Drugs- anti infectives Flashcards
Metronidazole use
-used therapeutically (antibacterial- clostridium, antiprotozoal- giardia)
Clinical signs of metronidazole toxicity
Vestibular signs
-head tilt, circling, nystagmus
-central vestibular disease
**commonly see cerebellovestibular ataxia and nystagmus
Management of metronidazole
discontinue use= should resolve rapidly
*diazepam may speed up recovery
Metronidazole diagnosis
-history of use
-bloodwork
-imaging
-discontinue use and see recovery
DDx for metronidazole toxicity
Anything with vestibular signs
-otitis media/interna
-intracranial neoplasia
-idiopathic vestibular disease
-lead poisoning
Prognosis of metronidazole toxicity
excellent
Ivermectin
-macrocyclic lactone (broad antiparasitic)
-pastes, liquids, tablets
Genetic predisposition of ivermectin toxicity
-ABCB1 mutation in dogs
-border collies, Australian shepherds, long haired whippets, silken windhound,
Exposure scenarios for ivermectin poisoning
-dermal or oral
-administration/ overdose of ivermectin products
-accidental exposure to large animal ivermectin
-ingestion of feces of treated livestock
Ivermectin poisoning target organ and mechanism
CNS
-Potentiation of glutamate and GABA gated Cl channels= CNS depression
*ABCB1 mutation means defective p-glycoprotein so drug not removed
Onset of ivermectin poisoning
Several hours or days (dose dependent)
Clinical signs of ivermectin poisoning
-lethargy, depressed mentation
-disorientation, ataxia
-vomiting, hypersalivation
-mydriasis
-blindness
*if severe= seizures, obtundation, resp depression
What animals are most susceptible to ivermectin?
-ABCB1 polymorphism dogs
-chelonians (turtles)
Ivermectin induced blindness
Huge pupils
Due to retinal edema and sometimes folds and separation
-no menace, slow to no PLRs
-may be due to GABA receptors in retina
How to diagnose acutely blind animal?
-fundic exam
-electroretinography (ERG)= decreased b-wave amplitude
Ivermectin management
-no antidote
-decontaminated if not contraindicated; especially dermal
-ventilation, seizure control, temperature control, IVFT
-sight will return slowly
What can’t the ivermectin induced blindness be detected PM?
Because edema cannot be fixed and it will just collapse and you cant see
Ivermectin poisoning diagnosis
-history, and clinical signs
-analysis of liver or serum for ivermectin
DDx for ivermectin poisoning
-CNS depressants
(barbituates, opiates, tremorgenic mycotoxins, nicotine, benzodiazepines)
-hypersalivation (OP/carbamates)
Ivermectin poisoning prognosis
Usually good with supportive care
-prolonged care needed for severe affected patients
Pyrethrins and pyrethroids
Derived from chrysanthemum flower
*pyrethroids=synthetic
-high potency against insects vs mammals
-used in flea and tick products (OTC treatments, K9 advantix, equine spot ons)
Exposure scenarios of pyrethrins and pyrethroids
Application of flea/tick products meant for dogs
Pyrethroids target organ and mechanism
Target: CNS
Mechanism: prolonged Na channel opening in nerves= CNS excitation
Which animals are most susceptible to Pyrethroids?
-cats
-animals with liver damage
Onset of pyrethroid toxicity
Within a few mins to days
Clinical signs of pyrethroid toxicity
-vomiting, diarrhea
-depressed mentation or hyperexcitability
-tremors, twitching, muscle fasciculations
-mydriasis
-hypersalivation
-ataxia
*if severe, seizures, coma. Can be fatal
Pyrethroid toxicity management
- no antidotes
-decontamination (dermal or GI)
-ensure cat cannot groom itself
-methocarbamol for tremor control
-IVFT
-thermoregulation
-monitor
Diagnosis of pyrethroids
-history of OTC flea products meant for dogs
-used on dogs in a household with a cat
DDx for pyrethroid toxicity
CNS excitation
-strychnine, fluoroacetate, OP/carbamate insecticides, organochlorine insecticides, stimulant drugs, bromethalin, salt, tremorgenic mycotoxins, lead
Pyrethroid toxicity prognosis
Good with early and aggressive treatment
-poor with seizures
