ABEM ABEM Pharmacology & Medical Management 2 — Questions and Answers
Question 1: Excessive use of isoniazid (INH) for tuberculosis can cause peripheral neuropathy due to depletion of which vitamin?
- Vitamin C
- Vitamin B6 (pyridoxine) (Correct answer)
- Folic acid
- Thiamine
Correct answer: Vitamin B6 (pyridoxine)
INH competitively inhibits pyridoxine phosphokinase, depleting active vitamin B6 and causing an axonal sensorimotor neuropathy.
Question 2: A patient on amiodarone develops a demyelinating neuropathy. Which finding would you expect on nerve conduction studies?
- Reduced CMAP amplitude with normal velocity
- Slowed conduction velocity with prolonged distal latencies (Correct answer)
- Normal NCS with abnormal EMG
- Conduction block at common entrapment sites only
Correct answer: Slowed conduction velocity with prolonged distal latencies
Amiodarone-induced neuropathy is demyelinating, so NCS shows slowed conduction velocities and prolonged distal latencies rather than reduced amplitudes.
Question 3: Which immunosuppressant is commonly used as a steroid-sparing agent in chronic inflammatory demyelinating polyneuropathy (CIDP)?
- Methotrexate
- Azathioprine
- Mycophenolate mofetil
- All of the above may be used (Correct answer)
Correct answer: All of the above may be used
Azathioprine, mycophenolate mofetil, and cyclosporine are all used as steroid-sparing agents in CIDP, with none clearly superior in randomized trials.
Question 4: Botulinum toxin injected for spasticity reduces muscle tone by:
- Blocking voltage-gated sodium channels at the axon
- Cleaving SNARE proteins, preventing ACh vesicle release (Correct answer)
- Blocking postsynaptic nicotinic receptors
- Inhibiting acetylcholinesterase
Correct answer: Cleaving SNARE proteins, preventing ACh vesicle release
Botulinum toxin cleaves SNARE proteins (such as SNAP-25 or synaptobrevin) required for synaptic vesicle fusion, blocking presynaptic acetylcholine release.
Question 5: A diabetic patient presenting with a painful, asymmetric motor neuropathy affecting the thigh is most likely experiencing:
- Distal symmetric polyneuropathy
- Mononeuritis multiplex
- Diabetic amyotrophy (lumbosacral radiculoplexus neuropathy) (Correct answer)
- Tarsal tunnel syndrome
Correct answer: Diabetic amyotrophy (lumbosacral radiculoplexus neuropathy)
Diabetic amyotrophy (also called lumbosacral radiculoplexus neuropathy) presents with acute painful, asymmetric proximal lower limb weakness and is immune-mediated.
Question 6: Which medication can cause myopathy characterized by elevated CK, myalgia, and proximal weakness in susceptible individuals?
- Metformin
- Statins (HMG-CoA reductase inhibitors) (Correct answer)
- Lisinopril
- Levothyroxine
Correct answer: Statins (HMG-CoA reductase inhibitors)
Statins can cause a spectrum of muscle injury from mild myalgia to rhabdomyolysis, and in rare cases an immune-mediated necrotizing myopathy with anti-HMGCR antibodies.
ABEM ABEM Pharmacology & Medical Management 2
Excessive use of isoniazid (INH) for tuberculosis can cause peripheral neuropathy due to depletion of which vitamin?