Drugs for Movement Disorders DSA Flashcards
Patients with what experience tics?
Gilles de la Tourette syndrome
Parkinsons disease pathological hallmark
- loss of dopaminergic neurons of substantia nigra
- lewy bodies–intracellular inclusions
dopaminergic neurons of SN–function
- inhibit the GABAergic output from the striatum
- cholinergic neurons exert an excitatory effect on GABAergic neurons
treats Parkinson disease
- levodopa
- dopamine R agonist
- MAO inhibitors
- COMT inhibitors
- Amorphine
- Amantadine
- Anticholinergic drugs
Levodopa MOA
Levodopa–coadmininistered with?
-precursor to dopamine; agonist at D Rs (mostly D2 R); absorbed from small intestine (peak plasma conc–1-2 hours after oral dose); 1-3% of levodopa enters the brain (the rest is metabolized extracerebrally by decarboxylation to dopamine)
- carbidopa!
- DOPA decarboxylase inhibitor that doesn’t cross the BBB–reduced peripheral metabolism, increased plasma levels, increased half life, increased levodopa for entry into brain
Levodopa clinical use
- Parkinsonian syndrome
- lowers mortality rate when initiated early
- best results–first few years of treatment
- 1/3 of patients respond very well, 1/3 respond less well, 1/3 unable to tolerate medication or doesn’t respond at all
Levodopa adverse effects–GI
- in absence of carbidopa–anorexia, nausea, vomiting (80% of patients)
- with carbidopa–less frequent side effects (20% of patients)
- vomiting–act of chemo R trigger zone in brainstem
Levodopa adverse effects–CV
- postural hypotension (asymptomatic frequently)
- hypertension when taking large doses
- increases in cardiac arrhythmias–rare–due to increased peripheral catecholamine synthesis
Levodopa adverse effects–dyskinesias
- 80% of patients
- Choreoathetosis of face and distal extremities
Levodopa–adverse effects behavioral effects
- ,amu changes in mood/personality
- atypical antipsychotic agents help counteract (clozapine, olanzapine, quetiapine, risperidone)
Levodopa–adverse effects–fluctutions in response; on-off phenomenon
- wearing off phenomenon (due to dose timing)–less effective as time goes on?
- on-off phenomenon–off periods of marked akinesia alternate of a few hours with on-periods of improved mobility but often marked dyskinesia
- apomorphine–provide temporary benefit
Levodopa drug interactions
-monoamine oxidase A inhibitors–may experience hypertensive crisis when combined with levodopa
Levodopa–contraindications
- psychotic patients
- angle closure glaucoma
- history of melanoma, skin lesions
- active peptic ulcer (GI bleeding)
Dopamine R agonsits–used when?
- in patients with PD–associated with lower incidence of response fluctuations and dyskinesias (that occur in long term levodopa therapy)
- usually patients who dont respond well to levodopa, dont respond well to dopamine agonists
- can be administered in addition to levodopa/carbidopa and in patients who are taking levodopa who have on-off phenomenon
Dopamine R agonits
- Bromocriptine (D2)
- Pramipexole (D3)
- Ropinirole (D2)
Bromocriptine
- D2 agonist
- also approved for treatment of endocrine disorders
- bioavailability 28% with peak plasma concentration attained
- half-life–15 hrs
- extensive first-pass metabolism (CYP3A4)
Prampipexole
- D3 Receptors
- also for treatment of RLS (restless leg syndrome)
- peak plasma conc in 2 hours; half life of 8 hours
- 90% excreted in urine (pts with renal insufficiency need dose adjustment)
Ropinirole
- D2 Receptors
- treats RLS
- metabolized by CYP450 (CYP1A2)–coadmin with agents that are also metabolized by CYP1A2 may reduce the clearance of ropinirole
- peak plasma concentration in 1-2 hours; half life of 6 hours