Identification—
Transfer a volume of Injection, containing the equivalent of 1 mg of neostigmine methylsulfate, to a small porcelain dish. Evaporate, if necessary, to 2 mL, add 0.5 mL of sodium hydroxide solution (2 in 5), and proceed as directed in
Identification test
B under
Neostigmine Methylsulfate, beginning with “evaporate on a steam bath.”
Assay—
Standard preparation—
Dissolve a suitable quantity of
USP Neostigmine Methylsulfate RS, accurately weighed, in water, and dilute quantitatively and stepwise with water to obtain a solution having a known concentration of about 40 µg per mL.
Assay preparation—
Pipet an accurately measured volume of Injection, equivalent to about 2 mg of neostigmine methylsulfate, into a 50-mL volumetric flask, add water to volume, and mix.
Procedure—
Proceed as directed for
Procedure in the
Assay under
Neostigmine Bromide Tablets. Calculate the quantity, in mg, of C
13H
22N
2O
6S in each mL of the Injection taken by the formula:
0.05(C / V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Neostigmine Methylsulfate RS in the
Standard preparation,
V is the volume, in mL, of Injection taken, and
AU and
AS are the absorbances of the solutions from the
Assay preparation and the
Standard preparation, respectively.
791
:
between 5.0 and 6.5.