A combined analysis of two long-term studies suggests that lamotrigine effectively delays relapse or recurrence of depressive episodes associated with bipolar disorder, according to a presentation at the annual meeting of the American Psychiatric Association. The drug is currently in phase III trials for this indication.

"Lamotrigine significantly delayed time to any bipolar episode and time to treatment intervention in some of the longest maintenance studies ever conducted in bipolar disorder," said presenter and lead investigator Joseph R. Calabrese, M.D. "The results support the favorable efficacy and safety profile seen in studies of lamotrigine to date, suggesting that it may be a promising treatment for bipolar disorder patients, particularly those experiencing the devastating lows of bipolar depression."

The double-blind, placebo-controlled trials enrolled a total of 1,315 current or recently symptomatic bipolar I patients. Of the total, 638 stabilized in the preliminary phase and were randomized to lamotrigine (280 patients), lithium (167 patients), or placebo (191 patients).

At the end of the 18-month follow-up period, 57 percent of the lamotrigine patients had not required intervention for depression compared with 51 percent of the lithium patients and 40 percent of the placebo patients.

The incidence rates of adverse side effects such as headache, infection, nausea, somnolence, or insomnia were similar across the three treatment arms with the exception of diarrhea and tremor, which were more prevalent among the lithium patients.