9: Toxicants Affecting Cardiac/Resp Systems 1

heart arrhythmias caused by acute toxicity

brady/tachycardia, AV blockage, QT prolongation, decreased function

what occurs during QT prolongation?

delayed ventricular polarization

what do anti-arrhythmic drugs do?

block Na/B/K/Ca chennels

what do CNS drugs do?

cause postural hypotension

what do local anestetics do?

block Na chennels

what do anthracyclines do?

cause cardiomyopathy

what do antineoplastic drugs do?

mess with ECG, cause hemorrhagic necrosis

what do aminoglycoide antibiotics do?

reduce Ca channels/binding

DRUGS CAUSING QT PROLONGATION

antihistamines, prokinetics, methylxanthines, sildenafil

signs of ionophore toxicity

weakness, trembling, sweating, froth from nose, collapsing, DOA

what are ionophores?

antibiotics isolated from Strep. cinnamonensis, given as a feed additive

ionophore commonly causing toxicity

monensin

signs of monensin toxicity in horse

prolong depolarization/repolarization, V-tach, AV block

signs of monesin toxicity in cattle

QT/QRS prolongation, muscle damage, 1 degree AV block

how does ionophore toxicity commonly occur?

error in mixing at feed mill

amitraz

insecticide/acaricide used in dog flea collars

MOA of Amitraz

α2 adrenergic agonist and MAO inhibitor

signs of Amitraz toxicity

bradycardia, 1/2 degree AV blocks, low CO

what toxin do blister beetles contain?

cantharidin

MOA of cantharidin

anti-adrenergic effect (block A1 receptors)

signs of cantharidin toxicity

increased HR, myocardial dysfunction, colic (horses)

what causes the THUMP cantharidin toxicity?

diaphragmatic contractions due to hypocalcemia

bufo toads

colorado river toad and cane toad

signs of bufo toad toxicity

profuse/frothy salivation, head shaking, pawing at mouth, retching, HR over 200

toxin of bufo toads

bufotoxin (bufadienolides are the glycosides)

how to decontaminate bufotoxin?

flush out oral cavity multiple times, go to vet for ECG/seizure monitoring

Digitalis spp

foxglove

toxic principle of foxglove

digitalis glycosides

toxokinetics of digitalis glycosides (foxglove)

absorbed in GI tract, eliminated by liver/urine

GI signs of digitalis glycoside toxicity (foxglove)

anorexia, colic, diarrhea

MoA of digitalis glycoside (foxglove)

inhibits Na/K pump

CV signs of digitalis glycoside toxicity (foxglove)

sinus bradycardia/arrest, AV block, atrial tachycardia, PVCs, VT/V fib

management of plant based cardiac toxicity

monitor ECG/BP, give IV fluids/anti-emetics/anti-arrthymitics

Ascelpias spp

milkweed

toxic principle of milkweed

cardenolies galitoxin (resinoid)

MoA of milkweed

same as foxglove

signs of milkweed toxicity

ataxia, depression, weakness, labored breathing, arrhythmias, seizures

nerium spp

oleander

toxins of oleander

oleandrin and neriine

MoA/CS/Txt of olenader

same as foxglove

convallarrio majalis

lilly of the valley

toxic principle of lilly of the valley

convallotoxin

rhododendron spp

azalea

toxic principle in azaleas

grayanotoxins

MoA of grayanotoxins (azaleas)

bind to voltage gated Na+ channels

signs of grayanotoxin toxicitiy (azaleas)

depression, excess salivation, vomiting, bradycardia, arrythmias, seizures

kalmia latifolia

mountain laurel

kalmia angustifolia

sheep laurel (Lambkill)

where are laurel plants found?

appalachains

toxic principle of laurel plants

grayanotoxins (same MoA then as azaleas)

signs of laurel plant toxicity

excess salivation, perspiration, vomiting, dizziness, weakness, paresthesia, low BP, sinus bradycardia

persea americana

avocado

toxic principle of avocado

persin

true or false: avocados are basically toxic to all animals except humans

TRUE

what does persin toxin cause?

myocardial necrosis

toxic principle of kalachoe species

bufadienolides

MoA of kalachoe species

similar to digitalis

toxic agents of dogbane (indian hemp)

resin, apocynin, cymarin

toxic agent in cottonseed/cotton plant

gossypol

what does gossypol toxin cause?

myocardial necrosis

taxus spp

yew

toxin of yew

taxine alkaloid

MoA of yew

direct effect on cardiac ion channels, causing conduction disturbances