Spasticity Flashcards
Activation of the GABAa receptors is inhibitory via an increase in ______ ______
chloride conductance (diazepam)
Describe the two types of GABAb receptors and how they are inhibitory
- Presynaptic receptors are inhibitory by mediating a decrease in Ca2+ conductance
- Postsynaptic receptors are inhibitory by increasing K+ conductance when activated.
Baclofen
Baclofen acts on which receptors:
GABA B (recall presynaptic Ca2+ and postsynaptic K+)
May also reduce substance P in the spinal cord
Max dose of baclofen
80mg/day is FDAs recommended max. Up to 300mg/day have been reported.
Diazepam acts on which receptors:
not substitute for GABA but rather facilitates GABA’s effects on the GABA A receptor (results in membrane hyperpolarization.
Increases chloride conductance.
Overdose of valium can be treated with what
Flumazenil
Dantrolene MOA
acts peripherally in the striated muscle by blocking the release of Ca2+ from the sarcoplasmic reticulum.
Fast twitch motor units are more sensitive that slow twitch
Max dose dantrium
400mg/day
Clonidine MOA
(AKA catapres)
Central acting alpha2-adrenergic agonist with effects in the locus ceruleus. In the spinal cord, provides presynaptic inhibition of sensory afferents.
Clonidine can impair _____ tachycardia. What complication arises?
hypoglycemia-induced tachycardia in diabetics – thus delaying the diagnosis of clinically significant hypoglycemia in this population.
Max dose clonidine
start with 0.05mg BID and increase up to 0.4mg/day
Tizanidine MOA
Central acting Alpha-2 adrenergic agonist, chemically related to clonidine.
Binds to alpha 2 receptors both spinally and supraspinally.
thought to act by enhancing presynaptic inhibitory modulation of spinal reflexes.
Less potent than clonidine in regards to BP.
Tizanidine is contraindicated with which IV medication? Why?
IV ciprofolxacin – due to inhibition of cytochrome P450
Max dose tizanidine
36mg/day
Cyproheptadine MOA
(Periactin) – nonselective histamine and serotonin antagonist. Some trial has demonstrated comparable anti-spasticity effects to baclofen and clonidine. Primarily used in SCI population.
How do local anesthetics work during diagnostic nerve blocks
They work by blocking the voltage-gated sodium channels in the axon. This prevents depolarization of the axon membrane an interrupts transition of the signal along the axon.
Chemoneurolysis agents:
How do they work?
Phenol, ethyl alcohol
Induce demyelination and axonal destruction via protein denaturation and axonal necrosis.
Phenol: common concentrations used for chemoneurolysis?
2-7%
for chemical denervation, higher concentrations (>5%) are required.
The effects of this increased concentration are neurolytic due to axonal destruction, typically lasting >6 months.
Ethyl Alcohol: common concentrations for chemoneurolysis?
45-100%
Less commonly used than phenol for neurolysis but is less toxic.
What is the dose limit of phenol?
20-30mL of 5%.
8.5grams of phenol can be a lethal dose, causing convulsions, CNS depression, and cardiovascular collapse.
Patient can also get skin sloughing with phenol.
How does all botox work (generally?)
all seven serotypes affect the NMJ where they produce denervation by blocking the presynaptic release (but not the production) of acetylcholine primarily at the terminal portion of the motor nerve.
Name the 7 types of botox and which part of the snare complex they cleave
A,C,E: snap-25
B,D,F,G: synaptobrevin
C: also does syntaxin
Botox should not be performed if patient is taking ____ or ____ abx
aminoglycoside or spectinomycin
Initial safe dose of botox:
400U total or 6U/kg for an adult.
In kids, doses of 4-8U/kg are commonly used (400 units considered as max body dose)
The ratio of baclofen concentration at the level of the spinal cord for intrathecally administered baclofen compared to orally administered baclofen is approximately:
100:1
Typical starting dose for pump?
double the effective trial dose.
____ may be given to reverse the respiratory depression caused by baclofen overdose
anticholinesterase physostigmine (2mg IV)
