Exam 3 - Lecture 27 & 28 General anesthetics, anxiolytics & sedatives, hypnotic drugs Flashcards
General anesthetics
Can induce a state of systemic anesthesia, lack of feeling
Anxiolytics
reduce anxiety
Sedatives (tranquillizers)
CNS depressants that induce calm
Hypnotics (soporifics or sleeping pills)
Typically psychoactive drugs that induce sleep
Modes of Drug delivery Anesthetics
Inhalation or injection
What is MAC
MAC - Minimum alveolar concentration, equivalent of potency
The lower the MAC, more potent the anesthetic
MAC is ~20% higher in red heads, due to mutations in melanocortin-1 receptor
Moving MAC curve left
Hypoatraemia (low sodium), increased age, pregnancy, opioid use, benzo, intoxication
Moving MAC curve right
Chronic amphetamine, cocaine, ephedrine, chronic alcohol use, decreased age
MAC: Zur Theorie def Alkoholnarkose Arguments for
Simple, diverse structures argues against obvious SAR
Suggest physicochemical mechanisms of action;
Bilayer thickness, curvature, fluidity
MAC: Zur Theorie def Alkoholnarkose Arguments against
Stereoisomers have similar oil:gas partition coefficients but different MAC
Many lipophilic drugs are not anesthetics
Change in body temp alter membrane fluidity but is not anesthetic
Changes in chain length increase lipophilicity but not MAC
Using EEG to measure anesthesia?
Distinction between anesthesia and sleep
If sleeping you can be arousable but if you’re anesthetized then you are unarousable.
Nonphysiological Oscillations in anesthesia
physiological Oscillations in Sleep
MAC value
The lower the better it will cross from Alveoli, into blood and then into Brain.
For example, drug with MAC 0.47 will cross better than one with a MAC of 2.3
Other considerations besides MAC for potency
The age and life-style of the patient
How fat
Other medications
Hair color
Blood/Gas partition coefficients and induction/recovery rate
The lower the blood/gas partition coefficient, the faster the induction of effect and recovery rate
Effect of isoflurane on Nav Channels
Inhibiting Nav channels in CNS neurons reduces excitability
Concentration dependent,
decreasing excitability in the brain
Effects on K2P channels
Activating K2P channels in CNS neurons reduces excitability
Open channel = less excitability, decreasing epilepsy and increasing anesthesia effects
K2P channel structure
not voltage gated
2 subunits
Subunit made of 4 Transmembrane proteins, 2 P loops
Ether
Cheap & easy to make, no longer recommended by WHO
MoA:
Positive Allosteric modulator at GABAa receptor
Agonist at GABAa-receptor at higher dose
Sympathomimetic effect, maintains BP
Side effect:
Post operative nausea and vomiting
Seizures and tremors
V flammable and explosive mixed with Oxygen
Nitrous Oxide
Laughing gas, non-flammable roomtemp
MAC >100%
Fast acting, can cause euphoria
MoA:
Weak PAM of GABAa and glycine receptor
Weak activator K2P, blocker NMDA, AMPA, kainite and GABAc
Halothane (fluothane)
MoA: #1 - Agonist at GABAa receptors Agonist at glycine receptors Antagonist at NMDA receptors and Nav channels Activates K2P channels
Side effect:
Arrhythmia
Respiratory depression
Hepatoxicity (metabolized into trichloroacetic acid = 30-70% mortality)
Not used in US anymore
Isoflurane (forane)
Widely used, non explosive
MoA: #1 Agonist at GABAa receptors Agonist at glycine receptors Antagonist at NMDA receptors and Nav channels Activates K2P channels
side effect:
Cardiac arrhythmia
Respiratory depression
Sevoflurane (Ultane, sojourn)
widely used, expensive bc hard to make
MoA:
#1 Positive allosetic modulator at GABAa (and GlyR?) receptors
NMDA receptor antagonist
Activated K2P channels
side effect:
Amongst safest agents available
All gas anesthetics associated with neurotoxicity
Neurodev/behavior abnormalities in kids?
Etomidate change % in BP/Heart Rate
- BP (low, ~2%)/ + Heart Rate