Packaging and storage—
Preserve in tight, light-resistant containers. Store below 40
, preferably between 15
and 30
, unless otherwise specified by the manufacturer.
Identification—
A:
Infrared Absorption 
197K
—
Test specimen—
Transfer a volume of Oral Solution, equivalent to about 24 mg of loperamide hydrochloride, to a separator containing about 100 mL of water and 1 mL of sodium hydroxide solution (1 in 2), and gently swirl the contents. Add 50 mL of methylene chloride, shake gently by hand, releasing pressure often, and then shake by mechanical means for 20 minutes. Allow the layers to separate. Transfer the lower methylene chloride layer to a separator containing 100 mL of water. Shake gently by hand, releasing pressure often, and then shake by mechanical means for 10 minutes. Allow the layers to separate. Transfer the lower methylene chloride layer to a 250-mL beaker, and evaporate on a steam bath with the aid of a current of air to dryness. Add 10 mL of methanol and 500 mg of potassium bromide to the beaker, and mix. Evaporate on a steam bath with the aid of a current of air to dryness, and use the residue.
B:
The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.
Assay—
Buffer solution—
Transfer 3.0 g of monobasic potassium phosphate to a 1-L volumetric flask, dissolve in and dilute with water to volume, and mix.
Mobile phase—
Prepare a mixture of
Buffer solution and acetonitrile (63:37), and adjust with 0.9 M phosphoric acid to a pH of 3.0. Mix, filter, and degas. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Loperamide Hydrochloride RS in methanol, and dilute quantitatively, and stepwise if necessary, with
Mobile phase to obtain a solution having a known concentration of about 10 µg per mL.
Assay preparation—
Transfer an accurately measured volume of Oral Solution, equivalent to about 1.0 mg of loperamide hydrochloride, to a 100-mL volumetric flask. Dilute with Mobile phase to volume, mix, and filter.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 214-nm detector and a 4.0-mm × 8.0-cm column that contains 5-µm packing L7. The flow rate is about 1.5 mL per minute. Chromatograph the
Standard preparation, and record the peak areas as directed for
Procedure: the tailing factor is not more than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 10 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 loperamide hydrochloride (C
29H
33ClN
2O
2·HCl) in each mL of Oral Solution taken by the formula:
100(C/V)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Loperamide Hydrochloride RS in the
Standard preparation; V is the volume of Oral Solution taken to prepare the
Assay preparation; and
rU and
rS are the peak areas obtained from the
Assay preparation and the
Standard preparation, respectively.
