What medication is a patient with involuntary, repetitive, non-rhythmic facial grimacing and chewing movements with occasional tongue protrusions most likely taking, given a history of psychiatric treatment with a medication for the past year?

Haloperidol

This patient has been most likely taking haloperidol, a typical (first-generation) antipsychotic that carries the highest risk for tardive dyskinesia among the medication options listed.

Clinical Presentation Confirms Tardive Dyskinesia

The patient's presentation is classic for tardive dyskinesia (TD):

• Involuntary, repetitive, non-rhythmic facial grimacing and chewing movements with tongue protrusions are pathognomonic for TD 1, 2
• The FDA label for haloperidol explicitly describes TD as "rhythmical involuntary movements of tongue, face, mouth or jaw (e.g., protrusion of tongue, puffing of cheeks, puckering of mouth, chewing movements)" 2
• The one-year duration of antipsychotic use aligns with TD's delayed onset, which typically appears after months to years of treatment 3, 4

Why Haloperidol is the Answer

Haloperidol is a high-potency typical antipsychotic with the highest TD risk among all options provided:

• Typical antipsychotics like haloperidol cause TD in >20% of adults after >3 months of use, with risk increasing by 5% per year 5
• Among antipsychotics, haloperidol has a 7 ms QTc prolongation rating and is classified as an older "typical" antipsychotic with higher TD risk 1
• TD occurs in 5% of young patients per year with typical antipsychotics, and is "more common with older, 'typical' antipsychotics" 1

Why Other Options Are Incorrect

The other medications listed have substantially lower or negligible TD risk:

• Imipramine (tricyclic antidepressant): Not a dopamine receptor blocking agent; does not cause TD 4
• Lithium (mood stabilizer): Not a dopamine receptor blocking agent; does not cause TD 4
• Mirtazapine (atypical antidepressant): Not a dopamine receptor blocking agent; does not cause TD 4
• Sertraline (SSRI): Not a dopamine receptor blocking agent; does not cause TD 4

Pathophysiology

TD results from chronic dopamine receptor blockade:

• The mechanism involves dopamine receptor supersensitivity from prolonged D2 receptor antagonism 4, 6
• Only dopamine receptor blocking agents (DRBAs) cause TD, which haloperidol is and the other options are not 6
• The FDA warns that "TD may develop in patients treated with antipsychotic drugs" and "the risk increases with duration of treatment and cumulative dose" 3

Critical Clinical Point

TD is potentially irreversible even after medication discontinuation 1, 2, 5. The FDA label states TD is "potentially irreversible" and "there is no known effective treatment for tardive dyskinesia" 2. This underscores the importance of recognizing the causative agent early.