Metoprolol Tartrate Oral Suspension
» Metoprolol Tartrate Oral Suspension contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of Metoprolol Tartrate [(C15H25NO3)2·C4H6O6]. Prepare Metoprolol Tartrate Oral Suspension 10 mg per mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 795. See also Metoprolol Tartrate Oral Solution):
Metoprolol Tartrate 1 g
Vehicle: a mixture of Vehicle for Oral Solution, (regular or sugar-free), NF and Vehicle for Oral Suspension, NF (1:1),  
a sufficient quantity to make 100 mL
If using Tablets, place the Metoprolol Tartrate Tablets in a suitable mortar, and comminute the Tablets, or add Metoprolol Tartrate powder. Add the Vehicle in small portions, and mix well. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add the Vehicle in portions to rinse the mortar. Add to the preparation to final volume, and mix well.
Packaging and storage— Preserve in tight, light-resistant containers. Store at controlled room temperature, or in a cold place.
Labeling— Label it to state that it is to be well shaken, and to state the beyond-use date.
USP Reference standards 11
USP Metoprolol Tartrate RS Click to View Structure
pH 791: between 3.6 and 4.6.
Beyond-use date: 60 days after the day on which it was compounded.
Mobile phase— Prepare a suitable filtered and degassed solution by dissolving 961 mg of 1-pentanesulfonic acid sodium salt, monohydrate, and 82 mg of anhydrous sodium acetate in a mixture of 550 mL of methanol, 470 mL of water, and 0.57 mL of glacial acetic acid. Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation— Dissolve USP Metoprolol Tartrate RS in water to obtain a solution having a known concentration of 100 µg per mL.
Assay preparation— Agitate the container of Oral Suspension for 30 minutes on a rotating mixer, remove a 5-mL sample, and store in a clear glass vial at –70 until analyzed. At the time of analysis, remove the sample from the freezer, allow it to reach room temperature, and mix with a vortex mixer for 30 seconds. Pipet 1.0 mL of the sample solution into a 100-mL volumetric flask, and dilute with Mobile phase to volume.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm analytical column that contains 5-µm 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 for metoprolol tartrate is about 7.3 minutes; and the relative standard deviation for replicate injections is not more than 1.3%.
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 responses for the major peaks. Calculate the quantity, in mg, of metoprolol tartrate [(C15H25NO3)2·C4H6O6] in the volume of Oral Suspension taken by the formula:
100(C/V)(rU / rS)
in which C is the concentration, in µg per mL, of USP Metoprolol Tartrate RS in the Standard preparation; V is the volume, in mL, of Oral Suspension taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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Monograph Jeanne H. Sun
Assistant Scientific Liaison
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