On this blog, I have repeatedly tried to alert consumers and patients to the risks of herbal medicine. The risks include:
- toxicity of one or more ingredients of the plant,
- interactions with other medicines,
- contamination with toxic non-herbal substances such as heavy metals,
- adulteration with synthetic drugs such as steroids,
- ineffectiveness in treating the target disease
- reduction of adherence to prescribed medicines.
A new paper throws more light on the latter issue which has been not well-studies so far.
The objective of this study was to investigate the relationship between the use of medicinal plants and medication adherence in elderly people. The authors conducted an observational, cross-sectional study of elderly residents in Cuité-PB, Northeastern Brazil, through a household survey. A stratified proportional and systematic random sample of 240 elders was interviewed in their homes and the use of pharmaceutical medicines and of medicinal plants was assessed by direct examination. The association of medication adherence with socio-demographic, clinical, medication and use of medicinal plants was analysed with multiple logistic regression.
The results showed that medication non-adherence increases with use of herbal medicines (adjusted odds ratio 2.022, 95% CI 1.059–3.862, p = 0.03), as well as with the number of different medicinal plants used (adjusted odds ratio 1.937, 95% CI 1.265–2.965, p = 0.002).
The authors concluded that this study provides first-hand evidence that the use of herbal medicines is associated with poor medication adherence. Given the high frequency of the use of herbal medicines, further research into the mechanisms of this association is justified.
This conclusion is well-put, I think. If these findings are confirmed in other populations, we are confronted with a somewhat paradoxical situation: combining herbal and synthetic medicines can reduce adherence to the synthetic drugs and, in cases where adherence is not affected, it could increase the risk of herb/drug interactions.