Question: why does zyprexa cause weight gain?
Answer: Most research has focused on clozapine and olanzapine, the two medications identified to cause the highest weight gain. The high likelihood of weight gain with these medications has been linked to their actions at serotonin 5-HT2A and 5-HT2C, dopamine D2 and D3, histamine H1 and muscarinic M3 receptors.