Sulfamethoxazole Oral Suspension
» Sulfamethoxazole Oral Suspension contains not less than 95.0 percent and not more than 110.0 percent of the labeled amount of sulfamethoxazole (C10H11N3O3S).
Packaging and storage— Preserve in tight, light-resistant containers.
A: Place a quantity of Oral Suspension, equivalent to about 100 mg of sulfamethoxazole, in a 50-mL centrifuge tube; add 5 mL of ammonium hydroxide; and shake gently. Add 25 mL of methanol, shake thoroughly for 3 minutes, centrifuge, decant the supernatant into a 50-mL volumetric flask, dilute with methanol to volume, and mix. Apply 50 µL of this solution and 50 µL of a solution prepared by dissolving 100 mg of USP Sulfamethoxazole RS in 5 mL of ammonium hydroxide and diluting with methanol to 50.0 mL to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of alcohol, n-heptane, chloroform, and glacial acetic acid (25:25:25:7) 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 allow the solvent to evaporate. Locate the spots on the plate by lightly spraying with a solution prepared by dissolving 0.10 g of p-dimethylaminobenzaldehyde in 1 mL of hydrochloric acid and diluting with alcohol to 100 mL: the RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
B: Transfer a quantity of Oral Suspension, equivalent to about 500 mg of sulfamethoxazole, to a 50-mL centrifuge tube; add about 25 mL of water; mix; and centrifuge. Decant and discard the supernatant, resuspend the residue in 25 mL of water, mix, and centrifuge again. Decant and discard the clear supernatant. Repeat the washing procedure an additional two times. Dissolve the residue in 10 mL of hydrochloric acid, and add 15 mL of sodium nitrite solution (1 in 100) and 5 mL of sodium hydroxide solution (1 in 10) containing 10 mg of 2-naphthol: a red-orange precipitate is produced.
Uniformity of dosage units 905
for oral suspension packaged in single-unit containers: meets the requirements.
Deliverable volume 698
for oral suspension packaged in multiple-unit containers: meets the requirements.
Assay— Mix an accurately measured volume of Oral Suspension, equivalent to about 1 g of sulfamethoxazole, with 20 mL of glacial acetic acid and 40 mL of water; and add 15 mL of hydrochloric acid. Cool to 15, and titrate immediately with 0.1 M sodium nitrite VS, determining the endpoint potentiometrically using a calomel-platinum electrode system. Each mL of 0.1 M sodium nitrite is equivalent to 25.33 mg of C10H11N3O3S.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Behnam Davani, Ph.D., M.B.A.
Senior Scientist
(MDAA05) Monograph Development-Antivirals and Antimicrobials
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 3627
Pharmacopeial Forum: Volume No. 29(6) Page 1990