Parkinson’s disease (PD) was first described by James Parkinson in 1817.
It is characterized by tremors, muscle rigidity, difficulty moving, and balance problems. It is a central nervous system disorder where cells are lost in the substantia nigra – midbrain region.
These cells produce dopamine, a neurotransmitter used in initiating and coordinating muscle movement. Most PD patients walk with a shuffling gait, lean forward, and are somewhat off balance. This is a progressive disease with no cure.
Other symptoms associated with PD include anxiety, depression, fatigue, slow thinking, dementia, fragmented sleep, and hallucinations. Some drugs can cause PD symptoms, which are usually reversible on discontinuation of the medications.
Drugs for Parkinson's Disease:
Drug therapy changes as Parkinson’s disease progresses from early symptoms to advanced.
Initial therapy begins with one drug, and anticholinergic or dopaminergic like levodopa.
Adjunct therapy is added to improve symptom control, this includes COMT inhibitors, selegiline, apomorphine, and amantadine. Dopaminergic agents are the mainstay of Parkinson’s disease treatment.
Levodopa is widely recognized as the most effective treatment for Parkinson’s disease because it significantly improves movement and restores normal function.
Effects of this drug wear off over time and the on-off phenomenon – a wide fluctuation between abnormally increased and diminished motor function, present in many Parkinson patients after about 5 years of levodopa therapy. This group of drugs replaces or mimics dopamine actions in the brain; either giving the brain more dopamine or provide a drug that has the same action.
Dopamine cannot cross the blood brain barrier (BBB), so its prodrug – a compound that, on administration and chemical conversion by metabolic processes, becomes an active pharmacological agent – levodopa.
Once levodopa enters the brain, it is broken down into dopamine.
Carbidopa is usually given in combination with levodopa because it slows breakdown of levodopa before it reaches the CNS, allowing more of it to enter.
Apomorphine (Apokyn) is a self-injected agent; not used regularly; saved for when levodopa wears off more quickly than anticipated; boosting the effects of levodopa until the next dose.
Side effects of levodopa/Carbidopa include nausea and dyskinesias – abnormal, involuntary movements of the arms, legs, neck, and mouth; taking with food can reduce the nausea; the only way to alleviate movement symptoms is to lower the dose or add adjunct therapy.
side effect of dopamin-
Common side effects of dopamine agonist include dizziness, constipation, nausea, insomnia, daytime sleepiness, “sleep attacks,” yawning, hallucinations, and mood elevations that increase risk taking behavior.
A patient’s ability to drive or participate in daily activities may be impaired by daytime sleepiness and “sleep attacks.”
Patients should avoid drinking alcohol because it can intensify certain side effects of this drug.
Apomorphine should not be taken with anti-emetic agents (ondansetron (Zofran), granisetron (Granisol), or alosetron (Lotronex)).
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