Rifampin Oral Suspension
» Rifampin Oral Suspension contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of rifampin (C43H58N4O12). Use Rifampin or the number of Rifampin Capsules that contain the designated amount of Rifampin, and prepare Rifampin Oral Suspension as follows (see Pharmaceutical CompoundingNonsterile Preparations 795):
Transfer 1.20 g of Rifampin, or the contents of Rifampin Capsules, into a mortar. [noteIf necessary, gently crush the Capsule contents with a pestle to produce a fine powder. ] Add about 2 mL of Syrup to the mortar, and triturate until a smooth paste is formed. Add about 10 mL of Syrup, and triturate to form a suspension. Continue to add Syrup, until about 80 mL has been added. Transfer this suspension to a 120-mL precalibrated light-resistant glass or plastic prescription bottle. Rinse the mortar and pestle with successive small portions of Syrup, and add the rinses to the bottle. Shake vigorously. If necessary, add Citric Acid or Sodium Citrate to adjust to a pH of 5.0. Add a suitable flavor if desired. Add sufficient Syrup to make the product measure 120 mL, and shake vigorously to produce the Oral Suspension.
Packaging and storage Preserve in a tight, light-resistant glass or plastic prescription bottle, with a child-resistant closure. Store at controlled room temperature.
Labeling Label it to state that the Suspension is to be well shaken. Label it to state that it contains 50 mg of rifampin in 5 mL of Oral Suspension.
USP Reference standards 11
pH 791: between 4.5 and 5.5.
Beyond-use date Thirty days after the day on which it was compounded.
Phosphate buffer, Solvent mixture, and Resolution solution Prepare as directed in the Assay under Rifampin.
Mobile phase Prepare a suitable mixture of water, acetonitrile, Phosphate buffer, 1.0 M citric acid, and 0.5 M sodium perchlorate (500:360:100:20:20), pass through a suitable filter having a 0.7-µm or finer porosity, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).
Diluent Prepare a mixture of acetonitrile and water (1:1).
Standard preparation Dissolve an accurately weighed quantity of USP Rifampin RS in Diluent to obtain a solution having a known concentration of about 0.5 mg per mL, sonicating for about 30 seconds, if necessary, to dissolve. Transfer 5.0 mL of this solution to a 50-mL, low-actinic volumetric flask, dilute with Diluent to volume, and mix. [noteUse this preparation within 1 hour. ]
Assay preparation Transfer 5.0 mL of Oral Suspension, freshly mixed and free from air bubbles, to a 100-mL, low-actinic volumetric flask, dissolve in and dilute with Diluent to volume, and mix. Transfer 5.0 mL of the resulting solution to a 50-mL, low-actinic volumetric flask, dilute with Diluent to volume, and mix.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 10-cm column that contains 5-µm packing L7. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.6 for rifampin quinone and 1.0 for rifampin; and the resolution, R, between the rifampin quinone and rifampin is not less than 4.0. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 1.0%.
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 rifampin (C43H58N4O12) in the portion of Oral Suspension taken by the formula:
1000C(rU / rS)in which C is the concentration, in mg per mL, of USP Rifampin RS, calculated on the dried basis, in the Standard preparation; and rU and rS are the rifampin peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 4553Pharmacopeial Forum: Volume No. 28(2) Page 363