Anti-parkinsons drugs Flashcards
dopamine synthesis originates from which amino acid
tyrosine
which transporter is used for tyrosine transport across BBB
SYSTEM L
Na+ independent
RLS in dopamine synthesis
tyrosine hydroxylase
DOPA decarboxylase
converts DOPA –> dopamine
D1 2nd messenger system
G(s) = increased adenylyl cyclase
D2 2nd messenger system
G(i) = decreased adenylyl cyclase - inc K+ conductance, dec Ca2+ conductance
parkinson’s tx goals
1) restore dopamine actions
2) antagonize acetylcholine
dopamine precursor
levodopa
levodopa
stereoisomer of dopa
dopamine/norepinephrine precursor
good for pt with early disease = requires presence of residual dopaminergic neurons for conversion of levodopa–> dopamine
carbidopa
dopa decarboxylase inhibitor
doesn’t cross BBB
given with levodopa to dec peripheral metabolism to dopamine
levodopa use
symptomatic use - only lasts while drug is in body
levodopa MOA
transported into CNS, there is converted to dopamine
a lot of it is decarboxylated to dopamine in periphery –> AE: n/v arrhythmias, hypotension
sinemet
carbidopa + levodopa prep
levodopa PK
food delays appearance in plasma == certain amino acids can compete for absorption from gut and for transport through BBB
levodopa metabolites
via COMT = 3-o-methyl dopa, 3-methoxytyramine
–> HVA
levodopa fluctuations in response
1) wearing off rxn = related to time of intake
2) on-off phenomenon = unrelated to timing - may benefit from apomorphine
levodopa contraindicatiosn
B6 - cofactor for dopa decarboxylase = inc peripheral metabolism
MAOI = HTN crisis
not used in psychotic pt
angle closure glaucoma
arrhythmias
which class doesn’t depend on capacity of nigrostriatal neurons
dopamine receptor agonist
classes of dopamine receptor agonists
1) ergot dopamine agonists
2) nonergot dopamine agonists
bromocriptine
D2 agonist (ergot dopamine)
pramipexole
nonergot dopamine agonists
ropinirole
nonergot dopamine agonists
nonergot dopamine agonists
better for younger pt
older pt more vulnerable to AE of dopamine agonists
rotigotine
nonergot dopamine agonists
available as transdermal
which nonergot dopamine agonists is used as a transdermal
rotigotine
AE of dopamine agonists
GI: anorexia, n/v, constipation, peptic ulcer bleeding
CV: postural hypotension, arrhythmias, periph edema
dyskinesias: abnormal movements
mental disturbances: confusion, hallucinations
misc:
ergot - pulmonary infiltrates, pleural fibrosis, erythromelalgia
nonergot - uncontrollable somnolence
dopamine agonists contraindications
pt with psych hx or recent mi
peripheral vascular dz
peptic ulceration
rescue therapy for nonergot dopamine agonist
apomorphine
apomorphine
nonergot dopa agonists rescue
used in “off” epsidoes of akinesia
emetogenic (given with antiemetic trimethobenzamide)
AE: QT prolonged, dyskinesias, drowsiness, sweating
MAOI
deprenyl/selegiline
selectively irreversibly inhibits MAO-B
retards breakdown of DA
enhances levodopa effects - and can dec its dose
levodopa adjunct*
metabolized to amphetamine –> insomnia
deprenyl
MAOI
rasagiline
MAOI
MAO-B inhibitor selective
use of carbidopa and levodopa, increases what substance peripherally?
3-o-methyl dopa
also competes with levodopa for an active transporter across intestinal mucosa and BBB
tolcapone
COMT inhib
entacapone
COMT inhib
COMT inhib function
dec levodopa metabolism
dec plasma 3-o-methyldopa
inc levodopa uptake – higher DA levels in brain
COMT AE
hepatic necrosis **tolcapone
entacapone = not hepatotoxic - preferred
amantadine PD application
increases synthesis, release/re-uptake of dopamine from surviving neurons
amantadine AE
restlessness
hallucination
aucte toxic psychosis
peripheral edema (give diuretics)
livedo reticularis - redness to skin
anti-muscarinics for PD
adjuvant
improve tremor, rigidty
little effect on bradykinesia
AE: mood changes, xerostomia, pupillary dilation, hallucination
contraindic: glaucoma, BPH, pyloric stenosis
DOC for PD
levodopa + carbidopa
2nd most effective drugs for PD
dopamine agonists
addition of which drug in addition to levodopa to reduce motor fluctuations in adv PD pt
COMT-inhib or MAO-B inhib