Principles of treatment of poisoning

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Principles of treatment of poisoning

Because of the acute onset of action and finite duration of action of most drugs, the treatment of poisoning
must be prompt and goal-directed.

The first goal is to maintain vital physiological functions from impairment.
The second goal is to keep the concentration of poison in tissues as low as possible by preventing
absorption and enhancing elimination.
The third goal is to combat the toxicological effects of the poison at the effector sites.

1. Supportive Care
Pre-hospital care
Hospital care
2. Decontamination
Ocular and Skin Irrigation
Gastrointestinal Decontamination
Activated Charcoal
Syrup of Ipecac
Gastric Lavage
Whole Bowel Irrigation
3. Enhancing Elimination
Diuresis or Alteration of Urine pH

Multiple-Dose Activated Charcoal
Hemodialysis and Hemoperfusion
4. Antidotes
Fomepizole etc.
5. Improving Outcomes
Poison Prevention
Child-Resistant Packaging

1. Supportive Care
Pre-hospital care

First Aid:
The presence of adequate airway, breathing, and circulation should be assessed, and cardiopulmonary
resuscitation should be started if needed. The most important step in preventing a minor exposure from
progressing to a serious intoxication is early decontamination of the poison. While awaiting transport,
placing the patient on the left side may afford easier clearance of the airway if emesis occurs and may
slow absorption of drug from the gastrointestinal tract.




Hospital care:

Initial Stabilization of the Poisoned Patient.
The “ABC” mnemonic of emergency care is popularly taught and applies to the treatment of acute
poisoning. In severe cases, endotracheal intubation, mechanical ventilation, pharmacological blood
pressure support, and/or extracorporeal circulatory support may be necessary and appropriate.



Identification of Clinical Patterns of Toxicity.
A carefully obtained medical history may allow for the creation of a list of available medications or
chemicals that might be implicated in a poisoning event. Often, an observation of physical symptoms and
signs may be the only additional clues to a poisoning diagnosis. Groups of physical signs and symptoms
associated with specific poisoning syndromes are known as toxidromes.

2. Decontamination of the Poisoned Patient.
Poisoning exposures may be by inhalation, by dermal or mucosal absorption, by injection, or by ingestion.
The first step in preventing absorption of poison is to stop any ongoing exposure. If necessary, eyes and
skin should be washed copiously. Gastrointestinal decontamination is the process of preventing or
reducing absorption of a substance after it has been ingested. The primary strategies for GI
decontamination are gastric emptying, adsorption of poison, and catharsis (laxative/purgatives).



Minimal indications for considering GI decontamination include: 1) the poison must be potentially
dangerous; 2) the poison must still be unabsorbed in the stomach or intestine, so it must be soon after
ingestion; and 3) the procedure must be able to be performed safely and with proper technique.
Gastric emptying is rarely recommended anymore, but the administration of activated charcoal and
the performance of whole bowel irrigation remain therapeutic options.

Gastric emptying may be attempted by induced vomiting or by gastric lavage. Historically,
pharmaceutical methods to stimulate vomiting included administration of potentially toxic doses of copper
sulfate or apomorphine; more recently, syrup of ipecac took their place as the favored drug to induce

Syrup of Ipecac.
The alkaloids cephaeline and emetine within syrup of ipecac act as emetics because of both a local irritant
effect on the enteric tract and a central effect on the chemoreceptor trigger zone in the area postrema of the
Ipecac is given orally at a dose of 15 mL for children up to 12 years, and 30 mL for older children and
adults. Administration of ipecac is typically followed by a drink of water, and reliably produces emesis in
15-30 minutes.
Contraindications for syrup of ipecac administration include existing or impending CNS depression,
ingestion of a corrosive or hydrocarbon drug (due to the emergence of chemical pneumonia), or presence
of a medical condition that might be exacerbated by vomiting.

Gastric Lavage.
Gastric lavage involves the placement of an orogastric tube and washing out of the gastric contents
through repetitive instillation and withdrawal of fluid. Gastric lavage may be considered only if a
potentially toxic agent has been ingested within the past hour for most patients. If the patient is comatose
or lacks a gag reflex, gastric lavage should be performed only after intubation with a cuffed or well-fitting
endotracheal tube. Lavage should be performed with warm (37°C to 38°C) normal saline or tap water until
the gastric return is clear; this usually requires 2 to 4 L or more of fluid. Relative contraindications for
gastric lavage include ingestion of a corrosive or hydrocarbon agent. Complications of gastric lavage
include aspiration pneumonitis, laryngospasm, mechanical injury to the esophagus and stomach,
hypothermia, and fluid and electrolyte imbalance.



