Spatial Hotspots and Supply Chain Determinants of Counterfeit Antimalarials in Sub-Saharan Africa: A Narrative Review of Post-Marketing Surveillance Studies

Counterfeit, falsified and substandard antimalarial medicines continue to threaten malaria control efforts, particularly in Sub-Saharan Africa where malaria remains highly endemic. This review examined the concepts, empirical evidence and regulatory frameworks related to counterfeit antimalarial medicines, with emphasis on pharmaceutical supply chains, medicine quality assurance, post-marketing surveillance, pharmaceutical regulation, spatial epidemiology and the application of Geographic Information Systems (GIS) in medicine surveillance. Relevant literature published between 2016 and 2025 was reviewed from peer-reviewed journals, reports from international health organizations and other reputable academic sources. The literature was synthesized narratively to examine evidence on counterfeit antimalarial medicines, pharmaceutical supply chains, medicine quality assurance, post-marketing surveillance, pharmaceutical regulation, spatial epidemiology and the application of Geographic Information Systems (GIS) in medicine surveillance. The review found that weaknesses in pharmaceutical supply chains, inadequate regulatory enforcement, poor post-marketing surveillance systems and cross-border medicine trafficking are major drivers of counterfeit medicine circulation. Empirical evidence further revealed that poor-quality antimalarial medicines contribute to treatment failure, increased malaria morbidity and mortality, antimicrobial resistance and economic losses. Studies also demonstrated that GIS and spatial epidemiological approaches enhance medicine surveillance by identifying geographic hotspots, improving risk-based inspections and supporting evidence-based regulatory decision-making. However, the review identified limited integration of GIS into pharmaceutical surveillance systems and inadequate location-specific evidence in many malaria-endemic countries, including Nigeria. The review concludes that strengthening pharmaceutical regulation, improving medicine quality assurance, expanding post-marketing surveillance, modernizing pharmaceutical supply chains and adopting GIS-based surveillance systems are essential for reducing counterfeit antimalarial medicines and improving public health outcomes. Future research should prioritize spatial analysis of counterfeit medicine distribution to support targeted interventions and strengthen national medicine quality surveillance systems.