Parkinson's Flashcards
Parkison’s
S/S
- Bradykinesia/akinesia
- Tremor (pill-rolling)
- Rigidity (cogwheel)
- Impairment of postural balance
*mask face, shuffling gait, autonomic, weight-loss, anorexia, depression
Parkinson’s
Pathology
- Dop neuron degeneration
- > 65 years
- more cells lost - worse disease
Parkinson’s
CNS pathway
Nigrostriatal projection DEGENERATE
*substantia nigra –> Striatum
Parkison’s
problem with replacing dopamine
Mesocorticolimbic = Ventral tegmental –> nucleus accumbens
Too much = psychosis
Parkison’s
Smoking
Neuroprotective
GABA pathway
Nigrostriatal = Dopamine (D2) inhibit GABA DIES
Cholinergic = Ach (M) excitatory
MPTP
Goes to MPP+, selectively destroys Substantia Nigra neurons
Selegiline
Stops development of parkinson in monkeys
Suspected source of parkinson’s?
Pesticides, chemical in (country?)
Pharm target =
Imbalance between striatal cholinergic + dopaminergic activity
Pharm strategies
- Dopa replacement
- Enzyme inhibition
- MAO-B inhibition
- Up Dopa release, block reuptake
- stim dopa receptor
- anticholinergic (m)
Dopamine replacement
- L-DOPA levodopa (dopa precursor)
- Use Aromatic amino acid transporter
- 95% lost in periphery
Dopa can’t cross
Peripheral Dopa Toxicity
- Nausea (CTZ)
- Cardiac palpitations + arrythmia (b-agonist)
- Postural HypoTN (vascular DA receptor)
DOPA
CNA toxicity
- Psychotic (accumbens, limbic system)
- Dyskinesias (striatum)
- On-off phenomenon (variable CNS metabolism)
- -Off = dystonia
- -ON = good but dyskenesia
Control on -off phenomenon
Enzyme inhibition =
COMT
MAO-B
L-DOPA
Contraindications
- Psychosis
- Melanoma
- Narrow angle glaucoma
look at slides for info
L-Dopa
Rx interaction
- Non-selective MAO inhibitors - gets MAO-A (selective for MAO-B ok)
- Vitamin B6 (up peripheral metab=More S.E.)
- anti-psycs (work against each other)
B6 effect on L-DOPA
Ups levodopa conversion to DA peripheral
L- DOPA
Clinical problems
- Tolerance
- Gradually degenerating CNS nerves = can’t convert L-Dopa
- Limited effectiveness (1/3)
L-DOPA best helps with these symptoms
Bradykinesia
Akinesia
Use L-Dopa in beginning?
Physicians prefer to start later (tolerance)
Cardidopa
Mech
Inhibits l-aad enzyme which converts L-dopa to peripheral Dopa = more goes in CNS
*COMT up (shunt) = inhibit too
Inhibiting COMT
- Tolcapone - ALSO IN CNS (helps w/ ON OFF SYNDROME )
* Entacapone
Enzyme inhibitors (cardidopa, -capone)
Advantages
- reduce L-dopa dose
- peripheral side effects reduces
- on-off reduced
Enzyme inhibitors (cardidopa, -capone)
Disadvantages
CNS toxicity of L-dopa
Enzyme inhibitors (cardidopa, -capone)
SIde effects
Due to up DA
Rx preparations
- L-DOPA
- Carbidopa
- Sinemet (cardidopa + L-DOpA)
COMT inhibitor
- entacapone (no in CNS
- tolcapone (liver toxicity)
Nausea caused by
Peripheral Dopa ????
How to inhibit MAO-B
Selegine
Rasagiline
Inhibiting MAO
Mech
MAO-B predominate form in striatum
MAO-A = don’t touch - need to handle catecholamines (avoid HTN)
Selegiline
May reduce neurotoxic metabolite
*Eldepryl
Nicotine
Neuroprotective + releases DA
MAO-B
S.E.
- UP CNS dopa effects
- Oral selegiline causes amphetamine metabolism
- no w/ non-selective MAO inhibitor
Direct D2 stimulators
No dopamine releasing neuron
- Ropinirole
- Pramipexole
- Bromocriptine
Direct D2 stimulator
On-off
NO ON-OFF
Skipping neuron
D2 ags
Use
- L-dopa dose reduced
- No on off
- Refractory L-dopa patient
- Used before L-dopa
D2 agonist
Contraindications
- Psychosis
- recent MI, PV dz
- peptic ulcer (N/V)
Enhance DA release + inhibit reuptake
*Amantadine
Need to have neurons to release dopa
Amantadine
Uses
- initial therapy
- LESS bradykinesia, rigidity, tremor
- L-dopa/cardidopa fluctuations/dyskinesias
- NMDA receptors - improve cognition
Amantadine
S.E.
Mild
OD = toxic psychosis
Antimuscarinics
Rx
Benztropine
Trihexyphenidyl
Antimuscarinic
Uses
- combo w/ L-dopa
- mild parkison’s (tremor only)
- better on tremor and rigidty than bradyinesia
Antimuscarinics
contraindications
- Prostatic hypertrophy
- Obstructive GI disease
- Narrow angle glaucoma
Early non-pharm treatment
Lifestyle / exercise
For Mild symptoms Tx/ initial tx
- MAO-B inhibtors
- Amantadine
- Anticholinergics
Younger = D2 agonist
for Moderate symptoms
Levodopa
D2 agonist
Antimuscarinic
S.E.
Peripheral = dry mouth, blurred vision, Blurred vision, mydriasis, urinary retention, nausea
Central = Drowsiness, mental slowness, Inattention, Restlessness
D2 agonist
S.E
Peripheral = nausea (CTZ), hypoTN
CNS =
Dyskinesia (less than L-DOPA)
Psychosis (more than L-DOPA)