Zyprexa^® (olanzapine) is a drug that is licensed to treat schizophrenia and bipolar disorder. The medication works by blocking or lessening the effects of several chemicals in the brain. Zyprexa comes in tablet form and is usually taken once a day. Some of the more common side effects seen with this drug include dizziness, drowsiness, and constipation. Seek medical attention immediately if you happen to overdose on Zyprexa. Symptoms of a Zyprexa overdose can include agitation or aggressiveness, changes in speech or language, a fast heart rate (tachycardia), and sleepiness or passing out.