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The "Top 10" Drug Errors and How to Prevent Them

Authors: Kathryn L. Hahn, PharmDFaculty and Disclosures



More than 7000 pharmacists gathered in Atlanta, Georgia, for the American Pharmacists Association (APhA) 2007 Annual Meeting to explore new challenges and the latest advances in pharmacy. Among the more than 80 programs presented were several sessions that dealt with reducing medication errors and adverse events, a topic that has received widespread media attention.

In addition, the author of a critically acclaimed book on drug errors was on-site to discuss his book and to autograph copies for attendees. Michael R. Cohen, RPh, MS, ScD, DPS, is President of the Institute for Safe Medication Practices (ISMP) and author of Medication Errors, which was published by the APhA.

Conference participants learned about common medication errors, steps to avoid or eliminate them, strategies to communicate effectively with prescribers, and ways to recognize and reduce stressful situations in the pharmacy workplace that may contribute to medication errors.

"Top 10" Medications Involved in Adverse Events

The Institute of Medicine (IOM) published findings in 1999 on the quality of healthcare in America. That report, "To Err Is Human: Building a Safer Health System," concluded that as many as 7000 Americans die from medication errors each year.[1] In July 2006, the IOM released a new report, "Preventing Medication Errors," stating that the frequency of medication errors and related injuries was still a serious concern.[2]

A common question that arises is: "What drugs are most often involved in medication errors?" Matthew Grissinger, RPh, FASCP, is a medication safety analyst with ISMP, the nation's oldest voluntary drug error reporting program, located in Huntingdon, Pennsylvania. His session on "The Top 10 Adverse Drug Reactions and Medication Errors" drew an audience that filled the meeting hall.[3]

Grissinger first referred to a study that identified the 10 drugs most commonly implicated in adverse events requiring treatment in a hospital emergency department (ED).[4] The study also documented the frequency with which each of the 10 drugs was involved:

  1. Insulin (8%);
  2. Anticoagulants (6.2%);
  3. Amoxicillin (s) (4.3%);
  4. Aspirin (2.5%);
  5. Trimethoprim-sulfamethoxazole (2.2%);
  6. Hydrocodone/acetaminophen (2.2%);
  7. Ibuprofen (2.1%);
  8. Acetaminophen (1.8%);
  9. Cephalexin (1.6%); and
  10. Penicillin (1.3%).

Unintentional overdoses made up 40% of these ED visits, representing the most prevalent mechanism of injury by far. Other mechanisms included side effects and allergic reactions. Some of the drugs on this list are especially common (eg, hydrocodone and amoxicillin), so the sheer volume of prescriptions written is a major factor.

The elderly also play a key role in this issue, as they account for 34% of all written prescriptions. The average number of prescriptions for an elderly person in the United States in 2000 was 28.5 per year. That number is estimated to reach 38.5 by the year 2010. Almost a quarter million seniors are hospitalized every year due to reactions between prescription and over-the-counter (OTC) medications.

Common misuses that lead to adverse drug events are taking incorrect doses, taking doses at the wrong times, forgetting to take doses, or stopping the medication too soon (all nonadherence issues). An example of commonly misused medications can be seen with arthritis therapies. Seventy million Americans suffer from arthritis and joint pain, which translates into 30 million people taking nonsteroidal anti-inflammatory drugs, either prescription or OTC. Misuse of these drugs leads to 103,000 hospitalizations and 16,000 deaths per year. Unnecessary use of nonsteroidal anti-inflammatory drugs also increases avoidable side effects, such as dyspepsia, peptic ulcer, and gastrointestinal bleeding.

Another high-volume prescription class is the antibiotics. This group represents significant inappropriate prescribing: Twenty-three million antibiotic prescriptions are written for colds, bronchitis, and upper respiratory infections each year, Grissinger said, despite the fact that antibiotics don't kill viruses.

