Haloperidol is an antipsychotic medication used in the treatment of schizophrenia, acute psychosis, and delirium. Haloperidol is a butyrophenone derivative and functions as an inverse agonist of dopamine. A long-acting decanoate ester of haloperidol is used as an injection given every four weeks to people with schizophrenia or related illnesses who have poor adherence to medication regimens and suffer frequent relapses of illness, or to overcome the drawbacks inherent to its orally administered counterpart. In humans, no controlled studies exist. Unconfirmed studies in pregnant women revealed possible damage to the fetus, although most of the women were exposed to multiple drugs during pregnancy. Following accepted general principles, haloperidol should be given during pregnancy only if the benefit to the mother clearly outweighs the potential fetal risk.