Herb drug and  herb food interaction 
(Part-1)

As per PCI Syllabus

(T. Y. B. Pharm Sem –VI)  Unit-II

Herb drug and herb food interaction
Drug interaction is a reaction between two or more drugs or between a drug and a food, beverage or supplement inside the body.
A drug interaction can make the drug less effective, increased activity or cause unwanted side effects.

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1.Drug-drug interaction


These are the most common type of drug interaction. More the medications administered, greater is the chance of drugs interacting with each other. One drug may potentiate the activity of another or inhibit its activity or serious unexpected side effects may occur.
Eg: vicodin a pain killer when taken along with sedating antihistamine drug, Benadryl produce an additive effect of drowsiness. 

2. Drug -food interaction

This is another type of drug interaction where drugs interact with food/ beverages and can produce various side effects.

Eg: Grape juice reduces the enzyme activity in liver which are responsible for metabolising drugs thus resulting in increased blood levels of certain drugs such as cholesterol lowering drugs (statins), this leads to toxic effects of the drug such as muscle pain and muscle injury. 

3. Drug-disease interaction :

Sometimes drugs also interact with certain diseases where the disease alter the way a drug works. 
Eg: Oral decongestants like pseudoephedrine, phenylephrine may increase the blood Pressure & can be dangerous in patients having hypertension. 



Pharmacodynamic interaction ;

This occurs when two or more drugs administered together act at the similar receptor sites leading to enhancement (additive or synergistic) effects or decreased (antagonistic) effects.

 Eg: Chlorpromazine given to prevent nausea and vomiting interacts with antipsychotic medications like haloperidol and produce serious and possible fatal irregular cardiac rhythm.

ii Pharmacokinetic interaction

This occurs when drugs interact during the process of absorption, distribution metabolism or excretion.

Absorption interactions

Some drugs can alter the absorption of another drug for example calcium can bind with some drugs like tetracycline and HIV drug dolutegravir and block its absorption. hence such drugs should not be taken along with milk and antacids.

Note*: Pharmacodynamic interactions occur due to the pharmacological effects of drugs. 


Distribution interactions :

One or more drugs can compete with each other for plasma protein binding sites resulting in displacement of one drug thereby increasing its blood levels and toxicity.

Eg: fenofibric acid (cholesterol lowering agent) and warfarin (blood thinner) when administered together, compete for the protein binding sites leading to displacement and increased blood levels of warfarin thus resulting in bleeding.

Metabolism interactions

Enzymes in the liver such as cytochromes are responsible for metabolising drugs and eliminating them from the body. Some drugs may alter the enzyme levels or its activity resulting in fast or slow metabolism of drugs.

Eg: Diltiazem (antihypertensive) inhibit the cytochrome enzyme responsible for metabolizing simvastatin (hypocholestremic) & elevates it’s blood levels resulting in serious liver & muscle side effects.  

Excretion interactions

Some non steroidal anti inflammatory drugs (NSAID,s) like indomethacin may lower the kidney function and reduce the excretion of lithium, a drug used for bipolar disorders. In such cases dose adjustment is required. 

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. 

General guidelines which help minimizing herb-drug or herb-food interactions.

Avoid taking mucilage containing herbs like isapgol, flax with other drugs, as mucilage can inhibit the absorption of many drugs. Even mucilage containing drugs can alter the blood sugar levels which have to be considered in case of diabetic patients. Spicy substances such as ginger, capsicum, etc can enhance the absorption rate of some drugs, hence they need to be taken one hour after drug administration.

Heart tonic herbs such as hawthorn/ digitalis/ cactus, should be avoided when taking heart medications.

Caffeine containing herbs like green tea, kola nut, coffee and herbal stimulants like ephedra should be avoided when taking heart medications or mood altering drugs or antidepressants.

Avoid herbs or formulations containing liquorice when using diuretics like furosemide because liquorice can cause potassium depletion from the body.

While taking antidepressants like mono amino oxidase (MAO) inhibitors, avoid African aphrodisiac herbs containing yohimbine. 

Green vegetables like broccoli, spinach, cabbage, etc which have high vitamin-K content are reported to interact with anticoagulant drugs as vit-K has coagulation promoting effects.

Grape fruit juice interacts with calcium channel blockers (antihypertensive), lipid lowering drugs, psychiatric medications, oral contraceptives and antiallergic medications. Grape juice modifies the metabolism pattern of these drugs in the liver.