This study confirms the unambiguity of adverse DDIs in critical cardiac patients. This study captured 284 episodes of adverse DDIs in 91 patients. This translates into 17.5% in 521 patients who suffered one or more adverse DDIs. The occurrence rate is slightly higher compared to other studies. Previous studies have demonstrated that ADE potentiated by DDIs is responsible for up to 11% of all hospitalized patients (16–18). The present study found a total of 236 clinically relevant adverse DDIs which has two breakdowns. First, inappropriate override by the physicians have resulted 46.5% (132/284) of adverse DDIs. Second, adverse DDIs were observed before warranting the physicians (before 24 hours) and intervention was undertaken following accepting the PDDIs alert (104/284; 36.6%). Both scenarios are classified as preventable ADEs. The other kind of ‘override alerts’ when ADE occurred however recommendations were ignored because the risk of subsiding any one of the drugs would decrease the therapeutic effect compared to the consequences of the adverse DDIs (48/284; 16.9%). This type of scenario is classified as ‘appropriate overrides’ as an outcome of clinically irrelevant ADE. Physician acknowledging the alert’s recommendation before an ADE were mediocre, compared to action taken after an ADE occurred (43:104). It is encouraging to find that over half; 270/543 unique PDDIs shares the same drug to drug class interactions. This finding is in agreement with Nanji et al. findings which showed that alerting PDDIs by drug class was more meaningful than by generic PDDIs in the multidiscipline outpatient practice (19). It can, therefore, be assumed that alerting the physicians on the PDDIs by grouping the drug class would reduce the multiple alerts. A typical example in this study is post-myocardial infarction stenting procedure medications (clopidogrel, aspirin and fondaparinux) which produced three alerts, and each warned about bleeding risk. This seems to ‘annoy’ the physicians because they were required to respond to each alert individually. Hypothetically, physicians only need to be warned once on the potential risk for anti-platelet-anticoagulant combination.
Alarming only high severity interactions did not reduce the growing exposure of alerts in this study. It is possible to hypothesize that the issue of alert fatigue can be curbed by decreasing the growing exposure of alerts. Initially it was thought that the reduction in the number of interactions could be achieved by only firing high severity alerts (20). Although this was thought to be a simple and direct approach to reduce alert fatigue and sensitivity, this study showed otherwise. For an example, it seems to be ‘pain in the neck’ for antiplatelet-anticoagulant combination. The physicians were attentive that co-prescriptions of antiplatelet and anticoagulants would raise the risk of bleeding episodes hence the alert is not going to alter standardized drug treatment protocol. In fact, there are guidelines on how to manage such elevated risk of bleeding and suggests that antiplatelet therapy should be co-prescribed with proton pump inhibitors (79). This was a classic example where not all PDDIs with high-risk alerts are relevant. This opens a higher chance to ignore and develop a habit to suspend the alerts without even reading it. While alerts can be lifesaving, flagging too many PDDIs are redundant, reminding physicians things they already know. To our surprise, physicians responded poorly even with just high severity PDDIs alerts. This gives an insight whose severity category was ambiguous needs an alteration in CDDSS. Indeed, the number of alerts is not an appropriate metric for the success or failure of CDDSS. The same was hypothesized in a previous study by Duke et al (21).
Fundamentally, CDDSS only allows the detection of ‘potential’ interactions which means the PDDIs may not manifest into an ADE in all patients. This finding confirms the relationship between overridden alerts and ADE. First, a huge number of alerts were overridden, and ADE was not indicative (2957/3137; 94.3%). Second, the tendency of physicians to suspend the alerts and caused ADE (180/284; 63.4 %). It is known that the proportion of PDDIs resulted in clinically relevant ADE including in this study (22). This reflects that justified override cannot always prevent an ADE (23), which translates as inappropriate overrode. Contrariwise, appropriate alerts can be overridden and that overriding may not necessarily cause ADE. Still and all, some patients may benefit from interacting with drug combinations because the additive effects may be necessary to adequately treat a disease or symptom. One sample of case study retrieved during the study period is presented here as an illustration of inappropriate override that subsidized for an ADE.
Case Study: A 69-year-old, woman developed shortness of breath associated with chest discomfort and was brought into the emergency department. Her past medical history included hypertension, diabetes mellitus type 2, ESRD and asthma. The patient is a known case of Non-ST elevation myocardial infarction and acute pulmonary edema with left ventricular ejection fractions of 35%. On admission at CCU, she had a pulse of 99 bpm (irregular), a respiratory rate of 27/min and blood pressure of 177/120 mmHg and was alert and conscious at CCU. She was on azithromycin 500g bd x 3 days and ivabradine 7.5mg bd x daily. Ivabradine was prescribed for symptomatic angina and azithromycin for atypical pneumonia. An ECG showed sinus rhythm with a baseline QTc reading of 497 milliseconds. The serum potassium finding was on the higher side; 5.4 mEq/L while her other electrolytes range were normal. The physician discontinued potassium chloride. CDDSS: Alerted for potential QT interval prolongation with concomitant use of ivabradine – azithromycin. Clinical judgement: Day 1: The physician overrode the alert and responded to observe the adverse effects. Medications were continued. Day 2: She was hemodynamically unstable. An ECG showed QT interval prolonged with a QTc reading of 522 milliseconds. The physician discontinued azithromycin in view of prolonged QT interval. Sudden cardiac arrest during hemodialysis later of the day and successfully resuscitated. Physician discontinued ivabradine. Day 3: She was hemodynamically stable. An ECG showed sinus arrhythmia with improved QTc reading of 468 milliseconds. DIPS: Revealed highly probable DDIs.