Previous studies of mice infected with Babesia microti have shown that a single dose of
tafenoquine administered orally is extremely effective at decreasing microscopically detectable
parasitemia. However, a critical limitation of studies to date is the lack of data concerning the plasma levels of
tafenoquine that are needed to treat
babesiosis. In the current study, we begin to address this gap by examining the plasma levels of
tafenoquine associated with the rapid reduction of B. microti patent
parasitemia in a mouse model of
babesiosis. In the current study, we infected BALB/c mice with 1 × 107B. microti-infected red blood cells. Two days post-
infection, mice were treated with 20 mg/kg of
tafenoquine succinate or vehicle control administered orally by gavage.
Parasitemia and plasma levels of
tafenoquine were evaluated every 24 h post-treatment for 96 h. This allowed us to correlate blood plasma levels of
tafenoquine with reductions in
parasitemia in treated mice. Consistent with previous studies, a single oral dose of 20 mg/kg
tafenoquine resulted in a rapid reduction in
parasitemia. Plasma levels of
tafenoquine 24 h post-administration ranged from 347 to 503 ng/mL and declined thereafter. This blood plasma
tafenoquine level is similar to that achieved in humans using the current FDA-approved dose for the prevention of
malaria.