Warfarin is a popular anticoagulant with high global demand. However, studies have underlined serious
safety issues when warfarin is consumed concomitantly with herbs or its formulations. This review
aimed to highlight the mechanisms behind herb-warfarin interactions while laying special emphasis on its PKPD
interactions and evidence on Herb-Warfarin Interaction (HWI) with regards to three different scenarios,
such as when warfarin is consumed with herbs taken as foods or prescribed as medicine, or when used in special
situations. A targeted literature methodology involving different scientific databases was adopted for acquiring
information on the subject of HWIs. Results of the present study revealed some of the fatal consequences
of HWI, including post-operative bleeding, thrombosis, subarachnoid hemorrhage, and subdural hematomas
occurring as a result of interactions between warfarin and herbs or commonly associated food products
from Hypericum perforatum, Zingiber officinale, Vaccinium oxycoccos, Citrus paradisi, and Punica
granatum. In terms of PK-PD parameters, herbs, such as Coptis chinensis Franch. and Phellodendron
amurense Rupr., were found to compete with warfarin for binding with plasma proteins, leading to an increase
in free warfarin levels in the bloodstream, resulting in its augmented antithrombic effect. Besides, HWIs were
also found to decrease International Normalised Ratio (INR) levels following the consumption of Persea americana
or avocado. Therefore, there is an urgent need for an up-to-date interaction database to educate patients
and healthcare providers on these interactions, besides promoting the adoption of novel technologies, such as
natural language processing, by healthcare professionals to guide them in making informed decisions to avoid
HWIs.