Tolazoline 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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Tolazoline Hydrochloride Injection is a sterile solution of Tolazoline Hydrochloride in Water for Injection. It contains not less than 95.0 percent and not more than 105.0 percent of the labeled amount of C₁₀H₁₂N₂ · HCl.

1 Packaging and storage

Preserve in single-dose or in multiple-dose containers, preferably of Type I glass.

1.1 USP Reference standards 〈11〉

USP Tolazoline Hydrochloride RS

2 Identification

Change to read:

A: Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K -Obtain the test specimen as follows. Steam-distill a volume of Injection, equivalent to about 250 mg of tolazoline hydrochloride, for 5 to 10 minutes, and discard the distillate. Transfer the remaining solution to a separator, add about 2 mL of 1 N sodium hydroxide, and extract with 20 mL of ether. Filter the ether extract through cotton into a beaker, evaporate to dryness, and dry the residue in vacuum over silica gel for 4 hours.

B: It responds to Identification test B under Tolazoline Hydrochloride.

C: To 1 mL of Injection add 1 mL of ammonium reineckate TS: a pink precipitate is formed.

Bacterial Endotoxins Test 〈85〉-It contains not more than 0.8 USP Endotoxin Unit per mg of tolazoline hydrochloride.

pH 〈791〉: between 3.0 and 4.0.

3 Other requirements

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

4 Assay

Standard preparation-Transfer about 30 mg of USP Tolazoline Hydrochloride RS, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix.

Assay preparation-Transfer an accurately measured volume of Injection, equivalent to about 150 mg of tolazoline hydrochloride, to a 100-mL volumetric flask, dilute with methanol to volume, and mix. Transfer 20.0 mL of this solution to a second 100-mL volumetric flask, dilute with methanol to volume, and mix.

Procedure-Transfer 3.0 mL each of the Standard preparation, the Assay preparation, and methanol to provide the blank, to separate 25-mL volumetric flasks. To each flask add 1 mL of 0.5 N sodium hydroxide and 1 mL of dilute sodium nitroferricyanide TS (1 in 2), mix, and allow to stand for 10 minutes. Add 3 mL of sodium bicarbonate solution (1 in 12) to each flask, dilute with water to volume, mix, and allow to stand for 10 minutes. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 565 nm, with a suitable spectrophotometer, against the blank. Calculate the quantity, in mg, of C₁₀H₁₂N₂ · HCl in each mL of the Injection taken by the formula:

(0.5C/V)(Aᵤ/Aₛ)

in which C is the concentration, in µg per mL, of USP Tolazoline Hydrochloride RS in the Standard preparation, V is the volume, in mL, of Injection taken, and Aᵤ and Aₛ are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.