Despite the frequent deadliness of the drug fentanyl, the Colorado legislature should not increase penalties for possession from a misdemeanor to a felony. Doing so would be unjust and counterproductive. What Is Fentanyl Fentanyl is a highly potent synthetic opioid sold legally for anesthesia and pain management. When sold in the black market created by drug prohibition, fentanyl often is sold in unlisted and unknown doses and laced, often without disclosure, with other drugs, including heroin, cocaine, and methamphetamines. Hence, because drug users often have little idea what they are taking, and because fentanyl is so potent, the drug can be deadly in a a nonmedical context.