Episode 303: Evaluating lithium levels in the setting of lithium toxicity

When lithium toxicity is suspected, a lithium level should be drawn immediately and every few hours until a downward trend is seen. Lithium levels should continue to be checked, as delayed peaks have been reported as long as 40 hours after presentation.  This is most likely to occur when extended-release lithium is taken in acute overdose.

The lithium level does not always correlate with toxicity. This is especially true in acute ingestions when lithium has not yet penetrated the CNS. For this reason, a combination of factors including lithium level, acute vs. chronic ingestion, and symptoms need to be considered when deciding on a course of treatment.

When lithium is at steady-state, the symptoms that correlate with the serum lithium level are:

1.5 to 2.5 mEq/L – mild lethargy, mild tremor, and slurred speech

2.5 to 3.5 mEq/L – increasing lethargy, increasing tremors, and clonus

>3.5 mEq/L – severe symptoms such as seizure and non-convulsive status epilepticus

For more on the treatment of lithium toxicity go to pharmacyjoe.com/episode130.