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1200 Antidotes and Reversal Agents

Antidotes and Reversal Agents
VetBooks.ir Antidotes can be divided into four broad categories: chemical (C), receptor (R), dispositional (D), and functional (F). The category may change, depending on the usage.

Chemical antidotes act directly on the toxicant to make it less toxic and/or to increase excretion. Receptor antidotes prevent the toxin from binding to the receptor site (can
bind directly or change the conformation of the receptor, preventing binding). Dispositional antidotes reduce the amount of toxin available to tissues by altering absorption,
metabolism, distribution, or excretion of the toxicant. Functional antidotes act on the symptoms caused by the toxicant.
Reversal Agent/Antidote Toxicant/Main Indication Dose Comment(s)
2-PAM (Pralidoxime) OP toxicosis (nicotinic signs) 20 mg/kg IM or slow IV, q 8h C; most beneficial within 24 hours of
exposure, may still be useful beyond
this time; discontinue after 3 doses if
no benefit
Activated charcoal Most organic compounds 1-2 g/kg PO D; does not bind alcohols, heavy metals,
nitrates, chlorates
Antivenins Pit vipers, coral snakes, etc. See product insert for directions C; multiple products available
Atipamezole (Antisedan) Amitraz, brimonidine, clonidine, 50-200 mcg/kg IM or IV R; preferred over yohimbine due to longer
detomidine, dexmedetomidine, duration of effect
imidazoline decongestants,
medetomidine, tizanidine, xylazine
Atropine sulfate OPs and carbamate toxicosis (muscarinic 0.02-0.04 mg/kg IV or IM (mushrooms); R; avoid atropinization (hyperthermia,
signs); muscarinic mushrooms 0.1-0.05 mg/kg, 1 4 dose IV with tachycardia, mydriasis)
remainder IM or SQ (cholinergic toxicosis)
BAL (British anti-Lewisite; Lead, arsenic, inorganic mercury, gold, 3-6 mg/kg IM q 6-8h C; nephrotoxic; injection can be irritating
dimercaprol) copper and painful; helps remove lead from
CNS
Calcium disodium EDTA (Calcium Lead, zinc, cadmium, iron, copper, Dog: 100 mg/kg SQ q 24h for 2-5 days C; nephrotoxic; painful injections; do not
disodium versenate) nickel, chromium, manganese (divide dose into 4 portions and dilute to use if metal still present in GI tract
10 mg CaEDTA/mL with 5% dextrose)
Cat: 27.5 mg/kg SQ q 6h for 5 days (dilute
in 15 mL 5% dextrose)
Cholestyramine Cholecalciferol, naproxen 300 mg/kg PO q 8h for 2-4 days D; binds to bile acids needed for
enterohepatic recirculation of some
toxins
Cyproheptadine (Periactin) Serotonin syndrome Dogs: 1.1 mg/kg PO or rectally q 6h for a R; appetite stimulant in cats
max of 2 doses
Cats: 2-4 mg (total) PO or rectally q 6h for
a max of 2 doses
Dantrolene Hops (dogs) 1-15 mg/kg PO q 8-12h; 1 mg/kg IV F; reverses the malignant hyperthermia-
like reaction
Deferoxamine (Desferal) Iron 40 mg/kg IM q 4-8h C; most effective in first 24 hours; urine
may turn wine color (vin rose) during
chelation
Digoxin immune Fab (Digibind) Digitalis, cardiac glycoside plants, toad Start with 1-2 vials IV over 30 minutes and C; expensive but rapid acting and
toxins increase as needed efficacious
D-penicillamine (Cuprimine) Lead, copper, iron, mercury, zinc, cobalt, Dog: 110 mg/kg/d PO divided q 6-8h for C; do not use when metal is still present
manganese 1-2 weeks in the GI tract; vomiting is common;
Cat: 125 mg (total) q 12h PO for 5 days nephrotoxic
Ethanol Ethylene glycol CRI dosing: D; proof is double the percentage of
7% ethanol; loading dose of 8.6 mL/kg, alcohol
then 1.43 mL/kg/h
Bolus dosing: 20% ethanol; Dog: 5.5 mL/kg
IV q 4h for 5 treatments, then q 6h for 4
treatments
Cats: 5 mL/kg IV q 6h for 5 treatments,
then q 8h for 4 treatments
Flumazenil (Romazicon) Benzodiazepines 0.01 mg/kg IV R; reverses severe CNS depression; short
half-life; repeat in 1-3 hours if needed
Folinic acid (Leucovorin) Methotrexate, trimethoprim, If known quantity of methotrexate, give on F; folinic acid is active form of folic acid
pyrimethamine, Gyromitra mushrooms a mg-to-mg basis (1 : 1); if unknown,
(false morels) 25-250 mg/m q 6h IV, IM for up to 72
2
hours
Fomepizole (4-methylpyrazole; 4-MP) Ethylene glycol Dogs: 20 mg/kg slow IV over 15-30 D; must be compounded; no longer
minutes, 15 mg/kg at 12 hours and 24 commercially produced
hours, 5 mg/kg at 36 hours
Cats: 125 mg/kg slow IV, 31.25 mg/kg at
12, 24, 36 hours

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