Carbidopa consists of decarboxylase inhibitors. It prevents the degradation of levodopa before it reaches the brain. It prevents decarboxylation of the compounds. It is used in inhibiting the activity of dopamine decarboxylase. Carbidopa is polar and charged compound. The quantity is generally increased in brain due to use of carbidopa.
Levodopa is a central nervous system agent. It gets converted into dopamine in the brain. These both are taken in combination for the treatment of various diseases like Parkinson’s disease. The symptoms of Parkinson’s disease are slow movement, tremors and many more. Dopamine is compound which is naturally found in brain. These symptoms are caused due to lack of dopamine.
Levodopa is being converted to dopamine in the brain. This conversion is facilitated by DOPA carboxylase. This reaction occurs only after the levopoda has crossed the blood brain barrier. Carbidopa cannot cross the blood barrier. Blood brain barrier is the barrier found in the central nervous system. This barrier acts as a highly selective semi permeable membrane which separates blood from the fluid of the brain.
Dopamine thus, formed prevent the symptoms of Parkinson’s disease to appear. But there are various side effects of dopamine that is nausea and vomiting. For prevention of these side effects, levopoda is taken in a combination with DOPA decarboxylase inhibitor (DDCI). This prevents the conversion of levodopa to L-DOPA to dopamine peripherally. Peripheral dopamine is thus, ineffective as it do not penetrate the blood brain barrier.