With the active ingredient Methyldopa it is an amino acid. It is produced synthetically and is used as an antihypertensive agent. It is primarily used to treat arterial hypertension.
What is methyldopa?
The substance methyldopa appears at room temperature as a crystalline, solid substance that has almost no color. The melting point of methyldopa is around 305 to 307 degrees Celsius. The substance dissolves in dilute mineral acids, but it has only a low solubility in water. Methyldopa is not soluble in the majority of organic solvents.
The active ingredient methyldopa is one of the best-selling medicines for lowering high blood pressure in pregnant women.
Pharmacological effect
Basically, only the L-form is responsible for the pharmacological effects of methyldopa. This means that the substance is left-rotating in its structure. The active ingredient primarily displaces sympathetic neurotransmitters and primarily attacks the biosynthesis of adrenaline and noradrenaline.
Since methyldopa is an amino acid, the substance crosses the blood-brain barrier and thus enters the brain. There the active ingredient is first converted into alpha-methyl dopamine and finally into alpha-methyl noradrenaline. Further processes lead to the production of norepinephrine being inhibited. Under normal circumstances, norepinephrine causes blood vessels to narrow and blood pressure to rise.
After taking the drug methyldopa, the effects will come about three to six hours later. The duration of action is 10 to 16 hours. At the beginning of the therapy, the blood pressure decreases primarily because the cardiac output decreases. With long-term treatment with methyldopa, the resistance in the vessels decreases, which lowers blood pressure.
In the majority of cases, the active ingredient methyldopa is administered orally in the form of tablets. The bioavailability is around 25 percent. The plasma half-life is around one and a half to two hours. However, the blood pressure is lowered over a period of approximately 10 to 16 hours.
About 50 percent of the active ingredient is absorbed in the small intestine. From there they pass into the blood and are transported to the brain. Eventually, the drug methyldopa is broken down in the liver and intestines. The last thing that remains is the substance methyldopa-O-sulfate, most of which is excreted renally in the urine.
Medical application & use
The active ingredient methyldopa is characterized by several possible areas of application. First and foremost, methyldopa is a drug that is used to treat high blood pressure.
The peculiarity of methyldopa is that there are a large number of studies regarding the use of the drug during pregnancy. For this reason, the active ingredient is very often used to treat high blood pressure in pregnant women. A similar drug is the drug dihydralazine, which is also used for hypertension during pregnancy or eclampsia.
Methyldopa works primarily by interfering with the functioning of the central sympathetic system. For this reason, the drug methyldopa is counted among the so-called antisympathotonics.
Risks & side effects
Methyldopa has several potential ailments and undesirable side effects. These vary depending on the individual case and differ in terms of their appearance and severity. Basically, the active ingredient tends to be rather poorly tolerated by numerous patients. This is particularly important when taking the drug during pregnancy. Because although there are numerous studies on the use of the drug in pregnancy, various side effects are possible.
The relatively poor tolerability results primarily from the fact that methyldopa is an antisympathotonic. A common side effect of this is fatigue, which manifests itself in more than ten percent of all treated patients. This side effect is usually reduced during treatment.
In addition, dry mucous membranes in the nose and digestive problems are possible. In addition, in some patients the urine turns dark when it comes into contact with air. However, this side effect is harmless. Sometimes there is sedation that only subsides after a few days.
Other potential side effects that may sometimes occur during methyldopa therapy include daytime sleepiness, bradycardia, and hypotension. The orthostatic reaction may be disturbed, causing tremors or hemolysis (also known as hemolytic anemia). In addition, dizziness, depression and edema are possible. Some patients also suffer from shortness of breath, fever or so-called extrapyramidal motor complaints.
Basically, all difficulties and undesirable side effects that occur during therapy with the drug methyldopa give rise to consulting a doctor. Pregnant patients in particular are encouraged to take any side effects seriously. Because in pregnancy side effects can lead to serious complications that endanger the health or even the life of the unborn child. In such cases a doctor should be consulted immediately. It may be necessary to discontinue methyldopa and look for an alternative therapy method or a better tolerated drug.
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