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Home > Hospital Pharmacy > Medication Safety > Adverse Drug Reactions (ADR)

Written By: Abier Hamami.RPH.CPHQ

  1. Adverse Drug Reaction (ADR) Definitions
  2. Adverse Drug Reaction (ADR) Program.

ADR Definitions:

Organizations should have a definition for what constitute an adverse Drug Reaction, so detecting, assessing, and reporting of these reactions could be clear.

Examples of commonly used definitions are:

ASHP defines a significant ADR as "any unexpected, unintended, undesired, or excessive response to a drug that:

1. Requires discontinuing the drug (therapeutic or diagnostic),

2. Requires changing the drug therapy,

3. Requires modifying the dose (except for minor dosage adjustments),

4. Necessitates admission to a hospital,

5. Prolongs stay in a health care facility,

6. Necessitates supportive treatment,

7. Significantly complicates diagnosis,

8. Negatively affects prognosis, or

9. Results in temporary or permanent harm, disability, or death".

WHO: Any response to a drug which is noxious and unintended, and which occurs at doses normally used in man for prophylaxis, diagnosis, or therapy of disease, or for the modification of physiological function.

FDA: Defines serious adverse event relating to drugs or devices as one in which the patient outcome is death, life-threatening (real risk of dying), hospitalization (initial or prolonged), disability (significant, persistent, or permanent), congenital anomaly, or required intervention to prevent permanent impairment or damage.

Preventable Drug Reaction: "An appreciably harmful or unpleasant reaction, resulting from an intervention related to the use of a medicinal product, which predicts hazard from future administration and warrants prevention or specific treatment, or alteration of the dosage regimen, or withdrawal of the product."

Karch and Lasagna: Any response to a drug that is noxious and unintended, and that occurs at doses used in humans for prophylaxis, diagnosis, or therapy, excluding failure to accomplish the intended purpose.

Adverse Drug Reaction (ADR) Program.

Organizations should establish an ADR program that facilitates monitoring, evaluating, documenting, and reporting of ADRs as well as providing education to prescribers, other health care professionals, and patients. Additionally, ADR programs should focus on identifying preventable ADRs, determining factors associated with their occurrence, and developing strategies for preventing them from happening in the future.Findings and information of the ADR program should be incorporated in the organizational quality improvement, and risk management activities.

ADR program is typically over sighted and directed by the pharmacy and therapeutics committee, the executive committee of the medical staff, and the organizations administration. Usually the pharmacy department is controlling, and maintaining the program in respect to data collection, analysis, and reporting.

  • Detecting and Monitoring ADRS

Systematic and ongoing review of patients' signs and symptoms could help a lot in identifying ADRs, but on the same time health professionals should be knowledgeable enough to differentiate between the disease state or the occurrence of an ADR.

ADR monitoring could be retrospective, concurrent, and prospective.

The retrospective monitoring is after the reaction had occurred; it involves the review of medical records for adverse drug reactions and certain diagnosis codes. Such a system is inadequate because most of the times ADR documentation in the medical records is inadequate or incomplete.

The concurrent monitoring occurs during drug therapy in hopes to minimize the drug reaction and control associated costs. It involves tracing special signals as:

Laboratory data as high INR, PTT, PT or high blood concentration of certain drugs as aminoglycosides and digoxin.

Sudden discontinuation of a drug.

Stat orders of antidotes as Vit K, antihistamines, steroids, and dextrose.

Non routine order for laboratory tests as BUN, drug serum level, creatinine, PT, and PTT.

The prospective monitoring of ADRs is the preferred one because reactions could be potentially avoided or minimized. It usually includes monitoring of high risk drugs as aminoglycosides, chemotherapeutics, narcotics, thrombolytics, and high risk patients like pediatrics, geriatrics, hepatic or renal failure patients, and patients receiving multiple drugs.

  • Documenting ADRs

A description of each suspected ADR and the outcomes from the event should be documented in the patients medical record and communicated to all involved in the patients care including the patient.

  • Evaluating ADRs, and Assigning Probability

The cause(s) of each suspected ADR should be evaluated on the basis of the patients medical and medication history, the circumstances of the adverse event, alternative etiologies, and a literature review.

Since all ADR reports are, for the most part, based on temporal or possible associations therefore most organizations use special tools to assess the probability of these reported ADRs (likelihood of a drug causing an untoward event). The ideal tool would be one that is reliable, easy, and quick to use. Among the used tools are the Kramer Algorithm, the Jones Algorithm and the Naranjo Algorithm which is most commonly used.

It includes a simple ten-item questionnaire that uses specifically assigned numerical values to arrive at an overall total score for probability assignment. Probability is assigned via a score termed definite, probable, possible, or doubtful. Advantages of the Naranjo algorithm include its ease and widespread use. However, tests of its reliability as a tool for serious cases of adverse drug reactions have not been performed.

  • Reporting ADRs

All ADRs should be reported especially if are unexpected, serious, or reactions to recently marketed or approved drugs. Reports could include prescription, non-prescription, biological (including blood products), complementary medicines (including herbals) and radiopharmaceutical drug products.

Organizations could develop specific reporting forms as deemed applicable to their settings, or could adopt other international organizations reporting forms. In general reporting forms should be simple and user friendly, and contain the following elements:

1. Patient information( Medical record number, age, sex, weight, height)

2. Adverse Drug Reaction

  • Patient outcome.
  • Description of the reaction.
  • Relevant laboratory tests or diagnostics.
  • Medical history.

3. Drug/Product


Indication for use.

Lot number/expiration date.

4. Treatment given.

5. Reporter information.

Several international reporting programs have been established to allow health professionals and others to report serious adverse drug reactions. Reporting of these medication-related problems serves an important public health benefit, to alert other health professionals of problems so that injury can be prevented to other patients from a repeat of the same problem in the future.

The following is a list of common international reporting agencies or programs:

1. Vaccine adverse drug reactions (VAERS).

  1. U.S. Food and Drug Administration's FDA (MedWatch Reporting Program).
  2. Canadian Adverse Drug Reaction Monitoring Program (CADRMP).
  3. The U.K Medicines and Healthcare products Regulatory Agency MHRA (Yellow Card).
  4. The Australia's Voluntary Reporting System for Adverse Drug Reactions (Blue Card).


ASHP Guidelines on Adverse Drug Reaction Monitoring and Reporting, Best Practices for Hospital & Health-System Pharmacy. 2005-2006.

Adverse Drug Reaction Reporting. Competence Assessment Tools for Health-System Pharmacies. Lee B.Murdaugh. ASHP 1998.

Canadian adverse drug reaction monitoring program guidelines for the voluntary reporting of adverse drug reactions by health professionals

Adverse Drug Reactions http://www.blacktriangle.org/adr.html Accessed Jan 2006

Adverse Drug Reactions, Kristin C. Oberg, American Journal of Pharmaceutical Education Vol. 63, Summer 1999.

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