Drugs for Parkinson�s Disease narration

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Drugs for Parkinson’s Disease : 

Drugs for Parkinson’s Disease Neuro.

Objectives : 

Objectives Explain the interrelationships between the central nervous system (CNS) activities of dopamine and acetylcholine as they affect the signs and symptoms of parkinsonism and as they relate to the general biochemical approach to correcting neurotransmitter imbalances with antiparkinson drugs. Discuss the drug treatment for Parkinson’s disease and discuss the current consensus about which agent(s) are recommended for initiating therapy in most patients with this disorder. Succinctly summarize the main antiparkinson mechanisms of action of levodopa, carbidopa, pramipexole, ropinirole, apomorphine, bromocriptine, pergolide, amantadine, entacapone, tolcapone, and selegiline. For each, also summarize their main adverse responses.

Parkinson’s Disease : 

Parkinson’s Disease Parkinson’s disease (PD) is a neurodegenerative disorder of the extrapyramidal system associated with disruption of neurotransmission within the striatum. Parkinson’s disease is characterized by dyskinesias and akinesia. Proper function of the striatum requires a balance between the neurotransmitters dopamine and acetylcholine (ACh). Imbalance between dopamine and ACh results from degeneration of the neurons that supply dopamine to the striatum. Neuro.

Parkinson’s Disease : 

Parkinson’s Disease Dyskinesias of Parkinson’s disease are Tremor at rest Rigidity Postural instability Bradykinesia Neuro.

Figure 21-1A A model of neurotransmission in the healthy striatum and Parkinsonian striatum. : 

Figure 21-1A A model of neurotransmission in the healthy striatum and Parkinsonian striatum. Neuro.

Figure 21-1B A model of neurotransmission in the healthy striatum and Parkinsonian striatum. : 

Figure 21-1B A model of neurotransmission in the healthy striatum and Parkinsonian striatum. Neuro.

Parkinson’s Disease : 

Parkinson’s Disease Therapeutic goals: Improve patient’s ability to carry out activities of daily life Drug selection and dosages are determined by extent to which PD interferes with work, dressing, eating, bathing, etc. Neuro.

Drug Therapy for Parkinson’s Disease : 

Drug Therapy for Parkinson’s Disease Two major categories Dopaminergic agents By far the most commonly used for PD Promote activation of dopamine receptors Levodopa [Dopar] Anticholinergic agents Prevent activation of cholinergic receptors Benztropine [Cogentin] Neuro.

Dopaminergic Agents : 

Dopaminergic Agents Mechanisms of action Levodopa: Promotes dopamine synthesis Dopamine agonists: Stimulate dopamine receptors directly Selegiline: Inhibits dopamine breakdown Amantadine: Promotes dopamine release COMT inhibitors: Enhance effects of levodopa by blocking its degradation Neuro.

Figure 21-2 Steps leading to alteration of CNS function by levodopa. : 

Figure 21-2 Steps leading to alteration of CNS function by levodopa. Neuro.

Figure 21-3 Conversion of levodopa to dopamine. : 

Figure 21-3 Conversion of levodopa to dopamine. Neuro.

Anticholinergic Agents : 

Anticholinergic Agents Mechanism of action Blockade of muscarinic receptors in the striatum Neuro.

Slide 13: 

Figure 21-4 Fate of levodopa in the presence and absence of carbidopa. (Data in the figure are extrapolated from Nutt JG, Fellman JH: Pharmacokinetics of levodopa. Clin Neuropharmacol 7:35, 1984) Neuro.

Drug Therapy for Parkinson’s Disease : 

Drug Therapy for Parkinson’s Disease Levodopa (drug holidays recommended) Levodopa/carbidopa Dopamine agonists: Pramipexole [Mirapex] Entacapone [Comtan] Amantadine [Symmetrel] Selegiline [Eldepryl, Carbex] Neuro.

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