MOAs Flashcards
Alcohol MOA
Binds GABAa receptor→ increased Cl- influx→ enhanced inhibitor GABA transmission
Synergistic with drugs that bind GABA at different sites: barbiturates, benzos
Increases dopamine in mesolimbic pathway (addiction)
Inhibits effect of glutamate on NMDA receptor
Naltrexone MOA for alcohol abuse
Blocks ability of alcohol to stimulate the reward pathway
Acamprosate MOA
Structural analogue of GABA→ restores disturbed GABA/glutamate balance (alcoholism) to normal
Disulfiram MOA
Inhibits aldehyde dehydrogenase→ aldehyde build up
Normal alcohol metabolism
Alcohol→ alcohol dehydrogenase (ADH)→ acetaldehyde→ aldehyde dehydrogenase (ALDH) oxidizes using NAD+→ acetate
Asians + Alcohol
lacking ALDH (aldehyde dehydrogenase)
Women + Alcohol
Lower levels of ADH (alcohol dehydrogenase)
Topiramate mechanism for alcoholism
Not understood, decreases craving and increases abstinence
Fomepizole MOA
alcohol dehydrogenase inhibitor
Barbiturates MOA
Bind GABA→ Cl- influx→ inhibitory
Produce inhibition independent of GABA: no ceiling effect
Hypnosis (CNS depressant)
Euphora→ abused
Benzodiazepines MOA
Specific site on GABAa receptor→ prolonged action
GABA dependent effects→ Ceiling effect
Flumazenil MOA
Benzodiazepine Antagonist→ competes for GABA receptor→ reverses effect of benzos and “z-drugs”
Z drugs MOA
Bind to BZ1 subtype of GABA receptor→ increased GABA-mediated inhibition
Suvorexant MOA
Antagonist at orexin receptors
Ramelteon MOA
Melatonin analogue
Chloral hydrate MOA
Converted to trichloroethanol→ similar effect as barbiturates on GABAa receptor→ sedation
Buspirone MOA
Partial agonist at postsynaptic 5-HT1a receptor (serotonin) → inhibition of cell signaling
Full agonist for presynaptic 5-HT1a receptor→ decreased release of 5-HT
Glutamate receptors are called
NMDA
also AMPA but never discussed
Glutamate causes seizures….
By activating NMDA receptors
Goal: decrease glutamate
GABA causes seizures
when GABA receptors are blocked
Goal: increase GABA
Phenytoin / Fosphenytoin MOA
Prolong inactivation of Na+ channels→ decreased glutamate activity
Carbamazepine MOA
Blocks Na+ channels→ decreased glutamate activity
Inhibits NE release + reuptake→ +/- potentiates GABA
Lamotrigine MOA
Inactivation of Na+ channels→ decreased glutamate activity
+/- inhibition of Ca++ channels
Topiramate MOA
Blocks Na+ channels→ decreased glutamate activity Some activity at Ca++ channels Potentiates GABA receptors Inhibits glutamate receptor (NMDA) \+/- Inhibits spread of seizures
Levetiracetam MOA
Binds SV2A→ apparent decrease in glutamate and increase in GABA release
Gabapentin MOA
GABA analog (but doesn’t act on receptor) May augment GABA release
Pregabalin MOA
GABA analog→ binds to alpha-2-delta subunit of voltage-gated Ca++ channels inhibiting excitatory neurotransmitter release
Tiagabine MOA
Inhibits reuptake of GABA (GAT-1) → enhances GABA activity
Vigabatrin MOA
Irreversibly inhibits GABA transaminase (GABA-T) → decreased metabolism→ increased activity
Ethosuximide MOA
Inhibits low threshold (type T) Ca++ channels→ inhibits pacemaker for rhythmic cortical damage
Valproic acid MOA
Blocks Ca++ channels and Na+ channels
+/- Enhances GABA activity
Synaptic vesicular protein (SV2A)
Binding SV2A increases GABA and decreases excitatory glutamate activity
Some glutamate targets that can be blocked
SV2A
Voltage-gated Na+ channels
Thalamic voltage gated-Ca++ channels
Increase GABA by….
Block GABA reuptake (tiagabine)
Inhibit GABA metabolism (vigabatrin)
Stimulate GABAa receptors (benzos, barbs)
Bind synaptic vesicular protein SV2A (levetiracetam)
Drugs that block Na+ Channels
Phenytoin
Lamotrigine
Carbamazepine
Valproate
Can cause SJS/TENS, screen for HLAB1502
Local Anesthetics MOA
Block Na+ channels and inhibit neuronal firing
Increase threshold for excitation and impulse conduction slows.
Binding increases→ rate of action potential declines→ complete block
A faster local anesthetic is
Smaller, lipophilic
A longer acting local anesthetic….
Binds more extensively to proteins
Elevated Ca++ makes local anesthetics
Less effective
Elevated Ca++ → hyperpolarize membrane → channels in resting state
Elevated K+ make local anesthetics
More effective
Elevated K+ → depolarizes membrane→ more channels inactivated state
Local anesthetics have a high affinity for the Na+ channel in the _______ states
Activated/open state
Inactivated state
Local anesthetics have a low affinity for the Na+ channel in the _______ state
Resting/closed state
Esters cause allergic reactions by
the P-aminobenzoic acid (PABA) metabolite
A myelinated neuron is ______ to local anesthetics than an unmyelinated neuron
Less sensitive
A myelinated neuron is ______ to local anesthetics than an unmyelinated neuron
Less sensitive
Metabolism of ester local anesthetics
rapidly metabolized by plasma butyrylcholinesterase
Mutations affect metabolism
Metabolism of amide local anesthetics
CYP450s
Bupivacaine + Cardio MOA
more lipophilic: increased binding to cardiac Na+ channels, slower dissociative times
More toxic
Cardiac effects of local anesthetics
Inhibition of Na+ and Ca++ channels→ arrhythmias, vasodilation hypotension
Why won’t sulfas work if you’re taking procaine?
PABA metabolite inhibits sulfonamide action
Benzocaine MOA
Pka 3.5→ lipophilic, always non-ionized at physiological pH→ readily transported through membrane, minimal binding to Na+ channel
topical OTC only
Secondary mechanism of cocaine
Inhibits Na+ channels (local anesthetic)
Primary mechanism of cocaine
increasing dopamine in CNS and periphery
What does a lipid sink do?
IV lipids pull lipophilic local anesthetics out of cardiac tissue in toxicity
Ropivacaine is…
S-enantiomer of bupivacaine→ less lipid soluble and cleared more rapidly
Etidocaine effects
Inverse differential block→ causes motor block before or without sensory block
Articaine is….
an Amide with an additional ester→ metabolism by plasma esterases→ decreases half life and systemic toxicity
Baclofen MOA
Agonist at GABAb receptors (Gi/o protein coupled, metabotropic)
- Open K+ channels→ hyper-polarization
- Presynaptic inhibition of Ca++ influx→ decreased transmitter release
- Inhibits adenylyl cyclase→ decrease cAMP→ decreased release of excitatory transmitters in brain and spinal cord