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Parkinson’s Disease (Dopamine-receptor agonists (:red_flag:Bromocriptine,…
Parkinson’s Disease
- Dopamine-receptor agonists
– the older ergot derivatives dopamine agonists: bromocriptine and pergolide
– the newer nonergot drugs: pramipexole, ropinirole, apomorphine and
rotigotine which has less side effect and they show the same effect
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:red_flag:Bromocriptine
a derivative of the vasoconstrictive alkaloid,
ergotamine, is a dopamine-receptor agonist
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should not be given to patients with psychiatric illness, a history of myocardial infarction, peripheral vascular disease, peptic ulcer
Apomorphine :red_flag: is used in severe and advanced stages of the disease
as an injectable dopamine agonist
Rotigotine :red_flag: is available as a once-daily transdermal patch, which is
used in the treatment of the signs and symptoms of early stage
Parkinson disease
in new patients, the therapeutic response to
levodopa is consistent
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is a metabolic precursor of
dopamine, which is actively transported into the
CNS and is converted to dopamine in the brain
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general information
Parkinson disease is a neurodegenerative diseases
characterized by the progressive loss of dopaminergic
neurons in the basal ganglia system
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Genetic factors do not play a dominant role in the etiology of
Parkinson disease,
- Monoamine oxidase (MAO-B) inhibitors
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Selegiline will decrease the metabolism of dopamine, thus leads to
increase dopamine levels in the brain and enhances the actions of levodopa when these drugs are
administered together
Rasagiline, an irreversible and selective inhibitor of brain
monoamine oxidase Type B, has five times the potency of
selegiline.
- Catechol-O-methyltransferase inhibitors
Normally, the methylation of levodopa by COMT to 3-O-methyldopa is a
minor pathway for levodopa metabolism.
Inhibition of COMT by Entacapone leads
to decreased plasma concentrations of 3-O-methyldopa, increased
central uptake of levodopa, and greater concentrations of brain dopamine
Oral absorption occurs
readily and is not influenced by food and extensively bound to plasma albumin with limited volumes of distribution.
25 Amantadine
has several effects on a number of neurotransmitters
implicated in causing parkinsonism, including increasing the release
of dopamine, blockading cholinergic receptors, and inhibiting the Nmethyl-D-aspartate
(NMDA) type of glutamate receptors.
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It is less efficacious than levodopa, and tolerance develops more
readily
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