The principal side effect of olanzapine is weight gain, which may be profound in some cases and/or associated with derangement in the blood lipid and blood sugar profiles (see section metabolic effects). Olanzapine extended-release injection is used to treat schizophrenia (a mental illness that causes disturbed or unusual thinking, loss of interest in life, and strong or inappropriate emotions). Olanzapine is used to treat schizophrenia, bipolar disorder, and depression. Learn about side effects, drug interactions, dosages, warnings, and more. Olanzapine is an antipsychotic medication that affects chemicals in the brain. Olanzapine is used to treat the symptoms of psychotic conditions such as schizophrenia and bipolar disorder (manic depression) in adults and children who are at least 13 years old. Common and Serious Side Effects of Zyprexa. The more common symptoms might include restlessness, depression, drowsiness, dizziness, weakness, difficulty walking, or unusual behavior. Defines the medication fluoxetine (Prozac, Sarafem, Prozac Weekly) a drug used in the treatment of depression, obsessive-compulsive disorders, panic attacks, and premenstrual dysphoric disorder. Article includes descriptions, uses, drug interactions, and side effects. Olanzapine oral tablet is available as brand-name drugs and generic drugs. Brand names: Zyprexa, Zyprexa Zydis. Olanzapine comes as a regular tablet and a disintegrating tablet. Olanzapine belongs to a group of medicines called antipsychotics. This medicine is used to treat a disease whose symptoms include hearing, seeing or sensing unreal things, to have mistaken beliefs or unusual suspiciousness and becoming withdrawn. How to take olanzapine. Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about olanzapine and it will also provide you with a full list of the side-effects which you may experience from taking it. In Summary. Commonly reported side effects of olanzapine include: asthenia, dizziness, drowsiness, extrapyramidal reaction, hyperkinetic muscle activity, akinesia.