Question
Posted on: March 6 2013A magical alternative to Sulfa 10 (Na-sulfacetamide 10%) collyre.
According to Martindale, a lower more physiological pH of 6.8 is achieved with the sulfacetamide 0.5% sulfacetamide-Na 9.5% mixture. But only the Na salt is available. Is a pH 6.5 buffer solution sufficient? What is the amount of NaCl needed for 10ml collyre?
Answer
The isotonic concentration of Nasulfacetamide is 3.85% so 10% is hypertonic. So 50 mg of sulfacetamide must be formed. This requires 0.01 mole acetic acid. For 10 ml, this means 0.06 g of pure acetic acid. To weigh this amount, I would make a 5% (m / m) dilution and add 1.2 g of this to the aqueous solution of Na-sulfacetamide, to which was added 10 mg of Na 2 EDTA. It is eventually supplemented with water for injections. This solution is filtered through a sterilized membrane filter in a sterilized eye drop bottle.