CASE CONTINUED
It has been 3 months since Mr. B was initiated on lamotrigine, and he has since been titrated to his current, stable dose of 100 mg/d. Mr. B is no longer experiencing the sedation he had with lithium and has the energy to commit to an exercise routine. This has allowed him to lose 15 pounds so far and greatly improve control of his diabetes.
Dosage summary
Most available evidence supports dosing lithium and divalproex to effect, typically seen between 0.6 to 1.0 mEq/L and 50 to 125 µg/mL, respectively. Higher plasma levels tend to correspond to more adverse effects and toxicity. Lamotrigine does not have such a narrow therapeutic window. Lamotrigine for psychiatric treatment yields greatest efficacy at approximately 200 mg/d, but doses can be increased if warranted, which could be the case in Mr. B.
Table 11-5 outlines dosing strategies and therapeutic serum levels for lithium, divalproex, and lamotrigine. Table 22 lists signs and symptoms of lithium toxicity, and Table 31,2 describes strategies for managing adverse effects of lithium and divalproex.
