Packaging and storage—
Preserve in tight, single-dose or multiple-dose containers, at controlled room temperature.
Labeling—
Label the Rectal Solution to state the content of anhydrous theophylline.
Identification—
Dilute a volume of Rectal Solution, equivalent to about 500 mg of aminophylline, with water to about 20 mL, and add, with constant stirring, 1 mL of 3 N hydrochloric acid or sufficient to precipitate the theophylline completely. Filter, wash with small portions of cold water until free from chloride, and dry at 105
for 4 hours. Use the precipitate and the filtrate for the following tests.
A:
Infrared Absorption 
197K
.
B:
The filtrate obtained as directed above meets the requirements for
Identification test
C under
Aminophylline.
Ethylenediamine content—
Measure accurately a volume of Rectal Solution, equivalent to about 500 mg of aminophylline, and dilute with water, if necessary, to make about 30 mL. Add
methyl orange TS, and titrate with 0.1 N hydrochloric acid VS. Each mL of 0.1 N hydrochloric acid is equivalent to 3.005 mg of C
2H
8N
2. The Rectal Solution contains between 218 mg and 267 mg of ethylenediamine (C
2H
8N
2) per g of anhydrous theophylline (C
7H
8N
4O
2) found in the
Assay.
Assay—
Standard preparation—
Dissolve an accurately weighed quantity of
USP Theophylline RS in dilute hydrochloric acid (1 in 100), and dilute quantitatively and stepwise with the same solvent to obtain a solution having a known concentration of about 8 µg per mL.
Assay preparation—
Pipet an accurately measured volume of Rectal Solution, equivalent to about 500 mg of aminophylline, into a 500-mL volumetric flask, dilute with water to volume, and mix. Pipet 5 mL of this solution into a second 500-mL volumetric flask, add 50 mL of dilute hydrochloric acid (1 in 10), dilute with water to volume, and mix.
Procedure—
Concomitantly determine the absorbances of the
Standard preparation and the
Assay preparation in 1-cm cells at the wavelength of maximum absorbance at about 270 nm, with a suitable spectrophotometer, using dilute hydrochloric acid (1 in 100) as the blank. Calculate the quantity, in mg, of anhydrous theophylline (C
7H
8N
4O
2) in each mL of the Rectal Solution taken by the formula:
50(C/V)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Theophylline RS in the
Standard preparation; V is the volume, in mL, of Rectal Solution taken; and
AU and
AS are the absorbances of the
Assay preparation and the
Standard preparation, respectively.
Auxiliary Information—
Staff Liaison :
Daniel K. Bempong, Ph.D., Scientist
Expert Committee : (MDPS05) Monograph Development-Pulmonary and Steroids
USP29–NF24 Page 142
Pharmacopeial Forum : Volume No. 27(1) Page 1748
Phone Number : 1-301-816-8143
between 9.0 and 9.5.