The antibiotic commonly known as "z-pack" is being linked to increased heart problems in patients.

Vanderbilt University researchers found that the drug Zithromax can cause a disturbance in heart rhythms, which can lead to sudden death.

The drug is more expensive than other antibiotics, but popular for treating bronchitis, sinus infections, and other common illnesses because it's only a five-day medication.

"If you are a patient who already has a high risk of heart problems, you have a relatively minor infection for which another antibiotic would work perfectly well, then you should consider that alternative," said Wayne Ray, professor of preventative medicine at Vanderbilt University.

The risk of heart problems is still relatively low but researchers concluded a noticeable difference.

The results suggest there would be 47 extra heart-related deaths per 1 million courses of treatment with Zithromax, compared with amoxicillin, another antibiotic.

More than 55 million Americans have been prescribed the z-pack antibiotic.