Carbidopa/Levodopa, that miracle drug for the treatment of Parkinson’s disease has only been in use a little over 60 years. In that time frame, research has accelerated, more knowledge of the brain has been revealed and more drugs have been added to the arsenal for fighting the symptoms of Parkinson’s disease. This article will look at the classes of drugs commonly used. It is not intended to replace the advice of your neurologist or physician. Parkinson’s disease is a very complex disease, and no two people with Parkinson’s manifest the symptoms in the same way. Treatments must be tailored to the individual, and only a Parkinson’s disease specialist can effectively determine what is best.
Before carbidopa/levodopa came on the scene, treatment often consisted of anticholinergic drugs. Anticholinergic drugs block the activity of the neurotransmitter acetylcholine which is involved in memory and control of movement; it has no affect on the dopamine systems in the brain. This class of drug is rarely used today because there are more effective ways to treat PARKINSON’S DISEASE now available. In some cases, particularly in people with severe dystonias that develop from periods when their usual medications fail to work, anticholinergic medications may help. One of the main side-effects of this class of drug is mental “fogginess”, problems with memory as well as dry mouth, constipation and blurred vision. The pharmacological name for this medication is trihexiphenidyl (Artane).
MAO-B or monoamine oxidase inhibitor B, is also used early in the treatment of PARKINSON’S DISEASE . It has only a rather limited effect on PARKINSON’S DISEASE symptoms, however, if used very early in the diagnosis, it can delay the need for carbidopa/levodopa medications. Sometimes it can be added later in the course of the disease to enhance the effect of levodopa. Basically, this drug works by breaking down the levodopa in the brain and making it more available to weakened neurons. It too has side effects; it may cause dizziness and low blood pressure, indigestion, nausea and headaches. Some of the drugs in this class may provide some neuroprotection, and studies are on-going, however there has not been any really conclusive evidence . Rasagiline (Azilect) and seligiline or deprenyl (Eldepryl or Zelapar) are the pharmaceutical and trade names for this medication.
Carbidopa/levodopa is the “gold standard” of treatment for symptoms of PARKINSON’S DISEASE . It has been around only since the 1960s, but has made a world of difference in patients’ lives. It is the most effective treatment available but it has also has generated a lot of discussion, both pro and con. There were concerns about extended levodopa replacement becoming toxic, however research has not found that to be true. Other issues revolved about the best time to introduce it into the treatment program. There have been arguments that beginning treatment with carbi/levodopa too early in the course of the disease will limit the length of time its benefits are effective without causing serious side effects. The other side thinks that delaying the introduction of carbi/levodopa lowers the quality of life of the patient and leaves them vulnerable to other aspects of the disease. Most neurologists favor an earlier start, but there are some modifying factors.
Carbidopa/levodopa is available in many different combinations. Dosing strategies have to be carefully worked out in collaboration with the neurologist in order to avoid serious side effects and to obtain maximum benefit. This is not a medication where one size fits all! It is possible that more than one form of this medication may be used at different times of the day, so people who are taking this need to be very aware of which pill is taken at what time; and timing is equally as important as the pill. The formulations come in different shapes and colors, but careful vigilance is still necessary. Perhaps the oversight of a caregiver can be enlisted.
The first “miracle” was carbidopa/levodopa, introduced as “Sinemet”. The small amount of carbidopa listed first in the fraction, was added to reduce the nausea that levodopa can cause. The medical terminology “sin = without” and “emesis = nausea” became the clever name for this drug. A bit later, scientists figured out a way to make a controlled release form of this medication, one that would dissolve slowly over time and eliminate taking so many shorter acting pills. This was called Sinemet-CR. Carbidopa/levodopa does have side effects such as low blood pressure, dizziness, dry mouth and sometimes nausea.
What are the Common Side Effects?
- Loss of appetite
- Lowered blood pressure
- Dyskinesia (if used as a long-term therapy; between 3-5 years)
- People who use levodopa longterm may experience dyskinesia at some point, usually three to five years after starting the medication.
- The term dyskinesia describes involuntary, erratic, writhing movements of the face, arms, legs, and/or trunk, which usually occur one to two hours after a dose of levodopa has been absorbed into the bloodstream and is having its peak clinical effect.
Eating Proteins with Levodopa/Sinemet*
- It is best to take Sinemet 30 to 60 minutes before eating a meal. This allows the Sinemet to be quickly absorbed before the food can interfere.
- Take the Sinemet along with foods that don’t contain proteins.
- Ginger tea is a good choice for many people, because it often “settles the stomach”.
- A graham cracker or soda cracker along with the ginger tea may help too. These foods are very low in protein and should not interfere with the absorption of Sinemet.
In the mean time, science found that adding another medication to the regimen kept the dopamine active in the brain, prolonging its effect and preventing “wearing off”. This was the addition of a COMT inhibitor. COMT is Catechol-O-Methyl Transferase and it was pharmaceutically known as entacapone (Comtan) or tolcapone (Tasmar). Both prescriptions were given together. This medication, too, must be carefully monitored. Anyone taking Tolcapone (Tasmar) must have regular blood tests to check liver function. COMT can also increase the side effects of carbi/levodopa and hallucinations can occur as well as increased movements, called dyskinesias.
Then a brilliant idea from a pharmaceutical company:…Why not combine the two in one pill? And Stalevo was born; a combination of carbidopa, levodopa and entacapone in one tablet. This medication also comes in multiple strengths. It has the advantage that only one pill is necessary instead of two, simplifying the regimen, but for some people, side effects can limit its usefulness. There is also some consideration that the combination may contribute to prostate problems for men, but this is still under scientific investigation.
What are the Common Side Effects?
- hyperkinesia (an abnormal amount of uncontrolled muscular action; spasm.)
- abdominal pain
- harmless discoloration of urine
- saliva and/ or sweat