haloperidol

Haloperidol is a typical antipsychotic in the butyrophenone class. It is a high-potency dopamine D2 receptor antagonist used to treat schizophrenia and other psychoses, and to manage acute agitation in emergency settings. It is also employed for Tourette syndrome to reduce severe motor and vocal tics and has been used for intractable hiccups and, in some contexts, as an antiemetic.

The drug’s therapeutic effect primarily derives from D2 receptor blockade in the mesolimbic pathway, which helps reduce psychotic symptoms. Blockade in the nigrostriatal pathway accounts for extrapyramidal side effects. Haloperidol typically has less activity at muscarinic, histaminergic, and alpha-adrenergic receptors than some other antipsychotics, contributing to its distinct side effect profile.

Haloperidol is available in oral tablets and solutions, and in intramuscular or intravenous forms for rapid control of agitation. A long-acting injectable form (haloperidol decanoate) is used for maintenance treatment in chronic psychosis. The depot preparation requires dosing at extended intervals, often weeks, to maintain steady therapeutic levels.

Adverse effects are dominated by extrapyramidal symptoms, including dystonia, akathisia, and drug-induced parkinsonism, as well as hyperprolactinemia. Other risks include sedation, orthostatic hypotension, and, with long-term use, tardive dyskinesia. Serious but uncommon risks include neuroleptic malignant syndrome and QT interval prolongation, which can lead to arrhythmias. Haloperidol may worsen outcomes in elderly patients with dementia-related psychosis and is generally avoided in that population. Pregnancy is category C; use only if clearly indicated.

Pharmacokinetically, haloperidol is well absorbed from the gut, is extensively metabolized in the liver, and is excreted in urine and feces. The half-life is typically around one day, with the long-acting formulation extending the duration of action.