Packaging and storage—
Preserve in single-dose containers, preferably of Type I glass, and avoid exposure to excessive heat.
Identification—
Prepare a
Substrate solution as follows. Transfer 237.0 mg of
N-acetyl-
L-tyrosine ethyl ester, suitable for use in assaying chymotrypsin, to a 100-mL volumetric flask, add 2 mL of alcohol, and swirl until solution is effected. Add 20 mL of
pH 7.0 phosphate buffer,
fifteenth-molar, prepared as directed in the
Assay under
Chymotrypsin, add 1 mL of methyl red–methylene blue TS, and dilute with water to volume. If necessary, adjust to a pH of 7.0 by the dropwise addition of monobasic potassium phosphate solution, prepared by dissolving 4.54 g of monobasic potassium phosphate in sufficient water to yield 500 mL of solution. Dissolve the contents of 1 vial of Chymotrypsin for Ophthalmic Solution in 1 mL of saline TS, transfer 0.2 mL to a suitable dish, and add 0.2 mL of
Substrate solution: a purple color is produced within 3 minutes.
[Note—distinction from trypsin, which produces no purple color within 3 minutes.
]
Uniformity of dosage units 
905
:
meets the requirements.
Procedure for content uniformity—
Assay 10 individual units as directed in the
Assay, and calculate the average of the 10 results. The average is not less than 80.0% and not more than 120.0% of the labeled amount. The contents of not more than 2 vials deviate by more than 10% from the average content. The contents of none of the vials deviate by more than 15% from the average.
pH 791:
between 4.3 and 8.7, in the solution constituted as directed in the labeling.
Assay—
Proceed with Chymotrypsin for Ophthalmic Solution as directed in the
Assay under
Chymotrypsin, but use the following as the
Chymotrypsin solution: dissolve the contents of 1 vial of Chymotrypsin for Ophthalmic Solution in 5.0 mL of 0.0012 N hydrochloric acid. Dilute an accurately measured volume (
V, in mL) of this solution, equivalent to about 300 USP Chymotrypsin Units, with 0.0012 N hydrochloric acid to 25.0 mL. Calculate the number of USP Chymotrypsin Units per vial taken by the formula:
300(5 /
V)(
A2 
A1) / [
T(2.4)(0.0075)],
in which
A2 is the absorbance straight-line initial reading,
A1 is the absorbance straight-line final reading,
T is the elapsed time in minutes between the initial and final readings, and 2.4 is the number of USP Chymotrypsin Units in the solution on which the absorbance was determined.
