(Bloomberg Business) — The Food and Drug Administration today warned that two drugs with similar names have been mixed up dozens of times by doctors and pharmacists.

The antidepressant Brintellix and the anti-clotting agent Brilinta have been confused at least 50 times. Though the agency has no records of cases in which patients took the wrong drug, it's concerned enough to alert the public.

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The agency has warned about name mix-ups before. A handful of errors involving drugs called Flomax (to aid urination for men with enlarged prostate) and Volmax (to improve breathing for people with lung disease) prompted a warning in 2000.

The antipsychotic Risperdal has been confused with Requip, used to treat symptoms of Parkinson's and restless leg syndrome.

Errors increased after generic versions, known as risperidone and ropinirole, became available. Even the packaging was similar, and the agency asked drugmakers to change it in 2011.

Brilinta, from AstraZeneca, was approved in 2011 to reduce the risk of repeat heart attacks. Brintellix, an anti-depressant from Takeda, was approved in 2013. The two drugs have tallied more than 1.5 million prescriptions.

The FDA has records of 12 cases in which the wrong drug was actually dispensed. In the software used to order prescriptions, both names come up as the doctor types the first three letters.

Sometimes the mix-ups started at the doctor's office, the agency says, while other times pharmacists had the right prescription but dispensed the wrong drug.

The FDA reviews proposed drug names to prevent confusion. This is a more exhaustive process than you might imagine. Regulators must consider "the spelling of the name, pronunciation of the name when spoken, and appearance of the name when scripted throughout the medication use system," according to the agency's explanation of its name review process.

It has to consider how a name will be filtered through myriad accents and rendered in physicians' notoriously inscrutable penmanship. "Handwritten communication of product names has a long-standing association with product name confusion, often leading to medication errors," the FDA says.

The FDA also warns against drug names that are "overly fanciful" and could mislead about their effectiveness or risk profile. No one will be getting CancerCurify or HerpesGone. The guidelines for drugmakers choosing names runs 22 pages. About one-third of proposed names are rejected. 

Brand names are only one moniker for medications. They also go by generic names, which are governed by a group called the U.S. Adopted Names Council. Generic names are intended to impose some linguistic order on the vast universe of medications, so similar medications are grouped together with the same word stem: Sildenafil and tadalafil are in the same family. They're better known as Viagra and Cialis.

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