Levodopa is a milestone in the treatment of Parkinson's disease. Levodopa has been the most effective drug for Parkinson's disease since it was used in clinic in 1967 for nearly 40 years. Although there have been monoamine oxidase B inhibitor selegilan, Da such as pergolide, pramipexole and other drugs, almost all patients eventually need to take levodopa. The clinical application in recent 40 years has proved that the symptom improvement rate of patients can reach 70%~100%, and the curative effect can last for 5 years or even more, which is enough to explain the position of the drug in the treatment of Parkinson's disease.

        As the "gold standard" for the treatment of Parkinson's disease, levodopa is reflected in the following points: before levodopa is applied in clinical practice, the life expectancy of patients is much lower than that of the general population of the same age. After levodopa is applied, the life expectancy of Parkinson's patients is close to that of the general population, and the quality of life is also significantly improved. Compared with other drugs, it is the most effective. In the pelmopet study, within the first 6 months of treatment, the efficacy of pergolide was equivalent to that of levodopa, but after 6 months, the efficacy was significantly worse than that of levodopa. In the calm Parkinson study and other studies, the comparison of other Da with levodopa also led to similar conclusions. So how does levodopa treat Parkinson's disease? The essence of Parkinson's disease is the death of dopamine secreting neurons in the midbrain of patients, which leads to the lack of dopamine in the brain, resulting in a series of symptoms such as tremor, rigidity and bradykinesia. Dopamine is a neurotransmitter. It is the starting signal for the brain to direct the movement of other parts of the body and promote all basic movements. But direct administration or intramuscular injection of dopamine is ineffective. Because dopamine cannot penetrate blood vessels of blood-brain barrier and enter brain tissue. In addition, many peripheral tissues and organs have dopamine receptors. If dopamine is taken orally or injected intramuscularly, it will lead to side effects that many patients can't tolerate.

　　levodopaIt is a precursor substance of dopamine and a drug name commonly used in the world. Different manufacturers have different trade names when the drugs are on the market. Oral levodopa first passes through the stomach. The tablets are generally disintegrated and dissolved in the stomach, then discharged to the duodenum, and then to the small intestine. It is absorbed into the blood at the upper end of the small intestine. About less than 1% of levodopa can finally enter the brain through the "blood-brain barrier" and be absorbed by substantia nigra nerve cells or other nerve cells. Under the action of dopa decarboxylase, it removes a carboxyl group and turns into dopamine, thus supplementing dopamine in the brain and reducing the symptoms of Parkinson's disease. It takes 15 to 30 minutes for levodopa to enter the brain through the blood-brain barrier and then convert to dopamine. Therefore, generally speaking, the drug starts to take effect 20 to 30 minutes after taking the drug, but the best effect of the drug can be achieved only in about 1 hour and 30 minutes.

However, the elderly should pay attention to the following points when taking levodopa to treat Parkinson's disease:
(1) The tolerance of the elderly to levodopa decreases, and the peripheral Doba decarboxylase also decreases with age, so the dosage should be reduced.
(2) Older people with osteoporosis who are effective with levodopa should slowly resume normal activities, because increasing activities will increase the risk of fracture.
(3) Older patients are more likely to have mental adverse reactions, such as anxiety, insanity or neuroticism, when they are treated with other anti Parkinson drugs (especially anticholinergic drugs).
(4) Elderly patients (especially those with coronary artery disease) are particularly sensitive to the cardiac effect of levodopa. If used with carbidopa or Benserazide, these adverse cardiac reactions can be reduced or completely eliminated.