Review on Adverse Drug Reaction

Abstract

ADVERSE drug reactions (ADRs) continue to pose a challenge in contemporary healthcare, especially due to the growing complexity of treatments, an older population, and an increase in multimorbidity. This article outlines several key details regarding ADRs and examines elements associated with their prevention, diagnosis, reporting, and management to assess the occurrence of fatal adverse drug reactions (FADRs) within a population. Adverse drug reactions (ADRs) pose a significant public health issue, serving as a leading cause of illness and death. Nonetheless, multiple countries lack recent studies. Since 2014, a forward-looking active pharmacovigilance initiative, designed to enhance ADRs monitoring in hospital units (FORWARD), has been conducted in Sicily. Adverse Drug Reactions (ADRs) pose a major issue in clinical practice, impacting patient safety and the results of treatment. This review examines different kinds of ADRs, highlighting the significance of a precise medication history in detecting possible reactions. We examine the materials and techniques employed for ADR detection and provide examples to demonstrate the clinical significance of these reactions. The document emphasizes the essential elements of ADR reporting, such as evaluating severity, preventability, and causation, offering an in-depth insight into how these aspects affect clinical management. Moreover, we investigate methods to improve medication safety, which includes enhancing ADR. This research, as part of the FORWARD project, aimed to outline ADRs that occurred during the hospitalization in Internal Medicine departments. ADRs connected to hospital admissions, their characteristics, and the possibility of prevention were also assessed. In this review, we cover the categories of ADRs, medication history, materials and methods, examples of ADRs, the reporting process for ADRs, their severity, preventability, and causation, as well as strategies to improve medication safety.

Introduction

Definition and Scope of ADRs

• ADRs are harmful and unintended responses to medications used in normal doses for prevention, diagnosis, or treatment.

• The WHO defines ADRs excluding therapeutic failures, overdoses, misuse, or non-compliance.

• Since 2012, the definition now also includes reactions from medication errors, misuse, off-label use, and counterfeit or unauthorized drugs.

• ADRs may require treatment changes, dose adjustments, or withdrawal of the drug.

Types of ADRs (Traditional Classification)

1. Type A (Augmented) – Dose-dependent and predictable based on pharmacological action.

2. Type B (Bizarre) – Idiosyncratic, unpredictable, and not dose-related; may involve immune or non-immune mechanisms.

3. Type C (Chronic) – Related to long-term use, e.g., corticosteroid-induced effects.

4. Type D (Delayed) – Occur after a delay, e.g., cancers after chemotherapy.

5. Type E (End-of-use) – Reactions after abrupt withdrawal, e.g., seizures post-anticonvulsant discontinuation.

DOTS Classification (Modern Approach)

• Dose-relatedness – Even immune responses can be dose-related.

• Time-relatedness – Reactions may depend on how quickly or how long a drug is taken.

• Susceptibility – Genetic factors, age, disease state, and drug interactions influence risk.

Clinical and Public Health Importance

• ADRs cause significant morbidity and mortality, leading to hospital admissions and longer stays.

• Frequency of hospital admissions due to ADRs ranges from 2.4% to 12%.

Studies and Methods

• Studies in Italy and Sweden used active pharmacovigilance and retrospective data linkage to evaluate ADRs.

• Standardization methods were applied to compare effects across age, gender, hospital stay, and medication number.

Medication History Importance

• A detailed medication history helps in:

  • Planning future treatment,

  • Identifying drug-induced symptoms,

  • Preventing medication errors and interactions.

ADR Management

• Managing ADRs often involves dose adjustment or discontinuation.

• Risk management plans (as required by EU regulations) are vital for newly approved drugs.

Case Examples

• Case 1: Red Neck Syndrome from vancomycin infusion.

• Case 2: Maculopapular rash after vancomycin or gentamicin use.

• Case 3: Hypertension linked to mexiletine use.

Reporting ADRs

• Report all suspected ADRs, especially:

  • With new drugs (within 5 years of approval),

  • Severe, unusual, or frequent reactions,

  • Reactions from drug interactions, errors, withdrawals, or lack of efficacy.

• ADRs should be reported using Case Report Forms (CRFs) provided by national regulatory authorities, which capture:

  • Patient info

  • Incident details

  • Suspected drug data

  • Reporter information

Conclusion

In this review, we explored the multifaceted aspects of Adverse Drug Reactions (ADRs), including their various types, examples, and the importance of a detailed medication history. We highlighted the methodologies used in identifying and assessing ADRs, along with established systems for reporting these reactions. Furthermore, we discussed critical parameters such as severity, preventability, and causation—key factors that influence clinical decisions and patient outcomes. Recognizing the growing need for safer pharmacological practices, we emphasized strategic approaches to enhance medication safety, including improved reporting systems, thorough clinical assessments, and education of healthcare professionals. A comprehensive understanding and proactive management of ADRs are essential steps toward minimizing drug-related harm and ensuring patient well-being. Herein we have discussed the identification, management and reporting of ADRs. We have described how modern technology is changing the way that ADRs are predicted, prevented, detected and managed, and how we continue to try to improve these processes with technological advances. Individualised therapy is becoming more of a possibility as not just pharmacogenetics but other phenotypic information can be combined to generate patient-specific advice to prescribers. Such regulatory science at national and international level can help achieve a positive benefit-to-harm ratio throughout the lifecycle of a medicinal product. For individual clinicians, achieving the best outcomes from therapies remains a key goal because avoiding or mitigating the risk of ADRs continues to challenge our everyday clinical practice Adverse drug reactions have been regarded to arise due to pharmacokinetic and pharmacodynamic variations of drug products. ADRs have been reported to exist in various types and mechanisms, depending on the health status and environmental factors of the individual. However, extensive research in the area of factors affecting the incidence and tendency of ADR’s have been performed but effective integration of theory and practice is needed to safeguard the patients requiring drug therapy.

References

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Copyright

Copyright © 2025 Mr. Vijay Dabade, Ms. Pooja Gaikwad, Mr. Prathamesh Gaikwad, Ms. Shweta Navale, Mr. Akash Badhe, Mr. Nitin Gawai. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.