The long half-life of chloroquine in the bloodstream creates a window of selection for development of resistance. This window opens when:
The drug is completely cleared from the bloodstream by the liver, but parasites are still present
The concentration in the blood drops to a level that is not lethal to all of the parasites
The parasite varies its surface antigen
The parasite load falls below the level of detection
Resistance to an antibiotic is a mechanism through which the pathogens gain beneficial genes that enables them to survive the lethal effects of the antibiotics. The progression of this gene in the population is favored by natural selection.
In parasites that are exposed to chloroquine will develop resistance to this antibiotic when they are exposed to a low concentration of this drug. Resistance will not develop if the drug is completely cleared from the bloodstream. The parasites need to come in contact with the antibiotic in order for selection of resistant strains to occur. Hence, option (B) is correct.
The long half-life of chloroquine in the bloodstream creates a window of selection for development of...