Page 1419 - Cote clinical veterinary advisor dogs and cats 4th

Organophosphate and Carbamate Insecticide Toxicosis 719

Advanced or Confirmatory Testing ○ Dermal exposure: bathe the animal with PROGNOSIS & OUTCOME
• AChE levels (p. 1299): serum, plasma, whole a mild dishwashing liquid, then rinse • Prognosis good unless the animal suffers
VetBooks.ir ○ An AChE result that is < 50% of normal ○ Emesis induction: only in asymptomatic from respiratory distress (excessive bronchial Diseases and Disorders
thoroughly, dry and keep patient warm.
blood (preferred), brain, or retina:
Wear gloves.
indicates significant exposure is likely, and
secretions, aspiration pneumonia) or seizures
AChE activity < 25% of normal indicates
of ingestion (p. 1188)
dose, compound, and species of animal.
toxicosis (activity can remain depressed patients; effective only within a few hours • Duration of signs depends on treatment,
for 6-8 weeks). ○ Gastric lavage: when a large amount
○ Because carbamates are reversible inhibi- of poison has been ingested or emesis PEARLS & CONSIDERATIONS
tors of AChE, the results may be normal is contraindicated (comatose); use
even in the face of carbamate toxicosis. a short-acting anesthetic and cuffed Comments
• AChE insecticide screen: liver, kidney, endotracheal tube to protect airway • The main difference of clinical importance
gastrointestinal tract contents, and source (p. 1117). between carbamates and OPs is that AChE
material to look for specific insecticide ○ Activated charcoal 1-2 g/kg PO or inhibition is generally irreversible in cases
labeled dosage of commercial product. of OP toxicosis but reversible in cases of
TREATMENT In animals showing overt clinical signs, carbamate toxicosis.
repeat in 8 hours (one-half the original ○ Pralidoxime (2-PAM, Protopam) is
Treatment Overview dose). indicated for treatment of OP toxicosis
Triage identifies cases with life-threatening • Supportive care: IV fluids as needed but not carbamate toxicosis (ineffective).
clinical effects on presentation, which are treated ○ Carbamates are generally short-acting
with atropine, pralidoxime (for OPs), ventilator Nutrition/Diet chemicals.
support if hypoventilation, seizure control if Tube feeding (p. 1106) or other nutritional • SLUDDE signs can have several causes. If
needed, and supportive care. Decontamination support may be necessary for cats that may be history of exposure to an anticholinesterase
and other treatment measures are carried out anorectic for days to weeks after being exposed insecticide is not known, a test dose of
after the animal has been stabilized. The treat- to chlorpyrifos. atropine can be given to determine whether
ment process is summarized in an algorithm the signs are caused by an anticholinesterase
found on p. 1438. Drug Interactions (OP or carbamate) insecticide.
Avoid: ○ Record baseline heart rate.
Acute General Treatment • Enhancing toxicity: phenothiazine tran- ○ Administer preanesthetic dose of atropine
• Treat life-threatening signs first if present. quilizers (e.g., acepromazine), opiates, (i.e., 0.02 mg/kg IV for dogs and cats),
○ Atropine sulfate (dogs/cats) 0.1-0.5 mg/ aminoglycoside antibiotics, theophylline and monitor the animal’s response for
kg; one-fourth dose IV and rest of dose • Administering neuromuscular blocking 15-30 minutes.
IM or SQ to reduce muscarinic signs; agents (levamisole, succinylcholine, nicotine, ○ If the heart rate increases and mydriasis
repeat as needed to control bradycardia and curare) can enhance the nicotinic effects occurs, the muscarinic signs are NOT due
and bronchial secretions. of OPs. to OP or carbamate toxicosis (it takes ≈10
○ Pralidoxime chloride (2-PAM; Protopam) times the preanesthetic dose of atropine
(dogs/cats) 20 mg/kg IM, SQ, or very slow Possible Complications to resolve signs caused by cholinesterase
IV q 12h for controlling the nicotinic • Pancreatitis, hemorrhagic enteritis, and inhibitor insecticides).
signs, although some benefit may be seen increased liver enzymes can occur in some • For dead animals, submit one-half the brain
by controlling CNS signs. 2-PAM should animals after OP toxicosis (disulfoton). (sagittal section, frozen) to the lab (put the
not be used with carbamates because it • Certain OPs can cause a delayed neuropa- other half in formalin for histopathologic
would not be beneficial. Oximes reverse thy 2-3 weeks after acute poisoning. This exam) but only if rabies is definitively
binding of toxin to AChE, but carbamate complication is characterized by hindlimb ruled out (otherwise, the material could be
binding to AChE is inherently reversible. ataxia, hypermetria, and proprioceptive hazardous to personnel opening the skull
If the OP-intoxicated animal shows no deficits. Chlorpyrifos (experimentally at and handling tissue).
response after 3 doses, discontinue high doses) is possibly associated with this • With the availability of safer insecticides for
treatment with 2-PAM. Oximes such as neuropathy in cats. controlling insects, the incidence of OP and
pralidoxime are ineffective once OP aging • There are usually no long-term effects in carbamate toxicoses in animals has decreased.
has occurred, but because the time of aging animals that recover from acute OP or • The table shows toxicity ratings.
varies with the compound, pralidoxime carbamate toxicosis unless there have been
may be effective even days after exposure. prolonged seizures. Technician Tips
• Seizure control Exposure to aldicarb- and methomyl-containing
○ Diazepam 1-2 mg/kg IV, repeat as needed, Recommended Monitoring carbamates by dogs can cause rapid seizures
or • Heart rate and death (within minutes). Ask the client to
○ Phenobarbital 2-5 mg/kg IV bolus, • Respiratory rate and effort, and lung sounds bring the patient to the clinic immediately if
repeated in 20 minutes up to two times • CNS signs such an exposure is encountered.
○ Pentobarbital to reach desired effect; repeat
as needed
○ Controlling tremors: methocarbamol
50-100 mg/kg IV; repeat as needed Toxicity Ratings
without exceeding 330 mg/kg/day Toxicity Rating LD50 Substances
• Oxygen and ventilatory support as needed
for animals in respiratory distress (pp. 1146 Highly toxic <50 mg/kg Disulfoton, coumaphos, famphur, phorate, terbufos, methomyl,
and 1185) aldicarb
• Decontamination of the animal: indicated Moderately toxic 50-1000 mg/kg Acephate, chlorpyrifos, diazinon, carbaryl, phosmet, propoxur
after any potentially life-threatening Lower toxicity >1000 mg/kg Malathion, tetrachlorvinphos
hemodynamic, neurologic, and respiratory
abnormalities have been addressed (p. 1087). LD50: Dose that is lethal for 50% of exposed individuals.

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