herb drug interaction

1. By:-
Nitin P. Kanwale
N.D.M.V.P. Samaj’s College of Pharmacy, Gangapur Road, Nasik – 422 002
(2014-2015)
HERB-DRUG INTERACTION

2. 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.

3. 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.

4. 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.

5. 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?

6. 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.

7. SJW INTERACTIONS
Drug 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

8. Warfarin-herb interactions:-
↓se absorption from GI.
 Herbs that decrease platelet aggregation.
 Decreased thromboxane synthesis.
 Green tea (Camellia sinensis) – Inhibits
platelet synthesis of thromboxane

9. 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.

10. 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.

11. 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.

12. CONCLUSION…

13. REFERENCES…
• Izzo AA. Herb-drug interactions: an overview of the
clinical evidence. Fundam Clin Pharmacol. 2005
Feb;19(1):1-16.
• Ernst E. Prescribing herbal medications appropriately.
J Fam Pract. 2004 Dec;53(12):985-8.
• Skalli S, Zaid A, Soulaymani R. Drug interactions with
herbal medicines. Ther Drug Monit. 2007
Dec;29(6):679-86
• Chavez P, Jordan MA, Chavez PI. Evidence-based drug-
herbal interactions.Life Sci. 2006;78:2146-57.

14.  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.
 Barone GW, Gurley BJ, Ketel BL, Abul-Ezz Sr.
Herbal supplements: a potential for drug
interactions in transplant recipients.
Transplantation 2001; 71: 239-241.