A patient on haloperidol develops involuntary lip smacking and tongue protrusion. Which drug is used for management?

Correct option is A

Haloperidol can cause drug-induced extrapyramidal side effects (tardive dyskinesia, dystonia). Trihexyphenidyl, an anticholinergic, relieves these symptoms.
Explanation of options: (a) ✔ Correct; trihexyphenidyl is used for drug-induced EPS. (b) ✘ Propranolol is useful in akathisia, not dystonia/dyskinesia. (c) ✘ Diazepam may reduce anxiety but not EPS directly. (d) ✘ Risperidone is another antipsychotic, not treatment of EPS.