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Quiz: Medicine for the Gut-Brain Axis

Test your understanding of Chapter 17. Choose the best answer, then click Show Answer to check.

Question 1

What are Rebyota and Vowst FDA approved for?

  1. Treating ulcerative colitis and Crohn's disease in teens and adults
  2. Treating a first episode of C. difficile infection in children
  3. Preventing C. difficile infection from coming back in adults 18 and older, after antibiotic treatment for recurrent infection
  4. Restoring a healthy microbiome in anyone who has taken antibiotics
Show Answer

The correct answer is C. Rebyota (November 30, 2022) and Vowst (April 26, 2023) are approved only to prevent recurrence of C. difficile infection in adults after antibiotic treatment for recurrent infection. Option A is a common mix-up: FMT for IBD is still experimental, and neither product is approved for it.

Concept Tested: Live Biotherapeutic Product Bloom's Level: Remember

Question 2

In what year was an implanted vagus nerve stimulator first FDA approved, and for what condition?

  1. 1997, as an add-on treatment for drug-resistant partial-onset epilepsy
  2. 2005, for all adults with depression
  3. 2017, for cluster headache
  4. 2025, for Crohn's disease
Show Answer

The correct answer is A. The VNS Therapy System was first approved on July 16, 1997, as an add-on treatment for drug-resistant partial-onset seizures. The 2005 approval (option B) was only for adults with treatment-resistant depression, and the 2025 approval was for rheumatoid arthritis, not Crohn's disease.

Concept Tested: Implanted VNS Device Bloom's Level: Remember

Question 3

According to the FDA, what is the main purpose of a Phase 1 clinical trial?

  1. Confirming that a drug works in thousands of patients
  2. Monitoring safety after the drug is approved
  3. Comparing the drug against all other treatments on the market
  4. Testing safety and dosage in a small group of people
Show Answer

The correct answer is D. The FDA describes Phase 1 as testing safety and dosage in about 20 to 100 healthy volunteers or people with the condition. Option A describes Phase 3, and option B describes Phase 4, which happens after approval.

Concept Tested: Clinical Trial Phases Bloom's Level: Remember

Question 4

The gammaCore handheld device received a De Novo authorization in 2017 and a 510(k) clearance in 2018. Why is it inaccurate to say gammaCore is "FDA approved"?

  1. Because the FDA has never reviewed it
  2. Because authorization and clearance are different FDA device pathways from premarket approval, which is the most stringent review
  3. Because it is only available outside the United States
  4. Because it is a dietary supplement, not a device
Show Answer

The correct answer is B. The FDA did review gammaCore, but through the De Novo (authorization) and 510(k) (clearance) pathways, not premarket approval, which the FDA calls its most stringent device review. Option A is wrong because authorization and clearance are real FDA decisions.

Concept Tested: Noninvasive VNS Bloom's Level: Understand

Question 5

How is the inflammatory reflex thought to work?

  1. Gut bacteria release electricity that travels to the brain.
  2. The immune system sends antibodies along the vagus nerve to the brain.
  3. The nervous system senses inflammation and sends signals, largely through the vagus nerve, that calm the release of inflammatory chemicals.
  4. Inflammation in the gut automatically switches off the brain's pain centers.
Show Answer

The correct answer is C. Kevin Tracey described the inflammatory reflex in 2002: nerve circuits regulate inflammation in real time, and cholinergic (acetylcholine-using) neurons can shut down acute inflammation. Option B confuses nerve signals with immune molecules; nerves carry electrical and chemical signals, not antibodies.

Concept Tested: Inflammatory Reflex Bloom's Level: Understand

Question 6

Why do doctors prescribe low-dose tricyclic antidepressants for some people with IBS?

