Pharmacology · patient case question
Which property of the benzodiazepine explains why she remembers nothing despite having been conscious and conversational?
Patient case: Anxiety, before and during treatment
Patient: Female, 44 years old
Chief Complaint: “I need something to get me through this appointment.”
Background: Longstanding dental anxiety. She had oral sedation for an extraction two years ago and reports that she ‘remembers nothing at all’ about the appointment, although her husband says she talked to the dentist throughout. Her physician started BUSPIRONE three weeks ago for generalised anxiety disorder.
Vital Signs: BP 128/80 mmHg · HR 88 bpm
Findings: Non-restorable tooth #14 requiring extraction. She is visibly apprehensive but cooperative.
Show answer and explanation
Correct answer: C. Anterograde amnesia
- A. Dissociative anaesthesia describes KETAMINE, in which the patient appears awake but is dissociated from the environment, with nystagmus, catalepsy and emergence phenomena on recovery.
- B. Benzodiazepines have NO analgesic property whatsoever. This is a practical point rather than a technicality — full local anaesthesia is still required, and a sedated patient who is inadequately anaesthetised will still respond to pain.
- C. CORRECT. ANTEROGRADE AMNESIA is impairment of the formation of NEW memories from the time of administration onward. The patient remains conscious, responsive and cooperative throughout — exactly as her husband describes — but does not consolidate a memory of the period. It is mediated through GABA-A potentiation affecting hippocampal consolidation, and it is most pronounced with TRIAZOLAM and MIDAZOLAM. Far from being an unwanted effect, it is a valued property in a phobic patient, because it prevents the appointment from reinforcing the fear.
- D. Retrograde amnesia is loss of memories formed BEFORE the event. Benzodiazepines do not cause it — memory for everything preceding the dose remains intact, which is why the patient still recalls arriving at the practice.
Note: The amnesia carries an obligation: post-operative instructions must be given in WRITING and repeated to a responsible escort, because the patient will not recall anything said to her during or shortly after the appointment. FLUMAZENIL is the reversal agent, a competitive antagonist at the benzodiazepine receptor — and its half-life is SHORTER than that of most benzodiazepines, so the patient must be observed for resedation after it is given.