PART 2

CLASSIFICATION:

WHO – with a time Uppsala Monitoring Centre Causality Categories scheme classifies the ADR into six category terms.

1. Certain

• Clinical event or laboratory test abnormality that occurs in a plausible time relation to drug administration.
• Cannot be explained by underlying concurrent disease or other drugs or chemicals
• Response to withdrawal of drug is clinically plausible
• The event is definitive pharmacologically phenomenologically (an objective, specific medical disorder or a recognized pharmacologic phenomenon)
• If necessary, a rechallenge is satisfactory.

2. Probable/Likely

• Clinical event or laboratory test abnormality that occurs in a reasonable time relation to drug administration unlikely to be attributed to underlying concurrent disease or other drugs or chemicals
• Response to withdrawal of the drug is clinically reasonable
• Rechallenge is not required.

3. Possible

• Clínical event or laboratory test abnormality that occurs with reasonable time in relation to drug administration
• Could also be explained by underlying concurrent disease or other drugs or chemicals
• Information on drug withdrawal may be lacking or unclear.

4.Unlikely

• Clinical event or laboratory test abnormality with a time to drug administration that makes. a relationship improbable, but not impossible
• Underlying concurrent disease or other drugs or chemicals provide plausible explanations.

5.Conditional/Unclassified

• Clinical event or laboratory test abnormality
• Reported as an adverse reaction
• More data needed for proper assessment or additional data being examined.

6.Unassessable/Unclassified

• Report suggesting an adverse reaction
• Cannot be judged because of insufficient or contradictory information
• Data cannot be supplemented or verified

Few ADRS are certain or unassessable / unclassifiable because most fall into one of the categories in between.

Determining the cause of a suspected ADR is a complex process. Because many patients take more than one drug, it can often be difficult to distinguish which agent caused the ADR. Furthermore, the suspected ADR may in fact be a manifestation of the patient’s underlying disease state.

An important step in identifying an ADR and determining causality is to obtain an accurate patient drug list. Not only is this an opportunity to screen for ADRs that could have led to the hospitalization, but maintaining an updated, accurate medication history for each patient can also help prevent future ADRs.