What Are the Facts?
- The drug levodopa is synthesized in the brain into dopamine. It is the most important first-line drug for the management of Parkinson's.
- Levodopa is almost always given in combination with the drug carbidopa, which prevents the nausea that can be caused by levodopa alone. Carbidopa is also a levodopa enhancer. When added, carbidopa enables a much lower dose of levodopa (80% less!) and helps reduce the side effects of nausea and vomiting. Pills containing both drugs are often labeled “carbidopa-levodopa,” with the active components listed in alphabetical order.
- Levodopa was developed in the late 1960s and was the first medication proven effective in treating a chronic neurodegenerative disease like PD. It remains the single most effective agent in the management of Parkinson’s symptoms.
- Levodopa in pill form is absorbed in the blood from the small intestine and travels through the blood to the brain, where it is converted into dopamine and stored in the neurons until needed by the body for movement.
- Carbidopa-levodopa tablets are available in immediate-release and slow-release forms as well as dissolvable tablets that are placed under the tongue.
- Carbidopa-levodopa extended release (ER) capsules (Rytary™) maintain levodopa concentrations longer than the immediate-release or other available oral levodopa formulations. Following an initial peak at about one hour, plasma levodopa concentrations are maintained for about 4 to 5 hours before declining. Clinical trials indicate that patients with motor fluctuations on other oral carbidopa-levodopa products may be able to switch to carbidopa/levodopa ER and experience a reduction in “off” time while requiring fewer medication administrations. Carbidopa/levodopa ER can be taken with or without food, but high fat meals may delay absorption. Dosages of carbidopa/levodopa ER are not interchangeable with dosages other carbidopa-levodopa products.
- Carbidopa/levodopa is also now available via a dopamine intestinal infusion pump (DUOPA™), which provides 16 continuous hours of carbidopa and levodopa for motor symptoms. The small, portable infusion pump delivers carbidopa and levodopa directly into the small intestine. In a clinical trial, the amount of “on” time without troublesome dyskinesia was better in the pump group when compared to the placebo group (4.1 vs. 2.2 hours). One of the major drawbacks to the pump approach is the need for a percutaneous gatrojejunostomy (a small feeding tube). These types of tubes can be the starting locations for infections and other complications.
Did you know?
Forty years after it was first introduced, levodopa is still the most effective medication available for the treatment of the motor symptoms.
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 long term 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.
Uncommon Side Effects
- Sleepiness, sudden onset sleep
- Impulse control disorders (compulsive behaviors) such as excessive gambling, shopping, internet use or increased sexual behavior
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.
Caution: PD medications may have interactions with certain foods, other medications, vitamins, herbal supplements, over the counter cold pills and other remedies. Anyone taking a PD medication should talk to their doctor and pharmacist about potential drug interactions.
For more information relating to prescribing Rytary™, please see How to Dose Rytary (Carbidopa and Levodopa extended release), by Dr. Robert A. Hauser of the University of South Florida, an NPF Center of Excellence.
Page reviewed by Dr. Joash Lazarus, NPF Movement Disorders Fellow, Department of Neurology at Emory University School of Medicine.