Which property is characteristic of the antipsychotics chlorpromazine, clozapine, loxapine, olanzapine, perphenazine, thioridazine, and trifluoperazine?

Which property is characteristic of the antipsychotics chlorpromazine, clozapine, loxapine, olanzapine, perphenazine, thioridazine, and trifluoperazine?

• A. Weak dopamine antagonism
• B. High metabolic risk
• C. Strong anticholinergic properties
• D. Low sedation risk

Answer: (C)

The property at play is muscarinic (anticholinergic) receptor blockade. These antipsychotics commonly have significant anticholinergic activity, which shows up as dry mouth, constipation, blurred vision, urinary retention, and other parasympathetic-suppressing effects. This antimuscarinic action is a shared pharmacologic feature across both several low- and mid-potency typicals (like chlorpromazine and thioridazine) and several atypicals (like clozapine and olanzapine) in the list, making strong anticholinergic properties the best-fitting characteristic for this group. In contrast, weak dopamine antagonism isn’t accurate because these drugs are effective dopamine blockers; metabolic risk varies among them and is not universal to all, and sedation risk also varies and is not consistently low—so those traits don’t consistently define the entire set.

The property at play is muscarinic (anticholinergic) receptor blockade. These antipsychotics commonly have significant anticholinergic activity, which shows up as dry mouth, constipation, blurred vision, urinary retention, and other parasympathetic-suppressing effects. This antimuscarinic action is a shared pharmacologic feature across both several low- and mid-potency typicals (like chlorpromazine and thioridazine) and several atypicals (like clozapine and olanzapine) in the list, making strong anticholinergic properties the best-fitting characteristic for this group.

In contrast, weak dopamine antagonism isn’t accurate because these drugs are effective dopamine blockers; metabolic risk varies among them and is not universal to all, and sedation risk also varies and is not consistently low—so those traits don’t consistently define the entire set.