!Drugs For Movement Disorders Flashcards
Levodopa and combinations
Levodopa
Carbidopa
Levodopa and carbidopa
Dopamine receptor agonists
Apomorphine
Bromocriptine
Pramipexole
Ropinirole
Monoamine oxidase inhibitors
Rasagiline
Selegiline
Catechol-O-methyltransferase inhibitors
Entacapone
Tolcapone
Amantadine
Amantadine
Anticholinergic drugs
Benztropine Biperiden Orophenadrine Procyclidine Trihexyohenidyl
Miscellaneous agents
Riluzole
Reserpine, tetrabenazine
What are the pathophysiological hallmarks of Parkinson’s disease
Loss of pigmented, dopaminergic neurons of the substantia nigra, with the appearance of intracellular inclusions known as Lewy bodies
Under normal conditions, dopaminergic neurons originating int he substantia nigra inhibit the GABAergic output from the ___ while cholinergic neurons exert an excitatory effect on GABAnrgic neurons
Striatum
The selective loss of dopaminergic neurons in patients with PD result in __ of GABAergic neurons and disturbed movement
Disinhibition
Based not he pathophysiology of PD, individuals with PD may be treated with what
Dopamine
Agonists and/or anticholinergic agents
Normal dopaminergic substantia nigra system
Neurons originating int he substantia nigra normally inhibit GABAergic output from he striatum whereas cholinergic neurons exert an excitatory effect
_lose dopamine in PD
Agents to treat dopamine
Levodopa
Dopamine receptor agonists
Monoamine oxidase inhibitors (MOA)
Catechol-O-methyltransferase COMT inhibitors
Apomorphine
Amantadine
Anticholinergic drugs
What is levodopa
Immediate metabolic precursor to dopamine
Levodopa enters the CNS via an ____. Does it cross the BBB
L amino acid transporter LAT
No
MOA levodopa
Agonist at dopamine receptors
What is the half life of levodopa. Why
1-2 hours
Rapidly absorbed from the small intestine with a peak plasma concentration usually between 1-2 hours after oral does
Only _% of administratered levodopa actually enters the brain unaltered (the remainder is metabolized extracerebreally, predominantly be decarboxyation to dopamine)
1-2%
Coadministration of levodopa with a __ __ ___ that does not cross the BBB (__) results in reduced peripheral metabolism, increased plasma levels, increased half life, and increased levodopa available for entry into the brain
DOPAMINE decarboxylase inhibitor
Carbidopa
Coadministation of levodopa with __ may reduce the daily requirements of levodopa by approximately 75%
Carbidopa
Clinical use for levodopa
Parkinsonian syndrome; does not stop the progression of PD but does lower mortality rate wen initiated early in the disease
The best results of levodopa are when
First few years..then wane off
Wearing off phenomenon
Can occur during long term treatment where each dose of levodopa effectively improves mobility for a period of time (1-2) hours but rigidity and akinesia return rapidly at the end of the dosing intercal; increasing the dose and frequency of administration can improve symptoms , but this is often limited by the development of dyskinesia (distortion or impairment of voluntary movement)
Does everyone respond to levodopa
1/3 yea
1/3 less
1/3 cant tolerate or do not respond at all
GI effects levodopa
If given without a peripheral decarboxylase inhibitor causes anorexia, nausea, and vomiting (due to activation of the chemoreceptor trigger zone) in 80% of patients; combo of levodopa/carbidopa causes less frequently and less troublesome GI side effects
CV effects levodopa
Postural hypotension (frequently asymptomatic) can occur but often dimishes with continuing treatment . Hypertensioncan occur when taking large doses of levodopaor levodopa in combination with nonselective monoamine oxidase inhibitors or sympathomimetics
Dyskinesia levodopa
Can occur in 80% of patients. Choreoathetosis of the face and distal extremities is the most common presentation
Behavioral effects levodopa
Depression, anxiety, agitation, insomnia, somnolence, confusion, delusions, hallucinations, nightmares, euphoria, ,other changes in mood or personality have been reported. Atypical antipsychotic agents (clozapine, olanzapine, quetiapine, risperidone) are able to help counteract behavioral complications
Fluctuations in response and the on-off phenomenon with levodopa
Can occur due to the timing of the dose (wearing off phenomenon,) or due to reasons unrelated to dose timing (on-off phenomenon). In the on-off phenomenon, off periods of marked akinesia alternate over the course of a few hours with on periods of improved mobility but often marked dyskinesia (exact mechanism is unknown)
Subcutaneous injections of ___ may provide temporary benefit to those patients with severe off periods
Apomorphine
MOA and levodopa
Patients taking MOA inhibitors may experiencehypertensive crisis when combined with levodopa
Who is levodopa contraindicated in
Psychotic patients, angle closure glaucoma(can be used in open), history of melanoma or suspicion of undiagnosed lesion(is a precursor of skin melanin); use with caution in patients with active peptic ulcer due to possibility of GI bleeding
___ __ ___ have a lower incidence of the response fluctuations and dyskinesia that occur with long term levodopa therapy, although patients who don’t respond well to levodopa generally don’t respond well to dopamine agonists
Dopamine receptor agonists
Dopamine receptor agonists can be administered in addition to __/__ and in patients who are taking levodopa and who have end of dose akinesia or on off phenomenon
Levodopa/carbidopa
What are the dopamine receptor agonists
Bromocriptine
Pramipexole
Ropinirole
Bromocriptine
Ergot alkaloid derivative that is a D2 agonist
What else can bromocriptine be used for besides parkinson
Endocrine disorders
Bioavailability of bromocriptine
28%(extensive first pass metabolism with cyp3A4) with peak plasma concentration usually attained within 1-3 hours; 15 hour half life
Pramipexole
Preferential affinity for D3 receptors
What else can pramipexole be used for besides PD
Primary restless leg syndrome
Pramipexole has a peak plasma concentration reached in _ hours with a half life of _ hours
2
8
Pramipexole excretion
Unchanged in the urine
Ropinirole
Preferential affinity for D2 receptors