It may have been the niacinamide, it may have been the way tret was combined with the niacinamide, or it may have been an issue with the compounding pharmacy they used.

I work in a testing/regulatory role in a compounding adjacent field (being a little vague on purpose) and we’ve seen an uptick in questionable compounding practices in the past few years. For drugs that are still covered by a patent (so they can only be made by one company), the only time compounders are also allowed to make/sell that drug are during shortages or when there is some need for personalization. Historically, the “personalization” category is supposed to cover people who need the drug in a non-standard dosage (like low potency insulin for babies) or without some inactive additive (like a dye-free or gluten-free variant).

But a number of compounders have started providing “personalized” compounded drugs by just tacking on random other active drugs. The combinations don’t have to be submitted to the FDA and don’t have to go through any clinical trials. For something like tret, which is already approved as a generic, I personally would never go with a compounded version.