Benzimidazole opioids

Etonitazene, also known as EA-4941 or CS-4640, is a benzimidazole opioid, first reported in 1957, that has been shown to have approximately 1,000 to 1,500 times the potency of morphine in animals.

Bezitramide is an opioid analgesic. Bezitramide itself is a prodrug which is readily hydrolyzed in the gastrointestinal tract to its active metabolite, despropionyl-bezitramide. Bezitramide was discovered at Janssen Pharmaceutica in 1961. It is most commonly marketed under the trade name Burgodin.

Nitazenes are a chemically defined class of substances derived from the parent compound nitazene. Nitazenes were developed in the second half of the 1950s by the Swiss company Ciba AG as pain-relieving agents. They are important as centrally active, selective μ-opioid receptor agonists. The high potency of fentanyl (in humans) is matched by only a few nitazenes and surpassed by etonitazene and isotonitazene. Due to unacceptable side effects, nitazenes were never included in the pharmacopoeia of human or veterinary medicine. Since 2019, highly potent nitazenes have proliferated as ″new syntheti

Clonitazene is an opioid analgesic of approximately three times the potency of morphine. It is in the nitazene family of benzimidazoles related to etonitazene, an opioid of significantly higher potency. Clonitazene is not currently marketed. It is a controlled substance; in the United States it is a Schedule I Narcotic controlled substance with a DEA ACSCN of 9612 and an established manufacturing quota of 25 grams for 2022.

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Protonitazene is a benzimidazole derivative with potent opioid effects which has been sold over the internet as a designer drug since 2019, and has been identified in various European countries, as well as Canada, the US and Australia. It has been linked to numerous cases of drug overdose, and is a Schedule I drug in the US.

Etomethazene (5-methyldesnitroetonitazene, 5-methyl etodesnitazene, Eto) is a benzimidazole derivative with opioid effects which has been sold as a designer drug over the internet since 2022, first being definitively identified in Sweden in January 2023. It is an analogue of etonitazene where the nitro (NO2) group has been replaced by a methyl (CH3) group. While formal studies into its pharmacology have yet to be carried out, it showed far less potency than etonitazene itself. Etomethazene has an analgesic potency around 20 times that of morphine with a relatively short duration of about 120 m

Isotonitazene is a synthetic opioid analgesic drug from the nitazene class and structural homolog of etonitazene, which has been sold as a designer drug. It has only around half the potency of etonitazene in animal studies, but it is likely even less potent in humans as was seen with etonitazene (1000 times as potent as morphine in animal models yet only 60 times as potent in humans). Isotonitazene (obtained from an online vendor) was fully characterized in November 2019 in a paper where the authors performed a full analytical structure elucidation in addition to determination of the potency a