Yohimbine 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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C₂₁H₂₆N₂O₃ · HCl      390.90

17α-Hydroxy-20-α-yohimban-16-β-carboxylic acid, methyl ester, hydrochloride CAS RN: 65-19-0; UNII: NB2E1YP49F.

Yohimbine Hydrochloride contains not less than 98.0 percent and not more than 102.0 percent of C₂₁H₂₆N₂O₃ · HCl, calculated on the dried basis.

Packaging and storage—Preserve in tight containers, and store at controlled room temperature.

Labeling—Where it is intended for veterinary use only, it is so labeled.

USP REFERENCE STANDARDS (11)

USP Yohimbine 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-Dissolve 10 mg of it in 1 mL of methanol, add 1 drop of ammonium hydroxide, and mix.

Application volume: 1 µL.

Developing solvent system: methylene chloride, methanol, and ammonium hydroxide (90:14:1), in a saturated chamber.

Procedure-Allow the plate to air-dry in a hood. Expose the dry plate for 30 minutes to short-wavelength UV light, then examine under long-wavelength UV light: the size, intensity, and R, value of the principal spot in the chromatogram obtained from the Test solution correspond to

those characteristics of the principal spot in the chromatogram obtained from the Standard solution.

Change to read:

C: SPECTROSCOPIC IDENTIFICATION TESTS (197), Ultraviolet-Visible Spectroscopy: 197U _{(CN 1-May-2020)}

Solution: 10 µg per mL.

Medium: 0.1 N hydrochloric acid in methanol.

D: To 10 mg of it add 3 drops of sulfuric acid. Mix, and add 50 mg of ammonium vanadate: a violet color is produced (differentiation from strychnine, which produces a red color). Add 1 mL of water: no color change occurs.

SPECIFIC ROTATION (781S): between +100° and +105°.

Test solution: 10 mg per mL, in water, prepared by warming on a steam bath and allowing to cool.

LOSS ON DRYING (731)-Dry it at 105° for 2 hours: it loses not more than 1.0% of its weight.

Chromatographic purity-Use the chromatogram of the Assay preparation obtained as directed in the Assay. Calculate the percentage of each impurity in the portion of Yohimbine Hydrochloride taken by the formula:

100(r_i/r_s)

in which r_i is the response of the individual impurity; and r_s is the sum of all the responses in the chromatogram: not more than 1.0% of any individual impurity is found, and the sum of all the impurities found is not more than 2.0%.

2 Assay

Mobile phase-Prepare a mixture of water, dibasic sodium phosphate dihydrate solution (11.88 g per L), and monobasic potassium phosphate solution (9.08 g per L) (355:100:50). Add 4 g of sodium dodecyl sulfate, and mix. Add 285 mL of acetonitrile, and mix. Make adjustments if necessary (see System Suitability under Chromatography (621)).

Standard preparation-Quantitatively dissolve an accurately weighed quantity of USP Yohimbine Hydrochloride RS in methanol to obtain a solution having a known concentration of about 0.2 mg per mL..

Assay preparation-Transfer about 50 mg of Yohimbine Hydrochloride, accurately weighed, to a 100-ml volumetric flask, dilute with methanol to volume, and mix. Transfer 10.0 mL of this solution to a 25-mL volumetric flask, dilute with methanol to volume, and mix.

System suitability solution-Quantitatively dilute an accurately measured volume of the Standard preparation with methanol to obtain a solution having a concentration of 0.40 µg of USP Yohimbine Hydrochloride RS per mL.

Chromatographic system (see CHROMATOGRAPHY (621))-The liquid chromatograph is equipped with a 229-nm detector and a 4-mm x 12.5-cm column that contains 4-um packing L.7. The flow rate is about 2 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the main yohimbine peak gives a measurable response. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not more than 2.5; and the relative standard deviation for replicate injections is not more than 1%. Procedure-Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph,

record the chromatograms, and measure the areas for the major peaks. Calculate the quantity, in mg, of C₂₁H₂₆N₂O₃ · HCl in the portion of Yohimbine Hydrochloride taken by the formula:

250C(r_u /r_s )

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