Safety monitoring of herbal medicines in Nigeria: worrying state of pharmacovigilance system based on WHO core pharmacovigilance indicators

Introduction: Herbal medicines (HMs) have shown therapeutic and toxicological potentials. Thus, the WHO expanded the pharmacovigilance (PVG) scope to include HMs. This study appraised the state of PVG system in Nigeria for the safety monitoring of HMs using WHO core PVG indicators. Methods: Between January and June 2019, 39 PVG experts were requested to independently appraise the PVG system in Nigeria for safety monitoring of HMs using WHO PVG core structural (CSIs), process (CPIs) and outcome (COIs) indicators. The 27 indicators (CSIs = 10, CPIs = 9 and COIs = 8) were scored 3, 2, 1 and 0 for adequate, fairly adequate, inadequate and uncertain states, respectively. CSIs index (CSII) was determined by dividing the summation of CSIs mean score by total obtainable score (30) and expressed in percentage. This was applied to CPIs and COIs to obtain CPIs index (CPII) and COIs index (COII), respectively. Results: The mean ± standard deviation (SD) of participants’ age was 43.6 ± 10.3 years with mean ± SD work experience of 15.3 ± 9.3 years. Majority had doctoral degree (35.9%; 14/39; P >0.05) and were medical doctors (28.2%; 11/39; P > 0.05). Twelve of the 27 indicators scored at least 2.0 and CSIs, CPIs, and COIs accounted for 75.0% (9/12), 0.0% (0/12) and 25.0% (3/12), respectively ( P < 0.05). The total mean score was 27.3 ± 0.2 for CSIs as against 8.0 ± 0.3 for CPIs and 11.2 ± 0.4 for COIs ( P < 0.05). The CSII, CPII and COII were 91.0%; 29.6% and 46.7%, respectively ( P < 0.05). Conclusion: Most of the structural elements are in place for safety monitoring of HMs in Nigeria. However, the process and outcome of PVG indicate an inadequate state. Thus, deliberate efforts are required to ensure the realization of PVG objectives.