Abstract

Herbal medicines are widely consumed worldwide as complementary or alternative therapies, often in combination 
with conventional drugs. While generally perceived as safe, concurrent use of herbs and pharmaceuticals may lead 
to significant herbal drug interactions (HDIs) with clinical consequences. These interactions occur primarily 
through pharmacokinetic mechanisms such as alterations in drug absorption, metabolism, distribution, or 
excretion, often mediated by cytochrome P450 enzymes and P-glycoprotein transporters, and pharmacodynamic 
mechanisms, where herbal constituents synergize or antagonize drug actions. Notable examples include St. John’s 
wort, which induces CYP3A4 and reduces the effectiveness of oral contraceptives and immunosuppressants; 
Ginkgo biloba, which increases bleeding risk when combined with anticoagulants; and Garlic, Ginseng, and 
Echinacea, which may interfere with cardiovascular, antidiabetic, and immunosuppressive drugs. The risk of HDIs 
is heightened in vulnerable populations such as the elderly, polypharmacy patients, and individuals with chronic 
illnesses. Despite growing recognition, many HDIs remain underreported due to inadequate patient disclosure and 
a lack of standardized monitoring. This review highlights the pharmacological basis, clinical relevance, and 
regulatory considerations of HDIs, underscoring the urgent need for patient education, healthcare provider 
vigilance, and more robust clinical trials to ensure safe integration of herbal remedies with conventional 
therapeutics.