Levodopa is the main treatment for Parkinson’s disease. However, doctors often prescribe it in combination with other dopa-decarboxylase-inhibiting drugs such as carbidopa and benserazide.
First and foremost, levodopa belongs to the medicine family of antiparkinsonian drugs. It performs its action in the central nervous system by becoming dopamine in the brain.
The first person to associate Parkinson’s disease with a dopamine deficiency was the biochemist Oleh Hornykiewicz. He examined the autopsies of people who died from Parkinson’s and suggested that it was a relationship. Oleh later began treating patients with a racemic mixture of DOPA. The results were positive.
Not long after, Curt Porter, another researcher, showed that the L-DOPA stereoisomer was the active one. Thus, this finding meant that only half the dose was effective.
Later, they began to synthesize various molecules, such as benserazide and carbidopa. These improved the results of the treatment. By using them, they also reduced the amount needed to achieve the desired effect.
Characteristics of Parkinson’s disease
Parkinson’s is a disease of the central nervous system caused by a deficiency of dopamine, a neurotransmitter in striated neurons. It occurs due to the death of nigrostriatal neurons. The origin of this disease is multifactorial and there is a high prevalence in the general population.
The elderly population is the most affected group. However , it affects only about 2% of those over 65 years of age. Nevertheless, it can also appear in young people.
Tremor is the most common symptom of Parkinson’s, and it is present in over 60% of people who are diagnosed with this disease. However, there may be other motor symptoms such as:
- Slow movements (this is called bradykinesia)
- Changes in postural reflexes and falls
Other symptoms that may appear during the course of the disease are:
- Dementia and memory loss
- Muscle pain
- Neuropathic pain
Furthermore, we know that there is a link between this disease and an increase in the alpha-synuclein protein. There is also a link between the latter and Alzheimer’s. Thus, the therapeutic strategy under investigation is to administer inhibitors of alpha-synuclein aggregation or immunization for these protein derivatives. There is also a study with Nilotinib investigating this type of therapy.
General properties of levodopa
Parkinson’s drug therapy consists of trying to increase dopamine levels by acting directly on the receptors. It inhibits either the breakdown of the neurotransmitter or LAAD, which is the enzyme that converts DOPA to dopamine.
In this way, you may wonder why dopamine is not administered directly to a patient. The problem is its high uptake and metabolism because it prevents absorption. In addition , dopamine is a water-soluble molecule. Therefore, it is not able to cross the blood-brain barrier that protects the brain.
For all these reasons, the current treatment for Parkinson’s is levodopa, a precursor to dopamine. This drug crosses the blood-brain barrier and becomes dopamine when it reaches the central and peripheral nervous system.
Although levodopa can effectively cross the blood-brain, it also has a strong metabolism at the peripheral level. The amount that reaches the brain is therefore very small. To solve this problem, doctors administer it together with other medicines that inhibit the LAAD enzyme. With this, it is possible to inhibit the transformation of levodopa into dopamine at the peripheral level, and eventually, more of it reaches the brain.
The benefits of administering levodopa with LAAD inhibitors
Concomitant administration of LAAd inhibitors reduces the required amount of Levodopa by 75%. This is because they increase the half-life of the drug and help maintain stable levels in the brain.
Thus, the administration is more efficient as it is manifested in faster measures. Cardiovascular and gastrointestinal effects decrease by reducing the amount of dopamine in peripheral tissue. Therefore, administration of levodopa in combination with benserazide or carbidopa is quite common.
Levodopa is the first line of treatment for Parkinson’s disease. Doctors prescribe it along with other medications to increase effectiveness.
Consult your doctor or pharmacist with any questions you may have about this disease and its treatment. Also, be sure to ask them about the latest advances and clinical trials that are currently available.