There is currently no cure for Parkinson's disease, nor any way to slow down its progression or reverse the damage that has been done. Treatment, thus, focuses on symptom management — and a wide variety of medications can come into play in the process of controlling both motor and non-motor symptoms.
1. Levodopa/carbidopa (Sinemet, Rytary)
Levodopa, a drug that can reach the brain, where it is converted into the dopamine Parkinon's disease patients progressively lose, has been around for decades now and is considered the single most effective medication for the motor symptoms of Parkinson's disease. It is prescribed together with another drug called carbidopa, which prevents the breakdown of levodopa on its way to the brain. This combination is available under the brand names Sinemet and Rytary. It is usually well-tolerated (not so many side effects) and helps reduce your slowness of movement, rigidity, and rest tremors.
Possible side effects that some patients encounter include:
- Nausea and vomiting
- A dry mouth
- Involuntary movements (dyskinesia)
- Occasionally, patients who take levodopa become confused and even experience delusions or hallucinations
Levodopa/carbidopa has also been associated with an increased likelihood of developing kidney, liver, and cardiovascular complications, as well as glaucoma.
2. Duopa: Carbidopa/levodopa in gel form
The US Food and Drug Administration approved a gel form of carbidopa and levodopa more recently, sold under the brand name Duopa. This form, which is given through a feeding tube, is more suitable for people in the later stages of Parkinson's whose carbidopa-levodopa wasn't effective in another way any longer. Because of the way in which Duopa is administered, the levels of the drug in your body remain more constant and predictable. Just like levodopa/carbidopa taken by mouth, however, Duopa does eventually lead to fluctuations in efficacy.
3. Dopamine agonists (pramipexole, ropinirole, rotigotine patch)
Dopamine agonists — which include pramipexole, ropinirole, and the rotigotine patch — behave like dopamine in the brain. They may be oral, injected, or come as a patch, and can be prescribed alongside levodopa or as a stand-alone treatment for the motor symptoms of Parkinson's. Dopamine agonists are less likely to lead to fluctuations in efficacy, and also have the advantage of a reduced risk of complications after taking the drugs for a long time. They do come with potential side effects that differ from those associated with levodopa:
- Nausea and vomiting
- Low blood pressure and associated lightheadedness
- Swollen legs
- Cramping within the muscles
Confusion and hallucinations are also possible, and some patients experience psychosis or impulse control issues. These may manifest as overeating, gambling, or hypersexuality, among other possibilities. Though rare, it is important to be aware of the possibility of this happening.
Apomorphine falls into the category of dopamine agonists, but it is specifically administered to manage "off periods" associated with other Parkinson's medications. Apomorphine can help improve your motor function during these times, but it cannot be taken to prevent "off episodes" in the first place.
5. MAO-B inhibitors
MAO-B inhibitors work by prolonging the action of dopamine in the brain by slowing the process of its breakdown, thus improving your symptoms. Examples are:
- Selegiline (Eldepryl, Emsam, Zelapar)
- Rasagiline (Azilect)
- Safinamide (Xadago)
Because MAO-B inhibitors can lead to severe adverse effects in some patients if they're taken together with certain antidepressants or opioids, it's very important for prescribing physicians to be aware of all the medications you are taking (not just specifically for Parkinson's).
Side effects will vary depending on the exact drug you are taking, but can include:
- Dry mouth
- Hallucinations in patients who also use carbidopa/levodopa)
6. Catechol-O-methyltransferase (COMT) inhibitors
COMT inhibitors serve to prevent the breadown of levodopa — and as such, patients will only be prescribed these drugs if they're also taking levodopa. The two medications you may be prescribed are Entacapone (Comtan) and Tolcapone (Tasmar), and they usually enter the picture in situations where levodopa isn't working well anymore and dopamine agonists cause too many side effects to be a viable option.
They, too, can have adverse effects:
- Discolored urine
- Vivid dreams
- Involuntary movements (if these occur, your dosage of levodopa should be adjusted)
7. Anticholinergic medications
Anticholinergic drugs have been around the longest, and they may be prescribed to reduce rigidity and tremors in certain patients. They do not have much of an effect on the other motor symptoms of Parkinson's disease, however, and won't be offered to patients who already suffer from confusion. Anticholinergics can be taken as a stand-alone, or together with drugs such as dopamine agonists and levodopa. Examples include:
Among the possible side effects are:
- Memory loss
- Constipation and trouble urinating
As such, the benefits of the drugs, like reduced tremor frequency, may not outweigh the trouble it brings.
Amantadine (Symmetrel) has an interesting story — initially designed as an antiviral medication to treat the flu, the fact that it can also help patients in the earlier stages of Parkinson's fight tremor, fatigue, and stiffness and increase their voluntary muscle control was discovered quite accidentally. Amantadine is often prescribed alongside levodopa.
Its potential side effects include:
- Loss of concentration
- Ankle swelling
- Blotchy skin
9. Parkinson's drugs to help with your non-motor symptoms
A significant portion of Parkinson's disease patients will suffer from depression, and though talk therapy can be an integral part of treating it, antidepressants are also very effective. Parkinson's patients are most commonly prescribed selective serotonin reuptake inhibitors (SSRIs), but tricyclic antidepressants are another option.
Parkinson's disease patients can suffer from a whole range of sleep disorders, from insomnia to fatigue and even acting their dreams out. Not all of these conditions can effectively be treated pharmacologically, but stimulants like modafinil and caffeine can help those patients who suffer from daytime fatigue.
Especially in the later stages of the disease, dementia is extremely commonly seen in Parkinson's patients. Cholinesterase inhibitors can be prescribed in this case. Initially developed for people suffering from Alzheimer's disease, they can improve your memory and cognitive function. Options include:
- Rivastigmine (Exelon)
- Galantamine (Razadyne)
- Donepezil (Aricept)
- Memantine (Namenda)
Psychosis and hallucinations
Because some of the medications commonly prescribed for the motor symptoms of Parkinson's disease can induce hallucinations and psychosis as adverse effects, lowering the dose of those drugs or even ceasing their use (after which another medication is substituted) is often a necessary part of treatment. This will be a treating doctor's first course of action. Should that not work, antipsychotic drugs can be introduced. They include:
- Quetiapine (Seroquel)
- Pimavanserin (Nuplazid)
- Clozapine (Clozaril)
The lowest possible dose will be used.
Another frequent problem in people who have Parkinson's disease, constipation can be improved through changes to your lifestyle and diet. Should that not offer sufficient relief, however, medications that can help include fiber supplements (like Metamucil), laxatives (like Dulcolax), and stool softeners (like Miralax).