Diphenhydramine Hydrochloride Injection

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 Injection is a sterile solution of Diphenhydramine Hydrochloride in Water for Injection. It contains NLT 90.0% and NMT 110.0% of the labeled amount of diphenhydramine hydrochloride (C₁₇H₂₁NO · HCI).

2 IDENTIFICATION

A.

Sample solution: Dilute a volume of Injection equivalent to 50 mg of diphenhydramine hydrochloride with 0.03 N sulfuric acid to 25 mL.

Analysis: Proceed as directed in Identification-Organic Nitrogenous Bases (181), beginning with "Transfer the liquid to a separator".

Acceptance criteria: Meets the requirements

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

Solution A: Buffer

Solution B: Acetonitrile

Mobile phase: See Table 1.

Table 1

Diluent: Acetonitrile and Buffer (35:65)

System suitability solution: 0.1 mg/mL each of USP Diphenhydramine Related Compound A RS and USP Diphenhydramine Hydrochloride RS in Diluent

Standard solution: 0.07 mg/mL of USP Diphenhydramine Hydrochloride RS in Diluent

Sample solution: Nominally equivalent to 0.07 mg/mL of diphenhydramine hydrochloride in Diluent prepared as follows. Transfer 5.0 mL of Injection, equivalent to 250 mg of diphenhydramine hydrochloride, to a 500-ml volumetric flask and dilute with water to volume. Transfer 7.0 mL of this solution to a 50-mL volumetric flask and dilute with Diluent to volume.

3.1.1 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 220 nm

Column: 4.6-mm x 25-cm; 5-um packing L.7

Flow rate: 1.2 mL/min

Injection volume: 10 µL

3.1.2 System suitability

Samples: System suitability solution and Standard solution

[NOTE-The relative retention times for diphenhydramine related compound A and diphenhydramine are about 0.9 and 1.0, respectively.]

3.1.3 Suitability requirements

Resolution: NLT 2.0 between diphenhydramine and diphenhydramine related compound A, System suitability solution

Relative standard deviation: NMT 2.0%, Standard solution

3.1.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of diphenhydramine hydrochloride (C₁₇H₂₁NO · HCI) in the portion of Injection taken:

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

r_U = peak response from the Sample solution

r_S = peak response 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)

Acceptance criteria: 90.0%-110.0%

4 IMPURITIES

4.1 ORGANIC IMPURITIES

Buffer, System suitability solution, and Chromatographic system: Proceed as directed in the Assay with a run time that is 10 times the retention time of diphenhydramine.

Mobile phase: Acetonitrile and Buffer (35:65)

Standard solution: 0.002 mg/mL of USP Diphenhydramine Hydrochloride RS in Mobile phase

Sample solution: Nominally equivalent to 2 mg/mL of diphenhydramine hydrochloride in water prepared as follows. Transfer a volume of Injection, equivalent to 500 mg of diphenhydramine hydrochloride, to a 250-ml volumetric flask and dilute with water to volume.

4.1.1 System suitability

Samples: System suitability solution and Standard solution

[NOTE-See Table 2 for the relative retention times. Inject a blank injection between the System suitability solution and Standard solution.]

4.1.2 Suitability requirements

Resolution: NLT 2.0 between diphenhydramine and diphenhydramine related compound A, System suitability solution

Relative standard deviation: NMT 5.0%, Standard solution

4.1.3 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each degradation product in the portion of Injection taken:

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

r_U = peak response of each degradation product from the Sample solution

r_S = peak response from the Standard solution s

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

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

F = relative response factor (see Table 2)

Acceptance criteria: See Table 2. Disregard any peaks less than 0.05%.

Table 2

^a Diphenylmethanol.

^b Diphenylmethanone.

5 SPECIFIC TESTS

PH (791): 4.0-6.5

BACTERIAL ENDOTOXINS TEST (85): NMT 3.4 USP Endotoxin Units/mg of diphenhydramine hydrochloride

OTHER REQUIREMENTS: It meets the requirements in Injections and Implanted Drug Products (1).

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in single-dose or multiple-dose containers, preferably of Type I glass, protected from light. Store at controlled room temperature.

USP REFERENCE STANDARDS (11)

USP Diphenhydramine Hydrochloride RS

USP Diphenhydramine Related Compound A RS

2-(Diphenylmethoxy)-N-methylethanamine hydrochloride.

C₁₆H₁₉NO · HCI             277.79