A Study to Assess the Availability of Oral Primaquine and Its Inert Metabolite, Carboxyprimaquine, in the Body

Inclusion Criteria: 1. Healthy as judged by a responsible physician with no significant abnormality identified on a medical evaluation including medical history and physical examination. 2. Male or female aged between 18 years to 60 years. 3. A female is eligible to enter and participate in this study if she is: • of non-childbearing potential including pre-menopausal females with documented (medical report verification) hysterectomy or double oophorectomy OR • postmenopausal defined as 12 months of spontaneous amenorrhea or 6 months of spontaneous amenorrhea with serum follicle stimulating hormone levels \>40 milli-international units per milliliter (mIU/mL) or 6 weeks postsurgical bilateral oophorectomy with or without hysterectomy OR • of childbearing potential, has a negative serum pregnancy test at screening and urine pregnancy test prior to start the study drug in each period, and agrees to abstain from sexual intercourse or use effective contraceptive methods (e.g., intrauterine device, tubal ligation or female barrier method with spermicide except hormonal contraceptive) during the study until completion of the follow-up procedures 4. Willingness and ability to comply with the study protocol for the duration of the trial. 5. Subject is willing and able to give written informed consent for full participation in the study Exclusion Criteria: 1. Females who are pregnant, trying to get pregnant, or are lactating. 2. Known to have any clinically significant disease or to have a clinically significant disease or disorder at this screening time 3. Donated more than 300 mL of whole blood within the previous 3 months 4. Non-smokers and non-tobacco user (i.e. having no past history of smoking and tobacco consuming for at least 3 months prior to study) 5. Consume alcohol or other alcohol containing products within 48 hours prior to the first dose of study drug and throughout the study 6. History or evidence of alcohol or substance abuse or dependence within 6 months before and throughout the study 7. Consume grapefruit and grapefruit containing products within 7 days prior to the first dose of study drug and throughout the study 8. Use of prescription drugs including but not limited to drugs with antimalarial activities and any drug contraindicated with the investigational drugs e.g. quinacrine, mefloquine or non-prescription drug, including, vitamins, herbal and dietary supplements (including St. John's Wort) within 7 days (or 14 days if the drug is a potential enzyme inducer) or 5 half-lives (whichever is longer) prior to the first dose of study medication and for the duration of the trial including follow-up will be prohibited 9. Have taken part in research involving an investigational drug within the past 8 weeks 10. Use of medications known to have a potentially clinically significant interaction with primaquine 11. History of allergy to primaquine 12. Hb \< 11 g/dL 13. Having malaria infection 14. Abnormal CYP2D6 genotype 15. Glucose-6-phosphate dehydrogenase (G6PD) deficiency by screening test 16. Aspartate aminotransferase (AST), alanine aminotransferase (ALT) \> 1.5 times the upper limit of normal (ULN) 17. A serum creatinine (Scr) above the upper limit of normal (\> 1.2 mg/dL) and estimated glomerular filtration rate (eGFR) \< 70 mL/min/1.73 m2 18. Methaemoglobin (MetHb) level \> 3% determined by oximetry 19. Positive for HIV-1, Hepatitis B or C virus infection 20. Subject who is likely to be unable to follow with the study procedures