Drugs to treat Parkinsonism
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9 terms
Terms | Definitions |
|---|---|
 Levodopa | -Absorbed by AAA active transportation system in small intestine (reduced by presence of other AA) -Absorption greatly affected by gastric emptying and gastric pH -95% decarboxylated by L-AAA Decarboxylase, which is widely distributed in intestinal mucosa, so must give large dose if given alone (not typically done) -Always given with a decarboxylase inhibitor -Actively transported into neurons -Decarboxylated into DA by AAAD and concentrated into synaptic vesicles -Short DOA with worsening of parkinsonism near end of the dose interval and toxicities at peak blood levels (alternating bradykinesia dn dyskinesia--"on-off" phenomenon) -To be effective some nigrostriatal neurons must still be alive -Effects will eventually decline as the disease progresses -AE: N&V and anorexia due to fx on GI tract and area postrema of CNS; tachycardia, extrasystoles, arrhytmias, HTN, postural hypotension due to sympathetic actions; dose-related dyskinesias (more promnenint with disease progression); changes in mood, personality, anxiety, insomnia, confusion, delusions, hallucinations, aggression, hypersexual behavior -Interactions: non-specific MAOIs for HTN, Antipsychotics and related antiemetics that block DA receptors, anticholinergic drugs that delay gastric emptying |
| Carbidopa | -Inhibitor of aromitic L amino acid decarboxylase -Does not cross BBB -Always given with L-DOPA -Helps reduce levodopa dose sunce less DA formed peripherally |
| Entacapone | -COMT inhibitor -Doesn't cross BBB -Less inhibit levodopa metabolism so less 3-O-methyldopa |
| Selegiline | -MAO-B (CNS) inhibitor -Large doses are less selective for MAO-B and can produce life-threatening drug interactions -some effects when used alone, but increases CNS effects of levodopa |
| Bromocriptine | -DA agonist -Rx: in combination with levodopa/carbidopa for PD, for Amenorrhea-galactorrhea (spontanous milk let-down) associated with hyperprolactinemia (since pituitary cells that release PRL receive DA inhibition) -Well absorbed and longer DOA than levodopa -AE: Orthostatic hypotension, N&V and anorexia, dyskinesias, mental disturbances, erythromelalgia (hypersensitivity where BVs in extremities are progressively blocked then inflammated, which causes pain) |
| Pramipexole | -DA agonist -Rx in combination with levodopa/carbidopa for PD -Well absorbed and longer DOA than levodopa -AE: Orthostatic hypotension, N&V and anorexia, dyskinesias, mental disturbances |
| Ropinirole | -DA agonist -Used to treat restless leg syndrome -Rx in combination with levodopa/carbidopa for PD -Well absorbed and longer DOA than levodopa -AE: Orthostatic hypotension, N&V and anorexia, dyskinesias, mental disturbances |
| Amantadine | -Stimulates presynaptic release of DA -Rx: alone for early stages of PD or in combo with Levo/Carbidopa -Beneficial effects are short lived, but averse effects are less common than with other drugs for parkinsonism -Well absorbed and is excreted unchanged in the urine |
| Benztropine | -AChR Antagonist with increased ratio of CNS: peripheral effects -USEFUL FOR ANTIPSYCHOTIC-INDUCED PARKINSONISM -for PD, less effective the L-DOPA; usually used in combination with drug affecting DA function |
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