Optimising age-based dosing of antimalarial medicines

Drug dosing for antimalarials is generally based on the patients’ body weight in kilograms. However, in many malaria-endemic countries antimalarial treatments are bought at pharmacies or prescribed in clinics in settings where weighing scales are not available. Rather than using the patient’s weight, the age is frequently used as an alternative method of deciphering the required dose, especially with young children. Decisions are, however, often made without detailed growth reference charts or based on western standards and, as such, patients have in some cases been systematically under and over-dosed, leading to treatment failure and potentially driving resistance to current antimalarials.

The study published in the WHO Bulletin, led by Drs Daniel Hayes and Anja Terlouw at the Liverpool School of Tropical Medicine in the UK, has compiled the first ever robust analysis of actual bodyweight distribution in Africa, Asia and Latin America, and provided suitable regional weight-for-age reference tables. The results demonstrate that significant differences in weight-for-age distributions exist and that age-based dosing approaches should be reconsidered at a regional rather than a global level.

To develop this analysis, Drs Hayes and Terlouw worked with statisticians from the Netherlands and the United Kingdom to create modelling tools with population-based data from 64 different malaria-endemic countries. The data were gathered from household surveys and research institutions and included children, men and women, collected between 1995 -2012.

“We hope the paper will raise awareness of the considerable differences in body weight between regions. These growth references can be used to estimate the variation in antimalarial treatment dose that occurs when age-based dosing regimens are employed in malaria control programmes.” comments Dr Hayes, lead author of the paper from the Liverpool School of Tropical Medicine, ‘selecting an appropriate age-based dosing regimen can contribute to better treatment results and fewer patients suffering with the affects of malaria”

The pooling of large data sets enabled the research team to develop region-specific average weight achieved by age in all three regions. These references can now be used to more effectively optimise the dose of antimalarial drugs and ensure that appropriate age-based dosing regimens are used in health clinics and patient trials.

In addition, the modelling approaches could be adapted for other medicine treatments and diseases, and to help review nutrition levels in vulnerable populations over time.

Access the Weight-for-Age (WFA) reference tables:

• Africa WFA data
• Asia WFA data
• Latin America WFA data

Hayes DJ et al. Developing regional weight-for-age growth references for malaria endemic countries to optimise age-based dosing of antimalarials. Bulletin World Health Organization 2015; 93:74–83. DOI 10.2471 BLT.14.139113

For further information, please email your questions to Dr Daniel Hayes d.j.hayes(at)liverpool.ac.uk