The active ingredient pyrimethamine is a so-called antiparasitic drug. Pyrimethamine belongs to the category of antiparasitics and is primarily used for the prophylaxis of malaria as well as for the treatment of toxoplasmosis. The substance pyrimethamine is a derivative of diaminopyrimidine and, in combination with other agents, is suitable for the prevention of pneumonia caused by Pneumocystis jirovecii.
What is pyrimethamine?
In principle, the drug pyrimethamine belongs to the diaminopyrimidines and is used to treat infections caused by protozoa. Very often, the drug is used for toxoplasmosis. In Germany and Switzerland, the substance pyrimethamine is a component of the drug Daraprim from the pharmaceutical producer GlaxoSmithKline. In principle, the active substance pyrimethamine should always be taken together with sulfonamide. The drug pyrimethamine causes inhibition of dihydrofolate reductase. This is a special enzyme that plays an important role in the availability of the vitamin folic acid. The active ingredient pyrimethamine is characterized, among other things, by antiparasitic properties. The effect of the substance is primarily due to the fact that it inhibits the metabolism for the production of folic acid. For this reason, it is imperative that the affected patient take folic acid during treatment. Pyrimethamine is also known synonymously as pyrimethaminum or pirimethamine. The substance is usually present as a crystalline powder of white color. In some cases, pyrimethamine appears as a crystal and is nearly insoluble in water.
Pharmacological action
The drug pyrimethamine is characterized by a typical mechanism of action. First, it possesses antiparasitic properties and is an antiprotozoal agent. Thus, the drug is effective against plasmodia, Toxoplasma gondii, and Pneumocystis carinii, among others. Basically, the active ingredient pyrimethamine interacts with folic acid metabolism. Pyrimethamine is characterized by an enormously long half-life, which is up to 85 hours. It is believed that the active ingredient pyrimethamine interferes with the energetic metabolism of parasites. When the drug pyrimethamine is taken orally, it interferes with the parasites’ dihydrofolate reductase. In this way, the synthesis of folic acid is prevented. It is often used together with sulfonamides or even sulfones, which increases the effect. The absorption of the active substance pyrimethamine is exclusively gastrointestinal. Finally, the drug is excreted from the organism renally, i.e. via the kidneys. In this process, the half-life of the substance is two to six days.
Medical application and use
The drug pyrimethamine is suitable for medicinal treatment of various diseases and ailments, as well as for prevention of some infections. Very often it is used in the therapy of toxoplasmosis, where it is usually used together with a sulfonamide. The dosage of the drug is always in accordance with the enclosed professional information. During therapy with the active substance pyrimethamine, it is necessary to take folic acid. This reduces the risk of bone marrow suppression. As a general rule, all sulfonamides should be taken with plenty of water. In addition to toxoplasmosis, the drug pyrimethamine is also suitable for the treatment of malaria and Pneumocystis jirovecii pneumonia.
Risks and side effects
During treatment with the drug pyrimethamine, some patients experience undesirable side effects. However, these differ depending on the individual case and also occur with varying frequencies. Most frequently, the active ingredient pyrimethamine causes disturbances in the blood count and anemia. In addition, some patients suffer from gastrointestinal complaints such as nausea, diarrhea and vomiting. Headaches and rashes on the skin are also possible. In addition, some individuals complain of dryness of the oral mucous membranes, thrombocytopenia, and leukopenia while taking the drug. If the drug pyrimethamine is taken together with sulfones or sulfonamides, some other undesirable side effects are possible. These include, for example, dermatitis, photodermatoses, Lyell’s syndrome, and Stevens-Johnson syndrome. If pyrimethamine is taken long-term, depression, drug fever, hepatotoxicity, and agranulocytosis may be seen.Administered in particularly high doses, the active ingredient pyrimethamine causes tremor, seizures, and ataxia in some cases. In addition, neurotoxicity, circulatory collapse, and stomatitis are possible. In addition, some contraindications should be considered before taking the drug pyrimethamine for the first time. If pyrimethamine is prescribed in high doses, there is a risk of embryotoxicity. For this reason, use of the drug pyrimethamine during pregnancy should be thoroughly weighed. The drug pyrimethamine is also not the drug of first choice for immunocompromised people. In addition, its use may cause complications for people with gallbladder or liver problems. In the event of hypersensitivity to the active ingredient pyrimethamine, therapy with the drug should be discontinued in any case. During treatment, various possible interactions with other drugs must also be taken into account. These are primarily folic acid antagonists, antacids and lorazepam. In principle, regular monitoring of blood values is necessary during therapy. Among other things, this involves checking the decline in pathogens. It is the responsibility of the respective patient to report any complaints or undesirable side effects that occur during therapy to a physician. In some cases, it is necessary to discontinue the drug pyrimethamine and find a better tolerated preparation or an alternative method of treatment for the patient.
