L-Dopa and Dopamine Agonists In Treatment of Parkinson’s Disease

Medication is the most commonly used treatment for Parkinson’s disease. While there is no cure for Parkinson’s, taking certain medications can help ease many of the symptoms that are associated with Parkinson’s that make life more difficult. Many of the medications that are used to treat Parkinson’s have side effects that may eventually interfere with daily life, but during the time that they are effective, they can allow you to continue your normal daily activities, sometimes for years.

As your condition changes, your needs for medication will change. It’s important to work closely with your doctor to establish the best dosage and timing to take your medicine, as well as the right medicines. The times that you eat and your physical activities may also make a difference in how effective your medications are.

Levodopa

The most commonly prescribed medication for Parkinson’s disease, levodopa (L-dopa) helps replace the dopamine that the brain of a person with Parkinson’s disease can no longer produce. Levodopa is a natural substance that’s found in plants and animals. Chemically, it’s a precursor to dopamine, which means that your body can convert it into dopamine. By increasing the levels of dopamine that the brain produces, L-dopa can help minimize some of the symptoms of Parkinson’s disease.

Unlike dopamine, which can’t cross the blood brain barrier to work directly in the brain, L-dopa does make it into the brain, but in very small amounts. Doctors combat this by combining levodopa with a second drug, called carbidopa, which increases the amount of L-dopa that reaches the brain.

During the early stages of Parkinson’s disease, L-dopa works predictably and can eliminate many of the symptoms associated with the disorder. As the disease progresses, however, the drug works less evenly, and side effects may become a problem. The side effects of L-dopa include involuntary movements (dyskinesia), especially when the drug is at its peak. Other side effects include a drop in blood pressure while standing, and possible hallucinations.

Despite the side effects, L-dopa is the best treatment available for Parkinson’s disease, and most people willingly accept the side effects as a trade-off for the disappearance of symptoms.

Dopamine Agonists

Often, doctors will prescribe a dopamine agonist in the early stages of Parkinson’s disease or along with L-dopa, especially when the onset is at a young age. Unlike L-dopa, dopamine agonists are not converted to dopamine by the brain. Instead, they mimic the effect of dopamine on nerve cells, fooling the body into believing that there is sufficient dopamine being produced.

The commonly used dopamine agonists are Permax (pergolide), Parlodel (bromocriptine), Mirapex (pramipexole) and Requip (ropinirole). The most common side effects associated with the dopamine agonists are an increase in involuntary movements, hallucinations and sleepiness. Most doctors avoid prescribing dopamine agonists if there is already a history of hallucinations.