Haematological safety of long-term malarial prophylaxis with dapsone-pyrimethamine

There are no published haematological data on the long-term (more than one year) use of dapsone-pyrimethamine (Maloprim, Folaprim; one tablet a week) for malarial prophylaxis. In a study of 373 male Papua New Guinean soldiers who had used this combination for five years, we found no haematological abnormalities attributable to dapsone-pyrimethamine. Furthermore, the haematological parameters of these soldiers were not clinically different from those of Papua New Guinean university students who did not ingest antimalarial drugs prophylactically. In a parallel study, 9 of 159 white persons (6 children and 3 adult females) who had used dapsone-pyrimethamine prophylaxis for more than one year had haematological abnormalities attributable to the drug. Additionally, the mean leucocyte count of children aged 1-9 years who took dapsone-pyrimethamine was markedly lower--although within the normal range--than that of similarly aged children who received chloroquine for malarial prophylaxis. The appreciable incidence of haematological abnormalities observed in children during malarial prophylaxis with dapsone-pyrimethamine demonstrates the need to select a dose for this group on a weight rather than an age basis and to use a liquid formulation to facilitate the administration of the appropriate dose of this combination. Haematological monitoring of the long-term use of dapsone-pyrimethamine is recommended and a suitable monitoring regimen is suggested.