One drug pair name that often results in confusion


Our organization, the Institute for Safe Medication Practices (ISMP), often receives medication error reports that result from confusion with drug names that look or sound alike. One look-alike and sound-alike pair that often results in confusion is hydrALAZINE and hydrOXYzine.

HydrALAZINE, also known by the brand name Apresoline, is used to treat high blood pressure. HydrOXYzine, also known by the brand names Vistaril and Atarax, is an antihistamine used in the treatment of allergic reactions such as itching, rash, hives, sneezing and runny nose. HydrOXYzine is also used to treat anxiety, difficulty sleeping and nausea.

Most recently, a medication error was reported to us involving a 21-year-old man who was taken to the emergency department with headaches, numbness in his arms and legs, and difficulty breathing. The patient told the hospital staff the symptoms started after taking a new medication for anxiety/insomnia. The patient then showed them the bottle of medicine which was labeled hydrALAZINE 25 mg (take 1-3 tablets every 6 hours). The physician, who suspected an error likely occurred, called the pharmacy to question the prescription. The pharmacy confirmed the mix-up. The pharmacy had indeed received a printed prescription for hydrOXYzine but in error filled it with hydrALAZINE. The patient was treated and monitored for the medication error. When his symptoms resolved, he was eventually discharged from the emergency department with a new prescription hydrOXYzine.

In another case, a consumer reported a medication error with her dog. The veterinarian prescribed hydrOXYzine for the dog. The pet’s owner administered the medication for two days before noticing the drug information sheet stated the medicine was for blood pressure. The consumer called the pharmacist who confirmed a mix-up did occur. The dog was actually dispensed hydrALAZINE instead of the prescribed hydrOXYzine.

Over the last 10 years ISMP has written about dispensing errors between these two medications. However, despite warnings and multiple recommendations to healthcare practitioners, we continue to receive reports of mix-ups between these two drugs. Contributing factors leading to these frequent mix-ups are:

  • The first 4 letters of their names are identical
  • They are frequently stored next to one another on pharmacy shelves
  • They are listed alongside one another on computer screens
  • They have similar dosage strengths (10, 25, 50 and 100 mg)

If you receive a prescription for either hydrALAZINE or hydrOXYzine, it is important to be on the lookout for potential mix-ups between these two drugs. When picking up your prescription always be sure to confirm you have the correct medication before leaving the pharmacy. Additionally, ask your physician to include the reason for the medicine on your prescription. Knowing the medication's purpose can help the pharmacist verify the prescriptions purpose with the proper drug.

Created on April 27, 2016

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