The active ingredient methyldopa is an amino acid. It is produced synthetically and is used as an antihypertensive. In this context, it is primarily used for the treatment of arterial hypertension.
What is methyldopa?
The substance methyldopa appears at room temperature as a crystalline solid with virtually no color. The melting point of methyldopa is approximately 305 to 307 degrees Celsius. The substance dissolves in dilute mineral acids, but it has low solubility in water. Methyldopa is not soluble in the majority of organic solvents. The active ingredient methyldopa is one of the most widely sold drugs for lowering hypertension in pregnant women.
Pharmacologic action
Basically, only the L-form is responsible for the pharmacological effects of methyldopa. This means that the substance is left-handed in its structure. Primarily, the compound displaces sympathetic neurotransmitters, primarily attacking the biosynthesis of epinephrine or norepinephrine. Since methyldopa is an amino acid, the substance crosses the blood–brain barrier and thus enters the brain. There, the active substance is converted in the first step into alpha-methyldopamine and finally into alpha-methylnorepinephrine. Further processes lead to the production of norepinephrine being inhibited. Under normal circumstances, norepinephrine causes blood vessels to constrict and blood pressure to rise. After taking the drug methyldopa, the effect sets in about three to six hours later. The duration of action is 10 to 16 hours. At the beginning of therapy, blood pressure drops primarily because cardiac output decreases. In long-term treatment with methyldopa, resistance in the vessels decreases, reducing blood pressure. In the majority of cases, the active substance methyldopa is administered orally in the form of tablets. The bioavailability is about 25 percent. The plasma half-life is about one and a half to two hours. However, 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, it passes into the blood and is transported to the brain. Finally, the drug methyldopa is broken down in the liver and intestines. Last, the substance methyldopa-O-sulfate remains, most of which is excreted renally in the urine.
Medical use and application
The active ingredient methyldopa is characterized by several potential applications. Primarily, methyldopa is a drug used for the therapy of hypertension. The peculiarity of methyldopa is that a large number of studies are available regarding the use of the drug during pregnancy. For this reason, the drug is very often used to treat hypertension in pregnant women. A similar drug is dihydralazine, which is also used for hypertension during pregnancy or eclampsia. Methyldopa works primarily by interfering with the action of the central sympathetic nervous system. For this reason, the drug methyldopa is classified as one of the so-called antisympathotonics.
Risks and side effects
Methyldopa is characterized by several potential discomfort and adverse 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 poorly tolerated by numerous patients. This must be taken into account in particular when taking the drug during pregnancy. This is because, although numerous studies are available on the use of the drug during pregnancy, various side effects are possible. The relatively poor tolerability results primarily from the fact that methyldopa is an antisympathotonic drug. A common side effect of this is fatigue, which is seen in more than ten percent of all patients treated. This side effect usually reduces during treatment. In addition, dry mucous membranes in the nose and digestive problems are possible. In addition, some patients experience a dark discoloration of their urine when it comes into contact with air. However, this side effect is harmless. In some cases, sedation is experienced, which only subsides after a few days.Other potential side effects that occur in some cases during therapy with methyldopa include daytime sleepiness, bradycardia, and hypotension. In some circumstances, the orthostasis response is disturbed and tremor or hemolysis (including hemolytic anemia) occurs. In addition, dizziness, depression, and edema are possible. Some patients also suffer from shortness of breath, fever or so-called extrapyramidal motor symptoms. Basically, all difficulties and undesirable side effects that occur during therapy with the drug methyldopa give reason to consult a doctor. Pregnant patients in particular are urged to take any side effect seriously. This is because during pregnancy, side effects may 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 method of therapy or a better-tolerated agent.
