The experts say their research threw up a disturbing trend
Africans suffering from malaria may be getting sub-standard treatment, a study by US-based experts has suggested.
Researchers from the Pharmacopeia group found that between 26% and 44% of anti-malaria drugs in Uganda, Senegal and Madagascar were of poor quality.
The group, conducting the study for the World Health Organization, said low-grade drugs were being used in both public and private health practices.
Some 90% of malaria deaths in the world occur in Africa.
The experts subjected 200 samples of anti-malaria drugs to quality-control testing in a US laboratory.
They found 44% of the drugs from Senegal failed the testing, followed by 30% from Madagascar and 26% from Uganda.
Patrick Lukulay, director of the US government-funded Pharmacopeia programme, said it was a "disturbing trend".
"It is worrisome that almost all of the poor-quality data that was obtained was a result of inadequate amounts of active [ingredients] or the presence of impurities in the product," he said.
The particular problem they identified was with artemisinin-based drugs.
The chemical is one of the few affordable and effective treatments for malaria.
But the WHO's malaria programme chief Robert Newman said low-quality versions of the drug could increase resistance because they would not kill all of the parasites.
"There are a number of things that need to be done - as a global community we need to support countries in strengthening their regulatory controls," Mr Newman said.
The researchers also studied drugs from seven other countries - Cameroon, Ethiopia, Ghana, Kenya, Malawi, Nigeria and Tanzania - but have not yet released data from those nations.
However, Mr Lukulay said Ghana had already withdrawn more than 20 drugs from the market after seeing initial results.