Movement Disorders Pharm Flashcards
Which 4 drugs are Dopamine receptor agonists?
- Apomorphine
- Bromocriptine
- Pramipexole
- Ropinirole
What 2 drugs are Monoamine oxidase inhibitors?
- Rasagiline
- Selegiline
What are the 2 Catechol-O-methyltransferase inhibitors?
- Entacapone
- Tolcapone
What are the 5 anticholinergic drugs used for movement disorders?
- Benztropine
- Biperiden
- Orphenadrine
- Procyclidine
- Trihexyphenidyl
Under normal conditions, dopaminergic neurons originating in the substantia nigra inhibit the GABAergic output from the _________
Striatum (caudate and putamen)
Cholinergic neurons exert an _________ effect on GABAergic neurons of the striatum
Excitatory
How does Levodopa enter the CNS?
L-amino acid transporter (LAT); dopamine does not cross the BBB
What is the MOA of Levodopa?
Agonist at dopamine (D) receptors
What is the absorption of Levadopa like?
How long to reach peak plasma concentration and what is the half life?
- Rapidly absorbed from the small intestine w/ a peak plasma concentration usually between 1-2 hours after an oral dose
- Half-life usually between 1-3 hours
How is the problem of Levadopa being metabolized extracerebrally (in the periphery) solved?
What effects will this decrease and increase?
- Coadministration with a DOPA decarboxylase inhibitor that does NOT cross the BBB (carbidopa)
- This will significantly decrease the adverse peripheral effects of: nausea, vomiting, and postural hypotension!
- But may enhance the adverse behavioral effects!
What is the result of co-administration of carbidopa with levodopa?
- Reduced peripheral metabolism of levadopa
- Increased half-life
- Increased levodopa available for entry into the brain
*May reduce the daily requirments of levodopa by approximately 75%
What are the adverse GI effects of levadopa?
- Given in absence of peripheral decarboxylase inhibitor causes: anorexia, nausea, and vomiting (activation of chemoreceptor trigger zone)
- Less troublesome effects when combo of levodopa/carbidopa given
What are the cardiovascular effects of levodopa?
- Postural hypotension (frequently asymptomatic), diminishes with continuing tx
- HTN can occur when taking large doses of levodopa or in combo w/ non-selective monoamine oxidase inhibitors or sympathomimetics
What are some adverse effects on movement that can result from treatment w/ Levodopa?
How common?
- Dyskinesias in 80% of patients!!!
- Choreoathetosis (movement of intermediate speed) of FACE and distal extremities
What are some of the adverse behavioral effects caused by treatment with Levodopa?
Depression, anxiety, agitation, insomnia, somnolence, confusion, delusions, hallucinations, nightmares, or euphoria
What is the “on-off phenomenon” associated with Levodopa?
Off-periods of marked akinesia alternate over the course of a few hours with on-periods of improved mobility but often marked dyskinesia
Administration of which drug and via what route, may provide temporary benefit to those patients with severe off-periods while taking Levodopa?
Subcutaneous injections of apomorphine (DA receptor agonist)
Levodopa is contraindicated in patients taking which drug?
May cause what adverse effect?
- Pts taking monoamine oxidase A inhibitors (or within 2 weeks of discontinuation)
- May experience hypertensive crisis
Levodopa is contraindicated in which patients?
- Psychotic patients
- Patients w/ angle-closure glaucoma (can be used with well-controled open-angle glaucoma)
- Hx of melanoma or w/ suspicious undiagnosed skin lesions (levadopa is precursor of skin melanin)
- Use w/ caution in pt w/ active peptic ulcer due to possibility of GI bleeding
Which drug class has a lower incidence of the reponse fluctuations and dyskinesia that occur w/ long-term levodopa therapy?
Dopamine receptor agonists
Which dopamine receptor agonist is an ergot alkaloid derivative and acts on the D2 receptors?
Bromocriptine
Bromocriptine (dopamine receptor agonist) is also approved for the treatment of which disorders?
Endocrine (i.e., hyperprolactinemia, prolactin secreting adenomas, acromegaly)
Which CYP metabolizes Bromocriptine?
CYP3A4 (extensive first pass metabolism, bioavailabilty 28%)
Which Dopamine receptor agonist has preferential affinity for D3 receptors?
Pramipexole