Pyrimethamine

Definition

Pyrimethamine is an antiparasitic medication primarily used in the treatment of protozoal infections, particularly those caused by Plasmodium species, which are responsible for malaria. This drug functions by inhibiting dihydrofolate reductase, an enzyme crucial for the synthesis of folate, thereby disrupting the folate metabolism in parasites and preventing their growth and reproduction.

5 Must Know Facts For Your Next Test

1. Pyrimethamine is often used in combination with sulfadoxine to enhance its effectiveness against malaria, a treatment regimen known as Fansidar.
2. This drug can cause side effects such as bone marrow suppression, which can lead to anemia or leukopenia, making monitoring essential during treatment.
3. Resistance to pyrimethamine can develop due to mutations in the dihydrofolate reductase enzyme in the Plasmodium species, leading to decreased treatment efficacy.
4. Pyrimethamine is also used in prophylactic treatment for individuals at high risk of developing malaria, especially in endemic regions.
5. In addition to malaria, pyrimethamine is used in treating toxoplasmosis, a parasitic infection caused by Toxoplasma gondii.

Review Questions

• How does pyrimethamine affect folate metabolism in protozoa, and what are the implications for its use as an antiparasitic drug?
  • Pyrimethamine inhibits the enzyme dihydrofolate reductase, which is essential for converting dihydrofolate to tetrahydrofolate, a form of folate necessary for DNA synthesis. This disruption in folate metabolism effectively stunts the growth and reproduction of protozoan parasites like Plasmodium. The implications are significant; while it can successfully treat infections, monitoring for resistance and potential side effects is crucial to maintain its effectiveness.
• Discuss the significance of combining pyrimethamine with sulfadoxine in the treatment of malaria.
  • The combination of pyrimethamine with sulfadoxine creates a synergistic effect that enhances the overall efficacy of malaria treatment. Sulfadoxine inhibits a different step in the folate synthesis pathway, complementing the action of pyrimethamine. This dual action not only improves therapeutic outcomes but also helps delay the development of resistance, making it a preferred choice for treating uncomplicated malaria in certain regions.
• Evaluate the impact of resistance development against pyrimethamine on malaria control efforts globally.
  • The emergence of resistance to pyrimethamine among Plasmodium species poses a significant challenge to global malaria control efforts. As resistant strains spread, treatment options become limited, resulting in higher morbidity and mortality rates associated with malaria. This necessitates ongoing surveillance of resistance patterns and highlights the need for developing new therapeutic strategies and alternative drugs to ensure effective management of malaria in affected populations.

Related terms

Dihydrofolate reductase: An enzyme involved in the folate metabolism pathway, crucial for DNA synthesis and cell division, which is inhibited by pyrimethamine.

Antimalarial drugs: Medications specifically designed to prevent or treat malaria, including various classes such as quinolines and antifolate agents like pyrimethamine.

Sulfadoxine: An antibiotic that, when combined with pyrimethamine, enhances its efficacy in treating malaria through synergistic action.