Carbidopa/levodopa

Carbidopa/levodopa, also known as levocarb and co-careldopa, is the combination of the two medications carbidopa and levodopa. It is primarily used to manage the symptoms of Parkinson's disease but does not change the course of the disease. It is taken by mouth. It can take two to three weeks of treatment before benefits are seen. Each dose then begins working in about ten minutes with a duration of effect of about five hours. Carbidopa/levodopa, also known as levocarb and co-careldopa, is the combination of the two medications carbidopa and levodopa. It is primarily used to manage the symptoms of Parkinson's disease but does not change the course of the disease. It is taken by mouth. It can take two to three weeks of treatment before benefits are seen. Each dose then begins working in about ten minutes with a duration of effect of about five hours. Common side effects include movement problems and nausea. More serious side effects include depression, low blood pressure with standing, sudden onset of sleepiness, psychosis, and increased risk-taking behavior. Carbidopa prevents the breakdown of levodopa outside the brain. In the brain, levodopa is broken down into dopamine by which it has its effects. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. It is available as a generic medication and is moderately expensive. The wholesale price in the developing world is about US$1.80 to $3.00 a month. In the United States, a month's supply costs about $50 to $150. In 2016, it was the 175th most prescribed medication in the United States, with more than 3 million prescriptions. It is primarily used to improve the symptoms of Parkinson's disease but does not change the course of the disease. It can take two to three weeks of treatment before benefits are seen. Each dose then begins working in about ten minutes with a duration of effect of about five hours. A formulation that can be given in an intra-intestinal pump, known as Duodopa, is being developed. Other uses include for dopamine-responsive dystonia (DRD) and restless legs syndrome. There is tentative evidence that it is useful in amblyopia when used with other treatments. Common side effects include movement problems, and nausea. Most common early side effect is hallucinations, as movement problems manifest 5–10 years after initiation of treatment. More serious side effects include depression, low blood pressure with standing, sudden onset of sleepiness, and the compulsion to gamble, engage in sexual behavior, or other risk-taking behavior. Levodopa is converted to dopamine via the action of a naturally occurring enzyme called DOPA decarboxylase. This occurs both in the peripheral circulation and in the central nervous system after levodopa has crossed the blood brain barrier. Activation of central dopamine receptors improves the symptoms of Parkinson's disease; however, activation of peripheral dopamine receptors causes nausea and vomiting. For this reason levodopa is usually administered in combination with a DOPA decarboxylase inhibitor (DDCI), in this case carbidopa, which is very polar (and charged at physiologic pH) and cannot cross the blood brain barrier, however prevents peripheral conversion of levodopa to dopamine and thereby reduces the unwanted peripheral side effects of levodopa. Use of carbidopa also increases the quantity of levodopa in the bloodstream that is available to enter the brain.