Digitoxin

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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C41H64013            764.94

Card-20(22)-enolide, 3-[(0-2,6-dideoxy-β-D-ribo-hexopyranosyl-(1-4)-0-2,6-dideoxy-β-D-ribo-hexopyranosyl-(1-4)-2,6-dideoxy-ẞ-D-ribo-hexopyranosyl)oxy]-14-hydroxy, (3β,5β)-.

Digitoxin   CAS RN^®: 71-63-6; UNII: E90NZP2L9U.

» Digitoxin is a cardiotonic glycoside obtained from Digitalis purpurea L., Digitalis lanata Ehrh. (Fam. Scrophulariaceae), and other suitable species of Digitalis. Digitoxin contains not less than 92.0 percent and not more than 103.0 percent of C₄₁H₆₄O₁₃ calculated on the dried basis. 

[CAUTION-Handle Digitoxin with exceptional care since it is highly potent.]

1 Packaging and storage-

Preserve in tight containers.

2 USP REFERENCE STANDARDS (11)-

USP Digitoxin RS

3 Identification-

Change to read:

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

B: Prepare a test solution in methanol containing 1 mg per mL. Apply 1 µL of the test solution and 1 µL of a Standard solution of USP Digitoxin RS in methanol containing 1 mg per mL to a suitable thin-layer chromatographic plate (see Chromatography (621)) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the applications to dry, and develop the chromatogram in a solvent system consisting of a mixture of methylene chloride and methanol (93:7) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and dry the plate at 100" to remove the solvent. Spray the plate with a 6 in 10 solution of sulfuric acid in methanol, heat at 105° for 10 minutes, and examine the chromatogram under long-wavelength UV light: the R_F value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

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

LOSS ON DRYING (731)-Dry it in vacuum at 105° for 1 hour: it loses not more than 1.5% of its weight.

RESIDUE ON IGNITION (281): negligible, from 100 mg.

4 Assay-

Mobile phase-Prepare a filtered and degassed mixture of water and acetonitrile (55:45). Make adjustments if necessary (see System

Suitability under Chromatography (621)).

Standard preparation-Dissolve an accurately weighed quantity of USP Digitoxin RS in Mobile phase, and dilute quantitatively, and stepwise if

necessary, with Mobile phase to obtain a solution having a known concentration of about 40 µg per mL.

Assay preparation-Transfer about 50 mg of Digitoxin, accurately weighed, to a 200-mL volumetric flask. Dissolve in and dilute with Mobile

phase to volume, and mix. Pipet 4 mL of this solution into a 25-mL volumetric flask, dilute with Mobile phase to volume, and mix.

System suitability preparation-Prepare a solution in Mobile phase containing about 40 µg each of digitoxin and Digoxin per mL.

Chromatographic system (see Chromatography (621))-The liquid chromatograph is equipped with a 218-nm detector and a 3.9-mm x 30-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation and the System suitability preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.35 for digoxin and 1.0 for digitoxin; the resolution, R, between the digoxin and digitoxin peaks is not less than 2.0; the tailing factor for the analyte peak is not more than 2.0; and the relative standard deviation for replicate injections of the Standard preparation is not more than 2.0%.

Procedure-Separately inject equal volumes (about 50 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 C₄₁H₆₄O₁₃ in the portion of Digitoxin taken by the formula: 

                1.25C(r_U/r_S)

in which C is the concentration, in µg per mL, of USP Digitoxin RS in the Standard preparation, and r_U and r_S are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.