Caffeine Citrate Injection

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

DOWNLOAD PDF HERE

1 DEFINITION

Caffeine Citrate Injection is a sterile solution containing Caffeine and citric acid in Water for Injection. It contains NLT 90.0% and NMT 110.0% of the labeled amount of caffeine citrate (C₁₄H₁₈N₄O₉). It contains no bacteriostat or other preservative.

2 IDENTIFICATION

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

B. IDENTIFICATION TESTS GENERAL (191), Citrate: Meets the requirements

C.

Solution A: Transfer 4 g of potassium iodide to a 100-mL volumetric flask, and add 10 mL of water. Shake until the potassium iodide is dissolved. Add 2 g of iodine to the volumetric flask, and shake until dissolved. Dilute with water to volume.

Sample solution: 5.0 mL of Injection

Analysis: Transfer the Sample solution to a 25-mL centrifuge tube, and add 5 drops of Solution A. Add 0.5 mL of 2.0 M hydrochloric acid.

Acceptance criteria: A brown precipitate that dissolves on neutralization with 0.5 ml. of sodium hydroxide TS is produced.

3 ASSAY

PROCEDURE

Mobile phase: Acetonitrile, tetrahydrofuran, and 0.01 M sodium acetate (5:4:191) adjusted with glacial acetic acid to a pH of 4.5

Theophylline stock solution: 0.02 mg/mL of theophylline in water

Standard solution: 0.2 mg/mL of USP Caffeine RS and 0.004 mg/mL of theophylline from Theophylline stock solution in water

Sample solution: Nominally 0.4 mg/mL of caffeine citrate (equivalent to 0.2 mg/mL of caffeine) from Injection in water, prepared as follows.

Transfer a volume of Injection, equivalent to 50 mg of caffeine, to a 250-mL volumetric flask. Dilute with water to volume, pass through a polyvinylidene difluoride or equivalent membrane of 0.45-µm pore size, and use the filtrate

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 275 nm

Column: 4.6-mm x 15-cm; 5-µm packing 11

Flow rate: 1 mL/min

Injection volume: 10 µL

System suitability

Sample: Standard solution

[NOTE-See Table 1 for the relative retention times.]

Suitability requirements

Resolution: NLT 6.0 between theophylline and caffeine

Tailing factor: NMT 2.0 each for theophylline and caffeine

Relative standard deviation: NMT 2.0% for caffeine

Analysis

Samples: Standard solution and Sample solution

Calculate the concentration (C_A), in mg/mL, of caffeine citrate in the Sample solution:

Result = (r_u /r_s ) × C_s × (M_r1 /M_r2 )

r_u = peak response from the Sample solution

r_s = peak response from the Standard solution

C_s = concentration of USP Caffeine RS in the Standard solution (mg/mL)

M_r1 = molecular weight of caffeine citrate, 386.31

M_r2 = molecular weight of caffeine, 194.19

Calculate the percentage of the labeled amount of caffeine citrate (C₁₄H₁₈N₄O₉) in the portion of Injection taken:

Result = (C_A /C_u ) × 100

C_A = concentration of caffeine citrate in the Sample solution

C_u = nominal concentration of caffeine citrate in the Sample solution

Acceptance criteria: 90.0%–110.0%

4 IMPURITIES

ORGANIC IMPURITIES

Mobile phase, Theophylline stock solution, Standard solution, Sample solution, and Chromatographic system: Proceed as directed in the Assay.

Sensitivity solution: 5 µg/mL of caffeine and 0.1 µg/mL of theophylline from the Standard solution in water

System suitability

Sample: Sensitivity solution

Suitability requirements

Sensitivity: The theophylline peak is discernible.

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each impurity in the portion of Injection taken:

Result = (r_u /r_s ) × (C_s /C_A ) × (M_r1 /M_r2 ) × (1/F) × 100

r_u = peak response of each impurity from the Sample solution

r_s = peak response of caffeine from the Standard solution

C_s = concentration of USP Caffeine RS in the Standard solution (mg/mL)

C_A = concentration of caffeine citrate in the Sample solution as determined in the Assay

M_r1 = molecular weight of caffeine citrate, 386.31

M_r2 = molecular weight of caffeine, 194.19

F = relative response factor (see Table 1)

Acceptance criteria: See Table 1.

Table 1

5 SPECIFIC TESTS

Color and Clarity

Analysis: Transfer a suitable portion of the Injection to a clear glass test tube, and visually examine the solution in a well-lighted area.

Acceptance criteria: The solution is colorless and free of haze, obvious turbidity, and precipitate.

Bacterial Endotoxins Test 〈85〉: NMT 0.25 USP Endotoxin Units/mg of caffeine

Sterility Tests 〈71〉: It meets the requirements of the Test for Sterility of the Product to Be Examined, Membrane Filtration.

pH 〈791〉: 4.2–5.2

Particulate Matter in Injections 〈788〉: NMT 150 particles are equal to or greater than 10 µm, and NMT 25 particles are equal to or greater than 25 µm.

Other Requirements: It meets the requirements under Injections and Implanted Drug Products 〈1〉.

6 ADDITIONAL REQUIREMENTS

Change to read:

Packaging and Storage: Preserve in single-dose, tight containers preferably _{(RB 1-Apr-2023)} of Type I glass, and store between 15°–30°.

USP Reference Standards 〈11〉

USP Caffeine RS