Loss of neurons in the brain that use dopamine to communicate is one of the hallmark features of Parkinson’s disease (PD), causing slowness, stiffness, tremor and balance problems. Replacing the brain’s dopamine is therefore one of the key treatment strategies to help improve the motor symptoms of PD. Dopamine itself does not cross the blood-brain barrier and therefore can’t be used to treat PD. Instead levodopa, a precursor of dopamine, which does cross the blood-brain barrier is used. If levodopa is ingested by itself however, it breaks down in the bloodstream before it crosses into the brain, so levodopa is typically ingested with another medication that stops it from breaking down. In the US, the combination of carbidopa/levodopa is used. When levodopa is taken with carbidopa, much lower doses of levodopa can be consumed and side effects such as nausea are minimized. Carbidopa/levodopa is the mainstay of treatment for PD and is the most effective medication available for PD. APDA research funding played a role in the discovery of levodopa for PD treatment, when we funded the work of Dr. George C. Cotzias back in the 1960s.
Despite its common and widespread use as a treatment for PD, our readers often have questions about carbidopa/levodopa therapy. This week I will address some of these common questions that have been sent to us by readers like you.
Are there any negatives to consider if I want to postpone starting carbidopa/levodopa? The only symptom that I currently notice is tremor which affects my non-dominant hand and does not affect my daily functioning. I have no problems with my walking or balance and I exercise every day.
In general, there is no downside to postponing levodopa to treat a tremor that is not affecting function. Please discuss with your neurologist or physical therapist to determine if you are able to exercise effectively and up to your maximal capabilities while unmedicated. If you are not able to exercise maximally when untreated, then you should consider starting medication.
Does carbidopa/levodopa treat Parkinson’s progression?
Carbidopa/levodopa unfortunately does not change the progression of PD as far as we are aware, it just treats the symptoms. It is best at treating the slowness and stiffness of PD, but in many cases, treats the tremor as well.
Does carbidopa/levodopa treat the tremor associated with Parkinson’s?
The answer is, sometimes. In many people, carbidopa/levodopa is very effective in controlling the tremor of PD. Yet for some people, carbidopa/levodopa does not seem to help the tremor much. Because tremor is present at rest and often goes away when the person is using the limb, a tremor can be more of a nuisance than a source of disability. For this reason, many movement disorders specialists will focus on whether the carbidopa/levodopa is helping the symptoms that do cause the disability, namely stiffness and slowness. It should also be noted, that for people whose tremor does not improve with medication, deep brain stimulation (DBS) can be considered as a treatment option.
