View as “PDF version

Patient Safety Tip of the Week

November 2, 2021

Adverse Drug Events After Hospitalization



Adverse drug events (ADE’s) are both a major cause for emergency department visits and hospitalizations but also a significant result of hospital discharge. 19-23% of patients discharged from hospitals experienced an adverse event, the majority being adverse drug events (Forster 2003, Forster 2004). Another study by Forster et al. (Forster 2005) found that, of adverse events occurring in patients discharged home from the general medical service, 27% were preventable and 33% were ameliorable.


So, it’s no surprise that a focus on preventing adverse drug events after hospital discharge is in order. Several recent studies have highlighted the magnitude and seriousness of adverse drug events occurring after hospital discharge.


In the recent PPSA (Pennsylvania Patient Safety Authority) analysis of medication reconciliation failures that led to serious events (Harper 2021) 16.1% (15 of 93) instances involved discharge. Events related to discharge often went unrecognized until the patient returned to the emergency room (ER) or was readmitted. Orders often contributed to the events. Dosage errors, omitted orders, and instructions that were unclear or that differed from the discharge medication list contributed to these types of events. The resulting medication error types were most often dose omission and wrong dose. The report also suggests that medication errors at discharge are also likely to be underreported and have the potential to be life-threatening.


Gurwitz et al. (Gurwitz 2021) conducted a randomized clinical trial to determine whether a multifaceted clinical pharmacist intervention improves medication safety for patients who are discharged from the hospital and prescribed medications within 1 or more of three high-priority, high-risk drug classes (anticoagulants, diabetes agents, and opioids). Interventions included an in-home assessment by a clinical pharmacist, evidence-based educational resources, communication with the primary care team, and telephone follow-up. Participants in the control group were provided educational materials via mail.


Disappointingly, there was no difference in the rate of adverse drug-related incidents or clinically important medication errors during the posthospitalization period between the intervention and control groups. 180 patients were randomized to the intervention group and 181 to the control group. 27.7% of all participants experienced 1 or more adverse drug-related incidents, and 18% experienced 1 or more clinically important medication errors. There were 81 adverse drug-related incidents identified in the intervention group and 72 in the control group. There were 44 clinically important medication errors in the intervention group and 45 in the control group. The intervention did not significantly alter the per-patient rate of adverse drug-related incidents or clinically important medication errors.


Those results somewhat mirror the results of the MARQUIS trial (Schnipper 2018). This trial studied the impact of a multifaceted medication reconciliation intervention at six US hospitals using the MARQUIS medication reconciliation implementation toolkit. The intervention included hiring or reallocating new staff to obtain medication histories, performing both admission and discharge medication reconciliation, improving access to preadmission medication sources, introducing policy, training staff on obtaining medication histories and patient counselling, implementing a gold standard medication reconciliation process including targeting of high-risk patients, improving healthcare information technology and utilizing social marketing and community engagement. The intervention was associated with a reduction in total, but not potentially harmful, medication discrepancies. Results also varied by site.


The accompanying editorial (Etchells 2018) suggested that, rather than the intervention being ineffective, it may simply have been difficult to implement. It noted that there were some encouraging signals. Of the four sites that implemented interventions, three did observe reductions in potentially harmful discrepancies.


A second study, MARQUIS2, was subsequently undertaken, utilizing a refined toolkit and larger number of North American hospitals (Schnipper 2021). Both the number of system-level interventions adopted per site and the proportion of patients receiving patient-level interventions increased over time. During the intervention, patients experienced a steady decline in their medication discrepancy rate from 2.85 discrepancies per patient to 0.98 discrepancies per patient. An interrupted time series analysis showed the intervention was associated with a 5% relative decrease in discrepancies per month over baseline temporal trends. MARQUIS2 included both system-level and patient-level interventions. The system-level interventions alone were not associated with decreased discrepancy rates. “In contrast, patient-level interventions, such as receipt of a BPMH or admission or discharge medication reconciliation performed by trained personnel, had a large effect” that grew over time. That suggested to the authors there might be a synergistic effect of patient-level and system-level interventions.


The patient-level interventions included:


The editorial accompanying the MARQUIS2 study (Grimes 2021) notes the importance of patient engagement and patient activation. Grimes notes that the MARQUIS2 results suggest either that patient-level interventions may be more important than system-level interventions, or that system-level interventions are necessary but not sufficient alone. Exploring ways to promote patient involvement and activation in their own care should be a focus of future research.


MARQUIS2 took place prior to the COVID-19 pandemic. One of the few positive aspects of that pandemic has been the flourishing of telemedicine. In our April 14, 2020 Patient Safety Tip of the Week “Patient Safety Tidbits for the COVID-19 Pandemic” we mentioned an interesting report from ISMP Canada (ISMP Canada 2020) about medication reconciliation and discharge communication using telemedicine. It described the process of medication reconciliation, including not only digital identification of medications but also visual identification (via video or sending photographs of the pills or containers via email). It went on to describe how the same systems can be used to educate patients at or just after hospital discharge (including ways to involve the patient’s PCP and community pharmacy).


