Glossary of Kap Pharm CNS drugs 2

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What are the inhaled anesthetic drugs?
nitrous oxide, halothane, isoflurane, and the "-fluranes"
What is the MAC value of an anesthetic?
the measure of anesthetic potency, is the minimal alveolar anesthetic concentration (% of inspired air) at which 50% of patients do not respond to a surgical stimulus.
What are the MAC values for the main inhaled anesthetics?
Halothane = 0.8
Isoflurane = 1.3
nitrous oxide = >100%
Which a MAC of over 100% why is NO used?
MAC values are additive
What are the circumstances which lower the MAC value?
lower in elderly and reduced by other drugs including opioids and sedative-hypnotics
What is the mech of action of the inhaled anesthetics?
mechanism of action may involve interaction with neuronal membrane lipids leading to inhibition of ion flux
What determined the rate of onset and recovery of inhaled anesthetics?
High blood solubility meas it takes longer to achieve a partial pressure that allows movement from the blood into the CNS.
Thus, high blood gas solubility ratio = slow onset

If the drug has a high solubility it will also take longer to get out of the blood once the anesthesia ends
What inhaled anesthetics have been developed which have low blood gas solubility rations, affording both rapid onset of anesthesia and rapid recovery
desflurane and sevoflurane
What are the actions of inhaled anesthetics?
-lower response to increased pCO2
-increased cerebral blood flow and relax uterine smooth muscle

-Vasodilation and some cardiodepression (hypotension) - although haloperidol may sensitize myocardium to catecholamines

-malignant hyperthermia (rare) with halogenated agents in combination with NM blockers

-Halothane associated hepatitis
What is the use of thiopental?
rapid-onset and short acting barbiturate used mainly for induction
What are the actionso f theopental?
decreased respiratory and cardiac function, but no increased cerebral blood flow
How is thiopental metabolized?
Rapid recovery via redistribution from CNS to peripheral tissues, but liver metabolism required for elimination
What is midazolam and what is it used for?
IV benzodiazepine for preop sedation and in anesthesia protocols
What are the effects of midazolam?
anterograde amnesia and decreased respiratory function
What is a drug given to assist in the recovery from midazolam?
What is the action of Ketamine?
rapid onset and short duration - "dissociative anesthesia" with amnesia, catatonia, and analgesia
What is unique about ketamine?
What are the adverse effects of ketamine?
emergence reactions (bad dreams, hallucinations)
What is one way of decreasing the effects of ketamine?
give a benzodiazipine before hand.
Which drug has a very rapid onset and recovery, plus antiemetic effects and is frequently used?
What is propofol used for?
induction and maintenance, especially outpatient surgury
What is the main opioid analgesic?
What is the main adverse effect of fentanyl?
chest wall rigidity with IV use
What is the action of fentanyl?
short duration IV, oral and patch forms
Which drugs in combination make upu Neurolept anesthesia?
fentanyl+droperidol+nitrous oxide
What are the intravenous Anesthetics?
Thiopental, Midazolam, Propofol, Fentanyl, Ketamine
What is a characteristic of local anesthetics and what are they used for?
weak abaes for regional anesthesis via infiltration near nerve bundles, or by epidural and subarachnoid injection
What are the two groups of drugs that make up the local anesthetics and that are the drugs in each group?
Esters - procaine, cocaine, benzocaine

Amides - lidocaine, bupivacaine
What are the esters metabolized by?

amides metabolized by?
esters - plasma and tissue esterases

amides - liver
What determines whether a locat anesthetic is able to cross membranes?
whether it is in it's ionized (protonated) or nonionized (nonprotonated) form
Which form for the drugs bonds to the Na channel and where is the Na channel located?
Ionized (NH3+)forms bind to a component of the Na ion channel located inside nerve membrane

For access to its "target" the local anesthetic must first cross the lipid bilayer and it does so in its non-ionized (NH2) form
What is the response of vasculature to a local anesthetic?
and what is the remedy to this?
vasodilation, except with cocaine
thus local anesthetic are often gives with alpha 1 receptor agonsits
Which fibers are most sensitive to local anesthetic?
Which fiber type?
smaller diameter and high firing rates (state-dependent)

Myelinated fibers are also more sensitive. But our only nonmyelinated fiber is Type C, which is small and highly firing, which makes it very vulmnerable
What are type C fibers involved in?
nociception (pain impulses)
What is the order of fiber type sensitivity to Anesthetics?
Type B and C > Type A Delty > type A beta and gamma > type A alpha
What are the adverse effects of local anesthetics?
neurotoxicity - dizziness, nystagmus, sensory impairment, SEIZURES (like lidocaine
-decrease CV parameters, except cocaine
-Allergies - esters via PABA formation
What is the pufferfish toxin and what is it's mechanism?
tetrodotoxin binds externally to the "ready state" of Na channels in both cardiac and nerve cell membranes and block the influx of Na, thus PREVENTING conduction
What is the exotic fish, Moray eel toxin and what is it's mechanism
Ciguatoxin binds in the Na channel, keeping it open to cause a persistent depolarization and channel inactivation
What is the South American frogs toxin and what is it's mechanism?
Batrachotoxin binds in the Na channel, keeping it open to cause a persistent depolarization and channel inactivation
What is the red tide/shellfish toxin and what is it's mechanism?
saxitoxin binds externally to the "ready state" of Na channels in both cardiac and nerve cell membranes and block the influx of Na, thus PREVENTING conduction
What are the actions of nicotinic receptor antagonists?

reversed by?
Non-depolarizing (competitive)

decrease frequency of Na channel opening at skeletal endplate causing progressive muscle paralysis

Reversed by ADhE inhibitors
What is the action of D-tubocurarine?
blocks ANS ganglia and releases histamine, thus decreasing BP
What serious analgesic situation is tubocurarine associated with?
malignant hyperthermia
What are the nicoting receptor antagonist drugs?
Any drug that ends in "onium" or "curium"
What is the Nicotinic receptor agonist and what is it's course?
Depolarizing (noncompetitive) acting in 2 phases:
phase 1: brief stimulation = fasciculations
Phase 2: depolarization = flaccid paralysis, not reversed by AChE inhibitors
What is significant about the metabolism of succinylcholine?
short duration since rapidly inactivated by esterases....genotypic veriants with low enzyme activity can greatly increase the duration of succinylcholine action
What are unique characteristics about succinylcholine?
low dose = decreased HR (vegal)

High dose = increased HR (ganglionic stimulation)

Hyperkalemia = implicated in malignant hyperthermia
What is the action of spasmolytics?
reduce excessive muscle tone or spasm in acute muscle injury and CNS dysfunction
What would spasmolytics be used?
cerebral palsy, MS, stroke
What are the drugs used as spasmolytics?
Benzodiazepines, Baclofen, and Dantrolene
What is the mechanism for benzodiazepine spasmolytics?
facilitate BABA at BABAa receptor, thus decreasing tonic output of primary spinal motoneurons
What is the mechanism of baclofen?
direct agonist at GABAb receptors in spinal cord. Activation of GABAb receptors leads to increased efflux of K and thus hyperpolarization and inhibition
What is the drug used to treat malignant hyperthermia?
Waht is the mechanism of Dantrolene?
blocks release of Ca from SR

Thus it has direct action on the skeletal muscle

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