Herb drug interactions

Herb drug interactions can and do occur, and must be actively taken care of by you and your physician. Although extensive literature is not available on this topic, here are possible interactions with Ayurveda and herbal supplements.  These are based on some observations and plausible confounding mechanisms. The list is not exhaustive and will be expanded.

In general, it is a good practice to leave a gap of atleast an hour between plant based supplements and conventional medicines.

Common in Ayurvedic medicine

1. Warfarin is combined with ginkgo (Ginkgo biloba), garlic (Allium sativum), dong quai (Angelica sinensis), or danshen (Salvia miltiorrhiza) may cause bleeding.

2.Liquorice (Glycyrrhiza glabra, yashtimadhu, jethimadh) may cause a potentiation of oral and topical corticosteroids.

3. Anthranoid-containing plants (including senna [Cassia senna] and cascara [Rhamnus purshiana]) and soluble fibres (including guar gum and psyllium) can decrease the absorption of drugs. Senna is the main ingredient of a common laxative – Kayam churna and avipattikar churna.

4.Indian gooseberry and turmeric (Amla- haldi), very commonly used by diabetics,  may reduce the bioavailability of metformin when used together in diabetes.(Ref 2)

5.Ayurvedic syrup shankhapushpi may decrease concentrations of anti-epileptic phenytoin.(Ref 3)

Common in Traditional Chinese medicine and Herbal medicine

1.Panax ginseng and antidepressants causes an induction of mania in depressed patients.

2.St John’s wort (Hypericum perforatum) with serotonin-reuptake inhibitors may cause mild serotonin syndrome. It may also decrease bioavailability of digoxin, theophylline, cyclosporin, and phenprocoumon.

3.Yohimbine (Pausinystalia yohimbe) and tricyclic antidepressants may lead to increased risk of hypertension.

4. Xaio chai hu tang (sho-salko-to) by decreased blood concentrations of prednisolone when taken with the Chinese herbal product.

1.Windrum P, Hull DR, Morris TC. Herb-drug interactions. Lancet. 2000 Mar 18;355(9208):1019-20.

2.Puranik A, Nabar N, Joshi J et al. Single dose metformin kinetics after co-adminstration of nisha-amalaki powder or mamejawa gahnwati, ayurvedic anti-diabetic formulations: A randomized crossover study in healthy volunteers. J Obes Metab Res 2014;1:99-104

3.Dandekar UP et al.Analysis of a clinically important interaction between phenytoin and Shankhapushpi, an Ayurvedic preparation.J Ethnopharmacol. 1992 Jan;35(3):285-8.


Other good resources on herb drug interaction



3.University of Maryland interactio checker: http://umm.edu/health/medical/altmed


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