Mapping Ghana’s antimalarial drug supply network

Study hopes to help governments, regulators and health organisations improve equitable access to medicines.

A new study has mapped the private-sector network that supplies antimalarial medicines across Ghana, revealing a system shaped by a small number of powerful distribution hubs. 

The work is a unique collaboration between the School of Physics and Astronomy and various departments at the University of Cape Coast, Ghana.  It forms part of a wider project on substandard medicines in Africa coordinated by Professor Kate Hampshire at Durham University.

By analysing survey data from across the country, scientists found that the network has a clear “hub-and-spoke” structure, dominated by companies based in Accra, with a secondary hub in Kumasi. Other regional centres, including Tamale and Cape Coast, play a significant smaller role in moving medicines through the system.

The study shows that antimalarial drugs typically pass through three to four intermediaries before reaching patients. In many parts of the country, pharmacies can buy from several suppliers, sometimes via multiple intermediaries, which makes the network relatively resilient if one intermediary fails. However, the quality of medicines - measured using expiry date - tends to decline as the number of intermediaries increases. This suggests that longer supply chains may increase the risk of poorer-quality products reaching patients.

Research in Edinburgh, primarily led by MPhys Computational Physics student Chia-Lin Wang, applied mathematical tools from network science to analyse extensive fieldwork carried out by Cape Coast researchers led by Professor Osman Adams.

The study, published in PLOS ONE, identified important differences in how influence is distributed within the market. One company stood out because it supplies a large number of customers directly, giving it a dominant position in terms of visible connections. However, another company emerged as more influential when the researchers looked at indirect influence through intermediaries, showing that power in the supply chain is not always concentrated in the businesses with the most direct customers.

The analysis also revealed differences between the experience of sellers and buyers. On the supply side, the network follows a “scale-free” or Pareto-type pattern, which is typical of a relatively open and weakly regulated market where a few sellers dominate. On the purchasing side, the network appears more log-normal, suggesting that individual buyers have less freedom and fewer meaningful choices than the number of suppliers might imply. Remote regions in northern Ghana were a notable exception: they often had fewer intermediaries, but were also more dependent on shipments from a single supplier, creating a different kind of vulnerability.

A similar study is underway in Tanzania.  Comparable self-organising and lightly regulated medicine supply networks operate in many low- and middle-income countries.

Better understanding how these networks function could help governments, regulators and health organisations improve equitable access to medicines, strengthen oversight, and reduce the circulation of substandard or falsified drugs.