By:-

Nitin P. Kanwale

N.D.M.V.P. Samaj’s College of Pharmacy, Gangapur Road, Nasik – 422 002

(2014-2015)

HERB-DRUG INTERACTION

INTRODUCTION

The popularity of herbal medicinal products (HMPs) makes it

important to understand potential interactions between herbs and

prescribed drugs.

Herbal-Drug interaction is higher than Drug-Drug interaction.

PHARMACOKINETIC INTERACTION.

PHARMACODYNAMIC INTERACTION.

MEDICATION ERRORS.

Medicines should be prescribed only when they are necessary, and in

all cases the benefit of administering the medicine should be

considered in relation to the risk involved.

Prescribing is an important area in terms of error occurrence

Types include: Wrong drug, dose, inadequate consideration of patient factors.

WHY DO PEOPLE USE HERBAL MEDICINES?

Used in developing countries where,

cost of drugs is High,

poor accessibility to drugs in rural areas,

shortage of physicians.

Cultural & religious beliefs

Perception that natural = safe

“More” ADRs reported with conventional medicines than herbal preparations.

STEPS FOR DETECTING AND ADVISING ON

HERBAL/DRUG INTERACTIONS

Is the patient taking any herbal supplements?

Does the herbal have efficacy for the intended use?

Is the product reliable? (i.e.,what are they REALLY taking?)

Is the Rx drug one with a narrow therapeutic margin?

HERB-DRUG INTERACTION:-

St. John’s Wort:-

Theophylline (CYP1A2), cyclosporin (CYP3A4) and warfarin (CYP2C9) - reports of a reduction in the serum concentrations.

Safety of concurrent administration of SJW with prescription or OTC medications has not been established

Inducer of Cytochrome P450

Documented interactions with a number of prescription drugs.

SJW INTERACTIONSDrug CYP Effect Management

HIV protease inhibitors

(nelfinavir,ritonavor,saquinavir)

Induce 3A4 Stop and measure

viral load

HIV non-nucleoside RTI

(efavirenz,nevirapine)

Induce 3A4 Stop and measure

viral load

warfarin Induce 2C9 Stop and adjust warfarin

dose

cyclosporin Induce P-

glycoprotein Stop and adjust

cyclosporine dose

oral contraceptives Induce 3A4 Stop and use alternate

birth control

anticonvulsants Induce 3A4 Stop and adjust

anticonvulsant dose

digoxin Induce P-

glycoprotein Stop and adjust digoxin

dose

theophylline Induce 1A2 Stop and adjust

theophylline dose

Triptans

(sumatriptan)

Increase

serotonin Stop

SSRI

(fluoxetine,sertraline, etc)

Increase

serotonin Stop

Warfarin-herb interactions:-

↓se absorption from GI.

Herbs that decrease platelet aggregation.

Decreased thromboxane synthesis.

Green tea (Camellia sinensis) – Inhibits

platelet synthesis of thromboxane

EPHEDRA:-

Illegal in US but possibly obtained internationally. Increase in blood

pressure, thus contraindicated with anti-hypertensives and stimulants

(e.g. caffeine).

Ginkgo Biloba:-May prolong bleeding time - caution in patients

taking anticoagulant/antiplatelet medication.

Ginkgo (Ginkgo biloba) – Ginkgolide B decreases PAF, extract inhibits thromboxane and prostacyclin in diabetics.

PRECAUTIONS IN GERIATRIC

PATIENTS.

Medicines plays a vital role in health care, as we grow

older.

As people age, they are much more likely to be

prescribed more than one kind of prescription

medication, and many seniors take three or more. This

increases the risk for drug interactions, mix-ups, and the

potential for side effects.

PRECAUTIONS TO BE TAKEN...

If patient already take a number of medications, ask your doctor:

> if the new medicine has any of the same actions or possible side effects.

> if the new medicine might interact with anything you are already taking.

> if there are any non-medicinal ways of treating your medical condition.

CONCLUSION…

REFERENCES…

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Miller LG. Herbal medicinal, Selected clinical considerations focusing on known or potential drug-herb interactions. Arch Int Med 1998; 158: 2200-2211.

Nebel A, Schneider BJ, Baker RK, Kroll DJ. Potential metabolic interaction between St. John's Wort and theophylline. Ann Pharmacother 1999; 33: 502.

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