Which best reduces kidney effects: lithium immediate release or lithium ER (extended release)?
We recommended giving lithium in its generic slow release formulation (lithium carbonate ER) rather than the generic immediate release lithium. The immediate peak of lithium in the immediate release is quite high and will affect kidney cells much more than in the slow release where that peak is cut off and lower immediate levels occur in the blood. The slow release formulation of lithium does not appreciably increase its already long half-life of 24 hours, and the somewhat higher levels of lithium for a few extra hours in a day are still much below the high peak that initially happens with immediate release lithium, and thus should have less harmful effects on the kidneys in long-term treatment. There are clinical studies which find a correlation between less long-term kidney effects with slow-release versus immediate-release lithium, and no studies which show the reverse, as long as both regimens were given once daily. What is clear is that once daily dosing, no matter what type of lithium is used, clearly produces less long-term kidney impairment than multiple daily dosing. Best reference: H Lokkegaard et al, Acta Psychiatrica Scandinavica, 71: 347-355.