Fentanyl is a synthetic opiod used in anesthesia as a potent analgesic and in the treatment of chronic pain as a transdermal therapeutic system.
It acts as a so-called agonist. In Germany as well as in Switzerland fentanyl falls under the narcotics law, in Austria under the drug law.
Fentanyl has primarily an analgesic (strong analgesic) and sedating (calming) effect. It is 120 times more potent than morphine, resulting in greater potency and shorter duration of action.
For example, fentanyl already works after two to five minutes when administered intravenously, the so-called half-life being around three to twelve hours. The dose for effective treatment is 0.01 mg per kilogram of body weight, the dose that causes death is 3.1 mg per kilogram of body weight, with the latter referring to rats. Already lower doses can therefore lead to death in humans due to respiratory depression.
The side effects, however, can generally be compared with those of morphine. Fentanyl dissolves well in fat and therefore can disperse well in fatty tissue. Mainly it is metabolised in the liver, less than ten percent are excreted unchanged by the kidneys. Depending on the condition of the patient and the dose administered, fentanyl may impair cognition, have a calming effect, cause diminution of consciousness or cause a sleep-like state. The latter point is reason for use in anesthesia.
Fentanyl is mainly used as a painkiller in operations involving a sleep aid and can also be used as a muscle relaxant. As fentanyl is stored in the fatty tissue in a heavily controlled manner due to lipophilicity and is released again, the substances remifentanil, alfentanil or sufentanil are often used as an alternative.
Fentanyl has a calming effect, which can be enhanced by other tranquilizers as well as alcohol, or reduced by the use of other opioids. Severe circulatory and respiratory disorders may be associated with the use of so-called monoamine oxidase inhibitors, which is why there should be a period of at least 14 days between each intake.
When using pain plasters, there may also be an interaction with drugs such as omeprazole, furosemide or glibenclamide. Even with preparations that contain St. John's wort, interactions can occur. For smokers it may be necessary to adjust the dose of fentanyl.
If a fentanyl-containing medicine is taken with a serotonergic drug, it can cause a dangerous serotonin syndrome, the symptoms of which may be a blood pressure crisis, hallucinations or even a coma.
Fentanyl is used as fentanyl dihydrogen citrate in three forms: as a transdermal therapeutic system, as an intravenous administration in anesthesia and emergency medicine, and as an oral-transmucosal therapeutic system (for breakthrough pain as a lozenge). Against breakthrough pain, Instyyl has been approved by Nycomed since 1st September 2009, the first approved fentanyl nasal spray in the EU.
This drug is suitable for treating breakthrough pain in adult patients already undergoing basic therapy with an opioid for chronic tumor pain. Fentanyl has a strong analgesic effect and is therefore usually used perioperatively (before surgery) or after surgery.
In severe, chronic pain of cancer patients, it is used in the form of a skin patch as an analgesic, also an application in the analgesia in chronic pain that is not related to a tumor is possible. The emergency doctor may use fentanyl in acute pain in the ambulance service.
As a side effect of fentanyl it can lead to an impairment of respiration and respiratory depression. Furthermore, side effects such as cramped or frozen muscles, slowed heart activity, euphoria or even anxiety, constricted pupils, vomiting, nausea and constipation are possible. If a quick injection is given, it may in rare cases lead to a short-term coughing sensation.