Phentolamine Mesylate for 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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>> Phentolamine Mesylate for Injection is sterile Phentolamine Mesylate or a sterile mixture of Phentolamine Mesylate with a suitable buffer or suitable diluents. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C₁₇H₁₉N₃O·CH₄O₃S.

1 Packaging and storage

Preserve as described in Packaging and Storage Requirements (659), Injection Packaging, Packaging for constitution.

2 USP REFERENCE STANDARDS (11)

USP Phentolamine Mesylate RS

3 Constituted solution

At the time of use, it meets the requirements for Injections and Implanted Drug Products (1), Specific Tests, Completeness and clarity of solutions.

4 Identification

Mix a portion of it, equivalent to about 40 mg of phentolamine mesylate, with about 15 mL of chloroform. Filter into a beaker, and evaporate to dryness, taking precautions against introducing moisture: the residue so obtained responds to Identification test A under Phentolamine Mesylate.

4.1 BACTERIAL ENDOTOXINS TEST (85)

It contains not more than 5.8 USP Endotoxin Units per mg of phentolamine mesylate.

4.2 UNIFORMITY OF DOSAGE UNITS (905)

Meets the requirements.

Procedure for content uniformity-Dissolve the contents of 1 container in water to provide a solution containing about 20 µg of phentolamine mesylate per mL. Concomitantly determine the absorbances of this solution and of a solution of USP Phentolamine Mesylate RS, in the same medium, at a concentration of about 20 µg per mL, in 1-cm cells at the wavelength of maximum absorbance at about 278 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in mg, of C₁₇H₁₉N₃O·CH₄O₃S in the Phentolamine Mesylate for Injection taken by the formula:

(T/D)C(A_U/A_S)

in which T is the labeled quantity, in mg, of phentolamine mesylate in the Phentolamine Mesylate for Injection, D is the concentration, in µg per mL, of phentolamine mesylate in the solution from the Phentolamine Mesylate for Injection, based on the labeled quantity per container and the extent of dilution, C is the concentration, in µg per mL, of USP Phentolamine Mesylate RS in the Standard solution, and A_U and A_S are the absorbances of the solution from the Phentolamine Mesylate for Injection and the Standard solution, respectively.

4.3 PH (791)

Between 4.5 and 6.5, in a freshly prepared solution having a concentration of about 1 in 100.

5 Other requirements

It meets the requirements for Sterility Tests (71) and Labeling (7), Labels and Labeling for Injectable Products.

6 Assay

6.1 Standard preparation

Transfer about 25 mg of USP Phentolamine Mesylate RS, accurately weighed, to a 50-mL volumetric flask, add water to volume, and mix.

6.2 Assay preparation

Dissolve the contents of 10 containers of Phentolamine Mesylate for Injection in a volume of water corresponding to the volume of solvent specified in the labeling. Transfer an aliquot, equivalent to about 25 mg of phentolamine mesylate, to a 50-mL volumetric flask, add water to volume, and mix.

6.3 Procedure

Pipet 5-mL portions, respectively, of the Standard preparation, Assay preparation, and water to provide a blank, into separate 125-mL separators. Into each separator pipet 5-mL portions of 0.1 N hydrochloric acid and saturated picric acid solution. Extract with three 25-mL portions of chloroform, filtering each portion through chloroform-washed cotton into a 100-mL volumetric flask. Dilute with chloroform to volume, and mix. Concomitantly determine the absorbances of the solutions from the Assay preparation and the Standard preparation in 1-cm cells at the wavelength of maximum absorbance at about 410 nm, with a suitable spectrophotometer, against the blank. Calculate the quantity, in mg, of C₁₇H₁₉N₃O·CH₄O₃S in the aliquot of Phentolamine Mesylate for Injection taken by the formula:

50C(A_U/A_S)

in which C is the concentration, in mg per mL, of USP Phentolamine Mesylate RS in the Standard preparation, and A_U and A_S are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.