Timolol Tablets
Action and use
Beta-adrenoceptor antagonist.
Definition
Timolol Tablets contain Timolol Maleate.
Content of timolol maleate, C13H24N4O3S,C4H4O4
90.0 to 110.0% of the stated amount.
Identification
1 volume of 18m ammonia, 19 volumes of methanol and 80 volumes of chloroform.
The principal spot in the chromatogram obtained with solution (1) corresponds in position and colour to that in the chromatogram obtained with solution (2).
Disregard any spot remaining on the line of application (maleic acid).
Tests
Related substances
Carry out the method for liquid chromatography, Appendix III D, using the following solutions in mobile phase.
42.5 volumes of 0.02m sodium octanesulfonate and 57.5 volumes of methanol, adjusted to pH 3.0 using glacial acetic acid.
In the chromatogram obtained with solution (1):
the area of any secondary peak, other than the peak corresponding to maleic acid, is not greater than the area of the peak obtained with solution (2) (0.4%);
not more than two such peaks have an area greater than that of the peak obtained with solution (3) (0.2%).
Assay
Weigh and powder 20 tablets. To a quantity of the powder containing 15 mg of Timolol Maleate add 25 mL of 0.05m sulfuric acid, shake for 20 minutes and centrifuge until clear. Add 5 mL of the resulting supernatant liquid to 15 mL of carbonate buffer pH 9.7 and extract with three 20-mL quantities and one 10-mL quantity of toluene. Wash each extract successively with the same 10-mL volume of carbonate buffer pH 9.7, combine the toluene extracts and extract with four 20-mL quantities of 0.05m sulfuric acid. Combine the acid extracts, dilute to 100 mL, filter and measure the absorbance at the maximum at 295 nm, Appendix II B, using in the reference cell a solution prepared by treating a mixture of 5 mL of water and 15 mL of carbonate buffer pH 9.7 in the same manner. Calculate the content of C13H24N4O3S,C4H4O4 taking 204 as the value of A(1%, 1 cm) at the maximum at 295 nm.