Muscle Relaxants, Anti-Convulsants, AEDs Flashcards
T/F: dantrolene is a centrally acting muscle relaxant
FALSE, peripheral (acts on muscle cell)
does dantrolene cross the BBB?
no, only peripheral
what is the MOA of dantrolene?
interferes w/ release of calcium from the SR
what is the drug of choice for malignant hyperthermia?
dantrolene
what can be a cause of malignant hyperthermia (hypermetabolic syndrome)?
ingestion of hops! watch out brewers
what is hypermetabolic syndrome?
- genetically determined idiosyncratic drug rxn
- life threatening hyperthermia, hyperkalemia, and cell death
- shock, MODS
- fatal
what species is more susceptible to hypermetabolic syndrome?
pigs
what is a hypermetabolic rxn of skeletal m. called?
rhabdomyloysis
how might you treat a tetanus (clostridium tetani) infection?
dantrolene, methocarbamol
-need a muscle relaxer!! have to keep calm and wait it out
what muscle relaxant is used to treat dogs, cats, and horses in acute inflammatory or traumatic conditions?
methocarbamol (think dachshunds)!
T/F: methocarbamol is recommended to be given IM/SQ
FALSE, irritating (IV or oral which has rapid absorption)
what drug do you use to treat intervertebral disk disease (IVDD), tetanus, and intoxication (tremorogenic)?
methocarbamol
what are examples of intoxication (tremorogenic)?
strychnine, metaldehyde, tremorogenic molds (“garbage gut”), pyrethrin/permethrin (cats)
how is methocarbamol excreted?
renally, caution w/ renal diseases
help! i gave my cat advanTIX instead of advantage!! what do i do?
give methocarbamol
guaifenesin is not only a centrally-acting muscle relaxant but also what?
an expectorant (helps break up cough, think mucinex)
besides acting as a muscle relaxant, what other effects does guaifenesin have?
sedative and analgesic
what muscle relaxant is considered a class 4 in the ARCI?
guaifenesin for use in horses
what is guaifenesin primarily used for?
- combined for intubation (pharyngeal and laryngeal mms.)
- “triple drip” (GG + xylazine + ketamine) for TIVA
T/F: guaifenesin used in high concentrations (>10%) is more likely to cause hemolysis in horses than cattle
FALSE, cattle are more sensitive
what drug is contraindicated in horses receiving guaifenesen?
physostigmine
seizure
clinical manifestation of abnormal electrical activity in brain, uncontrolled firing of neurons
epilepsy
chronic syndrome of seizures, “recurrent seizures”, occur intermittently over months to years for which contributing underlying cause cannot be identified
idiopathic epilepsy (IE)
“true epilepsy”, genetic or inherited
acquired/symptomatic epilepsy
intracranial vs extra-cranial causes
status epilepticus (SE)
repeated seizures w/out full recovery between them, or a single seizure that last >5 minutes
cluster seizures
more than one seizure occurring w/in a 24 hr period w/ recovery in between
anticonvulsants
drugs that prevent or treat seizures
antiepileptic drugs (AED)
drugs that prevent or treat seizures
refractory seizures
seizures that are not responding to therapeutic doses of AEDs
breakthrough seizures
seizures that occur at periodic intervals during treatment course w/ AEDs
generalized seizures consist of what two types of seizures?
convulsive (tonic clonic, autonomic release) and non-convulsive (absent, brief loss of contact w/ environment)
partial seizures consist of what two types of seizures?
simple partial (lateralizing motor activity, no loss of consciousness) and complex partial (altered motor activity and altered consciousness)
what type of partial seizure is more common?
complex
what maintains the resting membrane potential?
