Fentanyl
MethadoneCarfentanilAnother example of a synthetic opioid is fentanyl, which is about
100 times more potent than morphine and is widely used in human
medicine. Certain derivatives of fentanyl are the most potent opioids
known, and among the most potent of any drugs presently known,
naturally occurring or synthetic. The fentanyl derivative carfentanil is
approximately 10,000 times more potent than morphine, too strong
to be useful in human medicine. Its brand name, Wildnil, suggests
what it is used for—sedation of large animals, such as elephants.
How do opioids act in the body? Beginning in the early 1970s,
protein receptors were discovered in the brain and in the gut that bind
morphine and other opioids. These opioid receptors were found to
exist in several distinct subtypes (now called mu, delta, and kappa)
having different distributions in the brain and body and different
pharmacological properties (that is, different agonists and antago-