Chloroquine is an antiparasitic drug that blocks the breakdown of heme, causing an accumulation of heme. This accumulation is toxic to parasites that infect red blood cells, such as Plasmodium in malaria. As such, chloroquine is the archetypal antiparasitic treatment for malaria. Side effects of chloroquine use include myopathy, retinopathy, and pruritus. Resistance to chloroquine occurs through drug efflux, which reduces the levels of the drug inside parasites.

Key Points

  • Chloroquine
    • Mechanism
      • Blocks breakdown of heme to hemozoin
        • Via inhibition of heme polymerase
        • Heme accumulation is toxic to plasmodia
    • Clinical Use
      • Plasmodium spp. (Malaria)
        • Chloroquine-resistant P. falciparum is treated with artemisinins, atovaquone-proguanil, mefloquine (quinidine analog)
        • P. vivax and ovale require additional primaquine treatment to kill hypnozoites
    • Adverse Effects
      • Retinopathy
        • Rare, severe side effect seen with chronic use
      • Myopathy
        • Muscle atrophy is a rare side effect seen with chronic use
      • Pruritus
        • Occurs more commonly in dark-skinned individuals
      • GI upset
        • Abdominal discomfort, vomiting, and diarrhea
      • Headaches/dizziness
    • Resistance
      • Membrane efflux pump
        • Decreases intracellular concentration of the drug