α-Methylfentanyl an opioid analgesic that is an analog of fentanyl. It is sometimes sold as "China White".
Parafluorofentanyl is an opioid analgesic analogue of fentanyl developed by Janssen Pharmaceuticals in the 1960s.
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.
3-Allylfentanyl is an opioid analgesic that is an analogue of fentanyl.
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.
Acetylfentanyl is an opioid analgesic drug that is an analog of fentanyl. Studies have estimated acetylfentanyl to be 15 times more potent than morphine, which would mean that despite being somewhat weaker than fentanyl, it is nevertheless still several times stronger than pure heroin. It has never been licensed for medical use and instead has only been sold as a designer drug. Acetylfentanyl was discovered at the same time as fentanyl itself and had only rarely been encountered on the illicit market in the late 1980s. However, in 2013, Canadian police seized 3 kilograms of acetylfentanyl. As a μ-opioid receptor agonist, acetylfentanyl may serve as a direct substitute for heroin or other opioids. Common side effects of fentanyl analogs are similar to those of fentanyl itself, which include itching, nausea and potentially serious respiratory depression, which can be life-threatening. Fentanyl analogs have killed hundreds of people throughout Europe and the former Soviet republics since the most recent resurgence in use began in Estonia in the early 2000s, and novel derivatives continue to appear.
Benzylfentanyl (R-4129) is a fentanyl analog. It was temporarily placed in the US Schedule I by emergency scheduling in 1985 due to concerns about its potential for abuse as a designer drug, but this placement was allowed to expire and benzylfentanyl was formally removed from controlled substance listing in 2010, after the DEA's testing determined it to be "essentially inactive" as an opioid. Benzylfentanyl has a Ki of 213 nM at the mu opioid receptor, binding around 1/200 as strong as fentanyl itself, though it is still slightly more potent than codeine.
Furanylfentanyl (Fu-F) is an opioid analgesic that is an analog of fentanyl and has been sold as a designer drug. It has an ED50 value of 0.02 mg/kg in mice. This makes it approximately one fifth as potent as fentanyl.
3-Methylbutyrfentanyl (3-MBF) is an opioid analgesic that is an analog of butyrfentanyl.
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.
4-Methoxybutyrfentanyl is an opioid analgesic that is an analog of butyrfentanyl and has been sold online as a designer drug.
Acrylfentanyl (also known as acryloylfentanyl) is a highly potent opioid analgesic that is an analog of fentanyl and has been sold online as a designer drug. In animal studies the IC50 (the half maximal inhibitory concentration for acrylfentanyl to displace naloxone) is 1.4 nM, being slightly more potent than fentanyl itself (1.6 nM) as well as having a longer duration of action.
4-Fluoroisobutyrylfentanyl (also known as 4-FIBF and p-FIBF) is an opioid analgesic that is an analog of butyrfentanyl and structural isomer of 4-Fluorobutyrfentanyl 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. 4-fluoroisobutyrylfentanyl is a highly selective μ-opioid receptor agonist whose analgesic potency is almost ten times of that reported for morphine.
Butyrnorfentanyl or butyrylnorfentanyl is an inactive synthetic opioid analgesic drug precursor. It is an analog of fentanyl.
Despropionyl-p-fluorofentanyl is an inactive synthetic opioid analgesic drug precursor to 4-fluorofentanyl. It is an analog of fentanyl.
Furanylnorfentanyl is an inactive synthetic opioid analgesic drug precursor. It is an analog of fentanyl.
Norfentanyl is an inactive synthetic opioid analgesic drug precursor. It is an analog and metabolite of fentanyl with the removal of the phenethyl moiety from fentanyl chemical structure.
para-Methoxyfentanyl or p-methoxyfentanyl or 4-methoxyfentanyl is a potent short-acting synthetic opioid analgesic drug. It is an analog of fentanyl, with similar effects but slightly lower potency.
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.
