Carbidopa/levodopa

The combination of carbidopa and levodopa is used to treat Parkinson's disease and Dopa-Responsive Dystonia (DRD). This combination is sold under several brand names, including Sinemet®, Parcopa®, and Atamet®.Please note that the following has been based heavily on Pharmacology for Nursing Care Fifth Edition ISBN 0-7216-9843-3. Chapter 21. ”The symptoms of Parkinson’s Disease (PD) relate to the overall dysfunction of the extrapyramidal system that helps regulate movement. When extrapyramidal function is disrupted dyskinesias (disorders of movement) result. Those that characterize PD are tremors, rigidity, postural instability, and bradykinesia which may progress to akinesia. Psychologic disturbances such as memory loss may also be a symptom. PD is generally agreed to be caused by a neurodegenerative disorder causing a loss of dopaminergic neurons in the substantia nigra. This results in an imbalance between the neurotransmitters dopamine and acetylcholine (too much acetylcholine vs. too little dopamine.) Dopamine inhibits the neurons that release GABA , acetylcholine excites the neurons that release GABA. The balance of inhibition and excitement of GABA as needed for muscle movement is what allows us to function normally. When this balance is shifted the symptoms appear. Obviously the cure for PD would involve the cessation of destruction and the regeneration of dopaminergic neurons. Until then we rely on Levodopa to help. We have to use Levodopa because straight dopamine would be digested and chemically altered by enzymes before it reached the CNS to help, so we give Levodopa, a metabolic precursor to Dopamine. When Levodopa is ingested it makes its way to the Central Nervous System through the blood and by active transport across the blood-brain barrier. It is then ezymatically changed into the same chemical structure as endogenous Dopamine, thereby helping to restore balance and diminish symptoms. If given alone Levodopa is 98% inactivated peripherally by decarboxylase enzymes, and to a lesser extent COMT, leaving less than two percent to help out upstairs. Coadministration of Carbidopa allows 10% of the Levedopa to reach the CNS by partially inhibiting such enzymes. Benefits: At the beginning of treatment 75% of patients have a 50% reduction in symptoms. Although symptoms may be well controlled in the first 2 years, after 5 years, the patient may deteriorate to pretreatment levels. This is probably a reflection of the disease process and not evident of a tolerance to the drug. If you or a loved one is looking for answers it is strongly suggested that you consult a drug book as well as a physician with questions/ concerns.

External links

• Sinemet® datasheet