PersADE: About ADEs

What is an Adverse Drug Event?

An adverse drug event (ADE) is defined as an injury during medication administration related to medicine, which predicts hazard from future administration and warrants prevention or specific treatment, or alteration of the dosage regimen, or withdrawal of the product.

Key Characteristics of ADEs

May occur during treatment or as a result of medication errors
Can range from mild discomfort to life-threatening conditions
May be predictable (based on drug's pharmacological properties) or idiosyncratic
Often requires intervention, from monitoring to discontinuation of therapy
A significant factor in healthcare costs and patient outcomes

Key Concepts in Adverse Effect Classification

Adverse Effect

Encompasses all unwanted effects, it makes no assumptions about mechanism, evokes no ambiguity, and avoids the risk of misclassification.

Viewed from the perspective of the drug

Toxic Effect

One that occurs as an exaggeration of the desired therapeutic effect, and which is not common at normal doses.

Often related to overdose or accumulation

Side Effect

Related to the pharmacological properties of the drug but not part of the therapeutic effect.

May be harmless or potentially harmful

Distinguishing Important Terms

Adverse Effect vs. Adverse Reaction

"Adverse reaction" and "adverse effect" are interchangeable, except that an adverse effect is seen from the point of view of the drug, whereas an adverse reaction is seen from the point of view of the patient.

Adverse Effect vs. Adverse Event

"Adverse effect" and "adverse reaction" must be distinguished from "adverse event". An adverse effect is an adverse outcome that can be attributed to some action of a drug. An adverse event is an adverse outcome that occurs while a patient is taking a drug, but is not or not necessarily attributable to it.

The Impact of Adverse Drug Events

ADEs lead to an enormous amount of morbidity and mortality. Previous studies showed that about 6% of patients were hospitalized due to ADE in the U.S., and ADEs caused 197,000 deaths in Europe per year. The more people usually take medicines as they age, the more the risk of adverse events may take place. The good news is the most of ADEs are preventable.

6%

of hospital admissions in the U.S. are due to ADEs

197,000

deaths per year in Europe attributed to ADEs

$3.5B

estimated annual cost to the U.S. healthcare system

70%

of ADEs are potentially preventable

Classification of Adverse Drug Events

Classification by Type

Type A (Augmented)

Dose-dependent and predictable reactions related to the pharmacological action of the drug. They are usually mild but common.

Example: Drowsiness from antihistamines

Type B (Bizarre)

Rare and unpredictable reactions, often immune-mediated, not related to dose and unrelated to pharmacological action.

Example: Anaphylaxis from penicillin

Type C (Chronic)

Reactions associated with long-term drug use that may persist for a long time.

Example: Osteoporosis with long-term corticosteroid use

Type D (Delayed)

Reactions that occur or become apparent some time after use of the drug.

Example: Teratogenic effects

Type E (End of use)

Reactions that occur after the cessation of drug use, often withdrawal effects.

Example: Withdrawal seizures after stopping benzodiazepines

Type F (Failure)

Unexpected failure of therapy, often due to drug interactions or genetic factors.

Example: Oral contraceptive failure with concurrent antibiotics

Classification by Severity

Mild

No need for antidote, therapy, or prolonged hospitalization.

Example: Mild nausea, mild skin rash

Moderate

Requires change in therapy, specific treatment, but not necessarily hospitalization.

Example: Severe diarrhea, pronounced hypotension

Severe

Potentially life-threatening, requires hospitalization or prolongation of existing hospitalization.

Example: Stevens-Johnson syndrome, severe hepatotoxicity

Lethal

Directly or indirectly contributes to patient death.

Example: Fatal anaphylaxis, fatal hemorrhage

Classification by Predictability

Predictable ADEs

Can be anticipated based on the drug's known pharmacological properties. They are often dose-dependent and occur more commonly.

Typically Type A reactions
Based on drug's pharmacodynamic or pharmacokinetic profile
Often described in product labeling and documentation
Example: Hypoglycemia from insulin

Unpredictable ADEs

Cannot be anticipated based on the drug's known properties. They are often immune-mediated or based on genetic factors.

Typically Type B reactions
Often idiosyncratic or hypersensitivity reactions
Difficult to detect in pre-clinical or clinical trials
Example: Agranulocytosis with clozapine

Classification by Frequency

Category	Frequency Range	Description
Very Common	≥ 1/10	Occurs in 10% or more of patients
Common	≥ 1/100 to < 1/10	Occurs in 1% to 10% of patients
Uncommon	≥ 1/1,000 to < 1/100	Occurs in 0.1% to 1% of patients
Rare	≥ 1/10,000 to < 1/1,000	Occurs in 0.01% to 0.1% of patients
Very Rare	< 1/10,000	Occurs in less than 0.01% of patients

Note: These frequency categories are commonly used in drug labeling and regulatory documentation.

Prevention and Reporting of ADEs

Prevention Strategies

Proper Prescribing

Thorough review of patient history, allergies, current medications, and appropriate dose selection.

Monitoring

Regular follow-up and appropriate laboratory monitoring for early detection of ADEs.

Patient Education

Informing patients about potential side effects and when to seek medical attention.

Use of Electronic Systems

Implementation of electronic prescribing systems with drug interaction alerts.

Major ADE Reporting Systems

FDA

FDA Adverse Event Reporting System (FAERS)

The U.S. Food and Drug Administration's database that contains information on adverse event and medication error reports.

Learn more about FAERS

EMA

EudraVigilance

The European Medicines Agency's system for managing and analyzing information on suspected adverse reactions to medicines authorized in the European Economic Area.

Learn more about EudraVigilance

WHO