Monensin Granulated

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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Monensin Granulated contains Monensin mixed with suitable diluents, carriers, and inactive ingredients prepared in a granulated form that is free-flowing and free from aggregates. It may contain added Monensin Sodium. It contains not less than 140 mg of monensin per g.

1 Packaging and storage

Preserve in well-closed containers. Avoid moisture and excessive heat.

2 Labeling

Label it to indicate that it is for veterinary use only. Label it also to state that it is for manufacturing, processing, or repackaging.

2.1 USP Reference standards 〈11〉

USP Monensin Sodium RS

USP Narasin RS

3 Identification

The chromatogram of the Assay preparation obtained as directed in the Assay exhibits a major peak for monensin A and a minor peak for monensin B, the retention times of which correspond to those exhibited in the chromatogram of the Standard preparation, obtained as directed in the Assay.

3.1 Loss on drying 〈731〉

Dry it in vacuum at 60° for 2 hours: it loses not more than 10% of its weight.

4 Content of monensin A and B activity

Using the results of the calculations in the Assay, calculate the percentage of monensin A activity in the Monensin Granulated under test by the formula:

100A/P

in which A is the potency, in µg per mg, of monensin A in the Monensin Granulated under test, as determined in the Assay, and P is the potency, in µg of monensin, in each mg of the Monensin Granulated under test, as determined in the Assay: not less than 90% is found. Calculate the percentage of monensin A activity plus monensin B activity in the Monensin Granulated under test by the formula:

100(A + B)/P

in which B is the potency, in µg per mg, of monensin B in the Monensin Granulated under test, as determined in the Assay, and the other terms are as defined above: not less than 95% is found.

5 Assay

Mobile phase, Neutralized methanol, Diluent, Derivatizing reagent, Standard preparation, Resolution solution, and Chromatographic system-Proceed as directed in the Assay under Monensin.

Assay preparation-Transfer about 5 g of Monensin Granulated, accurately weighed, to a 250-mL flask, add 200.0 mL of Diluent, and shake by mechanical means for 1 hour. Allow the solids to settle, and dilute an accurately measured volume of the supernatant quantitatively with Diluent to obtain a solution containing about 20 µg of monensin per mL.

Procedure-Proceed as directed for Procedure in the Assay under Monensin. Calculate the quantity, in mg, of monensin A in each g of the Monensin Granulated taken by the formula:

(CFD/100,000W)(rᵤ/rₛ)

in which C is the concentration, in µg per mL, of monensin activity in the Standard preparation, based on the quantity of USP Monensin Sodium RS taken, its designated potency, in µg per mg, and the extent of dilution, F is the designated percentage of monensin A in USP Monensin Sodium RS, D is the dilution factor used in preparing the Assay preparation, W is the quantity, in g, of Monensin Granulated taken to prepare the Assay preparation, and rᵤ and rₛ are the monensin A peak responses obtained from the Assay preparation and the Standard preparation, respectively. Calculate the quantity, in mg, of monensin B in each g of the Monensin Granulated taken by the same formula, except that rᵤ is the monensin B peak response obtained from the Assay preparation and rₛ is the monensin A peak response obtained from the Standard preparation. Calculate the quantity, in mg, of monensin C/D in each g of the Monensin Granulated taken by the same formula, except that rᵤ is the monensin C/D peak response obtained from the Assay preparation. Calculate the potency, in µg of monensin, in each mg of the Monensin Granulated taken by the formula:

A + 0.28B + 1.5C/D

in which A is the quantity, in mg, of monensin A in each g of the Monensin Granulated taken, as calculated above, and B is the quantity, in mg, of monensin B in each g of the Monensin Granulated taken, and C/D is the quantity, in mg, of monensin C/D in each g of Monensin Granulated taken, as calculated above.