Drugs- Movement Disorders (Kinder) Flashcards
parkinsonism tremor
tremor at rest
associated with rigidity and impairment of voluntary activity
postural tremor
tremor during maintenance of sustained posture
athetosis
c) Athetosis – abnormal movements which are slow and writhing.
tics
sudden, involuntary, coordinated abnormal movements; tend to occur repetitively, particularly about the face and head; can be suppressed voluntarily for short periods of time.
may be single, multiple; transient or chronic
what is Gilles de la Tourette’s
chronic multiple tics
4 main features of parkinson’s
rigidity, bradykinesia, tremor, and postural instability
what is the pathology in Parkinson’s
iii) Loss of dopaminergic neurons in substantia nigra results in disinhibition of GABAergic neurons and disturbed movement.
These neurons normally inhibit output of GABAergic cells in the corpus striatum, while cholinergic neurons (ACh) exert an excitatory effect on GABAergic neurons
this is in the indirect loop using D2
does dopamine cross the BBB?
no
If given peripherally, does not have any therapeutic effects in parkinsonism.
what is Levodopa
precursor of dopamine
does enter the brain via LAT (L-amino acid transporter)
once in the brain it is decarboxylated to dopamine
stimulates D2 receptors
when is the best time to take levodopa
30 - 60 min before meal
carbidopa
dopa decarboxylase inhibitor - reduces peripheral metabolism of levodopa
results in higher plasma levels, t1/2, and increased availability for CNS entry
reduces side effects of L-dopa
therapeutic use of Levodopa
i) Does not stop progression of Parkinson’s disease but may lower mortality with early initiation.
ii) Best results obtained in 1st few years of treatment.
iii) Benefits begin to diminish after 3-4 years of therapy (regardless of initial response).
(1) Daily dose may have to be decreased overtime to avoid ADRs at doses initially well-tolerated.
(2) Some may become less responsive to levodopa; perhaps due to loss of dopaminergic nigrostriatal nerve terminals.
iv) 1/3 of patients respond very well, 1/3 respond less well, and 1/3 are either unable to tolerate the medication or do not respond at all.
what are the ADR”s of levodopa
4 main areas
Gi- anorexia, nausea, vomiting
CV- postural hypotension
- arrythmias- due to increased peripheral catecholamine formation
- HTN –> when taking large doses of L-dopa or in combination with MAOI’s or sympathomimetics
Behaviorial
-depression, agitation, insomnia, somnolence, confusion, delusions/hallucinations, nightmares
Dyskinesia
-chorea of face and distal extremities
what is the on-off effect and wearing off effect of L-dopa therapy and what can happening with increased frequency as treatment continues
wearing off–> at then end of dose of L-dopa an akinesia can develop
there is improvement of mobility with L-dopa for a period of time (1-2 hours) but rigidity and akinesia return at the end of the dosing interval
on-off
- (i) Off-periods of marked akinesia alternate over the course of few hours with on-periods of improved mobility but often marked dyskinesia.
(ii) Exact mechanism unknown, most likely to occur in those who responded well initially.
what are 2 DDI’s of L-dopa
i) Pyridoxine (vitamin B6) – increases extracerebral metabolism; may prevent therapeutic effect unless peripheral decarboxylase inhibitor (carbidopa) also given.
ii) MAOIs – hypertension; do not give if taking MAOIs or within two weeks of MAOI discontinuation.
what are MAOI’s
inhibit MAO (monoamine oxidase inhibitors)
MAO-A preferentially deaminates serotonin, melatonin, epinephrine, and norepinephrine. MAO-B preferentially deaminates phenethylamine and trace amines. Dopamine is equally deaminated by both types
inhibiting an MAO leads to increased availability of the substance (dopamine)
if a patient doesn’t repond well to L-dopa how will they respond to dopa agonist
not well
where is the site of action of dopamine agonists
dopamine postsynaptic receptor
bromocriptine
dopamine agonist D2
iii) Therapeutic use: additionally approved for treatment of endocrine disorders (e.g., hyperprolactinemia, prolactin secreting adenomas, acromegaly
pramipexole
Mirapex
dopamine agonist at D3
dose adjust in renal disease
iii) Therapeutic use: additionally approved for the treatment of moderate-to-severe, primary, restless legs syndrome (RLS).
Ropinirole
(requip)
dopamine agonist D2
ii) PK: metabolized by hepatic CYP450 enzymes (primarily CYP1A2); co-administration with agents that are also metabolized by CYP1A2 may reduce the clearance of ropinirole.
rotigotine
dopamine agonist
i) Approved for early Parkinson’s disease; may provide more continuous dopaminergic stimulation.
ii) May cause serious application site reactions.
apomoprhine
dopamine agonist
what are the ADR’s of Dopamine agonists
GI- n/v, anorexia
CV- postural hypotension (particularly at initiation)
Dyskinesia
Mental disturbance-(1) Disorders of impulse control (exaggeration of previous tendency or as new phenomenon) may lead to compulsive gambling, shopping, betting, sexual activity, and other behaviors.
what is a particular ADR of ergot derivatives (Bromocriptine)
painless digital vasospasm
pleural and retroperitoneal fibrosis have been reported with bromocriptine use
in pt’s taking pramipexole or ropinirole (non ergot derivatives dopamine agonists) what is a particular side effect
(2) Rarely, patients who are taking pramipexole or ropinirole may feel the uncontrollable tendency to fall asleep at inappropriate times.
what are the contraindications for taking dopamine agonists x4
history of psychotic illness
recent MI
active peptic ulcer disease
best avoided in PVD (ergots)
Rasagiline
Selegiline
Monoamine oxidase inhibitors (MAOI’s)
what does monoamine oxidase A metabolize
NE
serotonin
dopamine
what does monoamine oxidase B metaboilze
dopamine selectively