Monday, March 15, 2010

Something That Makes Me Mad--So We're Going To Learn About Drugs

I found out something that makes me super upset. And to spread the info, I need to explain a bit of organic chemistry to you. Don't worry, you won't be tested on it, and it's only a very basic concept -- chirality, or literally, handedness of molecules.

Put your hands palm down, like so:

Notice that when you put one hand on top of the other, they aren't superimposable -- meaning that you can't put one directly on top of the other and have them match up identically. Instead you get a funny awkward turtle thing going on.

The reason they don't match up exactly is because they're mirror images of each other.

And of course, in chemistry we have our own special word for two molecules that are not the same, but mirror images of each other: enantiomers. No matter how you turn them and twist them, you can't make them the same.

So basically, with that under your belt, you only need to understand two more things.

1) You call one the R enantiomer and the other the S enantiomer. There are rules for figuring out which is which, but that doesn't matter so much. R and S have slightly different properties, but sometimes it doesn't matter which one you have.

2) When you have a mixture that is 50% R and 50% S you have what is called a racemic mixture.

Okay, with that basic explanation of some strange chemistry-nerd-talk... here's what makes me SUPER mad.

Citalopram (Celexa) is a racemic mixture of the R and S enantiomers: it's half of the stuff on the left and half of the stuff on the right. It cost me $4 to get a whole month's supply.

At the center of the molecule you'll see one arm darkened, which is shorthand for 3-D coming OUT of the screen.  The other arm with a dashed line is shorthand for 3-D going into the screen.The difference between these two molecules is switching the dark and dashed arms.

Escitalopram (Lexapro) is the S enantiomer ONLY -- just the one on the left. It cost me $50 to get a whole month's supply. They remarketed essentially the same thing to make money. That's right: they're just BARELY different enough to get a new patent.

And that's why I'm mad. The Doctor 1 prescribed me escitalopram. Doctor 2 switched me to citalopram because I couldn't afford escitalopram every month. ... I'm a little bit peeved at Doctor 1.

Also keep on the lookout for arcitalopram... that'll be JUST the R enantiomer I'll bet. And it won't EVEN be worth as much as it costs.

*Oh gosh. I can't help but explain the following because it's SO exciting. Really, arcitalopram won't ever be marketed. Apparently R-citalopram can work against S-citalopram to an extent... but not enough to prevent Celexa from being an effective antidepressant because S-citalopram (the good stuff) is 20 times stronger than the R-citalopram (the bad stuff). So really, Lexapro IS better. But $46 better?I think not.)


  1. You know what? I think I actually kind of understood what you just said. Lol :)
    Unfortunate, isn't it, the way our pharmaceutical industry works?

  2. YES! Mission accomplished. I was afraid I was just going to confuse everyone instead of spreading rage. ... Is that even a worthy goal?