Fentanyl is a highly potent synthetic piperidine opioid primarily used as an analgesic. It is 20 to 40 times more potent than heroin and 100 times more potent than morphine; its primary clinical utility is in pain management for cancer patients and those recovering from painful surgeries. Fentanyl is also used as a sedative. Depending on the method of delivery, fentanyl can be very fast acting and ingesting a relatively small quantity can cause overdose. Fentanyl works by activating μ-opioid receptors. Fentanyl is sold under the brand names Actiq, Duragesic, and Sublimaze, among others.
An anesthetic or anaesthetic is a drug used to induce anesthesia — in other words, to result in a temporary loss of sensation or awareness. They may be divided into two broad classes: general anesthetics, which result in a reversible loss of consciousness, and local anesthetics, which cause a reversible loss of sensation for a limited region of the body without necessarily affecting consciousness.
Carfentanil or carfentanyl, sold under the brand name Wildnil, is an extremely potent opioid analgesic used in veterinary medicine to anesthetize large animals such as elephants and rhinoceroses. It is typically administered in this context by tranquilizer dart. Carfentanil has also been used in humans to image opioid receptors. It has additionally been used as a recreational drug, typically by injection, insufflation, or inhalation. Deaths have been reported in association with carfentanil.
Sufentanil, sold under the brand names Sufenta among others, is a synthetic opioid analgesic drug approximately 5 to 10 times as potent as its parent drug, fentanyl, and 500 to 1,000 times as potent as morphine. Structurally, sufentanil differs from fentanyl through the addition of a methoxymethyl group on the piperidine ring, and the replacement of the phenyl ring by thiophene. Sufentanil first was synthesized at Janssen Pharmaceutica in 1974.
Remifentanil, marketed under the brand name Ultiva is a potent, short-acting synthetic opioid analgesic drug. It is given to patients during surgery to relieve pain and as an adjunct to an anaesthetic. Remifentanil is used for sedation as well as combined with other medications for use in general anesthesia. The use of remifentanil has made possible the use of high-dose opioid and low-dose hypnotic anesthesia, due to synergism between remifentanil and various hypnotic drugs and volatile anesthetics.
Phenoperidine, is an opioid analgesic which is structurally related to pethidine and is used clinically as a general anesthetic.
Piritramide(R-3365, trade names Dipidolor, Piridolan, Pirium and others) is a synthetic opioid analgesic that is marketed in certain European countries including: Austria, Belgium, Czech Republic, Slovenia, Germany and the Netherlands. It comes in free form, is about 0.75x times as potent as morphine and is given parenterally for the treatment of severe pain. Nausea, vomiting, respiratory depression and constipation are believed to be less frequent with piritramide than with morphine, and it produces more rapid-onset analgesia when compared to morphine and pethidine. After intravenous administration the onset of analgesia is as little as 1–2 minutes, which may be related to its great lipophilicity. The analgesic and sedative effects of piritramide are believed to be potentiated with phenothiazines and its emetic (nausea/vomiting-inducing) effects are suppressed. The volume of distribution is 0.7-1 L/kg after a single dose, 4.7-6 L/kg after steady-state concentrations are achieved and up to 11.1 L/kg after prolonged dosing.
Parafluorofentanyl is an opioid analgesic analogue of fentanyl developed by Janssen Pharmaceuticals in the 1960s.
Trefentanil (A-3665) is an opioid analgesic that is an analogue of fentanyl and was developed in 1992.
Brifentanil (A-3331) is an opioid analgesic that is an analogue of fentanyl and was developed in the early 1990s.
Lofentanil or lofentanyl is one of the most potent opioid analgesics known and is an analogue of fentanyl, which was developed in 1960. It is most similar to the highly potent opioid carfentanil (4-carbomethoxyfentanyl), only slightly more potent. Lofentanil can be described as 3-methylcarfentanil, or 3-methyl-4-carbomethoxyfentanyl. While 3-methylfentanyl is considerably more potent than fentanyl itself, lofentanil is only slightly stronger than carfentanil. This suggests that substitution at both the 3 and 4 positions of the piperidine ring introduces steric hindrance which prevents μ-opioid affinity from increasing much further. As with other 3-substituted fentanyl derivatives such as ohmefentanyl, the stereoisomerism of lofentanil is very important, with some stereoisomers being much more potent than others.
Phenaridine (2,5-dimethylfentanyl) is an opioid analgesic that is an analogue of fentanyl. It was developed in 1972, and is used for surgical anasthesia.
Mirfentanil is a fentanyl derivative with strong selectivity for the μ opioid receptor. At lower doses, it antagonizes the analgesic effects of alfentanil and substitutes for naloxone in morphine-treated monkeys; however, it also reverses naloxone-precipitated withdrawal in pigeons trained to discriminate morphine from naloxone.
Ocfentanil is a potent synthetic opioid structurally related to fentanyl that was developed in the early 1990s as one of a series of potent naloxone-reversible opioids in an attempt to obtain an opioid that had better therapeutic indices in terms of cardiovascular effects and respiratory depression as compared to fentanyl. Ocfentanil was never developed for medical use despite reasonable results in human clinical trials, but subsequently started to be sold as a designer drug starting in around 2013.
4-Phenylfentanyl is an opioid analgesic that is a derivative of fentanyl. It was developed during the course of research that ultimately resulted in super-potent opioid derivatives such as carfentanil, though it is a substantially less potent analogue. 4-Phenylfentanyl is around eight times the potency of fentanyl in analgesic tests on animals, but more complex 4-heteroaryl derivatives such as substituted thiophenes and thiazoles are more potent still, as they are closer bioisosteres to the 4-carbomethoxy group of carfentanil.
R-30490 is an opioid analgesic related to the highly potent animal tranquilizer carfentanil, and with only slightly lower potency. It was first synthesised by a team of chemists at Janssen Pharmaceutica led by Paul Janssen, who were investigating the structure-activity relationships of the fentanyl family of drugs. R-30490 was found to be the most selective agonist for the μ-opioid receptor out of all the fentanyl analogues tested, but it has never been introduced for medical use in humans, although the closely related drug sufentanil is widely used for analgesia and anesthesia during major surgery.
Butyrfentanyl or butyrylfentanyl is a potent short-acting synthetic opioid analgesic drug. It is an analog of fentanyl with around one quarter of its potency. One of the first mentions of this drug can be found in document written by The College on Problem of Drug Dependence, where it is mentioned as N-butyramide fentanyl analog. This document also states that the article describing its clinical effects was published in 1987. It is an agonist for the μ-opioid receptors.
4-Fluorobutyrylfentanyl (also known as 4-FBF and p-FBF or para-fluorobutyrylfentanyl) is an opioid analgesic that is an analog of butyrfentanyl and has been sold online as a designer drug. It is closely related to 4-fluorofentanyl, which has an EC50 value of 4.2 nM for the human μ-opioid receptor.
Thiafentanil is a highly potent opioid analgesic that is an analog of fentanyl, and was invented in 1986. Its analgesic potency is slightly less than that of carfentanil, though with a faster onset of effects, shorter duration of action and a slightly lesser tendency to produce respiratory depression. It is used in veterinary medicine to anesthetise animals such as impala, usually in combination with other anesthetics such as ketamine, xylazine or medetomidine to reduce the prevalence of side effects such as muscle rigidity.
Remifentanilic acid is a metabolite of the potent short-acting synthetic opioid analgesic drug remifentanil. It is an analog of fentanyl and remifentanil, but is not active as an opioid in its own right.
