Clinical case: Valproate toxicity despite a valproic acid level in the usual therapeutic range

One of my outpatients with bipolar disorder and ADHD is being treated with divalproex extended-release (Depakote ER®), along with lurasidone, atomoxetine, and gabapentin. He was smoking natural cannabis intermittently and I was trying to get him to stop doing that. The patient’s valproic acid level would vary without a change in the dose. This was…