  1. Because IBS is a form of depression
  2. Because the medicines kill harmful gut bacteria
  3. Because they are FDA approved specifically for IBS
  4. Because, at low doses, they act as gut-brain neuromodulators that calm pain signaling
Show Answer

The correct answer is D. Low-dose TCAs are used to turn down pain signaling along the gut-brain axis, and in the ATLANTIS trial amitriptyline improved IBS symptoms without evidence of changing depression scores. Option C is wrong: using them for IBS is off-label, though supported by trials and US guideline recommendations.

Concept Tested: Tricyclic Antidepressant Bloom's Level: Understand

Question 7

Marcus, 15, sees an ad: "Our ear-clip vagus stimulator is backed by the same science as FDA-approved devices. Say goodbye to anxiety!" Which response best fits the evidence?

  1. Be skeptical: consumer wellness gadgets aren't the devices tested in trials, and no vagus stimulator is approved to treat anxiety.
  2. Trust it, because implanted VNS is FDA approved, so all vagus devices work.
  3. Trust it, because the ad says "science."
  4. Avoid all vagus nerve treatments, since none are ever approved.
Show Answer

The correct answer is A. Approval is always for a specific device and use; implanted VNS is approved for epilepsy, treatment-resistant depression, arm-movement rehabilitation after stroke (the Vivistim System), and rheumatoid arthritis, not anxiety. A 2021 meta-analysis also found ear stimulation didn't change a heart-rate sign of vagus activity in healthy people. Option D overcorrects, since several VNS devices are approved or cleared for specific conditions.

Concept Tested: Consumer Wellness Device Bloom's Level: Apply

Question 8

A doctor prescribes an approved medicine for a condition not listed on its official label, because no approved drug works well for that condition. What is this called, and what does the FDA say about it?

  1. Illegal prescribing, which the FDA does not allow
  2. Off-label use, which providers may choose when medically appropriate, though FDA hasn't determined the drug is safe and effective for that use
  3. Expanded approval, which automatically adds the condition to the label
  4. A Phase 4 trial, which the FDA requires for every prescription
Show Answer

The correct answer is B. The FDA explains that once a drug is approved, providers generally may prescribe it for an unapproved use when they judge it medically appropriate, but the FDA has not determined it is safe and effective for that use. Option A is a common misunderstanding; off-label prescribing is legal.

Concept Tested: Off-Label Use Bloom's Level: Apply

Question 9

In the 2013 van Nood trial, 81% of patients given donor stool were cured of recurrent C. diff, compared with 31% on vancomycin alone. Which conclusion is best supported?

  1. FMT works for every gut disease linked to the microbiome.
  2. FMT is completely safe because no deaths occurred in this trial.
  3. The trial proves FMT works in children and people with weak immune systems.
  4. In adults with recurrent C. diff, FMT likely caused much higher cure rates, though the trial was small and stopped early.
Show Answer

The correct answer is D. Random assignment means the large difference was likely caused by the treatment, but the trial had only 42 people and studied adults with recurrent infection. Option B is wrong: a small trial can't rule out rare harms, and a 2019 report linked one FMT donor to a fatal drug-resistant infection.

Concept Tested: Fecal Microbiota Transplant Bloom's Level: Analyze

Question 10

Why does FMT have a strong benefit-risk balance for an adult with a third C. diff recurrence, but a poor one for a healthy person who wants to "optimize" their gut?

  1. Because FMT only has risks in healthy people
  2. Because healthy people have no gut bacteria to replace
  3. Because the benefit is large and proven for recurrent C. diff, while there is no proven benefit for the healthy person, so any risk outweighs it
  4. Because the FDA bans FMT for anyone without C. diff
Show Answer

The correct answer is C. Benefit-risk balance weighs how much a treatment is likely to help against its possible harms for a specific person. For recurrent C. diff, about 3 people need to be treated for one extra cure, so a small infection risk is worth it; with no proven benefit, the same risk isn't. Option A is wrong because the infection risk exists for everyone who receives donor material.

Concept Tested: Benefit-Risk Balance Bloom's Level: Analyze