Levodopa/Carbidopa for Parkinson's
Medications that Raise and Maintain Dopamine Levels in the Brain
Jun 15, 2007
Parkinson's Disease and Dopamine
Parkinson's disease, a chronic, neurological illness, involves the destruction or impairment of dopamine-producing brain cells. This is considered a "motor system" disorder because it affects a person's movement and coordination. The area of the brain that produces dopamine is called the substantia nigra, and the dopamine is a neurotransmitter, sending information to other parts of the brain to produce smooth movements. Approximately 80% of dopamine-creating cells can be damaged when Parkinson's disease occurs.
What are Levodopa and Carbidopa?
The drug combination levodopa/ carbidopa works as a dopamine regulator, by increasing dopamine and making sure it stays in the brain. Levodopa and carbidopa are a combination of drugs that together, help to prevent Parkinson's symptoms. Levodopa is converted by the brain into dopamine. It is sometimes referred to as L-dopa. Carbidopa is given with levodopa to prevent it from being converted into dopamine outside of the brain. Carbidopa also prevents the side-effects that occur when too much dopamine is outside of the brain: nausea and vomiting. Also, carbidopa decreases the amount of levodopa needed. Together, the two drugs provide an increase in dopamine in the brain at an optimum level. This combination is also known as Sinemet, its brand name.
Levodopa itself is currently the most effective drug for relieving Parkinson's disease symptoms. It seems to improve muscle rigidity and slowness, but has less of an effect on balance, gait, and tremor issues. It is arbitrary whether levodopa actually slows the disease process.
Side-Effects from Levodopa/Carbidopa
While levodopa/carbidopa can help Parkinson's patients maintain better lives for longer periods of time, their side-effects can be quite daunting:
- nausea, vomiting, loss of appetite (even with carbidopa)
- low blood pressure
- possible irregular heartbeat
- confusion, anxiety, hallucinations
- headaches, vertigo, fainting
- sleep disturbances
- increased tremors
There is a drug tolerance that happens to many Parkinson's patients after about 5 years of levodopa use. It is termed the "wearing-off effect" and it is the process of the drug lasting for shorter periods of time. A patient grows tolerant of the drug, so that more is needed to do the same job. Signs include:
- slowness or tremor before the next dose is due
- dystonia, or muscle spasms
Compensating with more levodopa can cause more problems, including loss of muscle control.
Regulating Levodopa/Carbidopa
To avoid the side-effects and eventual tolerance to levodopa/carbidopa, doctors are prescribing other drug combinations or Sinemet CR, a continuous-release formula which evenly releases levodopa into the brain. Another option is prescribing a dopamine agonist, which is less effective than levodopa, but good for new and/or mild cases. Doctors believe that prescribing the least amount of levodopa/carbidopa, saving the drug combination for later stages of the disease, and using milder drugs in the beginning of the disease course can allow patients to benefit from levodopa/carbidopa's positive aspects while warding off its side-effects and eventual ineffectiveness. For further reference: http://health.yahoo.com/ency/healthwise/hw91023 and http://www.medicinenet.com/levodopa-carbidopa/article.htm
***For more information, read Parkinson's Disease and Coping and Muhammad Ali's Fight.
***For related neurological information, check out the Neurological ARTICLE INDEX and Blog.
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