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Chloroquine, a 4-aminoquinoline derivative that can be radically curative in the therapy of malaria due to Plasmodium falciparum, binds to glass to an extent which can seriously decrease the availability of the drug. Preparations of chloroquine in various solutions showed decreases in concentration of up to 40% in glass containers. Passage of solutions of chloroquine over columns of glass beads or glass wool decreased chloroquine concentrations by up to 70%. Chloroquine was found to bind extensively to cellulose acetate filters, but showed little binding to polycarbonate filters or to plastics of various types, including polycarbonate, polypropylene, and polystyrene. Human serum at concentrations from 5–50% inhibited the binding of chloroquine to glass. Equilibrium dialysis experiments indicated that human serum possesses a large number of binding sites for the drug; it is also possible that factors in the serum compete for drug-binding sites on glass. It is imperative for laboratory workers, especially those in the field, to recognize the significant reductions in chloroquine concentration which occur when the drug is prepared or stored in glass containers. Such reductions can alter the interpretation of chloroquine sensitivity studies and may lead to inaccurate reports of chloroquine resistance.
Present address: Malaria Control Division, Ministry of Health, Democratic Republic of Sudan.