Envenoming and the neuromuscular junction

===Lecture Details===
Andrew Hart; Week 11 MED1011; Pharmacology
===Lecture Content===
1:10 bites require antivenom, 2 fatalities per year. Signs and symptoms are partial opthalmoplegia, diplopia, dysarthria (difficulty speaking), loss of facial expression, pain on contracting muscle against resistance, muscle weakness, dark urine which tests positive for blood. Venom detection can be done from bite site, clothing, blood, urine. Lethality is LD50 (dose that kills 50% of mice in a 24/48h period). Venoms are antigens, peptide toxins that affect animal processes (neurotoxins, myotoxins, haemotoxins, nephro, cardiotoxins). Presynaptic are beta neurotoxins or postsynaptic is alpha neurotoxins. Neurotoxins respond to anticholinesterases and antivenom if postsynaptic; presynaptic is irreversible and only responds to antivenom if given early.
Phospholipase in venom hydrolyses phospholipids. There is procoagulant activity (DIC) usually (can be anticoagulant). First aid is due to pressure/immobilisation, crepe bandages in bitten area/upwards, binds splint firmly to limb, may be maintained for several hours. Antivenoms are made of antibodies from horses. Lace monitor decreases BP and clotting ability. Box jellyfish is effective at poisoning, tentacles and bells are covered with nematocysts (stinging cells). Irukandji syndrome is due to jellyfish species, severe hypertension, tachycardia, pain. Redback has adrenergic effects, venim acts presynaptically to release and deplete neurotransmitters, causes patchy paralysis of NMJ. Funnel web has phase 1 (autonomic storm), phase 2 resolves phase 1 but there can be cardiac arrest/cessation of breathing.
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