A patient with involuntary muscular movements is to receive dental treatment. Which agent is MOST appropriate to reduce the movements and allow safe treatment in the chair?

Correct answer: B. A benzodiazepine such as diazepam

• A. Nitrous oxide provides anxiolysis and mild analgesia and is useful as an adjunct, but it lacks meaningful muscle-relaxant properties and will not reliably control involuntary movement.
• B. CORRECT. A BENZODIAZEPINE such as diazepam or midazolam is the appropriate choice. Benzodiazepines potentiate GABA-A transmission, producing anxiolysis, sedation and — crucially here — central SKELETAL MUSCLE RELAXATION. That combination reduces involuntary movement and allows safe, controlled treatment, which is why oral or intravenous benzodiazepine sedation is standard for patients with cerebral palsy, dyskinesias and similar movement disorders.
• C. Antihistamines have sedative and mild antimuscarinic effects and are occasionally used for paediatric sedation, but they are not muscle relaxants and are not indicated for a movement disorder.
• D. PHENYTOIN is an anticonvulsant for seizure disorders, not a treatment for involuntary movements. It has no place in chairside management here, and it is notable in dentistry for causing GINGIVAL HYPERPLASIA.

Note: Non-pharmacological measures matter just as much: mouth props, careful head and body stabilisation with the patient's consent, shorter appointments, and treating in a wheelchair with a transfer board where appropriate. General anesthesia remains an option for extensive treatment in severe movement disorders.