Herbal Safety, Toxicology, Contraindications, and Herb-Drug Interactions
Safety framework
Herbal safety questions test dose, preparation, constitution, pregnancy, organ function, and interactions. Know the classic toxic herbs and their processing or contraindications; recognize that "natural" does not mean safe. Pregnancy categories and pediatric dosing require caution. Herbs can interact with anticoagulants, antiplatelets, antihypertensives, antidiabetics, immunosuppressants, lithium, digoxin, and CYP-metabolized drugs. Blood-moving herbs, for example, may increase bleeding risk with warfarin.
Traps
Examiners test assumptions: no side effects because it is herbal; no interaction because the patient did not disclose; safe because it is a food. Watch cumulative dose, long-term use, and duplicate ingredients in patent medicines. Do not overlook contaminated or misidentified products. A normal lab result does not rule out an interaction.
Worked example
A patient on warfarin asks about a formula containing Dan Shen and Hong Hua for chest discomfort. Both move blood and may increase bleeding risk. The safe response is not to dismiss the concern or to stop warfarin; it is to avoid unsupervised use, consult the prescriber, monitor INR, and document the discussion. Rule of thumb: ask about every prescription, over-the-counter drug, and supplement before recommending herbs.