Aminophylline Tablets
Action and use
Non-selective phosphodiesterase inhibitor; treatment of reversible airways obstruction.
Definition
Aminophylline Tablets contain Aminophylline or Aminophylline Hydrate.
Content of theophylline, C7H8N4O2
81.4 to 90.0% of the stated amount of aminophylline.
Content of ethylenediamine, C2H8N2
13.5 to 15.0% of the stated amount of aminophylline.
Identification
Tests
Dissolution of theophylline
Comply with the dissolution test for tablets and capsules, Appendix XII B1, using Apparatus 2.
Withdraw a sample of 10 mL of the medium and filter. Carry out the method for liquid chromatography, Appendix III D, using the following solutions.
45 volumes of methanol and 55 volumes of water.
Calculate the total content of theophylline, C7H8N4O2, in the medium using the declared content of C7H8N4O2 in theophylline BPCRS.
Related substances
Carry out the method for liquid chromatography, Appendix III D, using the following solutions.
7 volumes of acetonitrile and 93 volumes of a 0.136% w/v solution of sodium acetate containing 0.50% v/v of glacial acetic acid.
When the chromatograms are recorded under the prescribed conditions the retention time relative to theophylline (about 6 minutes) is: impurity G, about 0.6.
The test is not valid unless, in the chromatogram obtained with solution (3), the resolution between the peaks due to impurity G and theophylline is at least 2.0.
In the chromatogram obtained with solution (1):
the sum of the areas of all the secondary peaks is not greater than the area of the principal peak in the chromatogram obtained with solution (2) (0.2%).
Disregard any peak with an area less than half the area of the principal peak in the chromatogram obtained with solution (2) (0.1%).
Assay
For theophylline
Weigh and powder 20 tablets. Shake a quantity of the powder containing the equivalent of 80 mg of aminophylline with a mixture of 20 mL of 0.1m sodium hydroxide and 60 mL of water for 10 minutes, add sufficient water to produce 200 mL, mix and filter. Dilute 5 mL of the filtrate to 250 mL with 0.01m sodium hydroxide and measure the absorbance of the resulting solution at the maximum at 275 nm, Appendix II B. Calculate the content of C7H8N4O2 taking 650 as the value of A (1%, 1 cm) at the maximum at 275 nm.
For ethylenediamine
Weigh and powder 20 tablets. Shake a quantity of the powder containing the equivalent of 0.3 g of aminophylline with 20 mL of water, heat to 50° for 30 minutes and titrate with 0.05m sulfuric acid VS, using bromocresol green solution as indicator, until the colour changes from blue to green. Each mL of 0.05m sulfuric acid VS is equivalent to 3.005 mg of C2H8N2.
Storage
Aminophylline Tablets should be kept in an airtight container and protected from light.
Labelling
The quantity of active ingredient is stated in terms of the equivalent amount of anhydrous aminophylline.
Impurities
The impurities limited by the requirements of this monograph include those listed under Aminophylline.