CNS Flashcards
contains material emphasized in class.
what is primary type of action potential transmission in CNS, chemical or electrical transmission
chemical
influx of which ion into the presynaptic membrane stimulates NT exocytosis
calcium ion (Ca2+)
is changing the concentration of. NT OR up/downregulating a receptor a direct or indirect receptor interaction
indirect
are CNS drugs generally extremely selective for their target
no, they are RELATIVELY selective for their target
are both initial and delayed responses important for ultimate clinical effect
yes
the ability of a drug to penetrate the lipophilic BBB is critical to its activity in the CNS. what is often involved in the BBB penetration?
active metabolites (which may have a longer half-life than the parent drug)
what are the 5 classes of drugs that affect the CNS
anesthetics, analgesics, tranquilizers and sedatives, anti-depressants and anti-anxiety drugs, anti-epileptic drugs
what is the goal of anti-epileptic therapy
balance reduction of seizures with quality of life for patient
what is a major inhibitory NT in CNS
GABA
this first-line AED is moderately lipophilic (can cross BBB), has kinetics change in first few days, and there is considerable variation in serum concentration for any specific dose
phenobarbital
name 3 adverse effects of phenobarbital
behaviour changes (sedation or hyper excitability), immune mediated anemia/neutropenia, acute hepatotoxicity, polydipsia, polyphasic, hepatotoxicity, decreased serum T4 concentrations
what should you know about drugs that inhibit cytochrome P450 enzymes, eg. chloramphenicol, cimetidine, ketoconazole
can cause phenobarbital toxicity
what does the induction of cytochromeP450 enzymes by phenobarbital change
change the PK of some other drugs
why is therapeutic drug monitoring of phenobarbital important
serum concentrations at a given dose vary between individuals, so dose adjustments often needed
when should you monitor concentration of phenobarbital in patients
monitor concentration to first steady state concentration time point (2 weeks), again at first steady state clearance time point (6 weeks), monitor liver function every 6 months
this AED has an extremely long half life (15 days dog, 10 days cat) so is very slow to reach steady state, and no peak or trough. It is cleared really (no hepatic or protein binding) so patients with kidney disease may need dose reduction
KBr potassium bromide
when is steady state reached in KBr? when should serum drug concentrations be monitored?
3 months. monitor at 1 month, 3 months, annually (or sooner if evidence of toxicity or ineffectiveness)
this AED is primarily an add-on treatment and has a short half-life
levetiracetam
this benzodiazepine AED is used to treat acute seizures and status epileptics and impractical for long-term therapy in dogs due to short half-life, tolerance/dependance possibility, and abuse potential
diazepam
dog is emergency seizuring! what is the preferred emergency seizure drug and why? what is route of administration?
diazepam, it is more lipophilic that other benzodiazepines. can give per rectum (owner can use this route), orally, or IV, but not IM
this AED has a short half-life in dogs (2 hours) so no accumulation with typical chronic use, high therapeutic index, and no therapeutic monitoring is needed
imepitoin
potential behavioural consequence of behaviour modifying drugs
aggression
behaviour modifying drugs and antidepressants take how long to exert full effects?
several weeks
is it necessary to taper behaviour modifying drugs after long-term administration
yes
name 3 general clinical effects of benzodiazepines
anxiolytic, anterograde amnesia (good for pre-anesthetic), anticonvulsant; also sedative and hypnotic at higher effects, muscle relaxant, appetite stimulant
different effects of different drugs in benzodiazepine class are due to what?
variations in the GABA receptor
what are 3 PK and PD considerations about diazepines?
chronic administration can cause GABA receptor down-regulation, tolerance may occur, and gradual tapering is needed after chronic administration to prevent discontinuation syndrome
there are many different subtypes of serotonin receptors; are they presynaptic or postsynaptic?
some are presynaptic and some are postsynaptic
buspirone and SSRIs desensitize which receptor
5-HT1A
buspirone and SSRIs desensitize which receptor
5-HT1A
name 4 types of antidepressant drugs and an example drug from each type
SSRIs (selective serotonin reuptake inhibitors), eg. fluoxetine; tricyclic antidepressants, eg. clomipramine; MAOs (monoamine oxidase inhibitors), eg. selegiline HCl; atypical antidepressants, eg. trazodone
you are starting a kittycat on antidepressants. should you start at the low or high end of a dose? how long should you expect to see a response?
low end of dose (in order to assess response to minimize adverse effects). at least 2 weeks, but potentially 4-6 weeks to see full response
if you increase SSRI plasma concentrations, what change will you see in the clinical effect
there is no relationship between SSRU plasma concentrations and clinical effect
this most commonly used SSRI requires great caution if combined with MAOIs due to the risk of serotonin syndrome
fluoxetine
this fluoxetine drug (proprietary name) is specifically approved for treating separation anxiety
Reconcile
what is the effect of tricyclic antidepressants on serotonin, norepinephrine, acetylcholine, and histamine
inhibit serotonin reuptake, inhibit norepinephrine reuptake, anticholinergic effects, antihistaminic effects
there are multiple less common adverse effects of tricyclic antidepressants include constipation, diarrhea, ataxia, and mydriasis. these are often related to _____ effects
related to anticholinergic effects
3 most common adverse effects of tricyclic antidepressants?
sedation, mitosis, urinary retention
this tricyclic antidepressant is approved for use in dogs for OCD, dominance aggression, and separation anxiety
clomipramine
this atypical antidepressant is a serotonin antagonist and reuptake inhibitor
trazodone
