A report on medical drugs in Papua New Guinea says many anti-malarial drugs could be sub-standard.
Dr Inoni Betuela, from the Institute of Medical Research, says over 80 per cent of drugs are sourced from uncertified companies.
He says more than half of the content of the sampled tablets of primaquine, was made up of sugar and inactive ingredients.
He says while primaquine is not that widely-used, other common drugs like quinine and amoxicillin also had significant levels of failure.
The team sampled 360 samples, of seven different anti-malarial and antibiotic drugs.
Dr Betsuela says the result is a clear warning to the health department, and there needs to be more scrutiny of the sources of medicines.
"We should be using companies or factories that are WHO certified, to say that they comply to the good manufacturing practice and say that most of the drugs they're producing are of good quality."
Dr Inoni Betuela.