0071643192.pdf

TOXICOLOGY

PESTICIDES/INSECTICIDES/RODENTICIDES

EMS presents with a 54-year-old male farm worker who called EMS after

ingesting insecticide in a self-harm attempt. On ED arrival, he is confused

and smells of garlic. Further examination reveals pinpoint pupils, excessive

salivation, lacrimation, and muscle fasiculations. What is the most appropriate

initial medication to give in the treatment of this patient?

This patient is presenting with cholinergic excess consistent with

organophosphate poisoning. Atropine is the initial medication and should be

used to control airway secretions and symptomatic bradycardias. Large doses are

often needed.

Organophosphates and Carbamates

Organophosphates and carbamates are insecticides used extensively in agri-
cultural and commercial applications.

MECHANISM/TOXICITY

■ Inhibition of cholinesterase →increased activity at all nicotinic and mus-
carinic receptors.
■ Carbamates bind cholinesterase transiently (minutes to hours).
■ Organophosphates can undergo “aging” → irreversible binding of the
insecticide to cholinesterase.

SYMPTOMS/EXAM

■ Cholinergic toxidrome
■ Altered mental status (delirium to coma), seizures

DIFFERENTIAL

■ Toxicity from nerve agents (VX, Soman, Tabum) or nicotine

DIAGNOSIS

■ Usually apparent from clinical symptoms and a history of exposure
■ Measured RBC cholinesterase or pseudocholinesterase (plasma cholin-
esterase) levels
■ Reduced in toxicity, but are not available in a timely manner

TREATMENT

■ Immediate surface decontamination, as indicated
■ Supportive therapy
■ Benzodizepines or phenobarbital for seizures
■ Antidote = atropine, used for
■ Hemodyamically unstable bradycardia
■ Excessive secretions (endpoint is drying of airway secretions)
■ Very high doses often needed (>10 mg)
■ Antidote = pralidoxime (2-PAM)
■ Can potentially reactivate inhibited cholinesterase
■ Indicated in organophosphate poisoning, but is ineffective in after aging
has occurred

Unlike carbamates, the

organophosphate bond to

cholinesterase will “age” and

become irreversible over time.

Antidotes to organophosphate

poisoning: Atropine and

pralidoxime

Cholinergic

toxidrome—

SLUDGE

Salivation

Lacrimation

Urination

Defecation

GI symptoms

Emesis

and the

Killer Bs:

Bronchorrhea

Bronchospasm

Bradycardia