Anti-malaria drug dosages are questioned

A US study suggests lower dosages of anti-malarial drugs might be safer, preventing parasites from becoming drug-resistant. Penn State University researchers found the current dosage of drugs used in treating malaria might be helping parasites become drug resistant faster, without improving the long-term outcome in patients. Penn State evolutionary biologists said most malaria infections in the world comprised a mix of parasites, so that as resistant parasites spread in a population, they usually shared their human hosts with other parasites that were susceptible to drugs. Normally in the absence of drugs, the susceptible pathogens keep the resistant ones from proliferating. But when infections are treated with drugs, the dynamics change. "Drugs kill off the susceptible parasites letting their competitors, the resistant ones, fill the vacant space and expand their numbers," said Professor Andrew Read. "The more drugs you use, the worse you make the situation in terms of the evolution of drug resistance. This massively increases the rate of spread of resistance, so the drugs become less and less useful." The study's findings are reported in the online edition of the Proceedings of the National Academy of Sciences.