Medication Safety

What Does ADR Stand For In Drug Safety?

An adverse drug reaction (ADR) is defined as any injury caused by taking medication. ADRs may occur following a single dose or prolonged administration of a drug or result from the combination of two or more drugs. It can be considered a form of toxicity; however, toxicity is most commonly applied to effects of over-ingestion (accidental or intentional) or to elevated blood levels or enhanced drug effects that occur during appropriate use (e.g., when drug metabolism is temporarily inhibited by a disorder or another drug).

ADRs are a significant public health issue, and they affect patients of all ages and backgrounds. Here are some statistics related to ADRs:

1.      According to the World Health Organization (WHO), ADRs are among the top 10 causes of death globally.

2.      In the United States, it is estimated that ADRs are responsible for over 100,000 hospital admissions each year.

3.      A study conducted in Europe estimated that between 5% and 7% of all hospital admissions were due to ADRs.

4.      The incidence of ADRs is higher in older patients, with studies suggesting that up to 30% of hospitalized older adults experience ADRs.

5.      The most commonly reported ADRs are gastrointestinal issues, such as nausea, vomiting, and diarrhea, as well as skin reactions, such as rash and hives.

6.      ADRs can occur with any medication, but some drug classes are associated with a higher risk of ADRs. For example, chemotherapy drugs, antibiotics, and nonsteroidal anti-inflammatory drugs (NSAIDs) are known to have a higher risk of causing ADRs.

7.      Adverse reactions to medications can be costly, both in terms of healthcare costs and lost productivity. One study estimated that the annual cost of ADRs in the United States is around $177 billion.

Overall, these statistics highlight the importance of monitoring and managing ADRs to promote patient safety and ensure that medications are used effectively and appropriately.

What are the types of adverse drug reactions?

There are 3 broad classes of adverse drug reactions namely:

Dose-related adverse drug reactions. This represents an exaggeration of the drug’s therapeutic effects. For example, a person taking a drug to reduce high blood pressure may feel dizzy or light-headed if the drug reduces blood pressure too much. A person with diabetes may develop weakness, sweating, nausea, and palpitations if insulin or another antidiabetic drug reduces the blood sugar level too much. This type of adverse drug reaction is usually predictable but sometimes unavoidable. It may occur if a drug dose is too high (overdose reaction), if the person is unusually sensitive to the drug, or if another drug slows the metabolism of the first drug and thus increases its level in the blood (see Drug Interactions). Dose-related reactions may or may not be serious, but they are relatively common.

Allergic drug reactions. This are not dose-related but require prior exposure to a drug. Allergic reactions develop when the body’s immune system develops an inappropriate reaction to a drug (sometimes referred to as sensitization). After a person is sensitized, later exposures to the drug produce one of several different types of allergic reaction. Sometimes doctors do skin tests to help predict allergic drug reactions.

Idiosyncratic adverse drug reactions. This result from mechanisms that are not currently understood. This type of adverse drug reaction is largely unpredictable. Examples of such adverse drug reactions include rashes, jaundice, anemia, a decrease in the white blood cell count, kidney damage, and nerve injury that may impair vision or hearing. These reactions tend to be more serious but typically occur in a very small number of people. Affected people may have genetic differences in the way their body metabolizes or responds to drugs.

Some adverse drug reactions are not related to the drug’s therapeutic effect but are usually predictable, because the mechanisms involved are largely understood. For example, stomach irritation and bleeding often occur in people who regularly use aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs). The reason is that these drugs reduce the production of prostaglandins, which help protect the digestive tract from stomach acid.

What are the symptoms of ADR?

Adverse drug reactions are usually classified as mild, moderate, severe, or lethal. Severe or lethal ADRs may be specifically mentioned in black box warnings in the physician prescribing information provided by the manufacturer.

Symptoms and signs may manifest soon after the first dose or only after chronic use. They may obviously result from drug use or be too subtle to identify as drug-related. In older adults, subtle ADRs can cause functional deterioration, changes in mental status, failure to thrive, loss of appetite, confusion, and depression.

Allergic ADRs typically occur soon after a drug is taken but generally do not occur after the first dose; typically, they occur when the drug is given after an initial exposure. Symptoms include itching, rash, fixed-drug eruption, upper or lower airway edema with difficulty breathing, and hypotension. Idiosyncratic ADRs can produce almost any symptom or sign and usually cannot be predicted.

In general, some symptoms that may occur as an adverse reaction following the administration of a drug or medication can include:

  • Skin rashes
  • Gastrointestinal bleeding.
  • Heartburn.
  • Fatigue/sleepiness.
  • Nausea and diarrhea.
  • Lightheadedness or dizziness.
  • Diarrhea or constipation.

Importance Of Adverse Drug Reactions Monitoring In Drug Safety

Adverse drug reactions (ADRs) monitoring is essential in drug safety for several reasons:

1.      Early detection of ADRs: Monitoring of ADRs can help identify safety signals early in the drug development process, before the drug is widely used. This allows for timely intervention to prevent harm to patients.

2.      Improving patient safety: By monitoring ADRs, healthcare professionals can identify and mitigate the risks associated with drug therapy, potentially improving patient safety and outcomes.

3.      Regulatory compliance: Drug regulatory agencies require that drug manufacturers monitor and report ADRs. Failure to do so can result in regulatory action, including withdrawal of the drug from the market.

4.      Post-marketing surveillance: Even after a drug is approved and marketed, ongoing ADR monitoring is necessary to identify any previously unrecognized safety issues that may arise.

5.      Pharmacovigilance: ADR monitoring is a key component of pharmacovigilance, which is the science and activities related to the detection, assessment, understanding, and prevention of adverse effects or any other drug-related problem.

Overall, ADR monitoring is critical for ensuring the safety and efficacy of drugs and for protecting public health. It helps to identify potential safety issues early, which can prevent harm to patients, and can provide valuable information for drug manufacturers and regulatory agencies to make informed decisions about drug safety.


Dr. Oche Otorkpa PG Cert, MPH, PhD

Dr. Oche is a seasoned Public Health specialist who holds a post graduate certificate in Pharmacology and Therapeutics, an MPH, and a PhD both from Texila American University. He is a member of the International Society of Substance Use Professionals and a Fellow of the Royal Society for Public Health in the UK. He authored two books: "The Unseen Terrorist," published by AuthorHouse UK, and "The Night Before I Killed Addiction."
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