Neuro / Psych SketchyPharm Flashcards
Which benzos do not require microsomal monooxygenases to work?
OTL = Outside The Liver (still technically conjugated in the liver but do not require the slow Phase I reactions) O = oxazepam T = temazepam L = lorazepam
Is Triazolam long or short acting?
Short-acting, high addictive potential like alprazolam, oxazepam, and midazolam
What effect do benzos have on REM sleep?
Like alcohol, they decrease REM sleep
Are the three Z’s good for sleep maintenance?
No - they have a rapid onset of action but also a short halflife, reducing tolerance but at the same time only making them good for inducing sleep (maybe with the exception of eszopiclone which has a slightly longer halflife)
What is the firstline treatment of neonatal seizures?
Phenobarbital
How is essential tremor treated?
Drugs: Nonselective beta blockers + primidone (think of the lady getting a perm and combed with a shaking hand)
Self-medication: Transient suppression by alcohol
(also mediates GABA, like primidone)
What are the mechanisms of etomidate and propofol? What are the adverse effects?
Both potentiate GABA-A (think of the cab in the back)
Propofol - profound respiratory depression / hypotension
-> not good for those who aren’t hemodynamically stable
Etomidate - stable in those with cardiovascular risk, but profound nausea / vomiting post-op.
In what “state” are patients in when they take ketamine?
Cataleptic state - it is a dissociative agent - causes nystagmic gaze with eyes open
-> NMDA antagonist
Hallucinogen and irrational behavior during recovery
What are the advantages of ketamine?
Good analgesia, amnesia, and hypnosis. Can be used to induce or sustain anesthesia in patients with CV problems
How does blood:gas partition coefficient relate to induction speed, recovery time, potency, and MAC?
Increased blood:gas partition coefficient = increased solubility in blood = slower rate of rise to reach mass = slower induction speed
Also, since more gas will be soluble in blood = takes longer to clear from blood = longer recovery time.
How does oil:gas partition coefficient relate to induction speed, recovery time, potency, and MAC?
Increased solubility in lipids = increased potency = lower minimum alveolar concentration required to induce (potency is inversely proportional to MAC)
Lipid solubility has no relation to induction speed / recovery time
What does MAC mean?
Minimal alveolar concentration (ED50) - the concentration of inhaled anesthetic required to prevent 50% of patients from moving in response to noxious stimuli (MACs are additive btw, so you can give two adjacents at 0.5 their MACs and produce 1.0 MACs worth of sedation).
What is the order of anesthetic equilibration within the tissues? How do these compartment sizes differ)
Highly perfused tissues equilibrate first -> brain, heart, kidney, liver (small compartment)
Medium blood flow second -> muscles (medium size)
Low blood flow last -> fat (largest size)
What are the organ systemic effects of inhalation anesthetics (IA) and which one is the exception? Think CV, respiratory, brain, kidney, and liver.
Nitrous oxide is the exception
CV - drop in blood pressure by various mechanism
Respiratory - decreased minute ventilation, hypercapnia
Brain - Increased blood flow (increases ICP)
Kidney - Decreased RBF / GFR
Liver - Decreased hepatic blood flow
What is the primary toxicity of concern with nitrous oxide?
By inactivating methionine synthase, it can halt DNA production, leading to bone marrow depression and even pernicious anemia (B12-dependent enzyme)
What is the unique risk incurred by usage of halothane?
Hepatotoxicity - “H” - it is metabolized in liver, and can lead to trifuoloracetylated proteins which are hepatotoxic and can cause hepatitis / necrosis
-> centrilobular necrosis (Zone 3)
Which IAs are most likely nephrotoxic and what is its mechanism?
Sevoflurane -> metabolism in liver leads to the formation of inorganic fluoride ions
Also NEPHrotoxic = METHoxyflurane
What inhaled anesthetic is most likely to cause seizures?
Enflurane = Epileptogenic (think of the shaking pinata)
What agent other than the inhaled anesthetics can cause malignant hyperthermia? What is the mechanism? Treatment?
Succinylcholine. Remember than N20 can’t cause this however.
