A racemic mixture, or racemate, is a 50/50 combination of both the enantiomers of a drug. Enantiomers are two molecules that are mirror images of one another (much like your hands are mirror images of one another). They usually have similar effects, although in some cases, one enantiomer may have benefits or side effects that the other does not. Certain drugs are available as a racemic mixture, and a single enantiomer formulation at the same time.

What Is Racemic Ketamine?

Ketamine is an example of a drug that is available as a racemic mixture and as a single enantiomer.

Ketmamine is a prescription anesthesia drug that is also used in an off-label manner to treat depression and sometimes other mental health conditions like anxiety and post-traumatic stress disorder (PTSD).

Ketamine has two enantiomers. S-ketamine and R-ketamine. Racemic ketamine combines both enantiomers in equal proportion. This racemic mixture is the one typically administered for surgical anesthesia and for depression treatments.

What Is Esketamine?

Esketamine is an FDA approved nasal spray depression treatment which contains only the enantiomer S-ketamine. Esketamine is administered in a controlled medical setting, and patients are often observed for a few hours after treatment. Esketamine is used in conjunction with traditional antidepressants. The brand name for esketamine is Spravato®.

Racemic Ketamine Vs. Esketamine

Ketamine infusions are composed of racemic ketamine, meaning equal parts of both ketamine’s enantiomers are administered as a racemic mixture. So it contains S-ketamine and R-ketamine in proportion.

Both racemic ketamine and esketamine are used to treat depression, and both seem to produce similar side effects.

There isn’t much literature comparing esketamine to racemic ketamine for depression. But a 2020 review indicated racemic ketamine could have an advantage over esketamine. Since racemic ketamine contains both enantiomers, it seems possible that racemic ketamine affects more of the brain than esketamine does. But we’ll have to wait for more research to confirm that.