Pharmacoeconomics and Safe Medication Use

Pharmacist review and validation

Pharmacists are highly trained in pharmacology and drug interactions and are expected to apply

advanced analysis and clinical qualification/management of drug interactions.

Limitations include that not all medications a patient uses are filled by one pharmacy as well as

the lack of potential data that can be pulled from a patient’s EHR that can inform the existence and

clinical relevance of drug-drug interactions.

Examples include passive pop-up warnings (e.g., alerts), active alerts with soft stops (e.g., documented

allergy of nausea), and active alerts with hard stops (e.g., documented allergy of anaphylaxis).

May prompt prescriber or pharmacist during order verification with a high frequency of alerts,

leading to desensitization (i.e., alert fatigue)

Despite the potential benefits of CDS, within the ICU patient population overrides are common,

with a rate of around 80%, depending on the alert type. Inappropriate overrides of CDS alerts within

the ICU are associated with an increased risk of patient harm.

tiering of the interaction as a criterion for alert selection.

Education as a method to prevent drug interactions (e.g., lectures, patient care rounds)

How to Evaluate Drug Interaction Cases

Assessing causation of a drug interaction includes a temporal relationship, consideration of the

pharmacologic properties of the object and precipitant drug, patient factors and disease states, the

possible contribution of other drugs, and, when possible, a positive dechallenge. The temporal sequence

is the key element in these considerations to help determine the cause.

interactions; therefore, they should not be used to evaluate drug-drug interaction cases.

The drug interaction probability scale may be used to determine drug-drug interaction causation,

including the adverse outcomes in a specific patient (Appendix 2).

The drug interaction probability scale is patterned after the Naranjo ADR probability scale. A series

of 10 questions related to the drug interaction are assessed with “yes,” “no,” “unknown,” or “not

available” answers and then scored and tabulated. The total score determines the probability of the

drug-drug interaction occurring in the patient as follows:

Highly probable: More than 8

ii.

Probable: 5–8

iii.

Possible: 2–4

iv.

Doubtful: 2 or less

When using the drug interaction probability scale, the evaluator must have comprehensive

knowledge of the pharmacologic properties of both the object and the precipitator drug, especially

their pharmacokinetic and pharmacodynamic properties and their mechanisms of drug action and

mechanisms of drug interactions, which can be a limitation to its use.