Na/K-ATPase
kindling
process by which “seizures beget seizures”
what is the goal of maintenance (chronic) treatment of seizures?
reduce the frequency and/or severity of seizures
what is the goal for treatment of breakthrough seizures?
increase the time interval between seizure events, reduce the severity and duration
what must you ALWAYS keep in mind when treating a patient for seizures?
look for an underlying cause!
what is the drug of choice for treatment of a seizure in progress?
diazepam (IV, intranasal, per rectum)
what drug do you use to put a patient currently seizing in a medically induced coma?
IV propofol or alfaxalone, helps w/ overheating from muscle tremors, probably not stopping the firing
what must you do if you end up treating a patient currently seizing with propofol?
- intubate! airway protection required
- intensive monitoring
what might you worry about if you send a known epileptic with a history of status epilepticus or cluster seizures home with injectable diazepam?
- legalities (controlled substance)
- it binds to plastic
- light sensitive
how many seizures in what amount of time would drive you to treat a patient with maintenance therapy?
if patient has had more than 2-3 seizures in 6-12 months or cluster seizures (2 or more in an hour)
this type of monitoring is frequently used with antiepileptic drug therapy
therapeutic drug monitoring (TDM)
why might you want to avoid using bromide to treat a cat?
about 1/3 of cats on bromide develop asthma/pneumonitis
T/F: seizure pathophysiology is complex and incompletely understood
TRUE!
what is the most common first-line AED for chronic therapy?
phenobarbital
why do you need to check phenobarbital levels in the blood?
because its a POTENT inducer of hepatic microsomal enzymes AND is metabolized through that system (cytochrome P450)
what plasma protein is phenobarbital extensively bound to?
albumin
what are common adverse effects you’d see when using phenobarbital?
-PU/PD/PP, sedation, elevated liver enzymes (ALP)
T/F: phenobarbital can cause paradoxical hyperexcitability, nephrotoxicity, and pancytopenia
FALSE, all is correct except it can cause HEPATOtoxicity not nephrotoxicity
how many binding sites do GABA receptors have?
5
T/F: bromide acts by binding and prolonging the opening of chloride channels
FALSE, thats the MOA of phenobarbitol. bromide’s MOA is altering chloride transport across neuronal cell membranes
T/F: bromide is the primary or add-on anticonvulsant in cats
FALSE!! can show asthma-like pulmonary changes, use for dogs
T/F: chloride on serum chemistry reads falsely high for a patient taking bromide
TRUE! bromide is recognized as chloride
why might you be concerned about owner compliance when it comes to bromide?
you must keep salt intake constant, salt can significantly interfere w/ bromide levels
which anticonvulsant drug is NOT a GABA agonist?
- levetiracetam, mechanism is unclear
- zonisamide also does not work at GABAa receptors
what anticonvulsant is the excellent/preferred choice for treatment of seizures due to hepatic encephalopathy?
levetiracetam, primarily excreted unchanged in urine
what anticonvulsant is least appropriate for the treatment of seizures due to hepatic encephalopathy?
phenobarbital
what two anticonvulsants must you perform therapeutic blood level monitoring?
phenobarbital and bromide
T/F: clearance is increased if a patient is on phenobarbital and levetiracetam concurrently
TRUE!
which anticonvulsant is used for “pulse therapy” for use around breakthrough seizures?
levetiracetam
what anticonvulsant might you see tolerance or the “honeymoon effect”?
levetiracetam
which anticonvulsant is a sulfonamide derivative?
zonisamide
what type of channel does zonisamide inhibit?
voltage-gated sodium channels
T/F: clearance is increased if patient is on zonisamide and phenobarbital concurrently
TRUE!
what two anticonvulsants would be a good choice in treatment of seizures for cats?
levetiracetam and zonisamide
T/F: levetiracetam and zonisamide are used as adjunct AED agents for maintenance therapy
TRUE!
in which anticonvulsant might you see idiosyncratic agranulocytosis?
zonisamide (in dogs)
what anticonvulsant is only available in the UK and EU and is known for its sparing effects?
imepitoin
which anticonvulsant has the longest half life?
bromide
which anticonvulsant has the shortest half life?
levetiracetam
