Lithium is used in the treatment of both manic and depressive phases of bipolar disorder, as well as in unipolar depressive disorder to prevent future depressive episodes. Patients refractory to antidepressants may be treated with lithium as an adjunct to other drugs.
Depending on the indication for lithium treatment, target serum concentrations vary.
The reference range for therapeutic levels of lithium is 0.8-1.2 mEq/L.
However, a study by Hsu et al indicated that in patients with euthymic bipolar disorder, lithium serum levels of 0.4-0.8 mmol/L significantly inhibit the recurrence of major mood episodes, although this effect was found only in patients aged 40-60 years. The adjusted hazard ratio (aHR) was 0.75, compared with 0.77 for levels of 0.8-1.2 mmol/L, with the aHR for levels below 0.4 mmol/L being used as reference.
The toxic lithium level is >2 mEq/L.