Tetrodotoxin (TTX) found in pufferfish causes death primarily by which mechanism, and which feature distinguishes it from saxitoxin (paralytic shellfish poison) in terms of clinical presentation?

• A Both TTX and saxitoxin block voltage-gated sodium channel site 1; clinically TTX causes earlier GI symptoms while saxitoxin predominantly causes cardiovascular collapse first
• B TTX blocks fast voltage-gated sodium channels at site 1 (extracellular); the clinical distinction is academic as presentations are identical
• C TTX has a specific antidote (4-aminopyridine) while saxitoxin poisoning is treated only supportively
• D TTX blocks voltage-gated sodium channels; saxitoxin additionally blocks voltage-gated potassium channels, causing prolonged action potentials and more severe cardiac arrhythmias ✓

Explanation

Both TTX and saxitoxin block voltage-gated sodium channels at site 1 (outside the pore), preventing action potential generation. However, saxitoxin also inhibits voltage-gated potassium channels, prolonging action potentials and contributing to more pronounced cardiovascular effects including arrhythmias. TTX poisoning presents with progressive ascending paralysis with preserved consciousness until respiratory failure; both are treated supportively. 4-aminopyridine is not an established antidote for TTX.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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Written and medically reviewed by the StethoPrep medical team.