Most of the pharmacological effects on weight and hormones are thought to be mediated centrally. However, De Haan et al. (de Haan L, et al. Psychopharmacology (Berl). 2004;175:389-390) proposed that at least some of the difference could be attributable to local effects in the GI tract. In particular, the site of absorption was suggested as a possible explanation, with the orally disintegrating form (Zydis) yielding less exposure of the pylorus to olanzapine than the standard Zyprexa tablets.