Top 10 Medications Involved in Drug Errors

A somewhat different top 10 list identifies medications that are most commonly misused or mishandled in some way by healthcare professionals. This list is based on information from the United States Pharmacopoeia (USP), which maintains a database of medication errors that are reported anonymously. The figures represent drug errors associated with acute hospital care[5]:

  1. Insulin (4% of all medication errors in 2005);
  2. Morphine (2.3%);
  3. Potassium chloride (2.2%);
  4. Albuterol (1.8%);
  5. Heparin (1.7%);
  6. Vancomycin (1.6%);
  7. Cefazolin (1.6%);
  8. Acetaminophen (1.6%);
  9. Warfarin (1.4%); and
  10. Furosemide (1.4%).

Hospitals and healthcare systems use the USP database to track medication errors and identify trends. Drug errors are defined as unintentional acts committed by healthcare providers involving medications. Grissinger noted that comparable data are unavailable for outpatient care.

The number 1 error-prone medication is insulin. In fact, a 1998 ISMP study found that 11% of all serious medication errors involve insulin misadministration.[6] Errors include mixing up products with similar packaging (look-alike products); confusing generic listings on computer databases; similarity in names (eg, Humalog and Humulin); and most importantly, confusing the abbreviation "u" for units with the number 0. ISMP reports that these errors have been occurring for over 30 years.

The second drug on this list is morphine, which can be extrapolated to include all opioids, Grissinger said. Similar names for some of these drugs often cause confusion, such as:

  • Avinza and Evista;

  • Morphine and hydromorphone;

  • Oxycontin and MS Contin;

  • Hydrocodone and oxycodone; and

  • Oxycodone and codeine.

In the community pharmacy, these drugs often are stacked close together in a locked area, and many have similar packaging, making it easy to grab the wrong one when dispensing. Another common mistake is mixing up oxycodone with oxycodone ER (extended release), especially in handheld device order entry.

Morphine oral solutions cause many problems because of the multiple concentrations that are available, all stored close to each other. For example, it would be easy to confuse "mL" with "mg"; using 5 mL of morphine 20 mg/mL (100 mg) instead of the prescribed 5 mg (0.25 mL) would lead to overdosing the patient. Alternatively, an intended dose of 1 mL of morphine 20 mg/mL (20 mg) might be given as 1 mL of 10 mg/5 mL (2 mg), thus underdosing the patient. Grissinger also reported a case in which Avinza (morphine ER caps) 30 mg was misinterpreted and dispensed as "qid" (4 times daily) instead of "qd" (once daily), causing a near-fatal overdose.

Acetaminophen is another drug on the error list that causes many problems. It is available in many different strengths, and various measuring devices are available for dispensing it. In addition, it is found in many combination medications, both prescription and OTC. Prescription labels of combination products with acetaminophen can be very confusing for the patient. For example, hydrocodone 10/650 has 650 mg of acetaminophen, but many patients would not know how to interpret that.

Grissinger reminded the audience that acetaminophen can be toxic, even though it is sold OTC. A recent study showed that acetaminophen-induced liver toxicity accounts for more than 40% of US cases of acute liver failure.[7]

Antibiotics are the next big group of drugs associated with medication errors. As with opioids, the liquid dose concentrations increase the risk for mistakes. Confusion over measurements in "mL" vs "tsp" (teaspoons) can cause a 5-fold overdose or underdose if undetected. In one case, for example, azithromycin suspension was dispensed with directions to take 2.5 tsp daily (equivalent to 12.5 mL) instead of the intended 2.5 mL daily, Grissinger reported. The entire contents of the bottle were administered according to the labeled instructions, and the child developed diarrhea.

Reconstituting antibiotics can also be problematic. Pharmacists have mistakenly reconstituted antibiotic suspensions with alcohol instead of distilled water.

System Errors May Interfere With Individual Efforts

Most healthcare professionals have learned the "5 rights" of safe medication use: the right patient, the right drug, the right time, the right dose, and the right route of administration.

