What shelf life could be attributed to a gel based on methyl cellulose and glycerin with the active ingredients tetracaine, cocaine and adrenaline?

Of the three assets is mainly adrenaline little tenable due to oxidation and racemization. The first is the slightest in acidic middle while this middle is conducive to racemization. So a compromise must be made and that is to set a pH 3.5 a 4.5. An antoxidans such as nametabisulfite (0.1%) is also desirable. Therefore, I would determine the pH of the prepared gel and acidifying if necessary.