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In June 1995, a middle-aged man named Ramon Vasquez went to see his physician in Odessa, Texas, for chest pain. His physician, suspecting angina, prescribed a medication in addition to ordering further testing. The actual handwritten prescription is reproduced in Figure 4-1.

Despite the advent of electronic prescribing, millions of prescriptions each year, particularly in ambulatory settings, are still handwritten. In 1995, of course, handwritten prescriptions were the norm—and a major source of medical error. From the figure, can you determine whether the prescription is for Plendil (a calcium channel blocker that can be used to treat angina), Isordil (another anti-anginal that works through a different mechanism), or Zestril (an ACE inhibitor used to treat high blood pressure and heart failure)?

The physician actually intended to prescribe 120 tablets of Isordil at its typical dose of 20 mg by mouth (po) every (Q) 6 hours. Ramon Vasquez's pharmacist read the prescription as Plendil and instructed the patient to take a 20-mg pill every 6 hours. Unfortunately, the usual starting dose of Plendil is 10 mg/day, making this an eightfold overdose. A day later, Mr. Vasquez's blood pressure dropped to critically low levels, leading to heart failure. He died within the week.

The modern pharmaceutical armamentarium represents one of healthcare's great advances. There are now highly effective agents to treat or mitigate the effects of most common medical conditions: hypertension, hyperlipidemia, diabetes, heart disease, cancer, stroke, acquired immunodeficiency syndrome (AIDS), and more. Taken correctly, the benefits of these medications far outweigh their side effects, though the latter remains a concern even when medications are prescribed and taken correctly.

But the growth in medications (there are now more than 10,000 prescription drugs and biologicals—and 300,000 over-the-counter products—available in the United States1) and prescriptions (approximately 60% of American adults are taking some type of prescription medication2) has led to a huge increase in the complexity of the medication prescribing and administration process. It has been estimated that at least 5% of hospitalized patients experience an adverse drug event (ADE; harm experienced by a patient as a result of a medication, from either a side effect or the consequence of an error) at some point during their stay. Another 5% to 10% experience a potential ADE, meaning that they nearly took the wrong medicine or the wrong dose but didn’t, often thanks to a last minute catch or sheer luck.3 Elderly patients are particularly vulnerable; almost half of all nursing home residents are exposed to inappropriate medications.4 The cost of preventable medication errors in U.S. hospitals was estimated at $16.4 billion annually in 2010.5

Things are no safer outside the hospital. One surveillance study estimated that four emergency department visits for ADEs occurred per ...

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