Inclusion criteria:

• Clinical diagnosis of visceral leishmaniasis; symptoms and signs compatible with VL and diagnosis confirmed by visualisation of amastigotes in splenic aspirate or bone marrow.
• Written informed consent or witnessed oral consent.
• Willing to comply with the study visits and procedures.
• For female subjects, a negative urine pregnancy test at screening and before dosing and the subject agrees to use an established method of birth control (including abstinence).

Exclusion criteria:

• Past history of renal disease or impaired renal function at screening.
• History of any significant hepatic or biliary disease, or the following abnormal laboratory values at screening; hepatic dysfunction (AST or ALT 2.5 times upper limit of normal).
• Subjects with the following abnormal laboratory values; haemoglobin 6.5 g/dl, neutrophils <750/ mm3, platelets <50,000 / mm3, any clinically relevant abnormality identified on screening examination or clinical laboratories which would preclude the subject's safe participation in the study.
• History of cardiac disease, arrhythmias, conduction abnormalities or any clinically relevant abnormality identified on 12-lead ECG at screening.

Subjects suffering from a concomitant infection, blood disorder or any other serious underlying disease which would preclude evaluation of the subject's response to the study medication.

Methaemoglobin levels >5% at screening. G6PD deficiency.

• Positive HIV antibody, hepatitis B surface antigen or hepatitis C antibody at screening.
• Pregnant or nursing women; women of childbearing potential who are unwilling or unable to use an appropriate form of contraception, from prior to study medication administration until 2 weeks following the last dose of investigational product.
• Any contraindication to splenic aspirate (or bone marrow aspirate), including but not limited to PT prolonged >3 seconds longer than control or platelets <50,000 / mm3.
• Subjects with a known hypersensitivity reaction to 8-aminoquinolines (e.g. primaquine) or any of the investigational product excipients.
• Treatment with an established antileishmanial chemotherapeutic agent within 30 days or 5 half-lives (whichever is longer) preceding the first dose of study medication.
• Treatment with an investigational drug within 30 days or 5 half-lives (whichever is longer) preceding the first dose of study medication.