Nalidixic Acid Oral Suspension

» Nalidixic Acid Oral Suspension contains not less than 95.0 percent and not more than 105.0 percent of the labeled amount of nalidixic acid C12H12N2O3 in a suitable aqueous vehicle.

Packaging and storage— Preserve in tight containers.

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USP Nalidixic Acid RS

Identification— The retention time of the nalidixic acid peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

Uniformity of dosage units

905

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for oral suspension packaged in single-unit containers: meets the requirements.

Deliverable volume

698

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for oral suspension packaged in multiple-unit containers: meets the requirements.

Assay—

Mobile phase— Prepare a solution of 784 mg of dibasic potassium phosphate in 325 mL of water. To this solution add a solution of 2.62 g of hexadecyltrimethylammonium bromide in 350 mL of methanol. To the combined solution add 325 mL of methanol, mix, filter, and degas. This solution has an apparent pH of about 10. Make adjustments if necessary (see System Suitability under Chromatography

621

Internal standard solution— Prepare a solution of sulfanilic acid in Mobile phase containing about 0.8 mg per mL.

Standard preparation— Prepare a solution having a known concentration of about 0.18 mg per mL of USP Nalidixic Acid RS in methanol. Transfer 5.0 mL of this solution and 1.0 mL of Internal standard solution to a 25-mL volumetric flask, dilute with methanol to volume, and mix.

Assay preparation— Transfer an accurately measured volume of freshly mixed Oral Suspension, equivalent to about 150 mg of nalidixic acid, to a 500-mL volumetric flask, add about 400 mL of methanol, and sonicate for about 30 minutes. Shake by mechanical means for about 30 minutes, sonicate again for about 30 minutes, dilute with methanol to volume, mix, and filter. Transfer 3.0 mL of the clear filtrate and 1.0 mL of Internal standard solution to a 25-mL volumetric flask, dilute with methanol to volume, and mix.

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 relative retention times are about 0.7 for sulfanilic acid and 1.0 for nalidixic acid; the resolution, R, between sulfanilic acid and nalidixic acid is not less than 1; and the relative standard deviation for replicate injections is not more than 2.0%.

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 areas for the major peaks. Calculate the quantity, in mg, of nalidixic acid (C12H12N2O3) in each mL of the Oral Suspension taken by the formula:

(12,500/3)(C/V)(RU / RS)

in which C is the concentration, in mg per mL, of USP Nalidixic Acid RS in the Standard preparation; V is the volume, in mL, of Oral Suspension taken to prepare the Assay preparation; and RU and RS are the ratios of the peak areas for nalidixic acid and sulfanilic acid in the chromatograms obtained from the Assay preparation and the Standard preparation, respectively.

Auxiliary Information— Please check for your question in the FAQs before contacting USP.

Topic/Question	Contact	Expert Committee
Monograph	Leonel M. Santos, Ph.D. Senior Scientific Liaison 1-301-816-8168	(SM12010) Monographs - Small Molecules 1
Reference Standards	RS Technical Services 1-301-816-8129 rstech@usp.org

USP35–NF30 Page 3985

Pharmacopeial Forum: Volume No. 29(6) Page 1935