Quinidine Sulfate Capsules
» Quinidine Sulfate Capsules contain amounts of quinidine sulfate and dihydroquinidine sulfate totaling not less than 90.0 percent and not more than 110.0 percent of the labeled amount of quinidine sulfate, calculated as (C20H24N2O2)2·H2SO4·2H2O.
Packaging and storage— Preserve in tight, light-resistant containers.
USP Reference standards 11
USP Quinidine Sulfate RS Click to View Structure
USP Quininone RS Click to View Structure
    C20H22N2O2     322.40
Identification—
A: Shake a quantity of the contents of Capsules, equivalent to about 100 mg of quinidine sulfate, with 10 mL of dilute sulfuric acid (1 in 350), and filter: an appropriate dilution of the filtrate exhibits a vivid blue fluorescence. On the addition of a few drops of hydrochloric acid the fluorescence disappears.
B: In the test for Chromatographic purity, the RF value of the principal spot obtained from the Test preparation corresponds to that from the Standard preparation.
C: Shake a quantity of the contents of Capsules, equivalent to about 100 mg of quinidine sulfate, with 10 mL of dilute hydrochloric acid (1 in 100), and filter: the filtrate responds to the tests for Sulfate 191.
Dissolution 711
Medium: 0.01 N hydrochloric acid; 900 mL.
Apparatus 1: 100 rpm.
Time: 30 minutes.
Procedure— Determine the amount of (C20H24N2O2)2·H2SO4·2H2O dissolved by employing UV absorption at the wavelength of maximum absorbance at about 248 nm on filtered portions of the solution under test, suitably diluted with Dissolution Medium, in comparison with a Standard solution having a known concentration of USP Quinidine Sulfate RS in the same Medium.
Tolerances— Not less than 85% (Q) of the labeled amount of (C20H24N2O2)2·H2SO4·2H2O is dissolved in 30 minutes.
Uniformity of dosage units 905: meet the requirements.
Procedure for content uniformity— Transfer the contents of 1 Capsule to a 250-mL volumetric flask, add about 175 mL of dilute hydrochloric acid (1 in 100), and shake by mechanical means for 30 minutes. Add dilute hydrochloric acid (1 in 100) to volume, and mix. Filter a portion of the mixture, discarding the first 20 mL of the filtrate. Concomitantly determine the absorbances of this solution, quantitatively diluted, if necessary, and a Standard solution of USP Quinidine Sulfate RS in dilute hydrochloric acid (1 in 100) having a known concentration of about 40 µg per mL, in 1-cm cells, at the wavelength of maximum absorbance at about 345 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in mg, of active ingredients, calculated as quinidine sulfate [(C20H24N2O2)2·H2SO4·2H2O], in the Capsule taken by the formula:
(TC / D)(AU / AS)
in which T is the labeled quantity, in mg, of quinidine sulfate in the Capsule, D is the concentration, in µg per mL, of quinidine sulfate in the solution from the Capsule, based on the labeled quantity per Capsule and the extent of dilution, C is the concentration, in µg per mL, of USP Quinidine Sulfate RS in the Standard solution, and AU and AS are the absorbances of the solution from the Capsule and the Standard solution, respectively.
Chromatographic purity— Shake a quantity of the contents of Capsules, equivalent to about 150 mg of quinidine sulfate, with 25 mL of diluted alcohol for 10 minutes, and filter. Using this as the Test preparation, proceed as directed in the test for Chromatographic purity under Quinidine Sulfate.
Assay—
Methanesulfonic acid solution, Diethylamine solution, Mobile phase, System suitability solution, and Chromatographic system— Proceed as directed for Limit of dihydroquinidine sulfate under Quinidine Sulfate.
Standard preparation— Transfer about 20 mg of USP Quinidine Sulfate RS, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.
Assay preparation— Transfer the contents of not fewer than 20 Capsules to a container, and mix. Transfer an accurately weighed portion of the powder, equivalent to about 160 mg of quinidine sulfate, to a 100-mL volumetric flask, add 80 mL of methanol, and shake the flask by mechanical means for 30 minutes. Dilute with methanol to volume, mix, and filter, discarding the first 10 mL of the filtrate. Transfer 3.0 mL of the filtrate to a 25-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Procedure —Separately inject equal volumes (about 50 µL) of the Standard preparation and the Assay preparation into a chromatograph. Calculate the quantity, in mg, of the sum of quinidine sulfate and dihydroquinidine sulfate in the portion of Capsules taken by the formula:
(2500 / 3)C(rb,U + rd,U) / (rb,S + rd,S)
in which C is the concentration, in mg per mL, of USP Quinidine Sulfate RS in the Standard preparation; rb,U and rb,S are the peak responses of quinidine obtained from the Assay preparation and the Standard preparation, respectively; and rd,U and rd,S are the peak responses of dihydroquinidine obtained from the Assay preparation and the Standard preparation, respectively.
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Topic/Question Contact Expert Committee
Monograph Sujatha Ramakrishna, Ph.D.
Senior Scientific Liaison
1-301-816-8349
(SM22010) Monographs - Small Molecules 2
Reference Standards RS Technical Services
1-301-816-8129
rstech@usp.org
711 Margareth R.C. Marques, Ph.D.
Senior Scientific Liaison
1-301-816-8106
(GCDF2010) General Chapters - Dosage Forms
USP35–NF30 Page 4506