Divalproex and related formulations of valproic acid had superior efficacy compared with placebo (Bowden et al. 1994, 2006; Brennan et al. 1984; Emrich et al. 1981; Pope et al. 1991) and comparable efficacy compared with lithium (Bowden et al. 1994; T. W. Freeman et al. 1992), haloperidol (McElroy et al. 1996), and olanzapine (Zajecka et al. 2002) in randomized, controlled acute treatment trials of bipolar manic or mixed episodes. Olanzapine was superior to divalproex in mean reduction of manic symptoms and in proportion of patients in remission at study completion in a second head-to-head comparison trial (Tohen et al. 2002a). Muller-Oerlinghausen et al. (2000) found that the combination of valproate and typical antipsychotics produced significantly lower mean antipsychotic doses and higher response rates compared with placebo added to typical antipsychotics in patients with acute mania.