Question
Posted on: March 6 2013How can we best make the next lotion? Precipitated sulfur 14 g Sulpho resorcinol 3 G prednisolone 0.5 g sulfacetamide 20 g antis. Opl. 100 g water 160 g
< br/> In the & #039; Memento of Galenic Pharmacy & #039; is a preparation with sulfur, resorcine, Carbopol and triethylamine (from trade replaced by Triethanolamine) and ethanol 70 °. This gave a nice thick liquid lotion. But once we add Nasulfacetamide, it breaks.
Answer
In view of the high alcohol concentration, the choice of thickening agent is limited. Carbopol seems to be the first choice. But we use Nasulfacetamide then we risk that the thickening agent precipitates due to the high electrolietconcentration. If we use Sulfacetamide, which is supposedly soluble in the alcohol-water mixture, then we risk the reaction between sulfacetamide (pKa = 5.4) and triethanolamine, which we expect to neutralize the Carbopol. Therefore, it is better to appeal to Hydroxypropylcellulose (KLUCEL GF), which is also compatible with alcohol and less electrolite sensitive.