Determinants of adverse drug reaction reporting for antimalarial medicines: a mixed-methods study among healthcare workers in ogun State Southwest Nigeria

Abstract

Spontaneous adverse drug reaction (ADR) reporting is central to pharmacovigilance, yet underreporting remains common in malaria-endemic low- and middle-income countries (LMICs). This study examined determinants of ADR reporting among healthcare workers involved in malaria case management in Ogun State, Southwest Nigeria. A sequential explanatory mixed-methods cross-sectional study was conducted in all 490 functional public health facilities in Ogun State between September and October 2025. The quantitative component included 404 healthcare workers, and the qualitative component comprised 162 key informants (KIs). Structured questionnaires were administered using KoboCollect. Quantitative data were analysed using chi-square tests and logistic regression. Because only 23 respondents (5.4%) had ever reported an ADR, events-per-variable ratios were below conventional thresholds; regression estimates should therefore be interpreted as exploratory. Qualitative data were analysed thematically using Braun and Clarke’s framework. Only 23 of 404 respondents (5.4%) had ever reported an ADR. In bivariate and multivariable analyses, completion of ADR reporting forms, routine documentation of suspected ADRs in patient case notes, and knowledge of reporting channels were consistently associated with reporting practice. In the exploratory consolidated model, routine documentation, knowledge of reporting forms, time constraints, and perceived reporting burden remained significant predictors. Among 162 kIs, most reported no pharmacovigilance training in the preceding two years, and nearly half indicated that no formal ADR reporting system existed in their facilities. The qualitative analysis identified four main barriers: limited pharmacovigilance knowledge, weak or absent reporting systems, inadequate training and supervision, and patient-related barriers to ADR detection. ADR reporting for antimalarial medicines was very low among healthcare workers in Ogun State. Underreporting was driven mainly by system-level constraints, including lack of reporting forms, absence of trained focal persons, weak supervision, and limited feedback from regulators. Strengthening facility-level reporting systems, integrating ADR documentation into routine workflows, and improving feedback mechanisms are likely to yield the greatest gains in pharmacovigilance performance. Not applicable What is already known about this subject • Spontaneous adverse drug reaction reporting remains low in many malaria-endemic countries despite the widespread use of artemisinin-based combination therapies. What this study adds • This study advances pharmacovigilance research by combining quantitative and qualitative evidence to explain why ADR reporting for antimalarial medicines remains weak in primary health care settings in Ogun State Southwest Nigeria. It moves beyond describing reporting levels to show how facility-level systems, supervision, and reporting infrastructure shape reporting practice. • By integrating survey data with key informant perspectives, the study underscores that improving ADR reporting requires more than awareness raising. It points to the need for stronger operational support, including routine supervision, designated focal persons, consistent reporting tools, and functional feedback mechanisms.