Trials in pregnant women in Kenya show that combining the standard malaria drug for pregnant women with high doses of folic acid make the malaria treatment twice as likely to fail.
The findings, published in PLoS Clinical Trials yesterday (19 October), could mean that countries using Sulfadoxine pyrimethamine (SP) to treat malaria in pregnancy may need to reconsider their national guidelines for folic acid supplementation.
Health authorities worldwide recommend that pregnant women supplement their diet with 0.4 milligram (mg) of folic acid every day to protect against neural tube defects in the developing foetus, and possibly reduce the likelihood of anaemia in the mother.
But many African countries, including Kenya, use a higher dose of 5mg, as these tablets are more easily available.
The trials in western Kenya involved 415 pregnant women infected with the most common malaria parasite, Plasmodium falciparum.
They were given the standard dose of SP, together with a 14-day supply of either a high dose of folic acid at 5mg, a low dose of 0.4mg, or a placebo.
In the women receiving the higher dose of folic acid, the malaria treatment was approximately twice as likely to fail compared to women receiving a low dose or placebo.
The research team, led by Anna van Eijk of PATH (Program for Appropriate Technology in Health), urge countries using SP for malaria treatment or prevention in pregnancy to evaluate their antenatal policy on the timing or dose of folic supplementation.
The head of the Department of Malaria Control at Kenya's Ministry of Health, Willis Akhwale, says his department will keenly study the trial's findings to inform policy formulation.
Geoffrey Targett of the Department of Infectious and Tropical Diseases at the London School of Hygiene and Tropical Medicine, United Kingdom says the research deals with an important question, partly because there is uncertainty about best practice in malarial countries.
A complicating factor is that SP is becoming less effective in East Africa as people's resistance to the drug grows. Targett cautions that this "will probably play a part in the interaction between folic acid and SP. It is only a matter of time before SP resistance becomes too high to make the drug sufficiently effective".
He says a study in Gambia found that a low dose of folic acid plus iron proved beneficial and did not inhibit the anti-malarial action of SP in pregnant women, showing that "there are benefits from its use at a lower dose".
Link to full paper in PLoS Clinical Trials
Reference: PLoS Clinical Trials doi: 10.1371/journal.pctr.0010028 (2006)