About Hydroxychloroquine sulphate Aminoquinolone derivative, Antimalarial, antirheumatic. Mechanism of Action of Hydroxychloroquine sulphate Malarial parasites digest their own haemoglobin and release highly toxic heme.But this haeme is used up by parasitic polymerase enzyme and converted to non toxic haemozoin.Since Hydroxychloroquine is a weak base it has high affinity towards acidic lysosome.Hydroxychloroquine inhibits polymerase enzyme and interfere the formation of haemozoin and results in accumulation of toxic haeme and haeme - Hydroxychloroquine complex. Formations of these lead to membrane lysis and kill the parasite. Hydroxychloroquine binds to DNA and inhibits protein synthesis. Anti-inflammatory action: Hydroxychloroquine antagonizes the inflammatory mediators such as histamine and serotonin. It also inhibits the conversion of arachidonic acid to prostaglandin F2 and also inhibits the chemotaxis of polymorphonuclear leukocytes, macrophages and eosinophils.