Single dose activated charcoal
Reduction of toxin absorption can be achieved by administration of activated charcoal. It is a highly
purified, adsorbent form of carbon that prevents gastrointestinal absorption of a drug by chemically
binding (adsorbing) the drug to the charcoal surface. There are no toxin-related contraindications to its
use, but it is generally ineffective for iron, lead, lithium, simple alcohols, and corrosives. It is not indicated
for aliphatic hydrocarbons because of the increased risk for emesis and pulmonary aspiration. Activated
charcoal is most effective when given within the first few hours after ingestion, ideally within the first
Complications of activated charcoal therapy include vomiting, constipation, pulmonary aspiration, and

Whole Bowel Irrigation.
Polyethylene glycol electrolyte solutions are used routinely as whole-bowel irrigants prior to colonoscopy
and bowel surgery. These solutions also can be used to decontaminate the gastrointestinal tract of ingested
toxins. Large volumes of these osmotically balanced solutions are administered continuously through a
nasogastric or duodenal tube for 4 to 12 hours or more. They quickly cause gastrointestinal evacuation and
are continued until the rectal discharge is relatively clear. This procedure may be indicated for certain
patients in whom the ingestion occurred several hours prior to hospitalization and the drug still is
suspected to be in the gastrointestinal tract, such as drug smugglers who swallow condoms filled with
cocaine. In addition, patients who have ingested delayed-release or enteric-coated drug formulations or
have ingested substances such as iron that are not well adsorbed by activated charcoal may benefit from
whole-bowel irrigation. It should not be used in patients with a bowel perforation or obstruction,
gastrointestinal hemorrhage, ileus, or intractable emesis. Emesis, abdominal cramps, and intestinal
bloating have been reported with whole-bowel irrigation.

The two most common categories of simple cathartics are the magnesium salts, such as magnesium citrate
and magnesium sulfate, and the nondigestible carbohydrates, such as sorbitol. The use of simple
cathartics has been abandoned as a GI decontamination strategy, although sorbitol is sometimes
administered with single dose activated charcoal in an effort to add sweetness and reduce its predilection
toward constipation. If used, a cathartic should be administered only once and only if bowel sounds are
present. Infants, the elderly, and patients with renal failure should be given saline cathartics cautiously, if
at all.

3. Enhancing Elimination
Diuresis or Alteration of Urine pH
Diuresis can be used for poisons excreted predominantly by the renal route; however, most drugs and
poisons are metabolized, and only a good urine flow (e.g., 2 to 3 mL/kg/h) needs to be maintained for
most patients. Fluid and electrolyte balance should be monitored closely. Ionized diuresis by altering



urinary pH may increase excretion of certain chemicals that are weak acids or bases by trapping ionized
drug in the renal tubule and minimizing reabsorption. Alkalinization of the urine to achieve a urine pH of
7.5 or greater for poisoning by weak acids such as salicylates or phenobarbital can be achieved by
intravenous administration of sodium bicarbonate. Acid diuresis may enhance the excretion of weak bases,
such as amphetamines, but it is rarely used. Generally, diuresis or ionized diuresis is rarely indicated for
poisoned patients because it is inefficient relative to other methods of enhancing elimination, it is
associated with a risk of unacceptable adverse effects, and renal elimination of most drugs is not enhanced

Multiple-Dose Activated Charcoal
Multiple doses of activated charcoal can augment the body’s clearance of certain drugs by enhanced
passage from the bloodstream into the gastrointestinal tract and subsequent adsorption. Once the drug is
adsorbed to the charcoal, it is eliminated with the charcoal in the stool. Systemic clearance of several
drugs has been shown to be enhanced up to several-fold.

Hemodialysis may be necessary for certain severe cases of poisoning. Dialysis should be considered when
the duration of symptoms is expected to be prolonged, normal pathways of excretion are compromised,
clinical deterioration is present, the drug is dialyzable, and appropriate personnel and equipment are
available. Hemodialysis may be lifesaving for methanol and ethylene glycol poisoning and effective for
other poisons, such as lithium, salicylates, ethanol, and theophylline.

4. Antidotes



The search for and use of an antidote should never replace good supportive care. Specific systemic
antidotes are available for many common poisonings. e.g.
Acetylcysteine for Acetaminophen poisoning
Atropine for Anticholinesterase insecticides
Dimercaprol for Heavy metal poisoning Etc.