A patient develops a dramatic convulsive death — consciousness is intact throughout, the body is arched in opisthotonus, the face shows a fixed grin (risus sardonicus), and convulsions are triggered by the slightest touch or sound. The responsible poison is:
- A Tetanus toxin (tetanospasmin)
- B Camphor
- C Strychnine ✓
- D Atropine
Explanation
Strychnine (from Strychnos nux-vomica seeds — 'Kuchla') produces its toxicity by competitively antagonising glycine at inhibitory glycine receptors in the spinal cord anterior horn and brainstem. Glycine normally hyperpolarises motor neurons; its blockade allows unrestricted motor neuron firing. The key differentiating feature from tetanus is INTACT CONSCIOUSNESS throughout convulsions (the patient is fully aware), convulsions triggered by ANY sensory stimulus (reflex hyperexcitability), and rapid complete muscle relaxation between convulsions. Tetanus also causes opisthotonos and risus sardonicus but onset is subacute with progressive trismus, and there is no rapid complete interictal relaxation.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.