Herb drug and  herb food interaction 

(Part-2)

common herbs and their interactions

As per PCI Syllabus

(T. Y. B. Pharm Sem –VI)  Unit-II

HERB-DRUG/ FOOD INTERACTIONS


Even though herbal medicines are obtained from natural sources, their active ingredients are potent chemicals which can give rise to herb-drug or herb-food interactions.

Herbal supplements and nutraceuticals are been purchased over the counter (OTC) and may be labelled as ”All Natural” but that does not mean they are always safe.

Herbal supplements are not subject to review by the FDA and their use can often be risky when taken along with other drugs or foods. 

Study of some common herbs and their interactions 

 a) Hypericum perforation (St. ]ohn,s  Wort)

It is a popular herb used to treat mild depression. The active constituent of this herb is known as ”hypericin”,

 which has similar effects on the brain as that of mom amino oxidase (MAO) inhibitors (antidepressants).

If taken together, it may produce dangerous drug interactions resulting in rapid rise in blood pressure, severe head ache, collapse and death. Foods such as cheese, chicken liver, fish, legumes, soya Sauce & beer should be avoided with this drug. 

Hypericin has also reported to produce interactions with immune suppressant drug cyclosporine, anti Viral drug indinavir, oral contraceptives, digoxin and benzodiazepines resulting in increased sensitivity to light, anxiety, dizziness, dry mouth, fatigue and sexual dysfunction

b) Kava (Piper methysticum)

It is an herb that has antianxiety, pain relieving, muscle relaxing and anticonvulsant effects.
Kava should not be taken with drugs which act on nervous system such as barbiturates, antidepressants, antipsychotics and alcohol. 

It is reported that concomitant use of kava with central nervous system depressant can increase the risk of drowsiness and motor reflex depression.

Kava has also reported to produce hepatotoxic effects when taken with some drugs 


c) Ginkgo biloba ( Maiden hair tree)

Ginkgo has been used to treat symptoms of Alzheimer, dementia, Parkinson’s disease and to enhance the memory capabilities. 

Ginkgo is reported to decrease the antiviral effects of drugs used in HIV such as efavirenz or indinavir. 

Ginkgo can also alter the actions of drugs metabolized through liver such as omeprazole fluvastatin and donepezil.

Ginkgo should be avoided in patients who are on anticonvulsants, blood thinners and antidiabetic drugs.

Ginkgo is reported to interact with over 250 drugs, hence patient should take proper consultation before using it.


d) Ginseng (Panax ginseng)

Ginseng is used to improve the body’s resistance to stress, boost the immune system, and  improve the sense of well being and stamina. 

It is also used to improve physical and mental performance and treat erectly dysfunction, hepatitis C, symptoms related to menopause, lowering of blood glucose and controlling blood pressure.

Ginseng is reported to induce the activity of enzyme cytochrome P3A, in the liver which metabolizes various drugs resulting in their decreased activity and faster excretion from the body.

Ginseng decreases the effectiveness of warfarin (blood thinner) and increase the risk of clotting hence it should be avoided while taking anticoagulants.

Ginseng is also reported to decrease the activity of anti hypertensives resulting in high blood pressure. It is also reported to affect the activity of anti diabetic drugs, hence should be avoided in such cases. 

e) Garlic (Allium sativum)

Garlic is used in various conditions like to lower blood sugar levels, reduce menstrual pain, lowering blood cholesterol levels and decrease blood pressure.

Garlic does not interact with drugs at normal recommended doses, however exposure to concentrated garlic extracts for prolonged periods is reported to interact with several drugs.

Garlic is reported to reduce the efficacy of drugs whose distribution is dependent
on efflux transporter mechanism.

Garlic is reported to affect the blood clotting, hence should be avoided in patients taking blood thinning agents like aspirin and warfarin. 

Garlic alters the blood sugar level, hence used under supervision on patients with anti diabetics.

It is also reported that garlic supplements have decreased the blood levels of HIV protease inhibitors when used together.

Note*: Grape juice decreases the activity of cytochrome P450 3A4 enzymes that are responsible for breaking down many drugs & toxins. Grape juice contain compounds known as Furanocoumarins, that block the CYP 3A4 enzymes.

f) Pepper (Piper nigrum)

Black pepper contains piperine as the  chief active constituent.

It is used as spices as Well as carminative and to treat arthritis, asthma, stomach upset and sinus infection.

Piperine is reported to inhibit various cytochrome enzymes, resulting in increased blood level of certain drugs like carbamazepine, midazolam, diclofenc, phenytoin and warfarin.

Black pepper might increase the risk of bleeding when mixed with anticoagulants or blood thinning drugs like aspirin, clopidogrel, heparin and warfarin.

Black pepper might produce additive effect With antidiabetic drugs and increase the risk of hypoglycaemia.

Black pepper might increase the blood level of cefotaxime and cyclosporine resulting in increased drug effects as well as side effects.

Black pepper might also increase the blood levels thereby enhancing the effects as well as side effects of anti cancer drugs, anti hypertensive, anti convulsants and some antibiotics.

g) Ephedra (Ephedra gerardiana)

Ephedra is used to treat allergies, high fever, and respiratory tract conditions like  bronchspasm, asthma and bronchitis. 

•Ephedra contains ephedrine which is a potent drug and stimulates heart, lungs and nervous system. Overdose or improper use of ephedra results in various effects like high blood pressure, heart attack, muscle disorders, seizures; stroke, loss of consciousness and death.

•Ephedra may reduce the effectiveness of antihypertensive and could rise the blood pressure.


Ephedra should not be mixed with other central nervous system stimulants such as amphetamine and its derivatives as it may enhance hyperactivity and produce serious conditions.

Ephedra should be avoided with blood thinning medications such as aspirin and warfarin, as it may induce bleeding.

Ephedra may interact with anti depressants like imipramine, clomipraminer mortryptiline and mono amino oxidase (MAO) inhibitors and enhance their effects.

Ephedra should be avoided in people suffering from seizures, as it may worsen the onset of seizures.

Thank You