https://clinicalstudies.info.nih.gov/ProtocolDetails.aspx?id=20-NR-0003
Researchers hope that ketamine, compared to a drug called midazolam, can reduce fatigue in people with illnesses.
I don't understand why they think this. Both ketamine and midazolam will increase central fatigue. Edit - I think the expected mechanism is an analgesic effect... In the paper mentioned below, the authors speculate about AMPAR activation, by glutamate selectively binding those receptors instead of NDMA receptors (one difference between NDMARs and AMPARs is that the former has ion channels permeable to both calcium and sodium ions, whereas the latter is only permeable by sodium ions). But if we are to entertain that argument, then we also need to consider Kainate receptors and metabotropic glutamate receptors. (and I still don't know how this is supposed to decrease fatigue.) Ketamine is also associated with a transient increase in blood pressure and this may mediate some of the effect.
The principal author wrote a 2015 narrative review discussing potential causes of cancer related fatigue, with the following diagram:
https://pubmed.ncbi.nlm.nih.gov/25975676/
You've probably seen something like this before, only with "Chronic Fatigue Syndrome" at the centre, because the ideas are the same. It's very non-specific and doesn't actually explain anything.
On the trial description page, they cite a general article authored by Sharpe (that if being polite, I can only describe as speculative) and a trial of the effect of ketamine on fatigue in Bipolar patients, also authored by the principal author of the aforementioned trial.
https://pubmed.ncbi.nlm.nih.gov/26807672/
Note, they do discuss that the effect may be biased due to lack of an active placebo (and thus the results are simply reporting biases), hence the use of midazolam in the proposed trial.
The good news is that in the proposed trial, they're not merely relying on questionnaires, but actigraphy as well, so there is less chance of a false positive result due to study biases.
There was also a recent study of Ketamine for MS-related fatigue, with a null primary outcome, but a modest effect on a 28 day outcome:
https://journals.sagepub.com/doi/abs/10.1177/1352458520936226