Overall, the benefits of even a single ketamine injection occur rapidly, but are modest in magnitude. The best regimen to maintain these benefits by reinjecting ketamine has not been determined.

Ketamine can rapidly reduce symptoms of PTSD and depression, new study finds

The analysis shows that ketamine may start relieving symptoms of PTSD within one day, but it is still unclear how long the effects last and how many injections are needed to maintain benefits.

^{The Conversation}