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  • N-[(1R,5S)-8-methyl-8-azabicyclo[3.2.1]oct-3-yl]-2-oxo-3-(propan-2-yl)-2,3-dihydro-1H-benzimidazole-1-carboxamide hydrochloride
CAS Number
PubChem CID
Chemical and physical data
· HCl
3D model (JSmol)
  • Cl.O=C2N(c1ccccc1N2C(=O)NC4C[C@H]3N(C)[C@H](CC3)C4)C(C)C
  • InChI=1S/C19H26N4O2.ClH/c1-12(2)22-16-6-4-5-7-17(16)23(19(22)25)18(24)20-13-10-14-8-9-15(11-13)21(14)3;/h4-7,12-15H,8-11H2,1-3H3,(H,20,24);1H/t13?,14-,15+; checkY

BIMU-8 is a drug which acts as a 5-HT4 receptor selective agonist. BIMU-8 was one of the first compounds of this class.[1][2] The main action of BIMU-8 is to increase the rate of respiration by activating an area of the brain stem known as the pre-Botzinger complex.


The most obvious practical use of BIMU-8 is to combine it with opioid analgesic drugs in order to counteract the dangerous respiratory depression which can occur when opioids are used in excessive doses.[3] BIMU-8 does not affect the pleasurable or painkilling properties of opiates, which means that if combined with BIMU-8, large therapeutic doses of opiates could theoretically be given to humans without risking a decrease in breathing rate. Studies have shown BIMU-8 to be effective in rats at counteracting the respiratory depression caused by the potent opioid fentanyl,[4] which has caused many accidental deaths in humans. However, no human trials of BIMU-8 have yet been carried out.

Other studies have suggested a role for 5-HT4 agonists in learning and memory,[5] and BIMU-8 was found to increase conditioned responses in mice, so this drug might also be useful for improving memory in humans.

Some other selective 5-HT4 agonists such as mosapride and tegaserod (the only 5-HT4 agonists currently licensed for use in humans) have been found not to reduce respiratory depression.[6] On the other hand, another 5-HT4 agonist, zacopride, does inhibit respiratory depression in a similar manner to BIMU-8.[7]

This suggests that either the anti-respiratory depression action is mediated via a specific subtype of the 5-HT4 receptor which is activated by BIMU-8 and zacopride, but not by mosapride or tegaserod, or alternatively there may be functional selectivity involved whereby BIMU-8 and zacopride produce a different physiological response following 5-HT4 binding compared to other 5-HT4 agonists. Another alternative to this is that the 5-HT4 agonist currently available for use in humans do not have great enough potency or bioavailability in the brain to elicit the same effects.[6]

Other activity[edit]

Along with several other 5-HT4 ligands, BIMU-8 was also found to possess significant affinity for the sigma receptors, acting as a σ2 antagonist.[8][9][10] It is unclear as yet what contribution this additional activity makes to the pharmacological profile of BIMU-8 and other 5-HT4 ligands that also show sigma affinity.

See also[edit]


  1. ^ Turconi M, Nicola M, Quintero MG, Maiocchi L, Micheletti R, Giraldo E, Donetti A (August 1990). "Synthesis of a new class of 2,3-dihydro-2-oxo-1H-benzimidazole-1-carboxylic acid derivatives as highly potent 5-HT3 receptor antagonists". Journal of Medicinal Chemistry. 33 (8): 2101–2108. doi:10.1021/jm00170a009. PMID 1695682.
  2. ^ Dumuis A, Sebben M, Monferini E, Nicola M, Turconi M, Ladinsky H, Bockaert J (March 1991). "Azabicycloalkyl benzimidazolone derivatives as a novel class of potent agonists at the 5-HT4 receptor positively coupled to adenylate cyclase in brain". Naunyn-Schmiedeberg's Archives of Pharmacology. 343 (3): 245–251. doi:10.1007/bf00251122. PMID 1650917. S2CID 3173348.
  3. ^ Manzke T, Guenther U, Ponimaskin EG, Haller M, Dutschmann M, Schwarzacher S, Richter DW (July 2003). "5-HT4(a) receptors avert opioid-induced breathing depression without loss of analgesia". Science. 301 (5630): 226–229. Bibcode:2003Sci...301..226M. doi:10.1126/science.1084674. PMID 12855812. S2CID 13641423.
  4. ^ Wang X, Dergacheva O, Kamendi H, Gorini C, Mendelowitz D (August 2007). "5-Hydroxytryptamine 1A/7 and 4alpha receptors differentially prevent opioid-induced inhibition of brain stem cardiorespiratory function". Hypertension. 50 (2): 368–376. doi:10.1161/HYPERTENSIONAHA.107.091033. PMID 17576856.
  5. ^ Meneses A, Hong E (March 1997). "Effects of 5-HT4 receptor agonists and antagonists in learning". Pharmacology, Biochemistry, and Behavior. 56 (3): 347–351. doi:10.1016/S0091-3057(96)00224-9. PMID 9077568. S2CID 11866740.
  6. ^ a b Lötsch J, Skarke C, Schneider A, Hummel T, Geisslinger G (September 2005). "The 5-hydroxytryptamine 4 receptor agonist mosapride does not antagonize morphine-induced respiratory depression". Clinical Pharmacology and Therapeutics. 78 (3): 278–287. doi:10.1016/j.clpt.2005.05.010. PMID 16153398. S2CID 45695450.
  7. ^ Meyer LC, Fuller A, Mitchell D (February 2006). "Zacopride and 8-OH-DPAT reverse opioid-induced respiratory depression and hypoxia but not catatonic immobilization in goats". American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 290 (2): R405–R413. doi:10.1152/ajpregu.00440.2005. PMID 16166206. S2CID 224414.
  8. ^ Bonhaus DW, Loury DN, Jakeman LB, Hsu SA, To ZP, Leung E, et al. (October 1994). "[3H]RS-23597-190, a potent 5-hydroxytryptamine4 antagonist labels sigma-1 but not sigma-2 binding sites in guinea pig brain". The Journal of Pharmacology and Experimental Therapeutics. 271 (1): 484–493. PMID 7965749.
  9. ^ Weatherspoon JK, Gonzalez-Alvear GM, Werling LL (May 1997). "Regulation of [3H]norepinephrine release from guinea pig hippocampus by sigma2 receptors". European Journal of Pharmacology. 326 (2–3): 133–138. doi:10.1016/S0014-2999(97)85407-6. PMID 9196265.
  10. ^ Liu X, Nuwayhid S, Christie MJ, Kassiou M, Werling LL (June 2001). "Trishomocubanes: novel sigma-receptor ligands modulate amphetamine-stimulated [3H]dopamine release". European Journal of Pharmacology. 422 (1–3): 39–45. doi:10.1016/S0014-2999(01)01071-8. PMID 11430911.