Dibucaine

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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C₂₀H₂₉N₃O₂    343.46

4-Quinolinecarboxamide, 2-butoxy-N-[2-(diethylamino)ethyl]-.

2-Butoxy-N-[2-(diethylamino)ethyl]cinchoninamide  CAS RN®: 85-79-0; UNII: L6JW2TJG99.

Dibucaine contains not less than 97.0 percent and not more than 102.5 percent of C₂₀H₂₉N₃O₂, calculated on the dried basis.

1 Packaging and storage

Preserve in tight, light-resistant containers.

2 USP Reference standards 〈11〉

USP Dibucaine Hydrochloride RS

3 Identification

A: The IR absorption spectrum of a Mineral oil dispersion of it, previously dried, exhibits maxima only at the same wavelengths as that of a similar dispersion of the residue prepared by dissolving 30 mg of USP Dibucaine Hydrochloride RS in 5 mL of 0.5 N sodium hydroxide, extracting the resulting solution with 5 mL of ether, evaporating the ether, and drying the residue over phosphorus pentoxide.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

Melting range 〈741〉: between 62.5° and 66.0°, determined after drying.

Loss on drying 〈731〉-Dry it over phosphorus pentoxide for 16 hours: it loses not more than 1.0% of its weight.

Residue on ignition 〈281〉: not more than 0.2%.

Change to read:

4 Chromatographic purity

Proceed as directed for Organic Impurities under Dibucaine Hydrochloride, except to use a Test solution containing 36.2 mg of Dibucaine per mL: the principal spot obtained from the Test solution corresponds in R value, color, and intensity to that obtained from the Standard solution; the sum of the intensities of any secondary spots, if present in the chromatogram of the Test solution, corresponds to not more than 2.0% of that of the principal spot in the chromatogram of the Standard solution on the basis of comparison with the spots obtained from the Comparison solutions.

5 Assay

Mobile phase-Dissolve 1.20 g of sodium lauryl sulfate, 0.20 g of sodium acetate, and 2.0 mL of triethylamine in 300 mL of water. Adjust with glacial acetic acid to a pH of 5.6, add 700 mL of methanol, mix, and pass through a suitable filter having a 0.5-µm or finer porosity. Make adjustments if necessary (see System Suitability under Chromatography 〈621〉).

Solvent mixture-Prepare a mixture of methanol and water (70:30).

Standard preparation-Dissolve an accurately weighed quantity of USP Dibucaine Hydrochloride RS in Solvent mixture to obtain a solution having a known concentration of about 1 mg per mL. Pass through a suitable filter having a 0.5-µm or finer porosity.

Assay preparation-Transfer about 90 mg of Dibucaine, accurately weighed, to a 100-mL volumetric flask, add Solvent mixture to volume, and mix. Pass through a suitable filter having a 0.5-µm or finer porosity.

Chromatographic system (see Chromatography 〈621〉)-The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency, determined from the analyte peak, is not less than 1500 theoretical plates; the tailing factor for the analyte peak is not more than 3.0; and the relative standard deviation for replicate injections is not more than 2%.

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 area responses for the major peaks. Calculate the quantity, in mg, of C₂₀H₂₉N₃O₂ in the portion of Dibucaine taken by the formula:

(343.46/379.93)(100C)(rᵤ/rₛ)

in which 343.46 and 379.93 are the molecular weights of dibucaine and dibucaine hydrochloride, respectively; C is the concentration, in mg per mL, of USP Dibucaine Hydrochloride RS in the Standard preparation; and rᵤ and rₛ are the responses of the dibucaine peaks obtained from the Assay preparation and the Standard preparation, respectively.