One in five medicines in Africa is sub-standard or fake‚ say US scientists.

In southern Africa‚ Malawi has the most medicines commonly sold in sub-standard or falsified condition‚ according to pharmacists from the University of North Carolina.

South Africa’s problem is relatively small‚ they reported on Friday in the journal JAMA Network Open‚ after analysing 96 previous studies of falsified and substandard medicines in 63 low-income and middle-income countries.

In much of the developing world‚ more than 13% of essential medicines that satisfy people’s priority health care needs are problematic‚ and this rises to almost 19% in African countries.

Falsified medicines fraudulently misrepresent their identity‚ composition or source. Substandard medicines are genuine but fail to meet quality standards or specifications for a variety of reasons‚ including poor manufacturing‚ shipping or storage conditions‚ or because the drug is sold beyond its expiry date.

Sachiko Ozawa‚ an associate professor at the Eshelman School of Pharmacy‚ said his team found antimalarials and antibiotics were the most problematic medicines.

“[This] is a substantial public health problem because these medicines can be ineffective or harmful and can prolong illnesses‚ cause poisoning or lead to dangerous drug interactions‚” said Ozawa.

“Our study shows that a concerted global effort is needed to improve supply chain management for medicines and to identify solutions to this understudied issue.”

Co-author James Herrington said greater global collaboration was needed to implement laws on drug quality and improve quality control‚ surveillance and data sharing.

“This can strengthen the global supply chain against poor-quality medicines‚ improve health outcomes by reducing antimicrobial and anti-parasitic resistance and‚ ultimately‚ help governments‚ businesses and patients save money‚” he said.