Table 10. Summary of adverse effects and herb-drug interactions of the most common herbs.

SJW: St. John’s Wort, INR: International Normalised Ratio, CYP: Cytochrome P-450 enzymes, P-gp: P-glycoprotein, BP: Blood Pressure, HR: Heart Rate, PAD: Peripheral Artery Disease, CCB: Calcium Channel Blockers, HA: Headache, N: nausea, V: vomiting, ADHD: attention-deficit hyperactivity disorder, OCD: obsessive-compulsive disorder, GI: Gastrointestinal, ICB: intracerebral bleeding, BF: Breast Feeding, OC: Oral Contraceptives

Herb Name (Latin/Scientific)	Promoted for	Adverse Effect	Herb-Drug Interaction
			Interacting Drug	Effect of Interaction
Black Cohosh (Actaea racemosa, Cimicifuga racemosa)	hot flashes, other menopausal symptoms	stomach upset, cramping, HA, rash, feeling of heaviness, vaginal spotting or bleeding, weight gain	statins	reduced effectiveness
Garlic (Allium sativum)	high blood cholesterol, high BP	odor (breath & body), heartburn, stomach upset, risk of bleeding	Chlorpropamide	hypoglycemia
			Paracetamol	changes in pharmacokinetic variables
			Warfarin	increased INR
			Saquinavir	decreased concentration
Ginkgo (Ginkgo biloba)	anxiety, allergies, dementia, eye problems, PAD, tinnitus	HA, stomach upset, dizziness, N, V, palpitations, constipation, allergic skin reactions, bleeding risk, liver & thyroid cancer (animal study), early labor or extra bleeding during delivery (in pregnancy), ICB	Aspirin	spontaneous hyphaema
			Thiazide diuretic	increased BP
			Trazodone	coma
			Warfarin (Coumadin)	increased bleeding risk
					Ginseng, Asian (Panax ginseng)	to increase resistance to stress (adaptogen), for general well-being (general tonic), to improve physical stamina, concentration & memory; to stimulate immune function; to slow the aging process; to relieve respiratory & cardiovascular disorders, depression, anxiety, menopausal hot flashes, premature ejaculation (topical)	insomnia, menstrual problems, breast pain, increased HR, high or low BP, HA, loss of appetite, digestive problems, altered blood sugar, birth defects (animal study), questionable safety for infants, children, pregnancy or BF, platelet inhibition, lowering blood glucose	Drugs metabolized by CYP3A4 (Ginseng induces CYP3A4 enzymes)	decrease the effectiveness of drugs such as CCB, some chemotherapeutic & HIV agents, certain antihypertensive & statin medications, some antidepressants
Warfarin	decreased INR
Goldenseal (Hydrastis canadensis)	colds and other respiratory tract infections, allergic rhinitis, ulcers, digestive upsets such as diarrhea and constipation, mouthwash, eyewash	unsafe for pregnancy or breastfeeding, neonatal jaundice	Metformin	drop in metformin level
			Drugs metabolised by CYP2D6 and CYP3A4 (Goldenseal inhibits both CYP2D6 & CYP3A4)	increase in the level of many pharmaceutical agents currently in use
SJW (Hypericum perforatum)	depression, menopausal symptoms, ADHD, somatic symptom disorder, OCD, topical use for skin conditions (wounds & bruises) & muscle pain	GI disturbances, allergic reactions, fatigue, dizziness, confusion, dry mouth, photosensitivity/phototoxicity (skin rash, nephropathy), insomnia, anxiety, headache, or sexual dysfunction, unsafe for pregnancy or BF (infantile colic, drowsiness & fussiness)	Drugs with pharmacokinetics involving CYP3A4 and P-gp (SJW is a potent inducer of CYP and intestinal P-g)	reduction in cyclosporine, indinavir, nevirapine, OC, warfarin (reduce INR), digoxin, ivabradine, benzodiazepines, tacrolimus, irinotecan, imatinib theophylline, venlafaxine, statins
			Certain antidepressants	serotonin syndrome