What is the most likely cause of restlessness in a patient taking haloperidol?

In the context of a patient taking haloperidol, the most likely cause of restlessness is akathisia. Haloperidol is an antipsychotic medication that can lead to various side effects, particularly extrapyramidal symptoms due to its dopamine antagonist properties. Akathisia is characterized by a feeling of inner restlessness and an uncontrollable urge to be in constant motion, which aligns directly with the symptom of restlessness.

Patients experiencing akathisia may report the need to move constantly (for example, pacing or shifting in their seats), which is distinct from general agitation or other movement disorders. This specific symptom typically arises from the medication’s interaction with dopamine pathways in the brain, particularly among individuals receiving treatment for schizophrenia or other psychotic disorders.

Understanding akathisia's mechanism as a side effect of antipsychotics helps distinguish it from other potential causes of restlessness that could occur in patients, such as agitation stemming from anxiety or situational factors, Parkinsonism reflecting a different profile of movement disorders, or psychosis itself, which would lead to other symptoms more related to a loss of touch with reality rather than physical restlessness alone.