Lithium (click on this)

1. Lithium is an elemental substance used commonly for manic depression/bipolar disorder. Its mechanisms of action are not well-undersood; it may affect second messenger signalling in neurl pathways controlling behavior and mood. 
2. In the past, lithium salts were used as a therapy for neutropenia because they do induce a leukocytosis. Until 1950, lithium was used as a salt substitute in 7-Up soft drinks (in fact, perhaps coincidentally, lithium's molecular weight is 6.9). 
3. Lithium,like sodium, has almost total renal elimination; renal insufficiency or dehydration causes and complicates lithium toxicity.
4. Because brain and muscle tissues act as a "sponge" for lithium, chronic toxicity in a lithium user is worse (and harder to treat) than acute toxicity in a nonuser. Chronic toxicity is also associated with LOWER numerical levels of lithium (see below) because the "lithium level" only reflects the amount of toxin in the bloodstream, not in the tissues. 
5. Clinical effects: nausea, vomiting, lethargy, hyperreflexia; tremors; ECG changes (flat or inverted T waves; bradycardia); nephrogenic DI with hypernatremia and free water wasting (manifests after IVFs are started). Rare: hypercalcemia (hyperparathyroid); hypothyroidism; neurologic disfunction which may me irreversible; serotonin syndrome;  
6. Treatment: Maintain Euvolemia and maximize urine output.
7. Hemodialysis may be needed if level is greater than 4 in patients with severe symptoms. Usually requires multiple sessions or prolonged HD because CNS is a lithium “sink” and hard to detoxify.
8. NSAIDS, ACE-inhibitors, dehydration are frequent triggers for toxicity because they decrease GFR and promote lithium retention.
9. Kayexalate not useful in humans although animal data indicates this enhances GI elimination if given in massive doses