The role of outpatients’ medical history on current herbal medicines use: a cross-sectional multicenter study

Herbal medicine use is widespread globally, particularly in resource-constrained settings like Nigeria. This study aimed to assess the independent predictors of herbal medicine use among outpatients, focusing on medical history. A cross-sectional study was conducted among 1250 outpatients from three tertiary hospitals in Nigeria, selected for geographical diversity. Data were collected using a pretested, interviewer-administered questionnaire. Analyses included descriptive statistics and multivariable logistic regression to identify independent predictors of herbal medicine use and related outcomes, using SPSS at 95% confidence interval (p < 0.05). Current use of herbal medicines was reported in 48.4%. Having a chronic disease significantly increased the odds of current use (AOR = 1.72, 95% CI 1.31-2.26, p < 0.001) while illness duration > 5 years had 95% higher odds of current use (AOR = 1.95, 95% CI 1.22-3.11, p = 0.005). However, taking prescribed medication reduced the odds of current use (AOR = 0.59, 95% CI 0.45-0.77, p < 0.001), but more than doubled the odds of combining herbal and orthodox therapies (AOR = 2.35, 95% CI 1.78-3.10, p < 0.001). This combination behavior was linked to an 82% increased risk of reported side effects (AOR = 1.82, 95% CI 1.38-2.40, p < 0.001). Specific conditions like gastrointestinal disorders (AOR = 1.52, 95% CI 1.08-2.14, p = 0.017) and hypertension (AOR = 1.41, 95% CI = 1.06-1.88, p = 0.019 for combination use) were also independent predictors of herbal use. Herbal medicine use was significantly driven by the presence and duration of chronic illness. The high rate of concurrent use with conventional drugs and the associated increased risk of side effects highlight a critical public health concern regarding unmonitored herb-drug interactions. These highlight the urgent need for healthcare providers to routinely inquire about outpatients' herbal medicine use, and provides evidence for policies that promote the integration and safe regulation of herbal practices within the national health system.