Susceptible: Autosomal dominant mutation in RyR (voltage-sensitive Ca+2 channel). (think of RYAN)
-> excessive release in Ca+2 (due to mutation) results in excessive SERCA activity which generates excessive heat
Treatment: Dantrolene - RyR antagonist
Are local anesthetics analgesics?
No, they are not specific inhibitors of the pain pathway (i.e. opioid analgesics). They just nonspecifically inhibit the conduction of action potentials
What form of the local anesthetic (LA) is active and how does it work? That is, what is the mechanism of action?
Only the protonated form -> binds to the LA binding site on the OPEN sodium channel and stabilizes the inactive state of the channel
Extends refractory period by delaying return to closed / resting conformation (occurs in a progression from increased threshold to total action potential abolishment)
What lipid solubility profile for a LA is most clinically effective and why?
Moderate hydrophobicity
Too low - hydrophilic molecules cannot cross to interior of membrane
Too high - hydrophobic molecules will get stuck in the membrane and not want to enter the cellular cytoplasm
What does the pKa of the given local anesthetic determine? What is their relative pKa range?
The time of onset. All are weak bases overall -> protonated form is the charged form, with pkas between 8-9
Low pKa = LA is relatively acidic, will easier lose proton exist in deprotonated and uncharged form -> rapid crossing of membrane and rapid onset
High pKa = LA is relatively basic, will exist in protonated form which is charged -> slow crossing of membrane and slower onset
What are three examples of regional anesthesia procedures?
- Spinal anesthesia - injection into lumbar cistern for lower abdominal, pelvic, rectal, or orthopedic surgery
- Epidural anesthesia - Injection into epidural space -> for childbirth / labor
- Nerve block - injection around nerve truck for site distal to surgery -> i.e. brachial plexus for hand surgery
What are the types of A and C fibers and what information do they carry? How do they relate with respect to diameter / myelination?
A = heavily myelinated, in order of descending diameter
A-alpha - unconscious proprioception, motor
A-beta - DC-ML = fine touch, pressure
A-gamma - intrafusal spindle information
A-delta - ALS - acute pain, temperature
C= unmyelinated, small diameter
C - ALS - slow, aching and burning
For a local anesthetic, is it easier to block a myelinated or unmyelinated nerve, and a small or large nerve? Is nerve size or myelination more important?
Myelinated nerve -> only needs to block 3 consecutive nodes of Ranvier to block saltatory conduction
Small diameter nerve -> electrical field travels farther on sections of larger nerve, and the nodes of a large nerve will be much farther apart (need a wider area of anesthetic to cover)
Would a small, unmyelinated nerve or large, myelinated nerve be blocked first?
Size is more important, meaning a small, unmyelinated nerve will be blocked before a large, myelinated nerve.
What is often done to prevent toxicity of LA?
Reduce blood flow to the area of injection and reduction in systemic circulation by injection with epinephrine
How are ester LA’s metabolized? How about amides?
Esters - Via pseudocholinesterase enzymes in the plasma, very rapidly, with metabolites excreted in urine
Amides - Via CYP450’s in liver
What are the toxic effects of LA in the CNS and what is done prophylactically?
CNS stimulation by depressing cortical inhibition pathways
-> dizziness, tremors, metallic taste, confusion, respiratory depression
Premedicate with benzodiazepines
What are the cardiovascular effects of LA’s?
By blocking SANS conduction, they result in decreased cardiac output and arteriolar vasodilation (except cocaine) -> hypotension
What class of LA’s is most likely to cause an allergic reaction and why?
Esters -> derivatives of p-aminobenzoic acid (PABA)
If allergic to esters, give amides
List the clinically important amide LA’s?
Drugs containing ‘i’ before the caine (two I’s in the name)
- Lidocaine
- Bupivacaine
- Ropivacaine
What is the toxicity of concern with benzocaine? Is it an amide or an ester?
Benzocaine - ester (not two I’s)
Toxicity - Methemoglobinemia -> treat with methylene blue
Why would bupivacaine or ropivacaine be used over lidocaine?
Produce a much longer duration of action
Is ropivacaine or bupivacaine preferred and why?
Ropivacaine is preferred, because bupivacaine is severely cardiotoxic
What are the functions of the delta and kappa receptors? Which ones do most addictive opioids bind?
