Movement Disorders B&B Flashcards
which components of the basal ganglia are affected by the following movement disorders?
a. Parkinson’s
b. Huntington’s
c. Wilson’s
d. hemiballism
a. Parkinson’s: substantia nigra (pars compacta)
b. Huntington’s: striatum
c. Wilson’s: striatum + globus pallidus (externus/internus)
d. hemiballism: subthalamic nucleus
_____ is a compound that destroys dopamine neurons, causing Parkinson’s disease (may be contaminant of opioid drugs —> drug-induced Parkinson’s)
MPTP: methyl-phenyl-tetrahydropyridine
[now used in lab animals to study Parkinson’s]
describe the clinical symptoms of Parkinson’s Disease (6)
- rest tremor
- bradykinesia (can’t initiate)
- shuffling gate
- stooped posture
- cogwheel rigidity of joints
- movement gets BETTER with exercise
how do each of the following drugs treat Parkinson’s?
a. carbidopa
b. entacarpone, tolcapone
c. selegiline
d. bromocriptine
e. pramipexole, ropinirole
f. benztropine, trihexyphenidyl
g. amantadine
a. carbidopa: converted to dopamine in CNS
b. entacarpone, tolcapone: COMT inhibitors (prevent L-dopa breakdown)
c. selegiline: prevent dopamine breakdown
d. bromocriptine: dopamine agonist (ergot)
e. pramipexole, ropinirole: dopamine agonist (non-ergot)
f. benztropine, trihexyphenidyl: antimuscarinic
g. amantadine: dopamine agonist + anticholinergic (also antiviral)
what is the MOA and clinical use of Sinemet?
sinemet = L-dopa/carbidopa
L-dopa crosses BBB and is converted to dopamine in CNS by dopa decarboxylase —> treats Parkinson’s
note, peripheral decarboxylase limits benefits and causes cardiac side effects (tachycardia) + N/V (vomiting center outside of BBB)…
… carbidopa inhibits peripheral decarboxylase to prevent this (still get CNS side effects - anxiety, agitation, insomnia)
describe how L-dopa + carbidopa (= Sinemet) are used together to treat Parkinson’s
L-dopa crosses BBB, converted to dopamine by dopa decarboxylase
carbidopa prevents peripheral decarboxylase to enhance benefits and decrease peripheral side effects (tachycardia, N/V)
note, CNS side effects still occur - anxiety, agitation, insomnia… therefore, given lowest dose possible
describe the peripheral vs central adverse effects of L-dopa
peripheral: cardiac effects (tachycardia), N/V (vomiting center outside BBB)… these are prevented by combining L-dopa with carbidopa (= Sinemet)
central: anxiety, agitation, insomnia… can’t be prevented, so use lowest dose possible
which vitamin should be avoided in large quantities by patients taking Sinemet?
Sinemet = L-dopa + carbidopa, treats Parkinson’s
vitamin B6 promotes conversion of L-dopa to dopamine in periphery —> side effects (tachycardia, N/V)
this isn’t really as much of a problem anymore since we started combing L-dopa with carbidopa (Sinemet) because carbidopa inhibits peripheral dopa decarboxylase
describe the consequences of long-term use of Sinemet (L-dopa + carbidopa)
long term —> motor side effects because of reduced natural L-dopa production in the CNS
creates “on/off” phenomenon - patients are dependent on drug and dyskinesia or even akinesia (frozen, no movement) can occur between doses
because of this, use lowest dose possible, but unavoidable eventually and patients can only tolerate for several years before serious side effects
what is the MOA and clinical use of entacapone and tolcapone?
treat Parkinson’s by inhibiting COMT (catechol-O-methyltransferase), which breaks down L-dopa
only work in combo with L-dopa!!
entacapone works peripherally only; tolcapone works centrally and peripherally but is very hepatotoxic
what is different between entacapone and tolcapone? which one is prescribed more often and why?
both treat Parkinson’s by inhibiting COMT (catechol-O-methyltransferase)
entacapone works peripherally only; tolcapone works centrally and peripherally but is very hepatotoxic
therefore, entacapone is used more because LFT must be monitored closely with tolcapone
name a drug that treats Parkinson’s by inhibiting COMT, but has serious hepatotoxic side effects.
now name a drug that works by the same mechanism but is used more often to avoid this adverse effect.
tolcapone: inhibits COMT peripherally + centrally, but very hepatotoxic [that is the TOLL you pay]
entacapone: inhibits COMT only peripherally, but safer
what is the effect of MAO-a vs MAO-b? how is this clinically significant?