However, in his book Medication Errors, Michael Cohen wrote that these "rights" focus on individual performance and can overlook system errors. Examples of system errors are poor lighting, inadequate staffing, handwritten orders, doses with trailing zeros, and ambiguous drug labels. All of these can prevent healthcare professionals from verifying the 5 rights.[8]

Experts at ISMP have identified 10 key "system" elements that most influence medication use, reported Donna Horn, RPh, DPh, ISMP Director, Patient Safety - Community Pharmacy. Systems factors play a major role in increasing the likelihood that an individual will make an error. Deficiencies in any of these system elements can lead to medication errors[9]:

  1. Patient information (age, weight, allergies, diagnoses, and pregnancy status);

  2. Drug information (up-to-date information readily available);

  3. Communication (collaborative teamwork between all healthcare members and the patient);

  4. Drug labeling, packaging, and nomenclature (limit look-alike and sound-alike drug names, confusing packaging);

  5. Drug standardization, storage, and distribution (restricting access to high-alert drugs);

  6. Medication delivery device acquisition, use, and monitoring;

  7. Environmental factors (poor lighting, cluttered work spaces, noise, interruptions, nonstop activity, and deficient staffing);

  8. Staff competency and education;

  9. Patient education; and

  10. Quality processes and risk management (systems are needed for identifying, reporting, analyzing, and reducing the risk for medication errors with a nonpunitive culture of safety).

When an error occurs, it is tempting to blame individuals, Horn said. A "systems approach," however, looks at the whole system rather than individual errors. For instance, failures in the design or implementation of systems can lead to excessive reliance on memory, lack of standardization, inadequate access to information, and poor work schedules. Thus, with a systems approach, accountability is expanded to include anyone who had any influence over the error, setting the stage for broader solutions.

How Can We Prevent Medication Errors?

Nearly half of all adverse drug events have some form of "preventability," and many do not represent errors of commission but, rather, errors of omission. This implies a failure on the part of someone (pharmacist, physician, patient, or the interactions between these groups) to detect certain factors that most likely led to the adverse event. These factors include:

  1. Failure to detect a disease state contraindication to the drug therapy;

  2. Failure to detect a significant drug interaction;

  3. Failure to detect a significant drug allergy;

  4. Failure to prescribe the correct dose for a specific patient;

  5. Failure to monitor drugs with narrow therapeutic indexes; and

  6. Patient knowledge deficits.

Many of these can be avoided by spending a few minutes counseling the prescriber and/or the patient. Communication is key, Horn said. Barriers to effective communication include illegible handwriting, abbreviations, verbal orders, ambiguous orders, and fax or ePrescribing problems.

When communicating with prescribers, pharmacists should identify the issues clearly and concisely, said Marialice Bennett, RPh, FAPhA, Professor and Pharmacy Director of the University Health Connection at Ohio State University in Columbus, Ohio.[10] She offered these suggestions for such discussions:

  • Outline the specifics of the problem;

  • Keep focused on the patient;

  • Provide possible solutions;

  • Ask for prescriber feedback; and

  • Document the final decision.

Conflict can lead to poor communication, which can hinder the discovery of medication errors, she said. Conflicting opinions about patient care should be handled objectively and professionally. The ISMP recommends that healthcare organizations create a code of conduct that encourages behaviors supportive of team cohesion, staff morale, and sense of self-worth and safety.

Managing Stress in a Workplace Full of Risks

Pharmacy work can be highly stressful, and pharmacists who are under extreme stress are at risk for more errors, said Henry Cobb, PhD, MD, BS, CDM, Clinical Associate Professor, University of Georgia College of Pharmacy, Athens, Georgia.[11] Pharmacists need to identify their own personal stress triggers and anticipate their responses to stress. He presented 5 questions that could be used for such self-analysis:

  • How do you know whether stress is a problem for you?

  • What is causing most of your stress?

  • Is your supervisor aware of the problem?

  • How do you deal with stress?

  • What can you do to reduce the impact of stress?

