---
title: Adverse Drug Reaction Reporting
description: A clinical reference on the identification, reporting, and management of adverse drug reactions.
keywords: [adverse drug reaction, pharmacovigilance, FAERS, CIOMS, causality assessment]
category: clinical
---

## Introduction to Adverse Drug Reactions

Adverse drug reactions (ADRs) are unintended and harmful responses to a medication at normal doses. ADRs can range from mild (e.g. rash, nausea) to severe (e.g. anaphylaxis, agranulocytosis) and can lead to patient harm, hospitalization, or even death. Identifying and reporting ADRs is crucial for pharmacovigilance - the detection, assessment, understanding, and prevention of adverse effects of medications.

## Recognizing Adverse Drug Reactions

ADRs can present with a wide variety of clinical manifestations. Common signs and symptoms include:
- Gastrointestinal: nausea, vomiting, diarrhea, abdominal pain
- Dermatologic: rash, pruritus, Stevens-Johnson syndrome, toxic epidermal necrolysis
- Neurologic: headache, dizziness, drowsiness, confusion, seizures
- Cardiovascular: QT prolongation, arrhythmias, hypotension
- Hematologic: anemia, thrombocytopenia, agranulocytosis
- Hepatic: elevated transaminases, cholestasis, fulminant liver failure

The Naranjo Adverse Drug Reaction Probability Scale is a validated tool to assess the likelihood that a clinical event is caused by a specific drug. Scores range from -4 (definitely not) to +13 (definitely).

## Reporting Adverse Drug Reactions

Spontaneous reporting systems are the cornerstone of pharmacovigilance. In the United States, the FDA Adverse Event Reporting System (FAERS) collects ADR reports from healthcare providers, patients, and manufacturers. Internationally, the WHO Programme for International Drug Monitoring uses the VigiBase database.

The CIOMS (Council for International Organizations of Medical Sciences) VI Working Group has developed international standards for ADR reporting. Key elements include:
- Patient demographics (age, sex, weight)
- Suspected drug(s), dose, route, start/stop dates
- Description of the adverse event
- Relevant medical history and concomitant medications
- Outcome of the reaction (e.g. resolved, ongoing, fatal)
- Causality assessment using validated algorithms

Timely and complete reporting of ADRs is essential to identify emerging safety signals and enact appropriate regulatory actions.

## Causality Assessment

Determining the causal relationship between a drug and an adverse event is critical. The Naranjo algorithm, WHO-UMC criteria, and CIOMS criteria are commonly used causality assessment tools:

- Naranjo Adverse Drug Reaction Probability Scale
  - Scores range from -4 (doubtful) to +13 (definite)
  - Assesses temporal relationship, alternative causes, drug levels, rechallenge, previous patient experience, etc.
- WHO-UMC Causality Categories
  - Certain, probable/likely, possible, unlikely, conditional/unclassified, unassessable/unclassifiable
  - Considers timing, likelihood, alternative explanations, prior knowledge
- CIOMS (Council for International Organizations of Medical Sciences) Causality Assessment
  - Highly probable, probable, possible, unlikely, conditional, unclassifiable
  - Evaluates temporal relationship, dechallenge/rechallenge, alternative causes, pharmacology, previous knowledge

These standardized algorithms provide a framework to systematically evaluate the causal relationship between a drug and an adverse event.

## Monitoring and Management of Adverse Drug Reactions

Patients experiencing a suspected ADR should be closely monitored, with relevant laboratory tests, vital signs, and clinical assessments performed. Discontinuation of the offending medication is often required, along with supportive care measures.

In severe cases, specific antidotes or reversal agents may be indicated:
- Anaphylaxis: epinephrine, antihistamines, corticosteroids
- Opioid overdose: naloxone
- Warfarin-related bleeding: vitamin K, prothrombin complex concentrate

Rechallenge with the suspected drug may be considered in some cases to confirm the ADR, but should only be done with caution and close monitoring.

Healthcare providers should also educate patients on the potential risks of their medications and encourage them to report any adverse effects. Patients with a history of ADRs should avoid the implicated drug(s) in the future.

## Regulatory Oversight and Safety Monitoring

Regulatory bodies, such as the FDA in the United States and the EMA in Europe, are responsible for postmarketing surveillance and safety monitoring of approved drugs. They rely on spontaneous reporting systems, like FAERS, to identify emerging safety signals and take appropriate regulatory actions, such as:
- Issuing drug safety communications and black box warnings
- Requiring Risk Evaluation and Mitigation Strategies (REMS)
- Mandating additional clinical studies or post-approval safety trials
- Withdrawing or restricting the use of a medication

Healthcare providers play a crucial role in this process by reporting ADRs in a timely and comprehensive manner. Increased reporting leads to better detection of safety issues and improved patient outcomes.

## Conclusion

Adverse drug reactions can have significant clinical consequences and must be promptly identified, reported, and managed. Healthcare providers should be vigilant in recognizing ADRs, utilize standardized causality assessment tools, and submit detailed reports to regulatory authorities. Effective pharmacovigilance relies on the collaborative efforts of clinicians, patients, and regulatory agencies to enhance the safe use of medications.