The active substance levodopa is a precursor of the messenger substance dopamine in the brain. As a so-called "prodrug", it is first converted to effective dopamine in the brain. He is protected by the combination with other agents such as benserazide or carbidopa from premature degradation. Here you can read everything worth knowing about the effect and application of levodopa, side effects and interactions.ArtikelübersichtLevodopa
- application areas
- Proper application
- side effects
- Important instructions
- tax provisions
This is how Levodopa works
The messenger substance dopamine is used in the brain to transmit signals between nerve cells - especially those involved in controlling the movement. An important region for this is the "substantia nigra" (Latin for "black matter") in the midbrain. When dopamine-producing neurons die there, Parkinson's disease occurs.
The production of dopamine in the body takes place from the natural amino acid (protein building block) Tyrosin. This is converted to the intermediate levodopa and then further into dopamine. Dopamine itself can not be given to Parkinson's patients because it can not cross the blood-brain barrier. In addition, it would lead to many peripheral (affecting the body) side effects. These two problems are bypassed in the treatment with levodopa - it is a precursor, so does not work at first, can cross the blood-brain barrier and is then quickly converted in the brain to dopamine.
If levodopa were administered alone, it would convert to dopamine before reaching the brain. This is prevented by taking the active ingredient in combination with carbidopa or benserazide. Since both substances can not cross the blood-brain barrier, levodopa enters the central nervous system alone and can be converted to dopamine there.
Ingestion, breakdown and excretion of levodopa
Levodopa is absorbed into the blood after ingestion in the upper part of the small intestine. After about an hour, the highest blood levels are reached when taken before or after a meal (fasting). Levodopa enters the brain via the bloodstream, where it is converted into dopamine and can act at its docking sites (receptors). It is then degraded like natural dopamine.
For medicines that have also added entacapone in addition to levodopa and benserazide, the latter counteracts the degradation of dopamine. This prolongs the duration of action of the drug.
Levodopa is rapidly broken down and excreted. About one and a half hours after ingestion half of the active ingredient has already left the body. Therefore, the drug must be taken throughout the day.To the table of contents
When will levodopa be used?
One of the indications of levodopa is Parkinson's disease (shaking palsy). It is accompanied by tremor (tremor), muscle rigidity (rigor) and sedentary lifestyle (bradykinesis) or immobility (akinesis).
These Parkinson's symptoms can also be caused by poisoning, brain inflammation and "vascular calcification" (arteriosclerosis). Even such cases can be treated with the anti-Parkinson drug.
In contrast, Parkinson's symptoms that occur as a result of treatment with drugs such as neuroleptics (antipsychotics) should not be treated with levodopa. Instead, the causative agent should be changed as far as possible in the case of severe suffering.
The second application of levodopa is Restless Legs Syndrome (RLS), but previously iron deficiency has to be ruled out.
Since the symptoms in both cases are alleviated only symptomatically, the treatment is always longer term.To the table of contents
This is how levodopa is used
The active ingredient is usually used as a tablet. The total daily dose must not exceed 800 milligrams of levodopa (in combination with benserazide or carbidopa) and is given on four doses throughout the day in order to achieve as constant as possible blood levels.
The dosage is "creeping" increased, so slowly increased until the individually optimal amount of active ingredient is found. Thus, the initially occurring side effects are reduced.
It is taken no later than half an hour before or one hour after a meal, as levodopa is better absorbed.
Also for the treatment of Restless Legs Syndrome, the dosage is set individually.To the table of contents
What are the side effects of levodopa?
The marked side effects of levodopa on the cardiovascular system and the gastrointestinal tract are reduced by the combination with benserazide or carbidopa.
However, more than ten percent of patients experience loss of appetite, sleep disorders, depression, nausea, vomiting, diarrhea, and a change in liver enzyme levels. After prolonged treatment, a so-called "ON-OFF phenomenon" may occur, in which the mobility of the patient caused by levodopa rapidly changes to immobility.