Pharmacology Local and MR Flashcards
Ester-linked Local Anesthetic drugs
- cocaine
- procaine
- benzocaine
- tetracaine
local anesthetic mechanism of action
votalge-gated Na+ channel blocker
- decrease rate of depolarization
- increase threshold for electrical excitability
Nociception
- opioids = morphine
- voltage-gated = local anesthetics
- a2 agonists = dexmedetomidine
Susceptibility factors of local anesthetics
- fiber diameter
- myelination
- fiber position
- firing frequency
Myelination and local anesthetics
myelinated nerves are blocked before unmyelinated
fiber position and local anesthetics
outer nerves in a bundle are blocked more readily than inner nerves
Firing frequency and local anesthetics
LA have a higher affinity for the active Na+ channels compared to resting
- Rapidly firing neurons are more readily blocked by local anesthetics when compared to slowly firing neurons
Ionizable group of local anesthetics
most LA are weak bases
- LA must be unpronated and neutral to permeate cellular membranes
- Protonated LA are more potent than their unprotonated counterpart
Ester-Linked Local Anesthetics
rapidly hydrolyzed
- have a shorter half life
- have a lower Vd
- are less likely to elicit systemic side effects
“local” adverse effects of LA
tissue damage
- stinging sensation due to acidic nature
- hypoxia due to co-administration of vasoconstrictor
Large doses of which 3 LA may cause metheglobinemia?
prilocaine, benzocaine, lidocaine
Vasoconstrictors and LA
epinephrine or Levonordefrin
- limits escape of LA from site of administration
- decreases the potential for systemic toxicity
- increases the duration of action at target site
3 classifications of muscle relaxants
- neuromuscular blockers
- spasmolytics
- antispasmodics
Neuromuscular blockers
- exert effects on periphery
- do not cross the BBB
Spasmolytics
used to reduce spasticity assoicated with neuromuscular disorders
- mostly exert effects within the CNS
Antispasmodics
Used to treat musculoskeletal conditions such as back bain and fibromyalgia
- exert their effect within the CNS
Neuromuscular blocker mechanism of action
bidns to and blocks nicotinic cholinergic receptors (NM) located at the NMJ
- interferes with acetylcholine action
Nicotinic cholinergic receptors are ____ and ____
ligand-gated receptors and sodium channels
Structure of Nicotinic receptors
- Made from 5 types of homologous subunits
- NN located at ganglia
Acetylcholine binding sites on nicotinic receptors
2 (alpha2)
Describe the “pore” of nicotinic receptors
M2 region within each of the 5 subunits forms the pore that is selective for Na+
- 3 negatively charged amino acid rings pull Na+ through
- Leucine ring is important in channel desensitization
Succinylcholine
Depolarizing MR
- at low concentrations, acts like ACh and depolarizes membrane
- large doses cause muscle paralysis
- rapid onset (1-1.5 min)
- short duration (5-10 minutes)
Black box warning on Succinylcholine
acute rhabdomylosis with hyperkalemia in children with undiagonsed musclar dystrophies
