This document summarizes guidelines for treating exposure to various chemical and radiological agents. It provides details on the mechanisms and dosing of antidotes for nerve agents (atropine, benzodiazepines, 2-PAM), cyanide (nitrites, sodium thiosulfate), botulinum toxin (antitoxin), thallium (Prussian blue), and radiation (potassium iodide, Prussian blue). It emphasizes the importance of rapid administration of the correct antidote to prevent lasting effects of exposure and maximize survival.

1. Adapted from Lawrence DT and Kirk MA, Chemical Terrorism Attacks: Update on Antidotes. Emerg Med Clin N Am 25 (2007) 567–595
Chemical Terrorism Attacks: Update on Antidotes
Nerve agents
 Vapour exposures immediate symptoms (seconds to minutes)
 Dermal exposures delayed (minutes to 18 hours)
Farooq Khan MDCM
PGY3 FRCP-EM
McGill University
November 14
th
2011

2. Adapted from Lawrence DT and Kirk MA, Chemical Terrorism Attacks: Update on Antidotes. Emerg Med Clin N Am 25 (2007) 567–595
Mark-1 Kit
Atropine
Mechanism Atropine acts at muscarinic cholinergic receptors as a competitive antagonist. It is used to counter
muscarinic effects, and administration will result in drying of secretions, alleviating bronchospasm, and reversing central
apnea. Given within the first 5 minutes, it can prevent organophosphate-induced seizures
Delivery autoinjector is more effective than IM injections using a conventional syringe, can go through clothing or
protective garments. Additional atropine doses should be administered IV once access is obtained
Dosing
 Field treatment for severe poisoning is three autoinjectors or 6 mg initially with retreatment q 5-10 min
 The initial intravenous dose should be 2 mg for adults or 0.02 mg/kg for children
 Atropine doses should be repeated q 5 min until the therapeutic endpoint is reached (ie, until pulmonary
secretions are dried [reflected by improved oxygenation] and ease of breathing [or ease of ventilation])
 Typical total dose required after nerve agent poisoning has ranged from 5 to 20 mg (up to 200mg in cases)
Precautions. Excessive doses of atropine can result in deleterious effects including delirium, agitation, and tachycardia
and hypertension. Atropine will likely not improve miosis or skeletal muscle paralysis; therefore, reversal of these effects
is not a therapeutic endpoint.
Benzodiazepines
Indications
 Any patient who has significant symptoms from nerve agent exposure to prevent seizure and neuronal damage
 Infused rapidly to unresponsive patients who may have nonconvulsive seizures due to the onset of paralysis
 Alleviate extreme anxiety

3. Adapted from Lawrence DT and Kirk MA, Chemical Terrorism Attacks: Update on Antidotes. Emerg Med Clin N Am 25 (2007) 567–595
Dose/delivery
Diazepam 10 mg IM auto-injector in the field, Midazolam IM/IV in hospital
2-PAM
 Neither atropine nor benzodiazepines will alleviate symptoms affecting the nicotinic system.
 Over time, nerve agents will form an irreversible covalent bond with AChE in a process termed aging.
 Once aging occurs, the patient will not regain vital functions, such as muscle strength or respiratory drive, until
new enzyme is synthesized (may take weeks to months)
 Oxime reactivates AChE if administered before aging
Indications. 2-PAM should be given to any patient exposed to an organophosphate nerve agent who is showing any
systemic toxicity. This is particularly true if there are fasciculations or weakness.
Dose/Delivery
Mark 1 auto-injector 600mg IM per dose for the field (max
3 injections). IV preferred in hospital.
 Initial dose is 1- 2 g diluted in 100mL normal saline
and given over 15-30 min
 Initial pediatric dose is 20 to 50 mg/kg up to 2 g
 WHO recommendation >30mg/kg bolus then
>8mg/kg/hour infusion to maintain therapeutic levels
due to short t½ (90 min)
 For severely poisoned patients: 2 g IM or slow IV
infusion over 15-30 minutes then 500mg/h infusion.
Precautions. Rapid delivery can cause laryngospasm,
rigidity, and self-limited hypertension responding to
phentolamine 5 mg IV
Pediatrics
 ↑minute ventilation/kg → ↑ risk with exposure
 Small airways with bronchospasm and ↑secretions→ ↑rates of respiratory distress/failure
 ↑prone to seizures
 The dose for atropine can be up to 0.05 - 0.1 mg/kg either IV/IO/IM.
 40 kg can be administered an adult (2 mg) autoinjector
 20 kg can receive a 1-mg autoinjector
 10 kg can receive a 0.5-mg autoinjector
 The dose for 2-PAM is 25 to 50 mg/kg, up to a total of 2 g.
 12 kg will be able to tolerate the dose of one 600-mg 2-PAM autoinjector
 Diazepam should be dosed at 0.05 to 0.3 mg/kg IV,
 > 30 kg can receive an adult autoinjector
 Autoinjector needle is 1 inch, so choose site carefully
Stockpile antidotes if stocks run out, glycopyrrolate (no central effects), scopolamine (more potent central
effects), diphenhydramine, and jimsonweed extract can be used as alternatives

