Comparison of Blood Dopamine Levels in Idiopathic Parkinson's Patients Receiving Levodopa Carbidopa Entacapone or Levodopa Benserazide

After more than 40 years of routine clinical use, levodopa has remained the gold standard of symptomatic efficacy in the treatment of Parkinson's disease (PD). Levodopa benserazide and levodopa carbidopa entacapone are antiparkinsonian agents used to treat the motor symptoms of Parkinson's disease.

Parkinson's disease is a neurodegenerative disease characterized by the loss of dopamine-producing neurons in the brain. Dopamine is a neurotransmitter that is central to controlling movement in the brain. Dopamine deficiency leads to motor symptoms typical of Parkinson's disease. These symptoms are tremor, rigidity, bradykinesia and postural instability. Levodopa is an amino acid that is the precursor of dopamine. When levodopa reaches the brain, it participates in dopamine synthesis and increases dopaminergic activity. Levodopa is the most effective agent in treating the motor symptoms of Parkinson's disease. However, chronic use of levodopa can lead to motor complications. These may include end-of-dose worsening, motor fluctuations and dyskinesias. These complications are due to levodopa's short half-life and pulsatile stimulation of striatal dopamine receptors. A dopa decarboxylase inhibitor (DDCI) is added to levodopa to reduce the peripheral metabolism of levodopa and prevent nausea. These inhibitors may be carbidopa or benserazide. The main peripheral pathway of metabolism of levodopa given with DDCI is the catechol-O-methyl transferase (COMT) enzyme. Entacapone, a drug that inhibits the COMT enzyme, can also be added to the levodopa/DDCI combination. Entacapone prolongs the peripheral half-life of levodopa and increases its central bioavailability.

Levodopa is always combined with a dopa-decarboxylase inhibitor (DDCI), and available preparations use either carbidopa or benserazide to block the main levodopa-metabolizing enzyme. Previous randomized, controlled studies in PD patients reported that clinical effects and levodopa pharmacokinetics (PK) were comparable between carbidopa and benserazide.

Levodopa benserazide and levodopa carbidopa entacapone combinations are effective and safe antiparkinson agents in treating motor symptoms in Parkinson's disease. These drugs increase ON-time and decrease OFF-time in Parkinson's disease patients and provide symptomatic relief. In some selected patients with advanced stages and dyskinesia, levodopa carbidopa can be used in device-assisted treatments in the form of intestinal gel.

Apart from levodopa preparations, it is widely used in preparations containing rasagiline in our country as a monoamine oxidase (MAO) inhibitor in Parkinson's patients. Apart from this, another group of drugs aimed at reducing symptoms in young patients are drugs called dopamine agonists, which are given to the body to synthesize dopamine. Among these treatments, pramipexole, ropirinol and apomorphine, which can be given with device support or given by subcutaneous injection, are used in our country. Deep brain stimulation, also known as brain stimulation, is another treatment method applied to invasive selected patients.