MAO-a breaks down serotonin - inhibiting this can treat depression
MAO-b breaks down dopamine - inhibiting this can treat Parkinson’s (ex, selegiline)
what is the MOA and clinical use of selegiline?
treats Parkinson’s by inhibiting MAO-b, which breaks down dopamine in CNS (and 5HT a little - see side effects)
used to boost treatment with L-dopa/carbidopa (Sinemet)
side effects: N/V, hypotension, daytime sleepiness, serotonin syndrome, ”cheese effect”
name a drug that treats Parkinson’s by inhibiting MAO-b
selegiline: treats Parkinson’s by inhibiting MAO-b, which breaks down dopamine in CNS (and 5HT a little - see side effects)
used to boost treatment with L-dopa/carbidopa (Sinemet)
side effects: N/V, hypotension, daytime sleepiness, serotonin syndrome, ”cheese effect”
what are the side effects of selegiline? (5)
treats Parkinson’s by inhibiting MAO-b, (and 5HT a little - see side effects)
- N/V
- hypotension
- somnolence
- serotonin syndrome
- ”Cheese effect”: HTN crisis due to eating food with tyramine (red wine, aged cheese, aged meat)
what is the “Cheese effect”?
hypertensive crisis caused by eating foods containing tyramine (red wine, aged cheese, aged meat) while taking drug that inhibits MAO
MAO breaks down NT, but also tyramine - therefore, MAO inhibitors block breakdown of tyramine —> HTN
Pt is 74yo M presenting to the ED due to a hypertensive crisis. PMH includes Parkinson’s, for which the patient takes Sinemet and selegiline, and CHF, for which the patient takes a thiazide diuretic. The patient was at dinner at a nice steak restaurant celebrating their spouse’s birthday when they began to feel chest pain. Their heart exam appears normal. What might be going on?
”Cheese effect” due to selegiline
selegiline: treats Parkinson’s by inhibiting MAO-b, which breaks down dopamine in CNS, used to boost treatment with L-dopa/carbidopa (Sinemet)
MAO inhibitors prevent breakdown of tyramine (red wine, aged cheese, aged meat) —> HTN
how is trihexyphenidyl used to treat Parkinson’s? given what kind of drug this is, what are the expected side effects?
anti-muscarinic that is helpful for treating tremor
tremor is often the first presenting symptom
side effects: sedation, dry mouth
Tremor often is the first presenting sign of Parkinson’s. How is this typically treated?
trihexyphenidyl: anti-muscarinic that treats tremor
side effects: sedation, dry mouth
how are ropinirole and pramipexole used to treat Parkinson’s?
dopamine agonists used to treat bradykinesia, rigidity
name 2 dopamine agonists used to treat bradykinesia and rigidity caused by Parkinson’s
- ropinirole
- pramipexole
Patients with Parkinson’s often present first with tremor. This can be treated with ________. Once patients develop bradykinesia and rigidity, they are often treated with _______. If these become ineffective, patients are then usually treated with a combination of levodopa and carbidopa called _____.
Patients with Parkinson’s often present first with tremor. This can be treated with trihexyphenidyl (anti-muscarinic). Once patients develop bradykinesia and rigidity, they are often treated with ropinirole or pramipexole (dopamine agonists) If these become ineffective, patients are then usually treated with a combination of levodopa and carbidopa called Sinemet
what surgical intervention is used to treat Parkinson’s?
deep brain stimulation: high frequency energy suppresses neural activation of basal ganglia
this is used more often in young patients because of toxicity risk from long-term use of L-dopa/carbidopa
stimulation of globus pallidus internus or subthalamic nucleus for bradykinesia or rigidity; stimulation of VL for tremors