Medication regimen reviews (MRR’s) have increasingly been performed using telemedicine. A study on pharmacist‐conducted retrospective medication regimen reviews (MRR’s) using telemedicine in nursing homes showed very encouraging results (Kane‐Gill 2021). Upon admission, pharmacists conducted medication reconciliation and prospective MRR for residents and also used telemedicine for communication with cognitively‐intact residents. Post‐admission, pharmacists received clinical decision support alerts to conduct targeted concurrent MRR’s and telemedicine. The intervention group had a 92% lower incidence of alert‐specific ADE’s than usual care.


A recent Canadian study (McGillion 2021) assessed virtual care post-discharge after surgery, using remote automated monitoring (RAM) to remotely obtain data on patients’ biophysical variables. Virtual care and RAM did not significantly increase days alive at home within 31 days of discharge from hospital after surgery, the primary outcome variable. Interestingly, however, more participants in the virtual care group than standard care group had a drug error detected (29.7% vs. 5.5%) and a drug error corrected (22.6% vs. 1.3%). Drug omission (patients not taking a drug they were supposed to take) was the most common drug error detected (18.2% vs. 3.5%). Many such omissions were patient-related (eg. intentional omission, forgetfulness, mistake, or financial barriers). But doctors and nurses were responsible in 18.5% of cases, such as failure to communicate clear instructions on what drugs should and should not be taken at home, failure to write a prescription for a new drug, and failure to provide an instruction to discontinue a drug. Pharmacists were associated with 3.6% of the drug errors, always related to a failure to provide the drug as prescribed. Virtual care with RAM also resulted in substantial absolute reductions in pain at seven, 15 and 30 days.


We think that greater use of telemedicine for medication reconciliation and medication regimen review offers great opportunity to reduce adverse drug events following hospital discharge.


A key question is how to fund the resources necessary to do this well. Hospitals are reluctant to spend money on interventions that might reduce their admissions (excepting those that lead to readmission penalties or those that are part of a global budget). Insurers responsible for all medical costs would benefit from such a good system, as would entities like Accountable Care Organizations (ACO’s). Alignment of incentives will ultimately be the key to successful implementation of interventions to reduce adverse medication events after hospital discharge.




Some of our previous columns on medication reconciliation:


October 23, 2007 “Medication Reconciliation Tools

December 30, 2008 “Unintended Consequences: Is Medication Reconciliation Next?

May 13, 2008 “Medication Reconciliation: Topical and Compounded Medications

September 8, 2009 “Barriers to Medication Reconciliation

August 2011 “The Approach to Medication Reconciliation

January 2012 “AHRQ’s New Medication Reconciliation Tool Kit

September 2012 “Good News on Medication Reconciliation

October 1, 2019 “Electronic Medication Reconciliation: Glass Half Full or Half Empty?

July 2020 “Not Following Medication Changes after Hospitalization?






Forster AJ, Murff HJ, Peterson JF, Gandhi TK, Bates DW. The incidence and severity of adverse events affecting patients after discharge from the hospital. Ann Intern Med 2003; 138(3): 161-167


Forster AJ, Clark HD, Menard A, et al. Adverse events among medical patients after discharge from hospital. CMAJ 2004; 170(3): 345-349



Forster AJ, Murff HJ, Peterson JF, Gandhi TK, Bates DW. Adverse drug events occurring following hospital discharge. J Gen Intern Med 2005; 20(4): 317-323



Harper A, Kukielka E, Jones R. Medication Reconciliation Process Failures: A Study of Serious Events Reported by Pennsylvania Hospitals. Patient Safety Journal 2021; 3(1): 10-21



Gurwitz JH, Kapoor A, Garber L, et al. Effect of a Multifaceted Clinical Pharmacist Intervention on Medication Safety After Hospitalization in Persons Prescribed High-risk Medications: A Randomized Clinical Trial. JAMA Intern Med 2021; Published online March 01, 2021



Schnipper JL, Mixon A, Stein J, et al. Effects of a multifaceted medication reconciliation quality improvement intervention on patient safety: final results of the MARQUIS study

BMJ Quality & Safety 2018; 27: 954-964



Etchells E, Fernandes O. Medication reconciliation: ineffective or hard to implement? BMJ Quality & Safety 2018; 27: 947-949



Schnipper JL, Reyes Nieva H, Mallouk M, et al. Effects of a refined evidence-based toolkit and mentored implementation on medication reconciliation at 18 hospitals: results of the MARQUIS2 study. BMJ Qual Saf 2021; Epub ahead of print 29 April 2021



Grimes TC. Is it time for greater patient involvement to enhance transitional medication safety? BMJ Quality & Safety 2021; Published Online First: 20 August 2021



ISMP Canada. Virtual Medication History Interviews and Discharge Education. ISMP Canada Safety Bulletin 2020; 20(2): April 7, 2020



Kane‐Gill SL, Wong A, Culley CM, et al. Transforming the Medication Regimen Review Process Using Telemedicine to Prevent Adverse Events. J Am Geriatr Soc 2021; 69(2): 530-538 First Published 24 November 2020



McGillion MH, Parlow J, Borges FK, et al. Post-discharge after surgery Virtual Care with Remote Automated Monitoring-1 (PVC-RAM-1) technology versus standard care: randomised controlled trial BMJ 2021; 374 :n2209






Print “PDF version









Tip of the Week Archive


What’s New in the Patient Safety World Archive