Medication errors (ME) are important contributors to patient morbidity and mortality, and are associated with inadequate patient safety measures1. The severity of an ME can be graded according to its impact on the patient and/or its potential future risk to patients and the healthcare organization. This approach has the advantage that it can classify and analyse the severity of MEs that pass unnoticed because they have no effect on the patient. Moreover, this type of assessment is useful for prioritizing cases that require special monitoring, analysis, or urgent solutions2.

The National Patient Safety Agency (NPSA) designed a risk matrix for grading MEs according to their potential future risk to patients and the healthcare organization. This matrix has two categories: likelihood of recurrence; and most likely consequences. However, details were not provided on the criteria by which a specific type of ME is classified according to its likelihood of recurrence and consequences3. Thus, the lack of definition allows room for subjectivity and researchers will interpret the risk matrix according to their knowledge and expertise4.

Subjectivity can be reduced by standardizing the classification of the potential risk of an ME. In a previous article, we adapted the NPSA risk matrix to medication errors in medication administration records (ME-MAR). The definition of each grade of the likelihood of ME-MAR recurrence was based on the incidence of ME-MAR in our hospital, and that of the most likely consequences was based on the type of ME-MAR and the medication involved. We found that this adaptation was reliable. However, during this process, the degree of agreement differed according to the medication involved in the error. The highest degree of agreement was achieved on high-risk medications5.

All medications can cause adverse events if they are incorrectly used. Nonetheless, certain medications are more dangerous than others and can have very severe or even catastrophic effects on patient health6. The Institute of Safe Medication Practices (ISMP) has provided a list of high-risk medications in hospitals7,8. However, lists of low- and medium-risk medications are not available. The hospital pharmacotherapeutic guide (HPG) not only includes high-risk medications but also unclassified medications, which may range from low to high risk. Therefore, the aim of the present study was to stratify medications in the HPG according to their potential risk.

The study was conducted between October 2015 and March 2016 in a 947-bed teaching hospital. The RAND/UCLA Appropriateness Method (RAM)9,10 was used to stratify medications in the HPG according to their potential risk. The medications included in the HPG are classified according to the Anatomical Therapeutic Chemical (ATC) classification system11, and so the medications were evaluated per ATC subgroup.

The first step in the RAM was to identify scenarios, which were subsequently assessed by an expert panel in 2 consecutive rounds.

To the best of our knowledge, this is the first study to stratify medications used in hospital care according to their potential risk (low to high-risk). The RAM was used to classify the ATC subgroups included in the HPG into low, medium, and high potential risk. In the first evaluation round, 32 groups were classified as uncertain. Because the potential risk of a medication is driven by the clinical characteristics of the patient18, the majority of the disagreements between experts could have been due to their experience in attending and treating different types of patients. However, we believe that the final results were enriched by the different criteria applied by the experts.

Some subgroups classified as uncertain were subject to further discussion. These subgroups included some dermatological subgroups, some subgroups which belong to group C10 “Lipid-modifying agents”, and some anti-Parkinson drug subgroups. The dermatological subgroups were finally reclassified as low-risk. This classification is consistent with those reported by other studies that consider this group to have no association with patient harm19,20. The subgroups that belong to group C10 “Lipid-modifying agents” were also reclassified as low-risk. The expert panel considered that the potential risk for inpatients was low. Authors such as Saeder et al.21 have also classified fibrates as low risk. The anti-Parkinson drug subgroups were reclassified as medium-risk, although the nervous system group is associated with severe adverse events22. According to the clinical experience of the experts, severe adverse events are uncommon with anti-Parkinson drugs. This reclassification is consistent with the high-alert medication list for patients with chronic disease, which excluded anti-Parkinson drugs (see Otero et al.23).

The methodology used in this study has some limitations. Firstly, although the RAM has objective characteristics, it also has subjective ones because it measures opinions24. However, this method has advantages over other methods used to reach consensus, because it uses confidential ratings and group discussion. It has good reproducibility and is considered to be a rigorous method that can be used whenever a combination of scientific evidence and expert opinion is required9,23,25. Secondly, the results of the RAM always depend on the composition of the expert panel9. The RAM panel included physicians and nurses from different medical specialities, and pharmacists with different types of clinical expertise. Thus, several fields were covered by experts with deep knowledge of all medications assessed in this study.

The lists that were created provide an objective measure that could be used during routine data collection of MEs in order to reduce subjectivity and provide a standard by which the severity of an ME can be assessed and measured. These medication lists could be a useful tool for future pa- tient/medication safety studies, leading to better prevention measures and the improved management of follow-up activities after the detection of an ME.

Ideally, these lists could be integrated into an electronic tool to facilitate resource allocation for patients at high risk of severe MEs. It is relevant to individualize the risk assessment for each patient undergoing drug thera- py21,26. Given that resources are limited, the same intervention is currently provided to all patients in our hospital, even though they may receive medications with a higher risk of adverse events. The integration of these lists into an electronic tool would assist in patient stratification.

A RAM was used to classify ATC subgroups by their potential risk (low, medium, or high). The main contribution of this study is to make these reference lists available. These lists can be integrated into a risk-scoring tool for future patient/medication safety studies.

No funding.

No conflict of interests.

All medications can cause adverse events if they are incorrectly used. Nonetheless, certain medications are more dangerous than others. A list of high-risk medications has been published, but lists of low- and medium-risk medications are not available. This study is the first to classify medications used in hospital settings according to their potential risk. This classification is of relevance to future patient/medication safety studies and for patient resource allocation according to treatment.