Is lithium L-threonate a potential brain medicine? Lithium ions have known neuroprotective qualities. That would explain its therapeutic benefit in some mental disorders. It is also well known that lithium carbonate must be taken in toxic doses to get even small amounts into the brain. This makes lithium carbonate a very non-optimal medicine. On the other hand, lithium orotate promises to reach the brain much more efficiently and therefore require smaller doses. Unfortunately it contains orotic acid, which is a known carcinogen.

Magnesium L-threonate is a form of magnesium that easily penetrates the blood-brain barrier and therefore confers therapeutic effects on the brain. Is it then conceivable that lithium L-threonate is both safe and effective as a medicine for brain disorders?
Lithium has a diagonal relathionship with magnesium, so in effect, it makes sense to compare it to magnesium compounds. It may also substitute for sodium ions in transporters. I doubt the counter ions is relevant, since most Li coumpounds are quantitatively dissociated. Stable concentrations of lithium are only achieved after several week of treatment. Lithium carbonate, citrate and sulfate are used to my knowledge. Plasma concentrations are monitored so as to avoid reaching toxic levels (more than 1 milli molar). Some physicians also test for the concentration inside red blood cells to get an idea of the concentration in the brain, but this has not been confirmed to be relevant. What is important is not the amount of it, but the clinical effect : is the patient responding to treatment ? does he/she support it ?

Lithium has not only neuroprotective effects, but also mood-stabilizing effects. It is mostly used in case of bipolar disorder (mood swings), but also as an antidepressant. The mechanism of action is still elusive. It may enhance serotonin pathway, and, by competing with magnesium ions, inhibit some magnesium-dependent enzymes (typically enzymes handling MgATP). One of these enzymes is called glycogen-synthase-kinase (GSK).