Which preservative should be used for water-containing suppositories, specifically for emulsion suppositories consisting of 0.3 g hamamelis water per 3.0 g suppository prepared with a Novata E base for its high hydroxyl value and water-absorbing capacity, as well as Span 80 to incorporate the aqueous phase into the fatty phase?

For antibiotic ovules containing 35,000 UI neomycin sulfate, 35,000 UI polymyxin sulfate, and 100,000 UI nystatine per unit, is it better to use a gelatin-glycerin base or a classic suppository base (Witepsol), considering that only 3-gram conical molds are available instead of egg-shaped ovule molds?

How can a 5% flufenamic acid gel be correctly prepared using the same formula as the 3% version (Klucel) without the preparation becoming cloudy yellow, as currently observed when adding the hydroxypropyl cellulose gel?

How can the stability of a depigmenting cream containing 4% hydroquinone, 4% kojic acid, 0.05% tretinoin, and cetomacrogol cream be improved, given that the preparation breaks and releases a watery substance over time, whereas a version without kojic acid remains stable, and is the alternative formulation using 4% hydroquinone, 0.05% tretinoin, 0.01% butylhydroxytoluene as an antioxidant, and buffered cetomacrogol cream (unguentum emulsificans cum aqua) more effective?

Does anyone have knowledge of incompatibilities between certain products and plastic bottles, and what is the correct legal regulation regarding bottles for external use?

What is the cause of the pink-red discoloration after a few days in a compounded cream containing 0.9 g salicylic acid, 30 mg betamethasone valerate, and 30 g Nizoral cream, and is this interaction related to the sulfite present in the Nizoral specialty product required for reimbursement?

What is a reliable method for preparing unguentum emulsificans cum aqua to achieve a good result, given that attempts to add Tween have not been successful?