Xylazine Hydrochloride

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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C₁₂H₁₆N₂S · HCl       256.79

4H-1,3-Thiazin-2-amine, N-(2,6-dimethylphenyl)-5,6-dihydro-, monohydrochloride.

5,6-Dihydro-2-(2,6-xylidino)-4H-1,3-thiazine hydrochloride CAS RN: 23076-35-9; UNII: NGC3S0882S.

Xylazine Hydrochloride contains not less than 98.0 percent and not more than 102.0 percent of C₁₂H₁₆N₂S · HCl.

Packaging and storage—Preserve in tight containers. Store at 25°, excursions permitted between 15° and 30°.

Labeling—Where it is intended for veterinary use only, the label so states.

USP REFERENCE STANDARDS (11)-

USIP Xylazine Hydrochloride RS

1 Identification

Change to read:

A: Spectroscopic Identification Tests (197), Infrared Spectroscopy: 197K _{(CN 1-May-2020)}

B: Thin-Layer Chromatographic Identification Test (201)

Test solution: 5 mg per mL, in methanol.

Developing solvent system: methanol and ammonium hydroxide (98.5:1.5).

Procedure-Separately apply 1 µL of the Test solution and the Standard solution. Allow the applications to dry with the aid of a stream of nitrogen, develop in a saturated chromatographic chamber, and dry the plate in a current of air: the size, intensity, and R, value of the principal spot obtained from the Test solution correspond to those of the principal spot obtained from the Standard solution.

MELTING RANGE (741): between 164^o and 168°.

PH (791); between 4.0 and 6.0, in a solution (1 in 100).

LOSS ON DRYING (731)-Dry it at 105° for 4 hours: it loses not more than 1.0% of its weight.

RESIDUE ON IGNITION (281): not more than 0.1%.

Chromatographic purity Examine the chromatogram obtained from the Assay preparation. Calculate the percentage of impurities in the Xylazine Hydrochloride taken by the formula:

100r_s /(r_u + r_s )

in which r_s is the sum of the areas of all the impurity peaks observed, and r_u is the area of the xylazine peak: the sum of the impurity responses is not greater than 2.0%.

2 Assay

Mobile phase-Dissolve 6.0 g of sodium 1-heptanesulfo nate in 2500 mL of water, add 60 mL of glacial acetic acid, dilute with water to 3000 mL, and mix. Prepare a mixture of 2200 mL of this solution and 1800 ml of methanol, and pass through a filter having a 0.5-µm or finer porosity. Make adjustments if necessary (see System Suitability under Chromatography (621)).

Standard preparation-Prepare a solution of USP Xylazine Hydrochloride RS in Mobile phase having a known concentration of about 1 mg per mL.

Assay preparation-Transfer about 25 mg of Xylazine Hydrochloride, accurately weighed, to a 25-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.

Chromatographic system (see CHROMATOGRAPHY (621))-The liquid chromatograph is equipped with a 254-nm detector, a 2 - mm * 2 - 4 cm guard column that contains packing L1, and a 3.9-mm x 30-cm analytical column that contains packing L1 and is maintained at a constant temperature of about 40". The flow rate is about 2.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.0%. [NOTE-After daily use, rinse the

column with 100 mL of acetonitrile and with 100 mL of methanol, and store the column containing methanol.] Procedure-Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C₁₂H₁₆N₂S · HCl in the portion of Xylazine Hydrochloride taken by the formula:

25C(r_u /r_s )

in which C is the concentration, in mg per mL, of USP Xylazine Hydrochloride RS in the Standard preparation; and r_u and r_s are the areas of the xylazine peak responses in the chromatograms obtained from the Assay preparation and the Standard preparation, respectively.