Oral gel with triamcinolone acetonide and Nystatin?

You can use the HPMC base for Mouthgels from the TMF the Namonohydrogen phosphate gives you a pH, which is not optimal for nystatin. You use best 1% NaHCO3 for a pH = 7, optimal pH for Nystatin, which is a unstable molecule in aqueous medium. The shelf life is stored in a refrigerator for 2 weeks.  

You could also use the Hypromellosis ointment FNA which you can find the composition on the MFF site. This is because the stability of nystatin is much higher in water-free middle. This hypromellosis ointment is widely used as mouth paste. The FN 6 also has a mouth paste, which becomes long termjn. You must fill in the term oral paste in the search box on the website of the recipe helpdesk and you will find information that is useful to you.