Its a bit sad they don’t actually quote the Elemental lithium dose. The doses are still not “low dose” although they are still quite high.
Li2CO3 molecular weight, 73.891, Li2 = 13.882 hence 18.5% of mass is lithium. 150mg =28.18mg Lithium 300=56.36
I think Li should be kept below 50 micromolar and my own test results would imply this is above this level.
I think the mechanism that causes nephrotoxicity in high dose lithium is inhibition of the SLC13 series of citrate carriers and this obviously will happen at a lower level. Hence I would personally think this dosing has the ability to be harmful although not necessarily noticeably so.