Ketamine’s been in the news a lot as a potential treatment for depression, PTSD, and more. It’s not FDA-approved (yet), but its cousin esketamine is approved for treating some forms of depression.

That gets confusing, especially among lay people who don’t realize how important those extra two letters are. (Consider how you’d feel if you landed in Kansas instead of Arkansas, especially during tornado season.)

Luckily, the good folks at Medscape have a great overview of the differences between ketamine and esketamine, including how they’re delivered, what they’re approved for, and the issues popping up as clinics offer “treatment” that could be ineffective, dangerous, or somewhere in between.

While ketamine and esketamine are chemically related, they are very distinct in terms of their chemical compositions, the FDA-approved indications, dosing, and administration, as well as the level of study and data supporting their safe and effective use.