When comparing ketamine vs. esketamine, it’s important to note that esketamine is essentially one part of ketamine. Ketamine is composed of two mirror-image molecules that exist together but spin in different directions—this is called a racemic mixture. Ketamine is composed of two molecules known as R-ketamine and S-ketamine. Imagine your hands, mirror images of one another. The same, but different. When a racemic mixture is separated, each molecule on its own is called an enantiomer. Therefore, as the S-enantiomer of ketamine, esketamine (s-ketamine) is literally one-half of the molecular compound ketamine. Buy Spravato online. Buy Ketamine HCL online.