Monensin Sodium
C36H61NaO11(monensin Asodium) 692.88
C35H59NaO11monensin Bsodium) 678.85
C37H63NaO11(monensin Csodium) 706.91

Monensin,sodium salt.
Stereoisomer of 2-[2-ethyloctahydro-3¢-methyl-5¢-[tetrahydro-6-hydroxy-6-(hydroxymethyl)-3,5-dimethyl-2H-pyran-2-yl][2,2¢-bifuran-5-yl]]-9-hydroxy-b-methoxy-a,g,2,8-tetramethyl-1,6-dioxaspiro[4.5]decan-7–butanoic acid sodium salt [22373-78-0].
»Monensin Sodium has a potency of not less than 800µg per mg.
Packaging and storage— Preserve in well-closed containers.Avoid moisture and excessive heat.
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.
Identification— The chromatogram of the Assay preparationobtained as directed in the Assayexhibits a major peak for monensin Aand a minor peak for monensin B,the retention times of which correspond to those exhibited in the chromatogram of the Standard preparation,as obtained in the Assay.
Loss on drying á731ñ— Dry it in vacuum at 60for 3hours:it loses not more than 4%of its weight.
Content of monensin Aand Bactivity— Using the results of the calculations in the Assay,calculate the percentage of monensin Aactivity in the Monensin Sodium under test by the formula:
100A/P,
in which Ais the potency,in mg per g,of monensin Ain the Monensin Sodium under test,as determined in the Assay,and Pis the potency,in mg of monensin,in each g of the Monensin Sodium under test,as determined in the Assay:not less than 90%is found.Calculate the percentage of monensin Aactivity plus monensin Bactivity in the Monensin Sodium under test by the formula:
100(A+B)/P,
in which Bis the potency,in mg per g,of monensin Bin the Monensin Sodium under test,as determined in the Assay,and the other terms are as defined above:not less than 95%is found.
Assay—
Mobile phase ,Neutralized methanol,Diluent,Derivatizing reagent,Standard preparation,Resolution solution,and Chromatographic system—Proceed as directed in the Assayunder Monensin.
Assay preparation— Transfer about 100mg of Monensin Sodium,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with methanol to volume.If necessary,to achieve complete dissolution,sonicate for about 1minute,and mix.Dilute an accurately measured volume of this solution quantitatively with Diluentto obtain a solution containing about 20µg of monensin per mL.
Procedure— Proceed as directed for Procedurein the Assayunder Monensin.Calculate the quantity,in mg,of monensin Ain each g of the Monensin Sodium taken by the formula:
(CFD/100,000W)(rU/rS),
in which Cis the concentration,in µg per mL,of monensin activity in the Standard preparation,based on the quantity of USP Monensin Sodium RStaken,its designated potency,in µg per mg,and the extent of dilution;Fis the designated percentage of monensin Ain USP Monensin Sodium RS;Dis the dilution factor used in preparing the Assay preparation;Wis the quantity,in g,of Monensin Sodium taken to prepare the Assay preparation;and rUand rSare the monensin Apeak responses obtained from the Assay preparationand the Standard preparation,respectively.Calculate the quantity,in mg,of monensin Bin each g of the Monensin Sodium taken by the same formula,except that rUis the monensin Bpeak response obtained from the Assay preparation,and rSis the monensin Apeak response obtained from the Standard preparation.Calculate the quantity,in mg,of monensin C/Din each g of the Monensin Sodium taken by the same formula,except that rUis the monensin C/Dpeak response obtained from the Assay preparation.Calculate the potency,in mg of monensin,in each g of the Monensin Sodium taken by the formula:
A+0.28B+1.5C/D,
in which Ais the quantity,in mg,of monensin Ain each g of the Monensin Sodium taken,as calculated above;Bis the quantity,in mg,of monensin Bin each g of the Monensin Sodium taken;and C/Dis the quantity,in mg,of monensin C/Din each g of Monensin Sodium taken,as calculated above.
Auxiliary Information— Staff Liaison:Ian DeVeau,Ph.D.,Senior Scientist
Expert Committee:(VET)Veterinary Drugs
USP28–NF23Page 1310
Phone Number:1-301-816-8178