Current Drug Treatments for Parkinson's Disease
As yet there’s no cure for Parkinson’s disease so treatment is designed to manage the symptoms - this treatment, however, won’t halt the disease.
If the disease is diagnosed early an effective course of drugs is set in motion. Various different drugs - and sometimes a combination of drugs - are used to treat the various stages of the disease. Most have had good results in easing the specific symptoms they are designed to reduce. However, they do appear to have a limited lifespan and after about 10 to 15 years the initial effects start to wear off.
No two people with Parkinson’s disease will ever have the same symptoms at the same time and each person reacts differently to treatment. It’s initially trial and error to see which drugs are effective and which have the least side effects.
These are sometimes given in the early stages of the disease to help treat symptoms such as tremors. They block signals of a neurotransmitter in the brain called acetylcholine. This becomes overactive because the disease causes the degeneration of another neurotransmitter, dopamine. The drugs can help restore the balance with dopamine. They are not generally used in patients over 70 because they can exacerbate confusion and memory problems. Anticholinergics are sometimes used with other Parkinson’s drugs, like Levodopa, to increase their effectiveness.
This is the most commonly used drug once the disease is established and begins to progress. Levodopa can ease rigidity, slowness and tremors remarkably quickly but the side effects such as severe nausea and vomiting can be severe. Prolonged use, particularly in younger patients can lead to involuntary movements (known as dyskinesias).
It’s generally given with carbidopa, which helps minimize the side effects and allows more of the levadopa to get to the brain so the patient needs less of it.
Stalevo is one of the newest drugs and is a combination of carbidopa, levodopa and entacapone. It has been found to be useful in patients who may already be taking levadopa/carbidopa but find the effects are wearing off. Its mechanism is confusing but effective - carbidopa decreases the levodopa side effects and entacapone lengthens the time levadopa works on the brain. In the later stage of Parkinson’s some people notice that the duration of the drug’s effects can become shorter (this is called “wearing off”). In some cases controlled release drugs are effective. These can be used at night followed by a person’s usual levadopa combination during the day. Some patients develop “on-off” episodes during which the medication suddenly starts or stops working, leading to no symptoms one minute and the appearance symptoms the next. It may be a case of fine tuning the drug doses to help control this.
These act on the dopamine receptors in the brain and become a substitute for the neurotransmitter. These very strong drugs can reduce all the symptoms of Parkinson’s disease but their side effects are quite severe, particularly in the elderly. They include confusion, delusion and aggression. Used early on and before levadopa, they can delay the need for the drug and reduce the long-term problems associated with it (in particular dyskinesia and “on-off” problems). They can also be used with levadopa. Dopamine agonists are not as effective in easing symptoms in some people as the levodopa combinations and most people with Parkinson’s will need levadopa eventually.