Mu receptor - site of beta-endorphin binding, also the target of most opioid drugs. (Mu-ssage)
Delta - site of enkephalin binding, mediate analgesia, but less so than mu receptors
Kappa - analgesia with psychotomimetic effects -> partial agonist drugs can bind this strongly
What is the mechanism of action once mu receptors are bound?
Think of the closed calcium ice cream cooler and the open barrel of bananas
Close voltage-gated calcium channels on the PREsynaptic membrane -> inhibit neurotransmitter release
Also open K+ channels -> hyperpolarization of nerve
What is Tramadol and what do its parent and daughter compounds do?
A synthetic codeine derivative - think of the tram in sketchy
Parent compound: SNRI - think of the N/S compass on the tram
Daughter compound: Codeine derivative which is active
-> weak Mu opioid agonist
What are the side effects of concern for tramodol?
- Increased frequency of seizures -> lowers the seizure threshold
- Serotonin syndrome - especially if used with MAOs.
What is dextromethorphan used for? Mechanism?
An isomer of a full-agonist opiate - little orphan cough drops
Used in combination with quinidine for chronic cough, as well as pseudobulbar affect
Also think of the NMDA camel -> has NMDA-antagonist activity as well (reason for abuse / robitussin)
Remember it is also a weak SNRI -> can precipitate serotonin syndrome like tramodol
How can opioids can elevations of serum amylase / lipase?
They cause sphincter of Oddi contraction as well (cause contraction of many things) -> reflux of bile / pancreatic enzymes
- > think of the seagull sitting on the bile tree
- > this can precipitate biliary colic
What are the partial agonist opioids?
nalBU-PHINe, BUtorPHanol, BUPRENorphine PENTAzocine
think of blue-phin bar (buprenorphine is also a partial agonist)
What is the mechanism of action of pentazocine?
Another mu partial agonist. Think PENTAzocine - cuz that’s how you learned it before apparently
How does naltrexone differ from naloxone?
Naltrexone has the same receptor blocking profile, but naloxone is used acutely for OD whereas naltrexone is used to prevent relapse, especially in once monthly injection (highly politicized treatment for opiate addicts)
What is the role of the cortex to suppress pain and how can neurotransmitter imbalance affect this?
Cortex sends down descending pathways which release NE, 5-HT, and GABA to facilitate the inhibition of excitatory pain impulses
-> pain loop should shut off overtime
What channels are modified to cause central sensitization?
In the descending axon which is normally inhibitory:
- Enhanced NMDA release on pain receptors and hence calcium influx
- Reduced GABA activity
- Reduced norepinephrine
Gained excitatory pathways and loss of inhibitory pathways -> enhanced central activation of pain pathways.
-> need to reverse this to stop neuropathic pain
What drugs block calcium channels in treatment of neuropathic pain?
- Gabapentin
- Pregabalin
- Topiramate
What drugs block sodium channels in the treatment of neuropathic pain?
Carbamazepine
Lidocaine
TCA’s -> also effective because they enhance NE / 5HT reuptake
How does peripheral sensitization occur?
- Inflammation damages or destroys peripheral nerves
- Threshold for firing is lowered, as regeneration of nerve triggers development of excess Na+ and adrenergic channels.
- Peripheral neurons fire impulses spontaneously leading to pain
to recap: Central sensitization involves sensitization of descending nerves, activating pain pathways. Peripheral sensitization involves the intrinsic firing of the nerve targeted by the central pathways.
What is central vs peripheral neuropathic pain and which are the most well studied?
Distinction made between where the lesion occurs, though a given syndrome may have components of both. Example of central neuropathic pain: MS, or post-stroke pain.
Peripheral - all the most well studied neuropathic pain, including:
- Post-herpetic neuralgia
- Diabetic neuropathy
- Trigeminal neuralgia
What water balance problem can SSRIs cause?
SIADH - think of the changing of the water cooler
-> especially true with fluoxetine
How do you differentiate NMS vs serotonin syndrome?
NMS - rigidity / hyporeflexia
Serotonin syndrome - clonus and hyperreflexia