Toxicology

1. Decontamination, specific
antidotes
Domina Petric, MD

2. Introduction
Decontamination procedures should
be undertaken simultaneously with
initial stabilization, diagnostic
assesment and laboratory evaluation.
Decontamination involves
removing toxins from the skin or
gastrointestinal tract.

3. Skin
Contaminated clothing of the intoxicated patient
should be completely removed and double-bagged
to prevent illness in health care providers.
Contaminated clothing may be useful for
laboratory analysis.
It is important to wash contaminated skin
with soap and water.

4. Gastrointestinal tract
• Simple administration of
activated charcoal, to bind
ingested poisons in the gut
before they can be absorbed, is
usually enough.
• In unusual circumstances,
induced emesis or gastric
lavage may also be used.

5. Emesis
• Ipecac syrup can sometimes be used
for inducing emesis, but not in cases
when suspected intoxicant is a
corrosive agent, petroleum distillate or
a rapid-acting convulsant.
• Fingertip stimulation of the pharynx,
salt water and apomorphine are
inefective or dangerous and should
not be used.

6. Gastric lavage
If the patient is awake or if the airway
is protected by an endotracheal tube,
gastric lavage may be performed:
• orogastric
• nasogastric tube
Lavage solutions (0,9% saline)
should be at body temperature to
prevent hypothermia.

7. Activated charcoal
• Activated charcoal can adsorb many
drugs and poisons because of its large
surface area.
• It is most effective if given in a ratio of at
least 10:1 of charcoal to estimated dose
of toxin by weight.
• Charcoal does not bind iron, lithium and
potassium.
• It binds alcohols and cyanide only
poorly.

8. Activated charcoal
• It is not useful in poisoning due to
corrosive mineral acids and alkali.
• Repeated doses of oral activated
charcoal may enhance systemic
elimination of some drugs:
carbamazepine, dapsone,
theophylline.
• This mechanism is called GUT
DIALYSIS.

9. Cathartics
• Cathartics (laxative) agents may hasten
removal of toxins from the
gastrointestinal tract and reduce
absorption.
• Whole bowel irrigation with a balanced
polyethylene glycol-electrolyte solution
can enhance gut decontamination after
ingestion of iron tbl., enteric coated
medicines, illicit drug-filled packets and
foreign bodies.

10. Cathartics
The solution is
administered orally at
1-2 L/h (500 mL/h in
children) for several
hours until the rectal
effluent is clear.

11. SPECIFIC ANTIDOTES

12. Acetaminophen (paracethamol)
• Acetylcistein (Acetadote,
Mucomyst)!
• Best results if given within 8-10
hours of overdose.
• Follow liver function tests and
acetaminophen blood levels.
• Acetadote is given iv.
• Mucomyst is given orally.

13. Anticholinesterase intoxication: organophosphates,
carbamates
• Atropine!
• An initial dose of 1-2 mg (for
children, 0,05 mg/kg) is given iv.
• If there is no response, the dose
is doubled every 10-15 minutes
with decreased wheezing and
pulmonary secretions as
therapeutic end points.

14. Membrane depressant cardiotoxic drugs: tricyclic
antidepressants, quinidine…
• Bicarbonate, sodium!
• 1-2 mmol/kg iv. bolus usually
reverses cardiotoxic effects.
• Cardiotoxic effects: wide QRS,
hypotension.
• Give cautiously in heart failure
to avoid sodium overload.

15. Fluoride, calcium channel blockers
Calcium!
Large doses may be needed in
severe calcium channel blocker
overdose.
Start with 15 mg/kg iv.

16. Iron salts
Deferoxamine!
If poisoning is severe, give
15 mg/kg/h iv.
100 mg of deferoxamine
binds 8,5 mg of iron.

17. Digoxin and related cardiac glycosides
Digoxin antibodies!
One vial binds 0,5 mg of
digoxin.
Indications are serious
arrhythmias, hyperkalemia.

18. Theophylline, caffeine, metaprotenerol
Esmolol!
Short-acting β blocker.
Infuse 25-50 mcg/kg/min iv.

19. Methanol, ethylene glycol
Ethanol!
A loading dose is calculated so as to give
a blood level of at least 100 mg/dL and
that is 42 g/70 kg in adults.
Fomepizole is easier to use.

20. Methanol, ethylene glycol
Fomepizole!
More convenient than
ethanol.
Give 15 mg/kg and repeat
every 12 hours.

21. Benzodiazepines
Flumazenil!
Adult dose is 0,2 mg iv., repeated as
necessary to a maximum of 3 mg.
Do not give flumazenil to patients with
seizures, benzodiazepine dependence
or tricyclic overdose.

22. Βeta blockers
Glucagon!
5-10 mg iv. bolus may
reverse hypotension and
bradycardia.

23. Cyanide
Hydroxocobalamin!
Adult dose is 5 mg iv. over
15 minutes.
Converts cyanide to
cyanocobalamin.

24. Narcotic drugs, other opioid derivatives
• Naloxone!
• A specific antagonist of opioids.
• Give 0,4-2 mg initially by iv., im. or sc.
injection.
• Larger doses may be needed to reverse
the effects of overdose with propoxyphene,
codeine or fentanyl derivatives.
• Duration of action (2-3 hours) may be
significantly shorter than that of the opioid
being antagonized.

25. Carbon monoxide
Oxygen!
Give 100% by high-flow
nonrebreathing mask.
Use of hyperbaric chamber is
controversial, but it may be useful in
severe poisoning.

26. Delirium caused by anticholinergic agents
• Physostigmine!
• Adult dose is 0,5-1 mg iv. slowly.
• The effects are transient (30-60 minutes).
• The lowest effective dose may be repeated
when symptoms return.
• It may cause bradycardia, increased bronchial
secretions and seizures.
• Atropine can be used to reverse excess
effects.
• Do not use it for tricyclic antidepressant
overdose.

27. Organophosphate (OP) cholinesterase inhibitors
• Pralidoxime (2-PAM)!
• Adult dose is 1 g iv.
• The dose should be repeated every 3-4
hours as needed or preferably as a
constant infusion of 250-400 mg/h.
• Pediatric dose is approximately 250 mg.
• No proved benefit in carbamate
poisoning.
• Uncertain benefit in established OP
poisoning.

28. Methods of enhancing elimination of toxins
• Peritoneal dialysis is inefficient in
removing most drugs.
• Hemodialysis is more efficient.
• It assists in correction of fluid and
electrolyte imbalance.
• It may enhance removal of toxic
metabolites: formic acid in methanol
poisoning, oxalic and glycolic acids
in ethylene glycol poisoning.

29. Methods of enhancing elimination of toxins
• Forced diuresis may cause volume overload
and electrolyte abnormalities.
• It is not recommended.
• Renal elimination of a few toxins can be
enchanced by alteration of urinary pH.
• Urinary alkalinization is useful in cases of
salicylate overdose.
• Acidification may increase the urine
concetration of phencyclidine and
amphetamines, but it is not advised because it
may worsen renal complications from
rhabdomyolisis.

30. Literature
• Katzung, Masters, Trevor.
Basic and clinical
pharmacology.