Methohexital
;)
2,4,6(1H,3H,5H)-Pyrimidinetrione,1-methyl-5-(1-methyl-2-pentynyl)-5-(2-propenyl)-,(±)-.
(±)-5-Allyl-1-methyl-5-(1-methyl-2-pentynyl)barbituric acid [18652-93-2].
»Methohexital contains not less than 98.0percent and not more than 101.0percent of C14H18N2O3,calculated on the anhydrous basis.
Packaging and storage—
Preserve in well-closed containers.
Identification,Infrared Absorptioná197Sñ—
Solution:
1in 100.
Medium:
chloroform.
Melting range á741ñ:
between 92
and 96,but the range between beginning and end of melting does not exceed 3.
and 96,but the range between beginning and end of melting does not exceed 3.
Water,Method Iá921ñ:
not more than 2.0%.
Chloride á221ñ—
Dissolve 200mg in a mixture of 75mLof ether and 25mLof water,agitate,and allow to separate:the water solution shows no more chloride than corresponds to 0.17mLof 0.010Nhydrochloric acid (0.03%).
Heavy metals,Method IIá231ñ:
0.001%.
Ordinary impurities á466ñ—
Test solution:
methanol.
Standard solution:
methanol.
Eluant:
a mixture of chloroform and acetone (7:3).
Visualization—
Expose the plate to chlorine gas for 1minute,and air-dry the plate at room temperature for 2minutes.Prepare a solution of 0.5g of potassium iodide in 50mLof water,and prepare a solution of 1.5g of soluble starch in 50mLof hot water.Mix 10mLof each solution with 4mLof alcohol to obtain the Detection reagent.[NOTE—The Detection reagent so obtained may be used for up to 3or 4days.]Spray the plate with the Detection reagent.
Assay—
Dissolve about 100mg of Methohexital,accurately weighed,in chloroform,and dilute quantitatively and stepwise with chloroform to obtain a solution having a concentration of about 10mg per mL.Dissolve an accurately weighed quantity of USP Methohexital RSin chloroform,and dilute quantitatively and stepwise with chloroform to obtain a Standard solution having a known concentration of about 10mg per mL.Concomitantly determine the absorbances of both solutions in 0.1-mm cells at the wavelength of maximum absorbance at about 5.93µm,with a suitable spectrophotometer,using chloroform as the blank.Calculate the quantity,in mg,of C14H18N2O3in the portion of Methohexital taken by the formula:
10C(AU/AS),
in which Cis the concentration,in mg per mL,of USP Methohexital RSin the Standard solution;and AUand ASare the absorbances of the solution of Methohexital and the Standard solution,respectively.
Auxiliary Information—
Staff Liaison:Karen A Russo,Ph.D.,Scientist
Expert Committee:(PA1)Pharmaceutical Analysis 1
USP28–NF23Page 1247
Pharmacopeial Forum:Volume No.29(5)Page 1534
Phone Number:1-301-816-8379