What is the cause of discoloration and crystallization after one day in a solution containing 2% resorcinol, 4% erythromycin, 50% isopropyl alcohol, and water up to 100 mL?

What is the best preservative to use for a 10 ml eye drop solution containing 25 mg sodium bicarbonate, 25 mg sodium borate (borax), and 63 mg sodium chloride, is benzalkonium chloride suitable, and what is the purpose of sodium bicarbonate in eye drops?

How can 1% salicylic acid be solubilized in an external use emulsion containing 200 g miglyol, 50 g comperlan KD, 50 g eumulgin B1 (Eumulgine 05), and 50 ml cetiol, with paraffin oil added up to 500 ml, considering that adding cetomacrogol 1000 results in a solid form after cooling while levigating with cetiol leads to crystallization?

How can the incompatibility between trometamol and acids be resolved when preparing a flufenamic acid 3% gel using the TMF carbomer gel formulation?

What is the desired ratio of macrogol 4000, 1000, and 400 for a suppository base used in domperidone suppositories, similar to Motilium suppositories, according to the package leaflet?

Is it possible to dilute Diprosone cream with cold cream, and given that updated legislation requires the use of the raw active ingredient instead of the brand-name product, is it best to incorporate the corticosteroid into a mixture of cetomacrogol cream (O/W) and cold cream (W/O) or to use cold cream alone?

What are the stability problems of a solution containing 3 grams of Phenobarbital sodium and purified water up to 300 cc?