Carfentanil is an ultra-potent synthetic opioid. The Russian police force used both carfentanil and remifentanil to resolve a hostage incident in Moscow. This reported use sparked an interest in the pharmacology and toxicology of carfentanil in the human body. and data on its metabolites were later published. https://www.megavitamines.shop/product-category/vitamins-d-3/