Medium: 0.05 M, pH 6.9 phosphate buffer (see Buffer Solutions in the section Reagents, Indicators, and Solutions) containing 5 units of -amylase per mL; 900 mL. [NOTE—Use only freshly prepared solutions containing -amylase; and equilibrate the Dissolution Medium at 37 for not more than one hour before beginning the Dissolution test.]

Apparatus 2: 75 rpm.

Time: 60 minutes.

Mobile phase, Resolution solution, and Chromatographic system— Prepare as directed in the Assay.

Standard solution— [NOTE—A volume of acetonitrile not exceeding 2% of the final total volume of solution may be used to aid in dissolving the carisoprodol.] Prepare a solution of USP Carisoprodol RS in 0.05 M, pH 6.9 phosphate buffer having an accurately known concentration of about 0.4 mg per mL.

Procedure— Separately inject equal volumes (about 150 µL) of the Standard solution and a filtered portion of the solution under test into the chromatograph, record the peak responses, and measure the responses for the major peaks. Calculate the amount of C12H24N2O4 dissolved.

Tolerances— Not less than 80% (Q) of the labeled amount of C12H24N2O4 is dissolved in 60 minutes.

(Official January 1, 2007)

Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (60:40). Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluent— Prepare a mixture of methanol and 0.01 N sulfuric acid (60:40).

Standard preparation— Dissolve an accurately weighed quantity of USP Carisoprodol RS in Diluent, using sonication, if necessary, to obtain a solution having a known concentration of about 3.5 mg per mL.

Resolution solution— Prepare a solution in Mobile phase containing about 2.4 mg of 2-methyl-2-propyl-1,3-propanediol and 3.4 mg of carisoprodol per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 350 mg of carisoprodol, to a 100-mL volumetric flask. Add about 50 mL of Diluent, place in an ultrasonic bath for 30 minutes, and shake by mechanical means for 60 minutes. Dilute with Diluent to volume, and mix. Pass a portion of this solution through a membrane filter of 0.5 µm or finer porosity, and use the filtrate as the Assay preparation.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a refractive index detector and a 3.9-mm × 30-cm column that contains packing L1. Maintain the detector and the column at 30 ± 1. The flow rate is about 2 mL per minute. Chromatograph the Resolution solution and the Standard preparation, and record the peak responses as directed for Procedure: the resolution, R, between the 2-methyl-2-propyl-1,3-propanediol and carisoprodol peaks is not less than 2.0, and the relative standard deviation for three replicate injections of the Standard preparation is not more than 2.0%. The relative retention times are about 0.5 for 2-methyl-2-propyl-1,3-propanediol and 1.0 for carisoprodol.

Procedure— [NOTE—Use peak heights where peak responses are indicated.] Separately inject equal volumes (about 35 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C12H24N2O4 in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Carisoprodol RS in the Standard preparation, and rU and rS are the peak responses obtained for carisoprodol from the Assay preparation and the Standard preparation, respectively.