L-dopa
levodopa
Unfortunately, levodopa becomes less effective over time, and also produces unwanted and uncontrolled movements called dyskinesias.
Levodopa and carbidopa are given together to enhance the effectiveness of Parkinson's disease treatment. Levodopa is converted to dopamine in the brain, alleviating symptoms, but it can also be metabolized peripherally, leading to side effects. Carbidopa inhibits the enzyme that breaks down levodopa outside the brain, allowing more levodopa to reach the brain and reducing side effects like nausea and vomiting. This combination improves the overall efficacy of the therapy.
pyridoxine (vitamin B6) can decrease the effect of levodopa.
Levodopa itself is not well tolerated, which is why it is combined with carbidopa. Carbidopa decreases peripheral metabolism of levodopa, which allows for lower doses of levodopa and less-severe side effects.
Although levodopa can cross our BBB, but it will be decarboxylated to dopamine peripherally before reaching our CNS - only small amount of Levodopa will be left and available to pass our BBB.So, instead of giving levodopa in high dose (which can cause lots of side effects), we give levodopa with peripheral decarboxylase inhibitors (e.g. carbidopa, benserazide) which can inhibit decarboxylation of levodopa in GIT and peripheral tissues. (By combining levodopa and peripheral decarobxylase inhibitors, we will have less side effects too)
levodopa
Selegiline (deprenyl) inhibits monoamine oxidase B (MAO-B), which metabolizes dopamine in the brain. Selegiline can delay levodopa treatment for an average of nine months and also is used in combination with levodopa (Eldepryl) in early-stage PD.
yes
This may occur after five to 10 years or more of successful levodopa treatment.
Early on in PD, symptoms can be effectively treated with medication, especially levodopa and the dopamine agonists (drugs that act like levodopa).
Bromocriptine (dopaminergic agonist drug) has longer duration of action than levodopa (dopamine precursor).