Drugs for Neurodegenerative Diseases Flashcards
Drugs that increase Dopamine levels
Levodopa Carbidopa Amantadine Selegiline Rasagiline Tolcapone Entacapone
Levodopa - MoA
Increase dopamine levels by increasing the synthesis.
It is converted to dopamine by LAAD and metabolized to 3OMD by COMT. A drug that inhibits LAAD or COMT increases the amount of levodopa that enters brain tissue.
In the brain levodopa is taken up by dopaminergic neurons in the striatum and converted to dopamine by LAAD. Levodopa thereby increases the amount of dopamine released by the neurons in patients with PD, and is serves as a form of replacement thrapy. As the diseases progresses and more dopaminergic neurons are lost, the conversion of levodopa to dopamine therefor declines.
Levodopa - Indication
Idiopathic PD
Postencephalitic parkinsonism
Parkisonian symptoms caused by carbon monoxide poisoning, manganese intoxication, or cerebral arteriosclerosis
Levodopa - Adverse effects
Nausea and vomiting (when used alone)
Orthostatic hypotension
Cardias dysrhythmias. Adverse effects are reduced with the use of Carbidopa.
Long term; involuntary movements or dyskinesias
Psychotic effects, including hallucination and disoriented thinking
Sedation, agitation, delirium, vivid dreams or nightmares, euphoria after drug adm.
Discoloration of urine, sweat and or saliva
Loss of appetite
Levodopa - Interactions
Anticholinergic drugs –> slow levodopa absorption
Nonselective MOAIs inhibit the breakdown of dopamine and sometimes cause hypertensive crisis in patients receiving levodopa
Antipsychotic drugs block dopamine receptors and can reduce the effectiveness of levodopa and exacerbate motor dysfunction
Drugs that promote gastric emptying (antacids) can increase levodopa bioavailibility
Ingestion of high-protein foods can decrease the effectiveness of levodopa because amino acids can reduce the transport of levodopa into the brain
LAAD requires Vitamin B6 (pyridoxine) as a cofactor. For this reason, vitamin B6 supplements may enhance the peripheral decarboxylation of levodopa and shoult not be coadministered with levodopa
Carbidopa - Group + MoA
Analoug of levodopa
Inhibits LAAD thereby reducing the conversion of levodopa to dopamine in peripheral tissues and so increases the amount of levodopa that enters the brain
Carbidopa - Indication + Adverse effects
PD
Reduces the cardiovascular and GI side effects of Levodopa.
Amantadine - Group + MoA
Antiviral drug
Increases dopamine release from nigrostriatal neurons, may also inhibit the reuptake of dopamine by these neurons.
Amantadine - Indication
Early or mild cases of Parkinson disease
Prevention and treatment of influenza
Amantadine - Adverse effects
Sedation Restlessness Vivid dreams Nausea Dry mouth Hypotension Livedo reticularis- reddish-blue mottling of the skin with edema CNS side effects are more common in elderly pat.
Selegiline - Group + MoA
Modified phenylethylamine compound
Increase dopamine by inhibiting the breakdown.
Inhibits Monoamine oxidase type B (MAO-B) and thereby prevents the oxidation of dopamine to dihydroxyphenylacetic acid and hydrogen peroxide. By this selegiline increases dopamine levels in the basal ganglia and decreases the formation of hydrogen peroxide. In the presence of iron, hydrogen peroxide is converted to hydroxyl and hydroxide free radicals that may participate in the degeneration of nigrostriatal neurons in patients with PD.
Selegiline - Indication
Early or mild PD
Adjunct with levodopa for advanced disease, reduces the dose of levodopa needed, and may improve motor function in patients who experience wearing-off and on-off difficulties.
Selegiline + Rasagiline - Adverse effects
Confusion Dyskinesia Hallucinations Hypotension Insomnia Nausea.
Selegiline + Rasagiline - Interactions
Severe reactions may result if taken with meperidine or with fluoxetine or other SSRIs
Rasagiline - MoA
MAO-B inhibitor
Rasagiline - Indication
Monotherapy or adjunct medication in the treatment of parkinsonism
Tolcapone and Entacapone - MoA
Enhances the effectiveness of levopoa by inhibiting COMT, the enzyme that metabolize levodopa to 3OMD. By this action, it produces twofold increase in the oral bioavailability and half-life of levodopa.
Tolcapone: inhibits COMT in glial cells and inhibits conversion of dopamine to 3-methoxytyramine
Tolcapone and Entacapone - Indication
PD
Tolcapone and Entacapone - Adverse effects
Both: Diarrhea Nausea Discoloration of urine, sweat, saliva Tolcapone: Rare: fatal hepatitis
Dopamine receptor agonists
Bromocriptine Pramipexole Ropinirole Rotigotine Apomorphine Benztropine Trihexyphenidyl
Dopamine receptor agonists - MoA
Directly activate dopamine receptors in the stratum. Because they do not require functional dopaminergic neuron to produce their effects, they are sometimes helpful in advanced cases of PD, in which few dopaminergic neurons remain. They work by primarily activating D2 receptors and this leads to inhibition of the indirect neuronal pathway from the striatum to the thalamus and increase thalamic stimulation of the motor area of the cortex.
Dopamine receptor agonists - Adverse effects
Nausea
Orthostatic hypotension
Mental disturbances
Daytime sleepiness
Bromocriptine - MoA
Is a D2 agonist and a D1 antagonist.
Bromocriptine - Indication
Adjunct to levodopa in patients who have advanced PD and experience wearing off effects and on-off motor fluctuations.
Diabetes type 2