Evaluation of Herbal Medicines: Value Addition to Traditional Medicines Through Metabolism, Pharmacokinetic and Safety Studies

The safety and efficacy of herbal medicines remain major issues of concern especially in the developing world where the use is high. The World Health Organisation estimates up to 80% of the population in Africa relies on herbal medicines for treatment of many diseases. Minimum safety evaluations need to be done for both the herbal and conventional drugs, in particular when there is a high likelihood of co-administration. This is particularly important in Africa where there is increased access to antiretrovirals in the treatment of HIV/AIDS, which are being used in a population background characterized by rampant use of herbal medicines. Many techniques used in the discovery and evaluation of conventional drugs can be adapted to herbal medicines. Such evaluations will add value to herbal medicines as doctors and patients will be better informed on which drugs and herbal medicines to take or not take together. This can also lead to the adoption of guidelines by regulatory agents such as the European Medicines Agency (EMA), Food and Drug Administration (FDA) and governmental agencies controlling the use of medicines. Of current interest is the evaluation of drug-herb interactions (DHI) involving the absorption, distribution, metabolism and excretion (ADME) of medicines where there is a promising possibility to adopt the current FDA and EMA guidelines on the evaluation of herbal medicines for drug-drug interactions (DDI). In this review we demonstrate progress made so far in DHI and point to possible future developments that will contribute to the safe use of herbal medicines.