E1: Parkinsons Flashcards
What are the 4 major features of Parkinson’s disease?
- Bradykinesia
- Muscular rigidity
- resting tremor
- Impairment of postural balance and gait
What is the pathophysiology behind Parkinson’s disease?
- Loss of dopamine neurons in the Substantia Nigra pars compacta
- Symptoms develop when 70-80% loss of the DA neurons
How does L-Dopa treat Parkinson’s?
- “replacement”therapy
- Increases DA levels, dopamine does not cross the BBB, but L-Dopa does and si then converted to DA in the neuron
How long can L-Dopa treat the symptoms of Parkinsons?
- Improvement of PD symptoms for 3-4 years, and then the effectiveness will decrease
- Does not affect progression of disease and not effective in drug-induced Parkinsonism
Why Is Carbidopa often given with L-Dopa?
L-Dopa can be converted to DA in the periphery and Carbidopa inhibits Dopa-decarboxylase but doesn’t cross the BBB. Therefore conversion of L-Dopa to DA is inhibited in periphery but not in the brain
What are the side effects of L-Dopa/Carbidopa?
- N/V
- Postural hypotension, Arrhythmias, HTN
- dyskinesias
- Depression, anxiety, agitation (treat with atypical antipsychotics)
What is the “On-Off Phenomenon?”
- Fluctuations in the clinical response in patients on successful L-Dopa therapy
- “On” is improved mobility
- “Off” is Akinesia due to falling drug levels
What drug can be used as a rescue during an Off phase on L-Dopa therapy?
Apomorphine
What drugs cannot be given with L-Dopa and why?
- MAOI: may cause hypertensive crisis
- Pyridoxine: increases peripheral metabolism of L-Dopa thus decreases effectiveness
What are the contraindications of L-Dopa?
- Psychosis
- closed angle glaucoma
- Cardiac disease
- active peptic ulcer disease
- malignant melanoma
What kind of drugs are Selegiline, Rasagiline, and Safinaminde?
MAOIs
What is the MOA of MAOIs?
- Inhibits DA metabolism
- Inhibits MAO-B in the CNA and reduces striata metabolism of DA, does not affect peripheral metabolism of DA by MAO-B
** may inhibit progression of PD by decreasing free radicals produced during DA metabolism
What are the Adverse effects of MAO-BIs?
- Insomnia
- Severe HTN if combined with other MAOIs
- increase side effects of L-DOPA
- Do NOT combined with Meperidine: can lead to stupor, rigidity, agitation, serotonin syndrome
- Serotonin syndrome if combined with TCAs or SSRIs
What kind of drugs are Tolcapone and Entacapone?
COMT inhibitors: inhibits DA and L-Dopa metabolism
What is the MOA of tolcapone?
-Inhibits COMT in CNS and periphery, prolongs action of DA in the CNA, increases pool of L-Dopa for transport into the brain
What is the MOA of Entacapone?
-Inhibits COMT in periphery only, increases pool of L-Dopa for transport in the brain
What are the side effects of COMT inhibitors?
-Dyskinesia, confusion, nausea, hypotension, abdominal pain, sleep disturbance, and orange color to urine
What kind of drug is Stalevo?
A combination of L-Dopa, Carbidopa, and Entacapone
What is the MOA of DA receptor agonists?
- Stimulates DA receptors
- acts directly on receptors, Primarily DA D2
- because thy act directly on receptors, they continue to be effective as the disease progresses
What kind of drug is Bromocriptine, Ropinirole, Pramipexole, and apomorphine
-DA receptor agonist
What are the side effects of Bromocriptine?
Vasospasm, erythromelagia
Which drugs can be used as Monotherapy in mild PD and has a soothing response to L-Dopa in late PD?
Ropinirole and Pramipexole
What is the DOC of restless leg?
Ropinirole, a relatively pure DA D2 agonist
Since Apomorphine causes nausea, you should pretreat with an antiemetic. Which one should you use, and which should you avoid?
- Use trimethobenzamide
- avoid antiemetic that target the serotonin system (ondansetron) because it can cause HTN and LOC
- Avoid antiemetics that blocks DA D2 receptors (Prochlorperazine)
What are the side effects of DA agonists?
- Anorexia, N/V
- postural HTN, cardiac arrhythmias
- Dyskinesia
- mental disturbance
- increased prolactin
What is the MOA of Amantadine?
- Increase DA neurotransmission
- may increase release of DA and may inhibit DA reuptake
What is the use of Amantadine?
- antiviral use for influenza
- used to treat early or mild cases of PD
What are the side effects of Amantadine?
- livedo reticularis: reddish blue spotting of skin
- restlessness, depression, irritability, insomnia, hallucinations, peripheral edema
What kind of drugs are Benzotropine and Trihexyphenidyl?
-Muscarinic receptor antagonists that restore DA/ACh balance in the striatum
What is the use of Benztropine and trihexyphenidyl in PD?
- modest anti PD action
- improves rigidity, tremor, and has little effect on bradykinesia
- used in early and late stages, adjunct to DA therapy
What is Pimavanserin?
an atypical antipsychotic approved for the treatment of psychosis and delusions associated with PD
What is the MOA of Pimavanserin?
-Inverse agonist/antagonist for serotonin receptors, but does not affect dopamineragic, adrenergic, cholinergic, or histamine receptors
What are the non-pharmacologic treatments of PD?
- Neuroprotection with antioxidants and anti-apoptotic agents
- Pallidotomy
- transplants of fetal neurons or patient-derived stem cells
- Gene therapy
- DBS
What is the pathophysiology behind Alzheimer’s?
-degeneration of cholinergic neurons
What kind of drugs are Donepezil, rivastigmine, and Galatamine?
Cholinesterase inhibitors, can treat Alzheimer’s
What is the MOA of Cholinesterase inhibitors?
-Inhibit metabolism of ACh, increases the amount of ACh in the nerve terminal
How are Cholinesterase inhibitors metabolized?
CYP450s
What are the common side effects of Cholinesterase inhibitors?
-Peripheral cholinergic side effects such as nausea, vomiting, diarrhea, cramping
What kind of drug is Memantine?
-NMDA receptor antagonist that blocks pathological activation of NMDA receptors
What is the use of Memantine?
-reduces excitotoxic effect of glutamate and slows degeneration, used in late stages of Alzheimer’s in combination with AChE-Is
What are the side effects of Memantine?
Agitation, insomnia, urinary incontinence, diarrhea
What are the contraindications of Memantine?
-Use with meperidine and Dextromethorphan