Pharmacovigilance is the science relating to  the




and prevention of adverse drug reactions and adverse effects.


It is the practice of monitoring the effects of drugs after they are released for use for the identification of unreported adverse reactions.

Pharmacovigilance is also known as drug safety.  It mostly focuses on adverse drug reactions (ADRs) .

Adverse drug reactions (ADRs):

•unwanted,  uncomfortable or dangerous effect of a drug.

• how the body respond to a drug is adverse drug reaction.

According to WHO “ A response to a drug which is noxious and unintended occurs at doses normally used by man for the prophylaxis investigation,  diagnosis and treatment of disease or for modification of physiological functions”.

But according to WHO drug can cause ADRs but excipients can also cause harmful effects. And according to WHO normal doses can cause ADRs but test doses can also cause ARDs.

All ADRs are not harmful.* Pharmacovigilance 

Aronson And Edwards Et al definition of ADRs:

According to this definition “An appreciably harmful or unpleasant reaction which result from administration of a medicinal product which usually ( not always ) predicts hazards ( potential of something to cause harm) from future administration and warrants prevention,  specific treatment,  alterations of dosage regimens or withdrawal of the drug product.* Pharmacovigilance 

Adverse effects (AE):

Adverse effect is What the drug does to the body. All drugs don’t cause ADRs, doesn’t always show symptoms and don’t damage the organ.

For example:

How ACEIs cause cough?

When patient taking ACEI , it will block kininase II which is responsible for the breakdown of bradykinin,  substance P and amyloid-B-proteins in lungs . But when the kininase II is blocked there will be no breakdown of bradykinin so there will be the accumulation of bradykinin,  substance P and amyloid-B-proteins. So the accumulation of bradykinin is adverse effect (AE) . When bradykinin irritates airways cause bronchi constriction and trigger cough so this is Adverse drug reaction (ADR).

It is not necessary that all adverse effects leads to adverse drug reactions.* Pharmacovigilance 

For Example:

How aspirin cause haemorrhage?

Aspirin inhibit COX-1 ( present in platelets) when COX-1 inhibited it will inhibit the production of thromboxane A2 which is responsible for platelet aggregation,  so there will be decrease in platelet aggregation this is AE or hazard potential of something to cause harm. Decrease platelets aggregation may or may not cause haemorrhage but if cause haemorrhage this is ADR or Harm.* Pharmacovigilance 

ADRs cant be described at cellular or tissue level it describes in organ level.

Mechanistic classification of adverse drug effect ( ADE)


E =external moiety

I=internal moiety




When external moiety interacts with internal moiety both are distributed at the same tissues result as outcomes and some sequale may appear in few cases.


ACEI is external moiety and kininase is internal moiety both are distributed in lungs and outcome is increased bradykinin level which may produce sequelae that is cough .

Adverse effects have no signs and symptoms they are on cellular,  tissue or molecular level which is diagnosed by lab test.* Pharmacovigilance 

Adverse event:

The unwanted event which develops when the patient is taking/using the drug or medicinal product which may or may not be attributed to drug is known as adverse event.


•patient taking aspirin and died,  it is may or may not be died by aspirin. Adverse event is when we cant establish cause and effect.

When we can establish cause is called ADR. All ADR are adverse event but all adverse event are not ADR.

•patient taking antidiabetic and white hairs appear it may or may not be caused by antidiabetic. This is not establish but when established this will be ADR.* Pharmacovigilance 

Toxic effect:

Exaggerated pharmacological action by drug which is always occur at toxic doses more than recommended doses.

Toxic effect always causes by toxic doses but ADR cause by therapeutic or sub therapeutic doses.

In some patient effects cause at low doses but its called intolerance.


•Calcium channel blocker cause headache at toxic doses.

•antidiabetic cause hypoglycemia at toxic doses.

•antihypertensive cause hypotension at toxic doses.

Side effects:

Effects that are caused by secondary pharmacological actions which may be harmful or beneficial usually occur at normal doses.


How minoxidil cause hair growth / hypertricchosis ?

Minoxidil is antihypertensive vasodilator also increases blood flow and nutrients to hair cause hair growth called hypertricchosis. This is beneficial side effect.

•Antihistamines use for allergies but also called sedation this is beneficial side effect.

•BB marketed as antihypertensive but also used as antianginal.

Effects are due to secondary pharmacological action of normal doses or usually prescribed doses.

Serious ADR:

Result of any of one outcomes, death, life threatening reactions,  hospitalization,  prolonged existing hospitalization,  birth defects, significant disability which interrupt with normal daily functions of life.


Blindness,  deafness,  death, mild sino ventricular tachycardia,  mild hepatotoxicity , hypokalaemia .


Seriousness is the measurement of the extent to which a drug does can cause harm is known as seriousness.* Pharmacovigilance 


Severity is the measurement of the extent to which the reaction is called severity.


•Severe discoloration of urine cause by rifampine

•Severe taste change by captopril

It is not necessary that every serious ADR is severe.

 Learn more 

Searching tags

What is Pharmacovigilance?

What is adverse drug reactions?

Why adverse drug reactions cause?

How adverse drug reactions cause? 

What is adverse effects?

How ACEIs cause cough?

How aspirin cause hemorrhage?

Mechanistic classification of adverse drugs effects 

What is EIDOS?

What is adverse events?

How antidiabetic cause white hair?

What is toxic effects?

What is side effects? 

How minoxidil cause hair growth?

How antihistamines cause sedation?

What is serious ADRs?

What is seriousness?

What is severity?




Post a Comment