Difference Between ADR and ADE (With Table)

In the field of medical science, several drugs are formulated every day. Mankind has now advanced very much in the field of medicine and is now able to prevent and fight diseases that once were so fatal that death was unavoidable. Yet the formulation of these drugs brought about new threats that arise from their side effects, negligence in their consumption, and accidents in prescribing them.


Most of the time these mishaps are avoidable and can be prevented by taking precautionary measures, but not all of them are very serious or life-threatening. These can be divided into broadly two types, Adverse Drug Reaction (ADR) and Adverse Drug Event (ADE).


The main difference between Adverse Drug Reaction and Adverse Drug Event is that Adverse Drug Reaction refers to the side effects or allergic reaction that occurs from the consumption and a drug or medicine, while Adverse Drug Event refers to the effects that occur from the inappropriate use of the drug.

Difference Between ADR and ADE

Adverse Drug Reactions are common, known effects that happen from the consumption of the drugs and are oftentimes informed by the medical practitioners themselves, whereas Adverse Drug Effect are the effects that take place by wrong medication that is either excessive or inadequate dosage of the drug.

Comparison Table Between ADR and ADE

Parameters of ComparisonADR ADE
DefinitionThese are effects of drugs that are noxious but occur normally in the usage of the drug and are in most cases known.These are the effects that take place from error in prescription, insufficient or overdose or altogether discontinuation of the drug. 
TriggersThis occurs as a side effect of the drugs.This occurs in error in the consumption of the drug.
PreventionIt cannot be prevented.It can be prevented.
Errors in medicationThis does not happen in error in medication.This happens in the error in the medication and the dosage consumed.
Allergic reactions and Side EffectsThese are generally the allergic reactions or side effects of the drug that are not normally fatal and can resolve by themselves.These are not allergic reactions rather is a form of mishap and a medical practitioner should be consulted.
ExamplesCan normally involve skin allergy to laxative effects.Overdose of sleeping pills can result in heart stroke and other risks.

What is ADR?

An Adverse Drug Reaction is a reaction that happens in response to the normal dosage of a drug consumed for diagnosis or therapy. They may occur following a single dosage of the drug, a prolonged dosage, or as a result of two or more drugs being consumed together. 

They generally refer to the injury that occurs during the period of the drug being consumed. Different to ADE they are the only harm that occurs in the correct dosage of the drug, unlike ADE can occur due to omitting the dosage of drugs.

The most common ADRs are skin allergy, drowsiness, nausea, diarrhoea, fatigue, vomiting or even have laxative effects in certain medications. Adverse Drug Reactions are not that threatening and are often informed by the practitioner while prescribing, as often in case of antidepressants that arouse drowsiness.

What is ADE?

An Adverse Drug event can be defined as the injury resulting from errors in the consumption of medicine ranging from the errors in the prescription of the drug, omitting it, overdose or reduction of the dose. While these may be common instances of ADE, certain cases of them arise in the improper or negligent production of drugs where the drugs are not produced correctly and too, approved without proper testing. Certain medicines like morphine, insulins, medicines related to cardiac issues, etc.

It is important to note that people of the elderly age group are more vulnerable to ADE in comparison to others, and further ADE is among the highest reported case of emergency reported around the world. and up to 50% of them are preventable as most of them are caused by either negligence or cases of self-medication. They can broadly be characterised into Potential ADE that is predicted to occur, or Ameliorable ADE that, if not preventable, could have been controlled to avoid severe casualties.

Therefore one of the best ways to avoid ADE is to keep a list of prescribed medications. In addition, the past condition of the patient should also be highlighted to the practitioners while they are prescribing medications.

Main Differences Between ADR and ADE

  • ADRs are known effects of drugs that happen in the normal dosage and are generally informed by the medical practitioner, whereas ADEs happens from the error in prescription, insufficient, overdose or altogether discontinuation of the drugs.
  • ADR occurs as a side effect of the drugs, while ADE occurs in error in the consumption of the drug.
  • ADRs are non-preventable, while ADEs are preventable in most cases.
  • ADRs do not happen due to errors in medication, while ADE results from errors or negligence in medication.
  • ADR are generally allergic reactions or side effects and normally are not  fatal, contrary to it these are rather forms of mishaps and requires immediate consultation of the medical practitioners in most cases.
  • ADRs can vary from having skin allergy to laxative effects, while instances of ADE includes having a heart stroke from sleeping pill overdose.


Often confused to be the same, ADRs are the effect of the drug that occur during the process of treatment and in most cases are explained in the prescription of the drug. While ADE occurs due to the errors in the consumption of the Drug. ADRs are predictable but non-preventable, but ADEs are caused due to the personal experience of the patients with the drugs thus can be prevented by ensuring to avoid errors in the consumption of drugs.

It is therefore important for the patients to inform the medical practitioner of their past condition, and also for the practitioner to inquire about the same. Both of these are important medical injuries caused by drugs, therefore, should be dealt with concern to avoid fatal consequences.