We have characterised the pharmacokinetic properties of primaquine in two separate projects. For the first time, the enantiospecific pharmacokinetic properties of primaquine and its main metabolite, carboxyprimaquine, were described using nonlinear mixed effects modelling (J Antimicrob Chemother. 2018; 73(11):3102-13). Potential drug-drug interactions with three commonly used blood stage antimalarial drugs (i.e. chloroquine, dihydroartemisinin/ piperaquine and pyronaridine/artesunate) were also assessed in these volunteers.
Exposure to primaquine, but not the metabolite, increased by up to 30% when co-administered with commonly used antimalarial drugs. In the second project, we evaluated the distribution of primaquine into breastmilk (Clin Infect Dis. 2018; 67(7):1000-7).
The concentrations of primaquine in breast milk were low and therefore very unlikely to cause adverse effects in the breastfeeding infant. The estimated primaquine dose received by infants, based on measured breast milk levels, was 0.6% of a hypothetical infant daily dose of 0.5 mg/kg. There was no evidence of drug related haemolysis in the infants and we recommend that primaquine should not be withheld from breastfeeding mothers.