4. Adapted from Lawrence DT and Kirk MA, Chemical Terrorism Attacks: Update on Antidotes. Emerg Med Clin N Am 25 (2007) 567–595
Cyanide
Found in smoke inhalation, industrial accidents, suicide attempts, criminal poisonings and can be potent chemical
weapon.
Primary toxic action is inducing cellular hypoxia through inhibition of cytochrome oxidase, blocking oxidative
phosphorylation → shift from aerobic to anaerobic metabolism causes a depletion of cellular ATP and ↑lactic acid
Effects depend on dose/route/timing
o CNS and cardiac toxicity because these are the most O2-sensitive systems
o Concentrated exposure→ death within minutes (i.e. no time for medical intervention)
o Lesser exposure→ nonspecific symptoms including shortness of breath, hyperventilation, headache,
weakness, and dizziness, which can be attributed to anxiety or other exposures
o Progression to confusion, lethargy, seizures, and coma.
o Neurally mediated tachypnea along with an initial ↑BP
o Can progress to cardiac arrest heralded by bradycardia and hypotension
o Cherry red color and ↑O2 Sat
Cyanide antidote kit
Amyl nitrite, sodium nitrite, and sodium thiosulfate

5. Adapted from Lawrence DT and Kirk MA, Chemical Terrorism Attacks: Update on Antidotes. Emerg Med Clin N Am 25 (2007) 567–595
Mechanism
o Nitrites (amyl and sodium) induce methemoglobinemia
o Cyanide has a ↑affinity for methemoglobin and will leave the mitochondria to bind to it and allow the
mitochondria to resume oxidatitive phosphorylation.
o Sodium thiosulfate acts as a sulfhydryl donor for the enzyme for the enzyme rhodanese that converts cyanide to
the less-toxic renally excreted thiocyanate
Indications to initiate therapy
 High index of suspicion
o clusters of patients, structural fire victim, high risk activity (e.g. jeweller, lab worker)
 Clinical presentations
o sudden LOC, seizures, HD instability without probable cause
 Surrogate markers
o lactate, metabolic acidoses, narrow arteriovenous O2 Sat gap
Dose/delivery
 Crush amyl nitrite glass pearls and inhale or administer via BMV until IV line (goal to induce 3-5% MetHb)
 Then switch to sodium nitrite IV 300mg (10ml of 3% sol’n) over 2-4min,
 Peds: 10mg/kg with normal Hb, 6mg/kg in anemic or unknown Hb child
 Sodium thiosulfate 12.5g IV (50ml of 25% sol’n) over 10 min, peds 1.65ml/kg of 25% sol’n
 Give with high-level O2 , charcoal for oral exposures
Precautions
 Vasodilation, tachycardia, hypotension with high doses of nitrite
 ↓ O2 carrying capacity with MetHb, avoid in anemic, CO poisoned
 Thiosulfate can cause hemolysis in G6PD deficiency
 Thiocyanate can be toxic in renal failure (abdo pain, rash, vomiting, CNS dysfunction)
Hydroxycobalamin
 Combines with CN to cyanocobalamin a.k.a. Vitamin B12 (safe and renally excreted)
 Low threshold of administration given safety profile
 Dose
o 70mg/kg, max 5g(adult dose) IV over 15 min
o Each vial of 250ml contains 2.5g, which needs to be diluted in 100ml of NS to bind 250mg of CN
o Repeat dosing in severe toxicity
 Combine with sodium thiosulfate but either sequentially or in a different line (inactivated if in the same line)
 scavenges NO and prevents hypotension
 transient red discoloration of skin and mucus membranes, interferes with lab assays of bili, creat, mg, fe
 otherwise safe and preferred over nitrites
Mass exposure
 Most patients will not have significant exposures
 Patients presenting in cardiac arrest will have low survival
 Reserve antidotes for those most likely to survive
 Can use thiosulfate alone

