Antimalarial Drugs

Antimalarial Drugs (Resistant & Cerebral Malaria)

1. Definition, scope & global burden

• Antimalarials are drugs used for the prophylaxis, treatment, and prevention of relapse of malaria, achieving their goals by attacking the parasite at one or more stages of its life cycle in the human host (KDT 8e Ch.61, pp.873–4).
• Malaria is caused by protozoal parasites of the genus Plasmodium; five species infect humans: P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi (G&G 14e Ch.66, p.1289).
  • P. falciparum and P. vivax cause most infections worldwide; P. falciparum causes most severe disease and deaths (predominant in sub-Saharan Africa) (G&G 14e Ch.66, p.1289).
  • P. vivax accounts for ~half the malaria burden in South/East Asia and >80% in the Americas, and is increasingly recognised as a cause of severe malaria (Oceania, India) — historically underappreciated (G&G 14e Ch.66, pp.1289–90).
  • On genetic data, P. ovale is now subdivided into P. ovale wallikeri and P. ovale curtisi (G&G 14e Ch.66, p.1289).
  • P. knowlesi — previously thought restricted to macaques; misdiagnosed as P. malariae by light microscopy; distinguished by a shorter (24 h) erythrocytic cycle and higher parasitaemia → more severe presentation; generally chloroquine-sensitive (G&G 14e Ch.66, p.1290).
• Burden: ~a quarter of a billion people affected; >600,000 deaths in 2021; malaria remains among the top five causes of death in children <5 yr (G&G 14e Ch.66, p.1289). WHO 2016 estimate (KDT): ~216 million cases, ~0.445 million deaths globally, 90% of cases/deaths in Africa, 7% in SE Asia incl. India (KDT 8e Ch.61, p.873).
• India context (RGUHS-relevant): National Malaria Eradication Programme (NMEP, 1958) → renamed National Antimalaria Programme (NAMP) → now National Vector Borne Diseases Control Programme (NVBDCP). 2016: 1.06 million confirmed cases, ~50% falciparum, 242 deaths; ~80% of the Indian population lives in malaria-risk areas. Decline attributed to effective ACT use (KDT 8e Ch.61, p.873).
• Historical milestones: Cinchona bark (17th c.) → quinine isolated 1820; mepacrine (Germany, 1926); chloroquine ("Resochin", Germany 1934; US WWII); proguanil (Britain 1945); primaquine (WWII, the desirable 8-aminoquinoline); pyrimethamine (1951); artemisinin from Artemisia annua ("qinghaosu") — Chinese 1970s, Nobel Prize in Physiology/Medicine 2015 to Tu Youyou (KDT 8e Ch.61, pp.873–4; G&G 14e Ch.66, p.1292).