Cobb described 3 ways that most workers deal with stress on the job. The active-cognitive person draws on past experience, taking one thing at a time. He or she considers several alternatives, looking for the positive side, and is able to step back and be objective. The active-behavioral person finds out more about the situation and takes positive action. He or she may talk with a friend or spouse, exercise more, or talk with a professional in order to find a solution. The person who practices avoidance keeps feelings to himself or herself, prepares for the worst, takes out frustrations on others, and eats or smokes more to reduce tension.

Identifying the phases of stress can be helpful. Phase 1, or the warning phase, includes vague anxiety, depression, and apathy. Phase 2, or mild stress, includes sleep disturbances, muscle aches, and irritability. Entrenched stress, or phase 3, includes alcohol abuse, depression, ulcers, withdrawal, and marital discord. Phase 4, or severe stress, includes asthma, heart problems, severe depression, violence (or suicide), paranoia, and uncontrolled anger. It is important to note that professional help is needed for phases 3 and 4.

To reduce stress on the job, Cobb presented this list of quick strategies:

  1. Discontinue caffeine;

  2. Engage in regular exercise (30 minutes 3 times weekly);

  3. Practice relaxation-breathing exercises (20 minutes 2 times weekly);

  4. Get adequate sleep (try going to bed 30 minutes earlier than usual);

  5. Nurture your leisure time, engage in hobbies;

  6. Set realistic expectations and avoid perfection;

  7. Reframe your outlook to be optimistic, not pessimistic;

  8. Eat right;

  9. Maintain a sense of humor;

  10. Talk and vent;

  11. Write down your thoughts;

  12. Avoid unhealthy habits (such as alcohol);

  13. Set limits (learn to say "no"); and

  14. Get help from a professional.

In some cases, however, a person who is in a job that does not match his or her personality and preferences may need to switch to another role or job, Cobb added. That may be a much better stress-reduction technique than any other.



  1. Kohn K, Corrigan JM, Donaldson MS. To Err Is Human: Building a Safer Health System. Washington, DC: National Academy of Sciences, National Academy Press; 2000.
  2. Committee on Identifying and Preventing Medication Errors. Board on Health Care Services. Institute of Medicine of the National Academies. In: Aspden P, Wolcott J, Bootman JL, Cronenwett LR, eds. Preventing Medication Errors: Quality Chasm Series. Washington, DC: The National Academies Press; 2006.
  3. Grissinger M. Top 10 adverse drug reactions and medication errors. Program and abstracts of the American Pharmacists Association 2007 Annual Meeting; March 16-19, 2007; Atlanta, Georgia.
  4. Budnitz DS, Pollock DA, Weidenbach KN, Mendelsohn AB, Schroeder TJ, Annest JL. National surveillance of emergency department visits for outpatient adverse drug events. JAMA. 2006;296:1858-1866.
  5. United States Pharmacopeia Web site. Available at: Accessed April 27, 2007.
  6. Institute for Safe Medication Practices (ISMP). ISMP action agenda: Oct-Dec 1998. ISMP Medication Safety Alert! Available at: Accessed April 1, 2007.
  7. Larson AM, Polson J, Fontana RJ, et al; Acute Liver Failure Study Group. Acetaminophen-induced acute liver failure: results of a United States multicenter, prospective study. Hepatology. 2005;42:1364-1372.
  8. Cohen M, ed. Medication Errors. 2nd ed. Washington, DC: American Pharmacists Association; 2007:5-36.
  9. Horn D. Top 10 adverse drug reactions and medication errors. Program and abstracts of the American Pharmacists Association 2007 Annual Meeting; March 16-19, 2007; Atlanta, Georgia.
  10. Bennett M. Communicating drug therapy recommendations to prescribers. Program and abstracts of the American Pharmacists Association 2007 Annual Meeting; March 16-19, 2007; Atlanta, Georgia.
  11. Cobb H. Dealing with stress: decompression strategies for pharmacists. Program and abstracts of the American Pharmacists Association 2007 Annual Meeting; March 16-19, 2007; Atlanta, Georgia.
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