» Piroxicam Cream contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of piroxicam (C15H13N3O4S). Prepare Piroxicam Cream as follows (see Pharmaceutical CompoundingNonsterile Preparations 795):
In an appropriate container (final weight tared), mix the White Petrolatum and Stearyl Alcohol together, and heat to 80 ± 5 to form a clear oil phase. In a separate container, mix the Propylparaben, Methylparaben, Propylene Glycol, Sodium Lauryl Sulfate, and about 30 mL of Purified Water together, and heat to 80 ± 5 to form a clear aqueous phase. Add the aqueous phase to the oil phase with continuous stirring, and allow it to cool to 50 to form an emulsion. In a mortar, triturate the Piroxicam with the Sodium Hydroxide to form a suspension. Using additional water to rinse out the mortar, add the Piroxicam suspension to the previously prepared emulsion, transferring the suspension stepwise and quantitatively to the emulsion. Add sufficient Purified Water with stirring to bring to final weight. Package and label.
Packaging and storage Preserve in a tight, light-resistant plastic resealable container, and store at controlled room temperature.
Labeling Label it to state the beyond-use date.
USP Reference standards 11
Beyond-use date: 90 days at room temperature after the day on which it was compounded.
Buffer solution Dissolve 5.4 g of citric acid and 10.8 g of dibasic sodium phosphate in 2 L of Purified Water, and pass through a 0.45-µm filter.
Mobile phase Prepare a filtered and degassed mixture of Buffer solution and methanol (1:1). Make adjustments if necessary (see System Suitability under Chromatography 621).
Diluent: 0.01 N methanolic hydrochloric acid, made by diluting 0.9 mL of hydrochloric acid with methanol to a volume of 1 L.
Standard preparation Dissolve an accurately weighed quantity of USP Piroxicam RS in 2 mL of chloroform, and dilute with Diluent to obtain a solution having a known concentration of about 50 µg per mL.
Assay preparation Add about 340 mg of Piroxicam Cream to 4 mL of chloroform and 150 mL of Diluent. Shake the mixture on a wrist action shaker for 15 minutes, and dilute with Diluent to 200 mL. Pass the solution through a 0.45-µm filter, and discard the first 5 mL of the filtrate.
Blank Prepare as directed for the Assay preparation, without adding Piroxicam. Use Purified Water to offset the difference in weight between the Blank and the Assay preparation. Pass the solution through a 0.45-µm filter, and discard the first 5 mL of the filtrate.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 254-nm detector, a 4.6-mm × 30-cm analytical column that contains 10-µm packing L1, and a 4.6-mm × 2-cm guard column that contains packing L1. The flow rate is about 1.0 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the retention time is about 7 minutes, and the relative standard deviation for replicate injections is not more than 2.8%.
Procedure Separately inject equal volumes (about 20 µL) of the Standard preparation, the Assay preparation, and the Blank into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of piroxicam (C15H13N3O4S) in each mL of Piroxicam Cream taken by the formula:
200(C/V)(rU / rS)in which C is the concentration, in µg per mL, of USP Piroxicam RS in the Standard preparation; V is the volume, in mL, of liquid taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 4341Pharmacopeial Forum: Volume No. 32(1) Page 134