Levodopa is a precursor of dopamine. Oral levodopa tablets generally disintegrate and dissolve in the stomach, then discharge to the duodenum, and then reach the small intestine, where it is absorbed into the blood at the upper end of the small intestine. A small part of levodopa can finally enter the brain through the blood-brain barrier, which is ingested by substantia nigra nerve cells or other nerve cells. Under the action of dopa decarboxylase, a carboxyl group is removed to become dopamine, Thus, it can supplement dopamine in the brain and alleviate the symptoms of Parkinson's disease.
Definition of Parkinson's disease
Parkinson's disease (PD) is a common degenerative disease of the nervous system, which is common in the elderly. The average age of onset is about 60 years old, and Parkinson's disease in young people under the age of 40 is rare. In China, the prevalence of PD among people over 65 years old is about 1.7%. Most patients with Parkinson's disease are sporadic cases, and less than 10% of patients have a family history. The most important pathological change of Parkinson's disease is the degeneration and death of dopaminergic neurons in the substantia nigra of the midbrain, which leads to a significant decrease in the content of DA in the striatum and causes the disease.
Diagnose Parkinson's disease and use levodopa as soon as possible
Since its inception in 1967, levodopa has been the gold standard drug for the treatment of Parkinson's disease. Although other therapeutic drugs have appeared in the field of Parkinson's disease in the past half-century, the status of levodopa as the most basic drug has not been shaken at all. Compared with dopamine receptor agonists and monoamine oxidase-B inhibitors, levodopa has the advantages of being safer, having fewer side effects, and being low in price.
However, people do not have any concerns about levodopa. The biggest problem is that people believe that long-term use of levodopa may induce motor complications of Parkinson's disease, such as symptom fluctuations or dyskinesia. Therefore, some clinical views believe that young patients can appropriately postpone the use of levodopa, because the longer the course of Parkinson's disease is, the more likely it is to have levodopa-related motor complications patients can stop taking drugs. However, some studies in recent years have shown that the length of levodopa treatment has nothing to do with the occurrence of sports complications.
On this issue, the evidence-based medicine guidelines for the treatment of early motor symptoms of Parkinson's disease in China released at the end of 2021 clearly give the answer: the early single drug treatment of compound levodopa preparation is safe and effective, and it is not recommended to deliberately postpone the use. Relevant evidence shows that compared with a non-levodopa preparation treatment, levodopa has a small but lasting improvement in the ability of daily activities of patients. A foreign study showed that there was no difference in the time of motion fluctuations in patients, whether they used levodopa early or delayed. In other words, the existing evidence suggests that early application of low-dose levodopa (<400 mg/day) does not increase the incidence of ADHD. Therefore, once Parkinson's disease is diagnosed, patients can use levodopa as soon as possible, but the following points should be paid attention to when taking it:
1. Start with a small dosage and gradually add dosage. Compound levodopa preparation includes two dosage forms, Ben-L-dopa, and carbidopa. When starting to use, it needs to follow the principle of dose titration, that is, it needs to start from a small dose and gradually add it, so as to avoid acute adverse reactions, and strive to achieve the medication principle of achieving satisfactory clinical effects in a small dose as far as possible.
2. Take levodopa 1 hour before a meal or 1~2 hours after a meal. Levodopa is absorbed in the small intestine, and food intake will reduce the absorption rate and degree of levodopa. Moreover, the protein composition in food has a more obvious impact on the absorption of levodopa, so there should be no large amount of protein food in a meal, and the protein consumed every day should be evenly distributed in three meals.
3. Patients taking DOPA hydrazine should avoid taking vitamin B6 at the same time, which will enhance the peripheral side effects of levodopa and reduce the curative effect. The effect of carbidopa was not interfered with by vitamin B6.
4. Patients with Parkinson's disease should take drugs regularly. Intermittent drug therapy or pulse medication may accelerate the progress of Parkinson's disease. When taking large doses of levodopa, remember not to stop the drug suddenly, so as to avoid inducing malignant withdrawal syndrome.
Parkinson's disease has three core symptoms: static tremors, myotonia, and bradykinesia. Among them, levodopa is particularly effective for the symptoms of bradykinesia, as well as tremor and myotonia, but it has a poor effect on postural instability.
Parkinson's disease is a chronic progressive disease with high heterogeneity. Different patients have different rates of disease progression. At present, there is no cure. Early patients can control symptoms well through drug treatment. Although drugs still have a certain effect in the middle of the disease, the quality of life often decreases due to the occurrence of sports complications. In the late stage of the disease, due to the poor response of patients to drugs, the symptoms can not be controlled. Patients can be stiff all over the body, unable to take care of themselves, and even lie in bed for a long time, and eventually die of complications such as pneumonia.
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