A 25-year-old graduate student comes to the office for evaluation of anxiety. She describes episodes of sudden-onset palpitations, shortness of breath, and diaphoresis during which she wants to "run away before anyone notices." The patient arrives early for her classes to get a seat close to the door and has left during lectures due to feeling "out of control." There are no specific triggers for these events, but she is worried about having another episode next week during her final examinations. She does not drink alcohol or use illicit drugs. Physical examination, ECG, and laboratory evaluation are normal. The patient is diagnosed with panic disorder. After discussion of treatment options, she decides to pursue cognitive-behavioral therapy and start a short-term anxiolytic medication that also has muscle-relaxant and anticonvulsant properties. Which of the following best describes the mechanism of action of this medication?

Question

A 25-year-old graduate student comes to the office for evaluation of anxiety.  She describes episodes of sudden-onset palpitations, shortness of breath, and diaphoresis during which she wants to "run away before anyone notices."  The patient arrives early for her classes to get a seat close to the door and has left during lectures due to feeling "out of control."  There are no specific triggers for these events, but she is worried about having another episode next week during her final examinations.  She does not drink alcohol or use illicit drugs.  Physical examination, ECG, and laboratory evaluation are normal.  The patient is diagnosed with panic disorder.  After discussion of treatment options, she decides to pursue cognitive-behavioral therapy and start a short-term anxiolytic medication that also has muscle-relaxant and anticonvulsant properties.  Which of the following best describes the mechanism of action of this medication?

Quizplus · Accepted Answer

11ec160b_3c4f_da17_9249_cb65f6d57dec_MD0001_00 Benzodiazepines (eg, clonazepam, lorazepam) bind and modulate GABA_A receptors on CNS neurons, resulting in an increased frequency of chloride channel opening in the presence of GABA. This increase in chloride permeability hyperpolarizes and stabilizes the membrane, rendering it less excitable, resulting in the anxiolytic, muscle-relaxant, and anticonvulsant properties of benzodiazepines. Due to risk for dependence, benzodiazepines are generally prescribed for short-term use in anxiety disorders and alcohol withdrawal syndrome. (Choice A) Flumazenil is an antagonist at benzodiazepine receptor sites on GABA A receptors and is a reversal agent for benzodiazepine overdose. (Choice B) Barbiturates (eg, phenobarbital) increase the duration of opening of the GABA A receptor-chloride channel in the presence of GABA. Although barbiturates have anxiolytic properties, they are not indicated for the treatment of anxiety disorders because of their potential to induce fatal respiratory depression. (Choices D and E) Inhibition of serotonin reuptake is the mechanism of action of selective serotonin reuptake inhibitors (eg, fluoxetine). Inhibition of serotonin and norepinephrine reuptake is the mechanism of tricyclic antidepressants (eg, amitriptyline) and serotonin-norepinephrine reuptake inhibitors (eg, venlafaxine). These antidepressants are frequently used to treat panic disorder, but they take several weeks for symptom improvement. Unlike benzodiazepines, they do not have muscle relaxant or anticonvulsant properties. Educational objective: Benzodiazepines bind GABA A receptors, resulting in an increased frequency of chloride channel opening in the presence of GABA. Indications for prescribing include short-term treatment of anxiety disorders and alcohol withdrawal syndrome. __________ References: Benzodiazepines I: upping the care on downers: the evidence of risks, benefits and alternatives. (http://www.ncbi.nlm.nih.gov/pubmed/29385731)

A 25-Year-Old Graduate Student Comes to the Office for Evaluation