A Buffer System for Ophthalmic Solutions of Sodium Sulfonamides

An investigation has been made to determine whether a chemical incompatibility exists between the sulfonamides and borate buffers, since these sulfonamide salts in concentrations of 5% are not soluble at pH 8.6. The results of the study indicate that the salts of sulfadiazine and sulfathiazole are not incompatible with borate buffers. At a pH of 8.6, it was found that only about 2% concentration of sodium sulfathiazole and 1% concentration of sodium sulfadiazine may be attained in any buffer, regardless of chemical species, whereas buffers which provide a higher pH are required for 5% solutions of these sulfonamides. A formula for a buffer is suggested to replace the previously used vehicle of pH 8.6. Solutions of sodium sulfonamides are subject to color changes and mold growth during shelf life, and the use of certain stabilizers to overcome these features is discussed.