How does haloperidol work in the brain (what it “does”)
Haloperidol acts mainly by blocking dopamine D2 receptors in the brain. That D2 blockade reduces dopamine signaling, which helps calm psychotic symptoms such as hallucinations, delusions, and agitation. It also has an effect on other receptors (including some serotonin and alpha-adrenergic receptors), but the D2 antagonism is the key mechanism linked to its antipsychotic action. [1]
Why does haloperidol cause side effects tied to dopamine blockade?
Because haloperidol blocks D2 receptors in several brain pathways, the dopamine reduction can produce predictable adverse effects:
- Extrapyramidal symptoms (stiffness, tremor, restlessness/akathisia) come from dopamine blockade in the nigrostriatal motor pathway.
- Elevated prolactin and related sexual side effects come from dopamine blockade in the tuberoinfundibular pathway. [1]
What is “INJ haloperidol” used for, and how quickly does it act?
Injections of haloperidol are used to treat acute agitation or psychosis (including in emergency or inpatient settings). The parenteral route is chosen when fast symptom control is needed compared with oral dosing. The exact onset and duration depend on the dose and route (IM vs IV), but the intent of the injection is rapid control of dangerous or severe symptoms. [1]
How does haloperidol compare with other antipsychotics?
Haloperidol is a typical (first-generation) antipsychotic. Compared with many newer (second-generation) antipsychotics, it tends to have a higher risk of extrapyramidal side effects, largely because of strong D2 antagonism. [1]
What should clinicians monitor when giving injected haloperidol?
Common practical concerns include:
- Movement-related side effects (early and dose-related extrapyramidal effects)
- Sedation and blood pressure changes
- Cardiac rhythm risk (haloperidol can prolong the QT interval, so clinicians consider QT risk factors and any relevant ECG monitoring decisions) [1]
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Sources
[1] https://reference.medscape.com/drug/haloperidol-342974