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L-dopa
precursor of dopamine
- uses
- mechanism
- dose and half-life
- adverse drug reactions
- counter-indications and drug interactions
- metabolism and excretion
- dependency
Uses
Mechanism
- taken up by dopaminergic neurons in the substantia nigra and converted into DA by action of LAAD
- given with carbidopa, which does not enter brain; prevent peripheral transformation to dopamine
Dose and Half Life
Adverse Drug Reactions
- peripheral SNS side effects
due to DA formation
- nausea, orthostatic hypotension, arrhythmias
- can cause psychotic symptoms due to excess dopamine in the mesolimbic and mesocortical pathways
Counter-Indications and Drug Interactions
- anti-cholinergic drugs can block absorption of L-dopa
- MAOIs can slow metabolism, causing hypertensive crisis
- antipsychotics can block DA receptors and exacerbate motor dysfunction
Metabolism and Excretion
- large first-pass effect because of peripherally acting LAAD and COMT