6. Adapted from Lawrence DT and Kirk MA, Chemical Terrorism Attacks: Update on Antidotes. Emerg Med Clin N Am 25 (2007) 567–595
Botulism
 Clostridial toxins A, B, E, and F
 Highly potent (LD 50 of 1μg/kg)
 Food water (onset 2h-5 days), aerosolized (onset 3 days), injection
 Prevents fusion of synaptic vesicles with presynaptic membrane in PNS (cannot cross BBB) prevents
neurotransmission
 Descending weakness, EOMs and bulbar cranial nerves (diplopia/dysarthria/dysphagia) then motor function of
UE then LE. Can affect intercostals and diaphragm needing mechanical ventilation. Spared sensory and
mentation.
 Anti-muscarinic effects and nausea vomiting precede neurologic symptoms
 Paralysis is irreversible until cleaved protein is regenerated which can last months
Antitoxin
 halts progression of paralysis
 binds and neutralizes free botulinum toxin
 indicated on clinical suspicion (clusters of patients with similar geography etc)
 dose 1 vial of Ig IV over 30-60 min diluted 1:10 in NS
 1% allergic reaction to horse serum based Ig
 Baby-BIG is human derived and recommended in infants
Thallium
 Less well known toxic heavy metal odourless and colorless dissolved in water (used in myocardial scintigraphy)
 Minimum lethal dose of 12mg/kg
 Absorbed from GI tract, causes green discoloration of urine in 1h
 Unclear if Interferes with Krebs cycle, glycolysis, and oxidative phosphorylation, or forms stable complexes with
the active sulfhydryl sites on enzymes
 Nonspecific symptoms (early GI, mostly neuro)
 Reliable early clue for thallium toxicity is an ascending, rapidly progressive painful sensory peripheral
neuropathy (feet)
 Delayed alopecia (weeks)
Prussian Blue
 Enhances elimination by blocking enteroenteric and enterohepatic recirculation of thallium
 Indicated for any patient with toxicity or known exposure
 150-250 mg/kg/day divided tid until urinary thallium excretion is <0.5mg/day
 No side effects except blue tears and constipation (Dissolve in 50ml of 15% mannitol as cathartic)
 Can use activated charcoal as alternative if in low supply of Prussian blue

7. Adapted from Lawrence DT and Kirk MA, Chemical Terrorism Attacks: Update on Antidotes. Emerg Med Clin N Am 25 (2007) 567–595
Radiation
Potassium iodide (KI)
 Prevents thyroid cancer in patients exposed to radioactive iodine
 Subtotal protection
 Must be administered within hours
 Indications
o Children, pregnant or lactating women with >0.05 Gy exposure
o Adults over 40 with dose >5 Gy
 Dose
o Newborn – 1 month: 16 mg po qd
o Infants and children <3 : 32 mg po qd
o Children 3-18: 65 mg po qd
o Adults: 130 mg po qd
Prussian blue
 For cesium-137 (used in radiotherapy and medical devices, could be used in dirty bomb), behaves like
potassium. Physiological t½ of 50-150 days, renally excreted in 4:1 ratio with fecal excretion
 ↓urine/feces excretion ratio to 1:4 and ↓t ½ by 43%
 Dose 3-10g/day
 FDA recommendation : 3g bid for adults, 1g tid for children 2-12 ×30days
 Mostly non toxic and not absorbed, although not studied in ARS GI syndrome where there is severe
inflammation of mucosa.