Common name/Other name
Parkinson’s disease (PD) is a progressive neurodegenerative disorder of the brain. PD causes neurons in several parts of the brain to degenerate resulting in a decrease of dopamine release. It leads to an imbalance in the levels of the neurotransmitters in the brain – low dopamine, high acetylcholine. Thiscauses most of the characteristic symptoms of PD collectively termed Parkinsonism. The disease progression is classified into 5 stages with increasing severity of symptoms.
Stages of Parkinson’s Disease:
- Stage 1 manifests with tremors and difficulties in movement. There are changes in posture, walk, and facial expressions.
- Stage 2 produces moderate symptoms with more noticeable stiffness, tremors, and trembling. Difficulties in walking progress but balance is still normal.
- Stage 3 already causes a patient to lose balance and have decreased reflexes. Frequent falls are common in this stage. Daily activities are greatly affected because movements are significantly slower.
- Stage 4 PD patients stand without help from another person but require the use of assistive devices such as a walker. Patients already need help for daily tasks since living alone can be dangerous.
- Stage 5 inhibits the patient from standing or walking due to advanced muscle stiffness. Patients heavily require assistance. Hallucinations and delusions are common.
The exact cause of PD is still unknown, but several contributing factors have been identified. Some gene mutations can cause PD especially in a family with many members who have Parkinson’s. Certain toxins and environmental triggers also increase the risk of PD. Within the brain cells of PD patients, Lewy bodies or clumps of specific substances like A-synuclein are present.
There are no specific tests to diagnose PD. Physicians use the patient’s symptoms, medical history and results of various tests to conclude its presence. Neurological and physical exams are done as well as imaging tests of the brain to eliminate other disorders of the brain. Significant improvement of symptoms upon the use of carbidopa-levodopa can also confirm PD.
Commonly Prescribed Drugs
There are no current medications that cure PD. Parkinson’s drugs are used to control the symptoms of a patient. The goal of drug therapy is to increase or replace dopamine in the brain to improve the symptoms.
- Carbidopa-levodopa is the most common and effective drug combination for PD. Levodopa enters the brain and converts into dopamine which effectively increases the dopamine levels. Carbidopa protects levodopa from converting into dopamine outside the brain. However, levodopa does not have an effect on the disease progression and its effect decreases with time. High doses of levodopa promote dyskinesia or involuntary movements. Side effects: nausea, lightheadedness especially upon standing
- Dopamine agonists imitate the effects of dopamine in the brain. These are less effective than levodopa but can be used as a supplement to manage the wearing off of levodopa’s effects. Examples of dopamine agonists include pramipexole, ropinirole, and rotigotine. Side effects: lightheadedness, hallucinations, sleepiness, compulsive behaviors
- MAO-B inhibitors increase the levels of dopamine by inhibiting monoamine oxidase B which metabolizes it. These drugs can decrease the progression of PD. Rasagiline and selegiline are the available MAO-B inhibitors. Side effects: nausea, insomnia
- COMT inhibitors prolong the effects of levodopa by inhibiting another enzyme that breaks down dopamine, the catechol-O-methyltransferase. Entacapone is the main COMT inhibitor used. Side effects: dyskinesias, diarrhea
- Anticholinergics control resting tremor which is the primary symptom of PD. These drugs inhibit the effects of acetylcholine which causes some of PD symptoms. Examples of anticholinergics for PD include benztropine and trihexyphenidyl. Side effects: impaired memory, confusion, hallucinations, constipation, dry mouth, difficulty urinating
- Amantadine is usually given alone during mild, early stages of PD for a quick relief of symptoms. It is given during the later stages of PD in combination with carbidopa-levodopa. Side effects: purple mottling of skin, ankle swelling, hallucinations