Indirect clinical measures assessing anti-malarial drug transmission-blocking activity in falciparum malaria include
measurement of the duration of gametocytaemia, the rate of gametocyte clearance or the area under the
gametocytaemia-time curve (AUC). These may provide useful comparative information, but they underestimate
dose-response relationships for transmission-blocking activity. Following 8-aminoquinoline administration P. falciparum
gametocytes are sterilized within hours, whereas clearance from blood takes days. Gametocytaemia AUC and clearance
times are determined predominantly by the more numerous female gametocytes, which are generally less drug
sensitive than the minority male gametocytes, whereas transmission-blocking activity and thus infectivity is determined
by the more sensitive male forms. In choosing doses of transmission-blocking drugs there is no substitute yet for
mosquito-feeding studies.