Action and use
Folic acid synthesis inhibitor; treatment of leprosy.
Definition
Dapsone Tablets contain Dapsone.
The tablets comply with the requirements stated under Tablets and with the following requirements.
Content of dapsone, C12H12N2O2S
95.0 to 105.0% of the stated amount.
Identification
B. In the test for Related substances, the principal spot in the chromatogram obtained with solution (2) is similar in position, colour and size to that in the chromatogram obtained with solution (5).
Tests
Dissolution
Comply with the requirements for Monographs of the British Pharmacopoeia in the dissolution test for tablets and capsules, Appendix XII B1.
test conditions
(a) Use Apparatus 1, rotating the basket at 100 revolutions per minute.
procedure
(1) After 45 minutes withdraw a 20 mL sample of the medium. To a volume of the filtered sample expected to contain 0.1 mg of Dapsone add 1 mL of a freshly prepared 0.5% w/v solution of
sodium nitrite, and allow to stand for 3 minutes. Add 1.5 mL of a 1% w/v solution of
sulfamic acid, allow to stand for 3 minutes, add 2.5 mL of a freshly prepared 0.2% w/v solution of N-
(1-naphthyl)-ethylenediamine dihydrochloride in
0.1m hydrochloric acid and dilute to 20 mL with 1
m hydrochloric acid (solution A). Carry out the procedure at the same time and in the same manner using a volume of
0.1m hydrochloric acid equal to that of the filtered sample and beginning at the words ‘add 1 mL of a freshly prepared 0.5% w/v solution of
sodium nitrite...’ (solution B). Allow solutions A and B to stand for at least 2 minutes and measure the
absorbance of solution A at the maximum at 538 nm,
Appendix II B, using solution B in the reference cell.
(2) Repeat the operation using a solution containing 0.1 mg of
dapsone BPCRS in a volume of
0.1m hydrochloric acid equal to that of the filtered sample and beginning at the words ‘add 1 mL of a freshly prepared 0.5% w/v solution of
sodium nitrite ...’ and using solution B in the reference cell.
determination of content
Calculate the total content of dapsone, C12H12N2O2S, in the medium from the absorbances obtained and using the declared content of C12H12N2O2S in dapsone BPCRS.
Related substances
Carry out the method for thin-layer chromatography, Appendix III A, using the following solutions.
(1) Shake a quantity of the powdered tablets containing 0.1 g of Dapsone with 10 mL of
methanol and filter.
(2) Dilute 1 volume of solution (1) to 10 volumes with
methanol.
(3) Dilute 1 volume of solution (2) to 10 volumes with
methanol.
(4) Dilute 1 volume of solution (3) to 5 volumes with
methanol.
chromatographic conditions
(b) Use the mobile phase as described below.
(c) Apply 10 µL of each of solutions (1), (3) and (4) and 1 µL of each of solutions (2) and (5).
(d) Develop the plate to 15 cm in an unsaturated tank.
mobile phase
1 volume of 13.5m ammonia, 6 volumes of methanol, 20 volumes of ethyl acetate and 20 volumes of n-heptane.
limits
Any secondary spot in the chromatogram obtained with solution (1) is not more intense that the spot in the chromatogram obtained with solution (3) (1%) and not more than two such spots are more intense than the spot in the chromatogram obtained with solution (4) (0.2%).
Assay
Weigh and powder 20 tablets. Dissolve a quantity of the powder containing 0.25 g of Dapsone in a mixture of 15 mL of water and 15 mL of 2m hydrochloric acid, add 3 g of potassium bromide, cool in ice and titrate slowly with 0.1m sodium nitrite VS, stirring constantly and determining the end point electrometrically. Each mL of 0.1m sodium nitrite VS is equivalent to 12.42 mg of C12H12N2O2S.