Carfentanil has been around for many years as a tranquilizer. It is used in the veterinary world to sedate or tranquilize huge animals like rhinos and elephants. When using Carfentanil, it is important to follow all the instructions in the drug package or label and only administer it as recommended. Never change the Carfentanil dosage or quit administering it abruptly since it can lead to adverse side effects. Never administer Carfentanil in higher amounts than recommended or take it for longer periods.