Which drug is a dopamine receptor antagonist used for drug-induced parkinsonism?

The drug used for drug-induced parkinsonism that is a dopamine receptor antagonist is Amantadine. This medication functions primarily as an antiviral but also has dopaminergic properties, which makes it beneficial in treating certain types of parkinsonism, particularly those caused by the use of antipsychotic medications that block dopamine receptors.

Amantadine works by increasing the release of dopamine and inhibiting its reuptake, enhancing dopaminergic transmission. This dual action helps alleviate the symptoms of drug-induced parkinsonism, such as rigidity, bradykinesia, and tremor, which can be precipitated by medications that antagonize dopamine receptors.

Other options provided do have roles in the management of Parkinson's disease but do not fit the specific criteria outlined in the question. Rasagiline and Selegiline are both monoamine oxidase-B inhibitors that help to increase dopamine levels in the brain, while Tolcapone is a catechol-O-methyltransferase (COMT) inhibitor that prolongs the action of dopamine but does not act as a dopamine receptor antagonist. This clarifies why Amantadine is indeed the most suitable choice for drug-induced parkinsonism.