Drugs For Movement Disorders Flashcards
What is a limitation of pharm tx of neurodegen disorders?
Limited mostly to symptomatic txs that do not alter the course of the underlying disease
Describe tremor
An involuntary trembling or quivering; rhythmic oscillatory movement around a joint; characterized by its relation to activity
What are different types of tremors?
- postural: a tremor of a part during maintenance of sustained posture
- essential: a tremor of a part during movement (intention tremor)
- Parkinsonian tremor: slow, regular movements of the hands and sometimes the lower limbsm neck, face, or jaw; stops upon voluntary movement; intensified by stimuli such as cold fatigue and strong emotions (rest tremor)
Describe chorea
Occurrence of a variety of continual, rapid, highly complex, jerky, dyskinesia movements that look well coordinated but are involuntary
-hereditary (HD); or occur as complication of other disorders and drugs
Describe tics
Involuntary, compulsive, rapid, repetitive, movement or focalization
- irresistible but can be suppressed for some length of time
- stress, lack of sleep
- psychogenic or neurogenic
- Gilles de la Tourette => tics
What are the four Cardinal features of Parkinsonism?
(1) . Bradykinesia
(2) muscular rigidity
(3) resting tremor (abates during voluntary movement)
(4) impairment of postural balance leading to disturbances of gait and falling
Based on the pathophysiligy of PD, what can PD Pts be treated with?
Dopamine agonists and/or aanticholinergic agents
(PD= loss of dopaminergic neurons of SN; selective loss of dopaminergic neurons is Pts results in disinhibition of GABAergic neurons and disturbed movement)
Levodopa (L-Dopa) MOA
Agonist as mostly D2 Rc; rapidly absorbed from small intestine w/ peak plasma concentration btwn 1-2 hours after Na oral dose; only 1-3% of levodopa actually enters the brain unaltered (rest metabolized by decarboxylation to dopamine)
What is the benefit of administering levodopa with a DOPA carboxylate inhibitor that does not cross the BBB (carbidopa)?
Reduced peripheral metabolism, increased plasma levels, increased half-life, and increased levodopa available for entry into the brain
-may reduce the daily requirement of levodopa by 75%
What is the clinical use of Levodopa in the to of Parkinsonian syndrome?
Doesn’t stop progression of PD but does lower the mortality rate when initiated early on
-best results in the first few years of tx:
What is the wearing off phenomenon that occurs during long-term tx?
Each does 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 interval
-increasing the dose and frequency of admin can improve symptoms (limited by development of dyskinesias)
How do you mitigate the adverse GI effects of Levodopa?
-anorexia, nausea, vomiting (activation of chemoreceptor trigger zone in brainstem outside BBB)
A combination of levodopa/carbidopa causes less frequent and less troublesome GI SEs in 20% of Pts
-individual can require larger doses of carbidopa to minimize the GI SEs and administration of carbidopa alone can be beneficial
What can happen when taking large doses of levodopa or levodopa in combination with nonselective MOA inhibitors or sympathomimetics?
Hypertension
What are some adverse affects of levodopa (CV)?
- postural hypotension
- HTN
- increases in cardiac arrhythmia (rare) due to increased peripheral catecholamines synthesis
What is the most common presentation of the adverse effect of dyskinesias (due to levodopa)?
Choreoathetosis (movement of intermediate speed ,btwn the quick, flitting movements of chorea and the slower, writhing movements of athetosis) Of the face and distal extremities
-development can be dose related
What are some of the mental effects associated with levodopa?
Depression, anxiety, agitation, insomnia, somnolence, confusion, delusions, hallucinations, nightmares, euphoria, changes in mood and personality
What are some atypical antipsychotic agents that can help counteract behavior complications?
Clozapine, olanzapine, quetiapine, risperidone
What causes fluctuations in response to levodopa?
Timing (wearing off phenomenon) of the dose or due to reasons unrelated to dose timing (on-off phenomenon)
What happens in the on-off phenomenon (levodopa)?
Off periods of marked akinesia alternate over the course of a few hours with on-periods of improved mobility but often marked dyskinesia
What could provide temporary benefits to those pt with severe off-periods (levodopa)?
Subcutaneous injections of apomorphine may provide temporary benefit
What is the drug interaction between levodopa and MAO A inhibitors (or within 2 weeks of discontinuation)
HTN crisp when combined with levodopa
What are contraindications for levodopa?
Psychotic Pts; Pts with angle-closure glaucoma (ok for open angle), Pts w/ hx of melanoma or w/ undiagnosed skin lesions (precursor of skin melanin); active peptic ulcer (possible GI bleed)
Dopamine Receptor agonists
PD; lower incidence of the response fluctuations and dyskinesia so that occur with long-term therapy with levodopa
- don’t response well to levodopa, don’t respond well dopamine Rc agonists
- can be administered in addition to levodopa/carbidopa and in Pts who are taking levodopa and who have end-of -dose on-off phenomenon
Bromocriptine
- ergot alkaloid derivative (D2 agonist)
- used for tx of endocrine disorders
- BA 28%; peak plasma concentration w/in 1-3 hours
- t1/2: 15 hours
- CYP3A4 (extensive first pass)