A molecule of atracurium. Each of the ten stereoisomers has the atoms in this order, but some parts of the molecule are rotated differently.
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Atracurium is an intermediate onset intermediate duration non-depolarizing neuromuscular blocker. It is classified as bis-benzyltetrahydroisoquinolinum (the name for its shape). It was developed in 1974 and was officially FDA approved on November 23, 1983.
One of the most interesting features of the atracurium molecule is the fact that it has 10 stereoisomers with varying degrees of potency and side effects.
Clinical Information[]
Note - The main reference I use is drugs.com, which gives excellent information on the drug. http://www.drugs.com/pro/atracurium-besylate-injection.html
Generic name: Atracurium Besylate
Trade names: Tracurium (the main one), Relatrac, Atracade
ED95 - 0.2 mg/kg (the official ED95 is 0.23 mg/kg, but you'll see 0.2 much more often.)
Onset time: 2 - 2.5 minutes
Time to 25% recovery: 35-45 minutes
Side effects - Histamine release, breaks down into laudanosine which lowers the threshold for seizures
The 10 Atracurium Isomers[]
All 10 isomers are stereoisomers, meaning the atoms are arranged in the same order and have the same shape. The only thing that changes is the 3-d orientations of the bonds. If you notice, some of the bonds are solid black triangles, meaning in 3-d space, they are popping out towards your face. The ones drawn as dashed lines are pointing away from you. This is just a list for reference.
The 10 atracurium isomers are:
Click the magnifying glass in this text box then "full resolution" on the page that comes up to see the 10 atracurium isomers and their different stereo bond orientations.
R-cis, R-cis (cisatracurium)
R-cis, R-trans ------ (same as R-trans, R-cis)
R-cis, S-cis --------- (same as S-cis, R-cis)
R-cis, S-trans ------ (same as S-trans, R-cis)
R-trans, R-trans
R-trans, S-cis ------ (same as S-cis, R-trans)
R-trans, S-trans --- (same as S-trans, R-trans)
S-cis, S-cis
S-cis, S-trans ------ (same as S-trans, S-cis)
S-trans, S-trans
Stereo isomers means the atoms are all in the same order, but some of the angles that parts of the molecules go in can be different. So all the isomers follow the same basic structure of 3 hexagons with some oxygens and an N+, a bridge of carbons and oxygens, then another 3 hexagons with oxygens and an N+.
The chemical formula is C53H72N2O12. Now, not all of the isomers of atracurium cause histamine release (histamine release is a bad thing, by the way). In an effort to make something similar to atracurium that didn't release histamine, scientists began investigating which isomers actually caused histamine release. They found that one of the isomers, the 1R-cis-1'R-cis isomer, did not cause histamine release. And thus, cisatracurium was born! Atracurium is 15% cisatracurium.
For any organic chemistry nerds out there, here's a patent showing how to make atracurium in a long series of steps.
Here's an even easier way to make atracurium, from only a few years after it first came out, and it's also complete with a nice history of NMB development and extra info on some of the more obscure and older NMBs such as alcuronium and fazadinium.