy]ethanamine.

^b 2-[(4-Bromophenyl) (phenyl)methoxy]-N,N-dimethylethanamine.

^c Diphenylmethanol.

6 SPECIFIC TESTS

MICROBIAL ENUMERATION TESTS (61) and TESTS FOR SPECIFIED MICROORGANISMS (62): NMT 5 x 10² cfu / g for the total aerobic microbial count; NMT 10² cfu/g for total combined yeasts and molds count. It meets the requirements for absence of Escherichia coli, Salmonella species, Staphylococcus aureus, and Pseudomonas aeruginosa.

7 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers and store at 20°-25°. Protect from light and excessive heat above 40°.

Add the following:

LABELING: When more than one Dissolution test is given, the labeling states the Dissolution test used only if Test 1 is not used._{▲ (RB 1-May-2020)}

USP REFERENCE STANDARDS (11)

USP Diphenhydramine Hydrochloride RS

USP Diphenhydramine Related Compound A RS

2-(Diphenylmethoxy)-N-methylethanamine hydrochloride.

C₁₆H₁₉NO · HCI                 277.79

USP Ibuprofen RS