Enantiospecific pharmacokinetics and drug-drug interactions of primaquine and blood-stage antimalarial drugs

J Antimicrob Chemother. 2018 Nov 1;73(11):3102-3113. doi: 10.1093/jac/dky297.


Objectives: Characterization of the pharmacokinetic properties of the enantiomers of primaquine and carboxyprimaquine following administration of racemic primaquine given alone and in combination with commonly used antimalarial drugs.

Methods: Enantiomeric pharmacokinetics were evaluated in 49 healthy adult volunteers enrolled in three randomized cross-over studies in which a single dose of primaquine was given alone and then, after a suitable washout period, in combination with chloroquine, dihydroartemisinin/piperaquine or pyronaridine/artesunate. Non-linear mixed-effects modelling was used to characterize pharmacokinetics and assess the impact of drug-drug interactions.

Results: The volume of distribution of racemic primaquine was decreased by a median (95% CI) of 22.0% (2.24%-39.9%), 24.0% (15.0%-31.5%) and 25.7% (20.3%-31.1%) when co-administered with chloroquine, dihydroartemisinin/piperaquine and pyronaridine/artesunate, respectively. The oral clearance of primaquine was decreased by a median of 19.1% (14.5%-22.8%) when co-administered with pyronaridine/artesunate. These interactions were enantiospecific with a relatively higher effect on (+)-S-primaquine than on (-)-R-primaquine. No drug-drug interaction effects were seen on the pharmacokinetics of either carboxyprimaquine enantiomer.

Conclusions: Population pharmacokinetic models characterizing the enantiospecific properties of primaquine were developed successfully. Exposure to primaquine, particularly to the (+)-S-primaquine but not the carboxy metabolites, increased by up to 30% when co-administered with commonly used antimalarial drugs. A better mechanistic understanding of primaquine metabolism is required for assessment of its efficacy and haematological toxicity in humans.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antimalarials / chemistry*
  • Antimalarials / pharmacokinetics*
  • Artemisinins / administration & dosage
  • Artemisinins / pharmacokinetics
  • Artesunate / administration & dosage
  • Artesunate / pharmacokinetics
  • Cross-Over Studies
  • Drug Interactions
  • Drug Therapy, Combination
  • Female
  • Healthy Volunteers
  • Humans
  • Malaria, Vivax / drug therapy*
  • Male
  • Middle Aged
  • Primaquine / chemistry*
  • Primaquine / pharmacokinetics*
  • Quinolines / administration & dosage
  • Quinolines / pharmacokinetics
  • Thailand
  • Young Adult


  • Antimalarials
  • Artemisinins
  • Quinolines
  • Artesunate
  • artenimol
  • piperaquine
  • Primaquine