Heavy metal contamination in pharmaceuticals: A narrative review of prevalence, health risks, and regulatory gaps in Nigeria.

Abstract

Pharmaceutical quality and safety are critical to public health, yet low- and middle-income countries such as Nigeria remain vulnerable to medicine safety challenges due to weak regulatory enforcement and limited market surveillance. A major concern is contamination of pharmaceutical products with toxic heavy metals, including lead, cadmium, mercury, arsenic, nickel, and chromium. These metals can bioaccumulate and cause adverse health effects even at low concentrations, such as neurodevelopmental impairment, renal and hepatic dysfunction, reproductive toxicity, and cardiovascular complications. This narrative review synthesised evidence on the prevalence of heavy metal contamination in pharmaceuticals marketed in Nigeria, associated health risks, and the adequacy of existing regulatory frameworks.Relevant literature published between 2005 and 2025 was identified through a comprehensive literature search of major databases such as PubMed, Google Scholar, African Journals Online, and Scopus, supplemented with reports from the National Agency for Food and Drug Administration and Control, the World Health Organisation, and grey literature. Studies assessing industrially manufactured or over-the-counter medicines for heavy metal contamination in Nigeria were included.The findings reveal recurrent contamination across several pharmaceutical categories, particularly syrups, locally manufactured analgesics, and herbal preparations. Lead and cadmium were the most frequently reported contaminants, with some products containing multiple metals and exceeding pharmacopeial limits. Heavy metal exposure induces oxidative stress and cellular damage, contributing to kidney injury, neurotoxicity, haematological effects, and endocrine disruption. Children, pregnant women, individuals with renal impairment, and frequent users of herbal medicines were identified as particularly vulnerable. Overall, heavy metal contamination remains a significant medicine safety concern in Nigeria, highlighting the need for stronger regulation, improved analytical capacity, and risk-based surveillance.