The skinny on errors with obesity drug names

Error Alert

More than half of the U.S. population is overweight. But being obese is different from being overweight. The following medications are in some way related to or used in the treatment of obesity.


X does NOT mark the spot 


Potential confusion exists between the trade names Xeloda (capecitabine), an anticancer medication, and Xenical (orlistat), an antiobesity drug. Both drugs are manufactured by Roche, and their bottles bear the same lettering, coloring, and design. Since they both start with “Xe,” the chances of their appearing consecutively in alphabetical order on drug selection screens and pharmacy shelves are extremely high. 


A for effort 


The similar-sounding trade names of Aciphex (rabeprazole) and Adipex (phentermine) also create a potential for error. Although Adipex’s product name is actually Adipex-P, many physicians write “Adipex” only. As reported to ISMP, a handwritten prescription for Adipex-P was entered but filled as Aciphex 20 mg (the “P” on the script looked like it could have been a “20”). After internal analysis, the reporter stated that the error was due to poor handwriting as well as the staff’s unfamiliarity with Adipex-P. Because the hospital has a very strict formulary, technicians and even some pharmacists were unaware Adipex-P existed. 


The Is have it 


A 27-year-old male patient with morbid obesity was admitted for increasing dyspnea on exertion and complaining of headache despite treatment with acetaminophen and ibuprofen. The admitting physician meant to give a verbal order for Imitrex (sumatriptan) 50 mg twice a day but accidentally gave an order for Imuran (azathioprine) 50 mg twice a day. The verbal order was given on a Friday afternoon and not noticed until rounds on Monday. The patient received six doses of Imuran. Fortunately, no adverse events were noted. The physician admitted that his background was transplant and that he confused the drug names.


T for two 


ISMP received two reports of Toprol XL (metoprolol) instead of Topamax (topiramate) being mistakenly prescribed for weight loss at a tribally run health care clinic pharmacy. Because of the clinic’s formulary restrictions, some medications must be filled at an outside pharmacy, including the weight-loss drug phentermine. One of the clinic’s nurse practitioners wanted to write a prescription for Qsymia, a new drug for weight loss that combines immediate-release phentermine with topiramate in an extended-release formulation, to be filled at an outside pharmacy. The medication is too costly for many patients, however, and the patient could not afford the $300 per month price tag. 


To help the patient, the nurse practitioner decided to write a prescription for the drugs individually, even though this would result in loss of the extended-release properties of topiramate in the trade-name drug. In writing for the separate drug ingredients, the nurse practitioner wrote for Toprol XL instead of Topamax and sent both of these prescriptions to an outside pharmacy. 


The error was discovered when the patient called the tribally run health care clinic pharmacy and asked one of the pharmacists if the Toprol XL could be filled onsite so she could avoid a copay at the outside pharmacy. The pharmacist said yes and inquired about the indication. The patient mentioned it was for weight loss and that she was also prescribed phentermine. The pharmacist discussed the situation with another pharmacist, and they guessed that the nurse practitioner meant to prescribe Topamax and not Toprol XL. The pharmacist contacted the nurse practitioner, and sure enough, the Toprol XL was prescribed in error. The nurse practitioner corrected the prescription, and Topamax was filled. 


This was not ideal 


A hospital reported that it had built rules into its computer system to alert pharmacists about the need for dosing adjustments based on patients’ estimated creatinine clearance. The system uses the Cockroft−Gault equation to estimate clearance according to patients’ ideal body weight. During order entry for Integrilin, staff was flagged for a clearance of <50 mL/min, at which point the recommended dose is adjusted to one-half the standard. Unfortunately, this drug (and several others) uses actual body weight to estimate clearance. In this patient, because of his obesity, use of his actual body weight put his clearance >70 mL/min, and his dose should not have been adjusted. Staff confirmed the dosing using the slide rule supplied by the manufacturer as well. 


To prevent future errors, the hospital’s IT department has built a separate rule to calculate clearance using actual body weight, and staff are now reviewing drug information to determine which drugs the modified rule should be applied to. Manufacturers should clearly (and boldly) state which equation, and in this case which version of an equation, they have used in studies to estimate renal function so health providers can use the same equations. 


A standard process across all drug trials and research would be ideal. This error could have been very detrimental to the patient, who had just undergone percutaneous coronary intervention and would have been significantly underdosed if the cardiologist had not caught the error.