Looking into this further, I see that Otomax also contains the antifungal agent clotrimazole. Clotrimazole is a well-known inhibitor of a liver enzyme called CYP3A4, which is the primary liver enzyme involved in detoxification (breakdown and subsequent elimination of drugs). CYP3A4 is the primary enzyme involved in betamethasone degradation. Thus, the presence of clotrimazole in the Otomax could well have caused an increase in the half-life of the betamethasone. I sincerely doubt that the regulations concerning betamethasone would have been determined in the presence of other compounds that may have affected its metabolism.
I'm no fan of Bob Baffert, from a horse-racing fan's perspective. Over the years he's cost me many times. While I did stand to gain substantially had Medina Spirit not spoiled my Mandaloun-Hot Rod Charlie exacta, as a scientist I think the presence of betamethasone in the plasma is easily explainable when one considers how these compounds are metabolized and how other medications can affect it. This is the same reason that doctors warn against eating grapefruit while taking certain medications- it interferes with CYP3A4 resulting in slower than normal degradation of legally administered drugs.
While Baffert may be guilty if the determining fact is whether there is any trace of betamethasone in the horse, I think there is a scientifically sound reason for the fact pattern that seems to have occurred.
