Tolnaftate
;)
Carbamothioic acid,methyl(3-methylphenyl)-,O-2-naphthalenyl ester.
O-2-Naphthyl m,N-dimethylthiocarbanilate [2398-96-1].
»Tolnaftate contains not less than 98.0percent and not more than 102.0percent of C19H17NOS,calculated on the dried basis.
Packaging and storage—
Preserve in tight containers.
Identification—
A:
Infrared Absorption á197Kñ.
B:
The UVabsorption spectrum of the solution employed for measurement of absorbance in the Assayexhibits maxima and minima at the same wavelengths as that of a similar solution of USP Tolnaftate RS,concomitantly measured.
C:
Prepare a test solution by dissolving 10mg in 10mLof alcohol.Apply 10µLof this test solution and 10µLof a Standard solution of USP Tolnaftate RSin alcohol having a concentration of 1.0mg per mLto a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatogram,using toluene as the solvent system,until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,allow the solvent to evaporate,and view under short-wavelength UVlight:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Loss on drying á731ñ—
Dry it in vacuum at 65
for 3hours:it loses not more than 0.5%of its weight.
for 3hours:it loses not more than 0.5%of its weight.
Residue on ignition á281ñ:
not more than 0.1%.
Heavy metals,Method IIá231ñ:
0.002%.
Assay—
Dissolve about 50mg of Tolnaftate,accurately weighed,in methanol,and dilute the solution quantitatively and stepwise with methanol to obtain a concentration of about 10µg per mL.Dissolve an accurately weighed quantity of USP Tolnaftate RSin methanol,and dilute quantitatively and stepwise with methanol to obtain a Standard solution having a known concentration of about 10µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 258nm,with a suitable spectrophotometer,using methanol as the blank.Calculate the quantity,in mg,of C19H17NOSin the portion of Tolnaftate taken by the formula:
5C(AU/AS),
in which Cis the concentration,in µg per mL,of USP Tolnaftate RSin the Standard solution,and AUand ASare the absorbances of the solution of Tolnaftate and the Standard solution,respectively.
Auxiliary Information—
Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 1950
Phone Number:1-301-816-8394