Question

A 25 year old man with a psychotic illness was treated with haloperidol 30 mg/day. On the third day he developed pacing and an inability to sit still at one place. Which medication is likely to help?

• A. Phenytoin
• B. Propranolol
• C. Methylphenidate
• D. Trihexyphenidyl

Hint:

Pacing and restlessness on haloperidol is akathisia, not dystonia or parkinsonism, and beta blockers work best for it.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
A young man on a high dose of haloperidol (30 mg/day, a potent typical antipsychotic) develops pacing and an inability to sit still just three days into treatment. This time course and picture point to a drug-induced movement disorder rather than a worsening of his psychosis.

Step 2: Key Concept:
This is akathisia, an extrapyramidal side effect of high-potency antipsychotics like haloperidol. The patient feels an inner restlessness and has to keep moving or pacing, and cannot sit still. Akathisia is different from acute dystonia (sudden muscle spasm) and drug-induced parkinsonism (rigidity, tremor, slow movement), which are the other extrapyramidal reactions caused by the same drugs.

Step 3: Detailed Explanation:
Beta blockers, mainly propranolol, are the best studied and most effective drugs for antipsychotic-induced akathisia. They calm the restlessness by blocking the beta-adrenergic overactivity thought to drive it. Benzodiazepines are a reasonable second option.
Anticholinergics such as trihexyphenidyl help acute dystonia and drug-induced parkinsonism well, but they are far less reliable for akathisia, since the mechanism of akathisia is not mainly cholinergic.
Phenytoin is an anti-epileptic and has no role in treating a movement side effect of an antipsychotic.
Methylphenidate is a stimulant. Giving a stimulant to a patient who is already pacing and restless would make the restlessness worse, not better.

Step 4: Final Answer:
The medicine most likely to help this patient's akathisia is propranolol.
Note: the original 2002 answer key for this paper marks trihexyphenidyl. Current psychiatry teaching (Kaplan and Sadock) is clear that beta blockers, not anticholinergics, are the first-choice treatment for akathisia, so this solution follows the updated, better-supported answer.