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187 – Parkinson medications (levodopa, Carbidopa, ETC.) USMLE STEP 1 WWW.USMLEACE.COM

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Parkinson medications (levodopa, Carbidopa, Bromocriptine, Pregolide, Ropinorole, Amantadine, Selegiline, Entacapone, Tolcapone)

The central nervous system contains three different dopamine tracks including the mesolimbic and mesocortical which affects the thought and mood the kubera infundibular which affects the release of the prolactin from the pituitary gland and then the nigrostriatal which affects the extrapyramidal motor movement so patients that parkinson disease have decreased

Activity of the dopaminergic neuron in the nitrous turtle tracks while patient the disgust of renia have increased activity of the dopamine in the mesolimbic and mesocortical tracks now in this video i would like to focus on the parkinson disease where the patients presented the loss of dopamine in these cells tan cha and the onset of the disease is usually after

The age of 50 so the diagnosis for parkinson’s disease is strictly clinical but then if you obtain the biopsy of the brain of these patients you will see that there are also lewy bodies that are present so patients with parkinson disease generally presented the tetrad of ataxia where there is postural instability they present with the brady kinesia where there

Is slowed movement they present with cogwheel rigidity so on examination while trying to move the limbs of these patients you will notice that there is a pattern of resistance and relaxation and thus this is referred to as cogwheel rigidity and then finally these patients present with resting tremor and then as the name implies this tremor is present when the

Patient is resting while it goes away when the patient tries to perform tasks or grab onto an object and then there is this other condition called shy-drager syndrome where there is a parkinson’s symptoms in addition to autonomic insufficiency such as sweating constipation and orthostatic hypotension next i would like to go over the mechanism of action of the

Parkinson medications which are directed at either inhibiting the acetylcholine or increasing the dopamine activities so i should also mention that in addition to the decrease activity of the dopamine in patients with the parkinson disease there is also uninhibited acetylcholine activity and thus this is what is causing the rigidity and tremor and thus some of

The medications are directed at inhibiting the acetylcholine now here is the pathway of the catecholamine synthesis and alanine converts to tyrosine which converts the dopa and the dopa converts the dopamine by the decarboxylase enzyme and the dopamine converts the norepinephrine and then later on or norepinephrine converts to epinephrine now the best medication

That is used for the treatment of parkinson is a combination of l-dopa and cabi dopa so l-dopa will cross the blood-brain barrier and inside the brain via the decarboxylase enzyme it converts to dopamine and then in addition carbidopa is added to this medication because kappa dopa inhibits the peripheral conversion of dopa into dopamine so kappa dopa inhibits the

Dopa decarboxylase enzyme and by doing that there is more efficiency of the eldar by reaching the brain and inducing its effects so now that i’ve covered the mechanism of these medications let’s go through the list that i’ve provided here so l-dopa and carbidopa this is the first-line treatment for patients with parkinson disease l-dopa is capable of crossing the

Blood-brain barrier and then inside the brain by the dopa decarboxylase it converts into the dopamine and in this medication is co supplemented with the carbidopa and the reason for that is that kappa dopa prevents the peripheral conversion of the l-dopa by blocking the dopa decarboxylase anza and thus there would be the increased bioavailability of the drug to the

Brain in addition to the decreased peripheral side-effects the next group of medications are dopamine agonists fish are listed here and then amantadine increases dopamine release in addition it’s an antiviral that is effective against influenza type egg so notice that amantadine increases the dopamine release as well as inhibiting the influenza type a not type b

Type a and the way it works is that it prevents the encoding of the virus the next medication is saline which inhibits the monoamine oxidase b which preferentially metabolizes the dopamine and then the n takapuna and the toll coupon will inhibit the catechol all metal transferase and thus it prevents the degradation of the l-dopa now in addition i mentioned that

Patients with parkinson disease have increased activity of the acetylcholine and thus the anticholinergic medications are also used to treat the tremors and rigidity in these patients so been stopped in and trihex panadol which as antimuscarinic agents can be used to treat the resting tremor or cardwell rigidity but it’s not effective against brady kinesia so for

Bradykinesia you will have to directly address the loss of the dopamine in these patients and that concludes our discussion

Transcribed from video
187 – Parkinson medications (levodopa, Carbidopa, ETC.) USMLE STEP 1 WWW.USMLEACE.COM By USMLE ACE INC