Abstract
BackgroundIn 2012, the World Health Organization recommended blocking the transmission of Plasmodium falciparum with single low-dose primaquine (SLDPQ, target dose 0.25 mg base/kg body weight), without testing for glucose-6-phosphate dehydrogenase deficiency (G6PDd), when treating patients with uncomplicated falciparum malaria. We sought to develop an age-based SLDPQ regimen that would be suitable for sub-Saharan Africa.MethodsUsing data on the anti-infectivity efficacy and tolerability of primaquine (PQ), the epidemiology of anaemia, and the risks of PQ-induced acute haemolytic anaemia (AHA) and clinically significant anaemia (CSA), we prospectively defined therapeutic-dose ranges of 0.15–0.4 mg PQ base/kg for children aged 1–5 years and 0.15–0.5 mg PQ base/kg for individuals aged ≥6 years (therapeutic indices 2.7 and 3.3, respectively). We chose 1.25 mg PQ base for infants aged 6–11 months because they have the highest rate of baseline anaemia and the highest risks of AHA and CSA. We modelled an anthropometric database of 661,979 African individuals aged ≥6 months (549,127 healthy individuals, 28,466 malaria patients and 84,386 individuals with other infections/illnesses) by the Box–Cox transformation power exponential and tested PQ doses of 1–15 mg base, selecting dosing groups based on calculated mg/kg PQ doses.ResultsFrom the Box–Cox transformation power exponential model, five age categories were selected: (i) 6–11 months (n = 39,886, 6.03%), (ii) 1–5 years (n = 261,036, 45.46%), (iii) 6–9 years (n = 20,770, 3.14%), (iv) 10–14 years (n = 12,155, 1.84%) and (v) ≥15 years (n = 328,132, 49.57%) to receive 1.25, 2.5, 5, 7.5 and 15 mg PQ base for corresponding median (1st and 99th centiles) mg/kg PQ base of: (i) 0.16 (0.12–0.25), (ii) 0.21 (0.13–0.37), (iii) 0.25 (0.16–0.38), (iv) 0.26 (0.15–0.38) and (v) 0.27 (0.17–0.40). The proportions of individuals predicted to receive optimal therapeutic PQ doses were: 73.2 (29,180/39,886), 93.7 (244,537/261,036), 99.6 (20,690/20,770), 99.4 (12,086/12,155) and 99.8% (327,620/328,132), respectively.ConclusionsWe plan to test the safety of this age-based dosing regimen in a large randomised placebo-controlled trial (ISRCTN11594437) of uncomplicated falciparum malaria in G6PDd African children aged 0.5 − 11 years. If the regimen is safe and demonstrates adequate pharmacokinetics, it should be used to support malaria elimination.
Highlights
In 2012, the World Health Organization recommended blocking the transmission of Plasmodium falciparum with single low-dose primaquine (SLDPQ, target dose 0.25 mg base/kg body weight), without testing for glucose-6-phosphate dehydrogenase deficiency (G6PDd), when treating patients with uncomplicated falciparum malaria
We plan to test the safety of this age-based dosing regimen in a large randomised placebo-controlled trial (ISRCTN11594437) of uncomplicated falciparum malaria in G6PDd African children aged 0.5 − 11 years
The main reasons cited by ministries of health for not enacting the World Health Organization (WHO) recommendation is the fear that SLDPQ would cause acute haemolytic anaemia (AHA) in G6PDd individuals and the impossibility of widely deploying a suitable G6PDd test to exclude such individuals from receiving SLDPQ [11]
Summary
In 2012, the World Health Organization recommended blocking the transmission of Plasmodium falciparum with single low-dose primaquine (SLDPQ, target dose 0.25 mg base/kg body weight), without testing for glucose-6-phosphate dehydrogenase deficiency (G6PDd), when treating patients with uncomplicated falciparum malaria. Younger children would be the prime recipients of SLDPQ in a programme that targets patients with symptomatic malaria Their median Hb concentrations at presentation may seem adequate (Table 4), a sizeable minority will have moderate anaemia and a small number will have severe anaemia (Hb < 5 g/dL). Children aged
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