Olanzapine (Adverse effects)

Olanzapine is in a class of medications called atypical antipsychotics, structurally similar to clozapine and having the same mechanism of action. Olanzapine binds to alpha-1, dopaminergic, histaminic H1, muscarinic and serotoninergic (type 5-HT2) receptors. Compared to the typical antipsychotics, olanzapine has more reduced cardiovascular effects and induces less hyperprolactinemia and extrapyramidal reactions. From a clinical point of view, olanzapine is effective in treating the symptoms of schizophrenia and is also used in treating acute mania with bipolar disorder, and in reducing agitation and other psychotic symptoms in dementia.

Olanzapine is an atypical neuroleptic with effects similar to other neuroleptics on is used to treat both negative and positive symptoms of schizophrenia, and is also effective for persistent positive symptoms. It works by changing the activity of certain natural substances in the brain.

Weight gain is one of the most important side effects associated with antipsychotic drug treatment. It has a negative influence on one's health (associated with diabetes, heart disease, and other serious disorders) and the personal well-being of the patient with a reduced fulfillment of treatment and the possible risk of recurrence of the illness. The importance of this problem was shown by Fontaine et al. who found that clozapine, in spite of preventing suicide in 492 out of 100,000 schizophrenic patients treated over a 10 year period, could also be considered responsible for 416 deaths caused by the consequences of weight gain induced by antipsychotics.

Among the atypical neuroleptic drugs, olanzapine and clozapine have been associated with a greater weight gain, with an average gain of 5 kg over short-term treatment and 6.7 kg over long-term treatment.

Genetic factors are believed to play an important role in an individual's response to antipsychotic drugs, both in the benefits of treatment and in the susceptibility to side effects. The variations in the gene sequence, called polymorphism, could influence the properties of the coded proteins and the results in individual response to the drugs.


The extrapyramidal side effects are less intense than those of the classic antipsychotics, with sedation at the beginning of the treatment but a greater incidence of metabolic effects.

Olanzapine may cause side effects:

  • drowsiness
  • dizziness
  • akathisia (restlessness)
  • unusual behavior
  • depression
  • difficulty falling asleep or staying asleep
  • weakness
  • difficulty walking
  • constipation
  • urine retention
  • weight gain
  • dry mouth
  • pain in arms, legs, back, or joints
  • breast enlargement or discharge
  • late or missed menstrual periods
  • decreased sexual ability
  • seizures
  • changes in vision
  • swelling of the arms, hands, feet, ankles, or lower legs
  • early onset or late developing dyskinesias (unusual movements of your face or body that you cannot control)
  • sore throat, fever, chills, and other signs of infection
  • very stiff muscles
  • excess sweating
  • tachycardia (fast or irregular heartbeat)
  • rash
  • hives
  • difficulty breathing or swallowing
  • Parkinson-like symptoms
  • hyperorexia (abnormal increased appetite)
  • hyperprolactinemia (higher-than-normal blood levels of the hormone prolactin; can be reversed on suspending treatment; can cause gynecomastia, galactorrhea)
  • hyperglycemia
  • orthostatic hypotension (drop in blood pressure upon standing)
  • cardiomyopathy
  • elevated hepatic enzymes
  • photosensitivity
  • leucopenia

Gene or region studied

  • SCARB1
  • APOA4
  • APOE
  • HTR2C
The DNA test you were looking for