Date of this Version
Bulletin of the World Health Organization, 62 (3): 439-444 (1984)
Antimalarial activities ofchloroquine, mefloquine, amodiaquine, and quinine in vitro against Plasmodium falciparum were diminished as a consequence ofmembranefiltration. Filtered drug solutions gave ID50 values up to 25-fold greater than those of non-filtered (ethanol-sterilized) drug solutions. Loss ofactivity byfiltration was overcome by increasing the drug concentration prior to filtration. Water solutions filtered through Millex-GSfilter units consistently showed an absorbance maximum at 277 nm, accompanied by a lesser peak at 225 nm. Water filtrates from Nucleopore and Millex-G Vfilters showed no absorbance at 277 nm and only slight absorbance was evidentfor the Gelmanfilter unit. Activity losses were attributed to extractable contaminating moieties in the membranefilters and/or drug binding to the membrane filters.