Drugs for Movement Disorders - Kruse Flashcards
Dopamine vs. ACh in the basal ganglia
Dopamine - inhibit GABA output from striatum
ACh - excite GABA output from striatum
How does loss of dopaminergic neurons lead to difficult movements?
Less inhibition of the inhibitor (striatum), thus leading to decreased movements
So, how would you treat Parkinson’s?
Increase Dopamine activity onto the GABAergic striatum neurons via Dopamine agonists or metabolism antagonists
Why treat with L-dopa, not dopamine?
L-dopa can cross BBB, but dopamine cannot
What is L-dopa?
Immediate metabolic precursor to dopamine
Levodopa action
Downside to levodopa alone
Dopamine receptor agonist
97-99% is metabolically altered before reaching the brain, via decarboxylation into dopamine
How to increase the effects of levodopa?
Give w/ a DOPA decarboxylase inhibitor
= CARBIDOPA
Causes reduced peripheral metabolism, so more enters the brain unaltered
A patient is taking Levodopa therapy for a long time. Eventually, each dose ends and rapidly leads to a return of symptoms. This is an example of?
Can you just give more levodopa?
Wearing-off phenomenon
Eventually you impair voluntary movements (dyskinesia)
A patient is on levodopa (with or without carbidopa). What symptoms are she most likely to exhibit? (4)
Anorexia, nausea, vomiting, choreoathetosis
Does carbidopa help with the side effects of levodopa?
Yes, but only in 20% of patients
A patient is on levodopa but has trouble with vomiting. What causes the vomiting?
Activation of chemoreceptor trigger zone within the brainstem (outside the BBB)
What is the choreoathetosis side effect of levodopa?
Intermediate-speed movements of the face and distal extremities
A patient is taking Levodopa therapy for a long time. Eventually, the patient starts having occasional episodes of inability to move at all. This is an example of?
How is this problem fixed?
On-off phenomenon
Apomorphine - DOPAMINE agonist that can provide temporary relief
A patient is taking Levodopa, but needs another drug to supplement. Which drug type should NOT be taken with Levodopa?
Why?
Non-selective MAO or selective MAO-A inhibitors
Lack of MAO-A leads to build-up of norepinephrine, which can cause a HYPERTENSIVE CRISIS in the patient
Contraindications for Levodopa therapy
Psychosis, closed-angle glaucoma, melanoma, active peptic ulcer
Why would a patient take a dopamine receptor agonist rather than Levodopa?
Less response fluctuation phenomena and dyskinesias
Can dopamine receptor agonists be given WITH Levodopa?
What about for wearing-off or on-off phenomena?
YES
YES (Apomorphine is a dopamine receptor agonist)
Bromocriptine
D2 agonist, ergot alkaloid
Extensive first pass metabolism (3A4)
Pramipexole
D3 agonist
Treats RLS also
A patient is taking Pramipexole and develops renal insufficiency. What might the doctor have to do?
Change the dose of Pramipexole, sine 90% is excreted renally
Ropinirole
D2 agonist
Treats RLS also
Metabolized by 1A2
Issue with Bromocriptine?
Causes digital vasospasm with long-term use
Should be discontinued if patient has peripheral edema, peripheral vascular disease, or cardiac arrhythmias
Issue with Pramipexole or Ropinirole?
May feel uncontrollable tendency to fall asleep at random times
Psychosis is a contraindication for Levodopa treatment. What about dopamine receptor agonists?
DO NOT USE - causes more severe mental disturbances than Levodopa
MAO-A vs. MAO-B
A = metabolism of NE and serotonin B = metabolism of phenylethylamine and benzylamine
Dopamine is metabolized by which MAO?
Both equally
A patient is taking Levodopa but needs something to help relieve the on-off and wearing-off phenomena. What can be taken along with it?
Selegiline (MAO-B inhibitor)
Selegiline
Irreversible MAO-B inhibitor
Prolongs the effects of Levodopa
Rasagiline
Irreversible MAO-B inhibitor
More potent form of Selegiline
COMT role in dopamine stuff
Breaks Levodopa into a competitor for transport across the BBB, thus making Levodopa less effective
Tolcapone
COMT inhibitor
Prolongs activity of levodopa by preventing its peripheral metabolism, thus decreasing clearance
CENTRAL and PERIPHERAL effects
Entacapone
Like Tolcapone (COMT inhibitor) But only PERIPHERAL effects
A patient is on Levodopa and Tolcapone. What is a potential side effect of the Tolcapone?
Hepatic toxicity (increased liver enzymes)
Benefit of Apomorphine vs. other dopamine agonists for relief of Levodopa phenomena
SubQ INJECTION = quick, temporary relief
A patient is taking Levodopa therapy for a long time. Eventually, the patient starts having occasional episodes of inability to move at all. How is this problem fixed?
What is the potential side effect of this fix?
How is this side effect fixed?
Apomorphine
Nausea, vomiting
Pre-treat w/ TRIMETHOBENZAMIDE (anti-emetic)
Trimethobenzamide
Anti-emetic, used in the relief of nausea and vomiting due to anti-parkinson drugs
A patient is on Levodopa therapy for PD that is supplemented with another drug. However, over time, the patient developed purple discoloration of the LE skin including very apparent superficial vasculature. What drug is he on?
What is this condition called?
Amantadine
Livedo reticularis (side effect of the drug)
Amantadine
Anti-viral agent that somehow helps with parkinsonism
Anticholinergic drugs used in the treatment of Parkinsonian symptoms
What are they?
Benztropine, biperiden, orphenadrine, procyclidine, trihexyphenidyl
Centrally-acting anti-muscarinic
Purpose of anticholinergic drugs here?
Improve tremor and rigidity by balancing the low dopamine level in the basal ganglia with an equally low acetylcholine level
Adverse effects of anticholinergic drugs here?
Sedation, confusion, constipation, urinary retention, blurred vision (typical CNS sympathetic symptoms)
Propranolol, Metoprolol
Beta-1 antagonists used to stop tremor
Primidone
Anti-epileptic drug used to stop tremor (smaller doses)
Topirimate
Serotonin receptor agonist used to stop tremor
BOTOX
IM injection used to help tremor
Reserpine
IRREVERSIBLE dopamine reuptake (MAT) agonist
Used for treatment of Huntington
Tetrabenazine
REVERSIBLE dopamine re-uptake (MAT) agonist
Used for treatment of Huntington
Patients with Huntington often need treatment for psychiatric symptoms (depressed, irritable). What are treatment options? (2)
Fluoxetine - depression and irritability
Carbamazepine - depression
Pimozide, haloperidol
Neuroleptic antipsychotics used for TICS
A patient needs meds for a TIC but doesn’t want the side effects of Pimozide. What are other options? (3)
Clonidine, Guanfacine (alpha agonists)
Botulinum toxin A
Treatment for restless leg syndrome
Dopamine agonists (non-ergot) - Pramipexole, Ropinirole
Riluzole
ALS
Penicillamine
Wilson’s disease (chelating agent)
Other drugs for Wilson’s disease besides Penicillamine? (3)
Trientine, Zinc acetate, Zinc sulfate