(meth'' oh hex' i tal).
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 98.0 percent and not more than 101.0 percent of C14H18N2O3, calculated on the anhydrous basis.
Packaging and storage Preserve in well-closed containers.
USP Reference standards 11
Identification, Infrared Absorption 197S
Solution: 1 in 100.
Melting range 741: between 92 and 96, but the range between beginning and end of melting does not exceed 3.
Water, Method I 921: not more than 2.0%.
Chloride 221 Dissolve 200 mg in a mixture of 75 mL of ether and 25 mL of water, agitate, and allow to separate: the water solution shows no more chloride than corresponds to 0.17 mL of 0.010 N hydrochloric acid (0.03%).
Heavy metals, Method II 231: 0.001%.
Ordinary impurities 466
Test solution: methanol.
Standard solution: methanol.
Eluant: a mixture of chloroform and acetone (7:3).
Visualization Expose the plate to chlorine gas for 1 minute, and air-dry the plate at room temperature for 2 minutes. Prepare a solution of 0.5 g of potassium iodide in 50 mL of water, and prepare a solution of 1.5 g of soluble starch in 50 mL of hot water. Mix 10 mL of each solution with 4 mL of alcohol to obtain the Detection reagent. [noteThe Detection reagent so obtained may be used for up to 3 or 4 days. ] Spray the plate with the Detection reagent.
Assay Dissolve about 100 mg of Methohexital, accurately weighed, in chloroform, and dilute quantitatively and stepwise with chloroform to obtain a solution having a concentration of about 10 mg per mL. Dissolve an accurately weighed quantity of USP Methohexital RS in chloroform, and dilute quantitatively and stepwise with chloroform to obtain a Standard solution having a known concentration of about 10 mg per mL. Concomitantly determine the absorbances of both solutions in 0.1-mm cells at the wavelength of maximum absorbance at about 5.93 µm, with a suitable spectrophotometer, using chloroform as the blank. Calculate the quantity, in mg, of C14H18N2O3 in the portion of Methohexital taken by the formula:
10C(AU / AS)in which C is the concentration, in mg per mL, of USP Methohexital RS in the Standard solution; and AU and AS are the absorbances of the solution of Methohexital and the Standard solution, respectively.
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 3853Pharmacopeial Forum: Volume No. 29(5) Page 1534