Chloroquine (CQ) remains an alternative cheap, safe and widely available drug. Our previous research has shown that double (50 mg/kg) standard dose CQ given in split doses had a 95% efficacy and was well tolerated and safe. Still, safety could be an issue when the dose of CQ is increased. Severe adverse events are caused by high peak concentrations of CQ. Using split doses of CQ avoids high peak concentrations enabling the safe administration of high doses, however, pharmacokinetic data are lacking.

Children included in the study will be given 50 mg/kg as split doses over 3 days or 70 mg/kg as split doses over 5 days. Treatment will be observed. Drug concentrations and adverse events will be monitored. On day 1, children and their mother/guardian will be requested to stay at the health centre between 9 am and 6 pm.

Fifteen children aged 2-10 years with uncomplicated P. falciparum malaria and fulfilling the inclusion criteria will be recruited into each study arm.

Following the end of treatment, the children will be seen on the morning of day 7, 14, 21 and 28.

Any child wishing to withdraw during the treatment phase and any child with reparasitaemia during the follow up will be given rescue treatment with arthemeter-lumefantrine or quinine according to treatment guidelines in Guinea-Bissau.

Final analysis will include a description of included children, proportions of adverse events and any serious adverse events, drug concentrations and their relation to adverse events, the proportion of children withdrawn or lost to follow up, the cumulative PCR corrected and uncorrected success and failure rates on day 28 and the proportion of early, late clinical and late parasitological treatment failures.

Inclusion Criteria:

• Age ≥ 2 years and < 10 years.
• Mono-infection with P. falciparum detected by microscopy. Parasitemia of 1.000-100.000/µl asexual forms.
• Axillary temperature ≥ 37.5 ˚C or a history of fever within 24 hours.
• Ability to swallow oral medication.
• Ability and willingness to comply with the study protocol.
• Informed consent from a parent or guardian

Exclusion Criteria:

• Signs or symptoms of severe malaria.
• Presence of general danger signs in children under 5.
• Persistent vomiting.
• Presence of severe malnutrition.
• Any evidence of chronic disease or acute infection other than malaria.
• Regular medication which may interfere with antimalarial pharmacokinetics.
• History of hypersensitivity reactions or contraindications to chloroquine.