In February 2018, the U.S. Drug Enforcement Administration indicated that illicit fentanyl analogs have no medically valid use, and thus applied a "Schedule I" classification to them.Fentanyl analogues may be hundreds of times more potent than heroin. Fentanyl is used orally, smoked, snorted, or injected. Fentanyl is sometimes sold as heroin or oxycodone, sometimes leading to overdoses. Many fentanyl overdoses are initially classified as heroin overdoses. Recreational use is not particularly widespread in the EU except for Tallinn, Estonia, where it has largely replaced heroin. Estonia has the highest rate of 3-methylfentanyl overdose deaths in the EU, due to its high rate of recreational use.Fentanyl is sometimes sold on the black market in the form of transdermal fentanyl patches such as Duragesic, diverted from legitimate medical supplies. The gel from inside the patches is sometimes ingested or injected.Another form of fentanyl that has appeared on the streets is the Actiq lollipop formulation. The pharmacy retail price ranges from US$15 to US$50 per unit based on the strength of the lozenge, with the black market cost ranging from US$5 to US$25, depending on the dose. The attorneys general of Connecticut and Pennsylvania have launched investigations into its diversion from the legitimate pharmaceutical market, including Cephalons "sales and promotional practices for Provigil, Actiq and Gabitril. "Non-medical use of fentanyl by individuals without opioid tolerance can be very dangerous and has resulted in numerous deaths. Even those with opiate tolerances are at high risk for overdoses.
Intranasal fentanyl appears to be equally effective as IV morphine and superior to intramuscular morphine for the management of acute hospital pain.A fentanyl patient-controlled transdermal system (PCTS) is under development, which aims to allow patients to control administration of fentanyl through the skin to treat postoperative pain. Adverse effects
Fentanyls most common side effects, which affect more than 10% of people, include nausea, vomiting, constipation, dry mouth, somnolence, confusion, and asthenia (weakness). Less frequently, in 3–10% of people, fentanyl can cause abdominal pain, headache, fatigue, anorexia and weight loss, dizziness, nervousness, anxiety, depression, flu-like symptoms, dyspepsia (indigestion), shortness of breath, hypoventilation, apnoea, and urinary retention. Fentanyl use has also been associated with aphasia. Despite being a more potent analgesic, fentanyl tends to induce less nausea, as well as less histamine-mediated itching, than morphine.The duration of action of fentanyl has sometimes been underestimated, leading to harm in a medical context. In 2006, the U.S. Food and Drug Administration (FDA) began investigating several respiratory deaths, but doctors in the United Kingdom were not warned of the risks with fentanyl until September 2008. The FDA reported in April 2012 that twelve young children had died and twelve more made seriously ill from separate accidental exposures to fentanyl skin patches. Respiratory depression
The most dangerous adverse effect of fentanyl is respiratory depression, that is, decreased sensitivity to carbon dioxide leading to reduced rate of breathing, which can cause anoxic brain injury or death. This risk is decreased when the airway is secured with an endotracheal tube (as during anesthesia).