Lithium is readily absorbed from the gastrointestinal tract. It is distributed to the body with higher levels in the kidney, thyroid, and bone as compared to other tissues. Since lithium is almost exclusively excreted by the kidneys, people with preexisting chronic kidney disease are at high risk of developing lithium intoxication. The drug itself is also known to be nephrotoxic, opening up the possibility of spontaneous emergence of toxicity at doses that were previously well-tolerated. Lithium toxicity can be mistaken for other syndromes associated with antipsychotic use, such as serotonin syndrome because lithium increases serotonin metabolites in the cerebrospinal fluid.
There are several drug interactions with lithium. Interactions can occur from typical antipsychotics or atypical antipsychotics. In particular, certain drugs enhance lithium levels by increasing renal re-absorption at the proximal tubule. These drugs are angiotensin-converting enzyme inhibitors, non-steroidal anti-inflammatory drugs and thiazide diuretics.