Figure 5.

Illustration of the possible drug effects. A, Volunteers who are not treated or are treated with an ineffective drug would be expected to have the same parasite growth after treatment as was seen 40 hours prior to treatment. B and C, Volunteers treated with a drug that has an effect on parasite growth should show retarded parasite growth after treatment. The observed effect of an active drug may depend on when, in the parasite life cycle, it is administered (B), or it may be independent of the timing of administration (C). A very effective drug that interrupts parasite replication and causes the rapid removal of parasites produces a reduction in parasite numbers independent of what parasite growth was expected (C).