CHARLOTTESVILLE, VA (CVILLE RIGHT NOW) – For years, patients were advised to finish their full course of antibiotics to treat infections. But new studies indicate that guidance should be more nuanced.

UVA Health physician Dr. Amy Mathers, who specializes in infectious diseases, recalled that when she first started in medicine, more common infections, such as pneumonia and strep throat, were treated with long courses of antibiotics, some lasting up to fourteen days.  

However, recent controlled trials have found that pneumonia can be treated with five-day courses of antibiotics, urinary tract infections can be treated in 3-7 days depending on complexity, and even bloodstream infections can be treated with shorter courses of antibiotics. 

The danger in using longer courses of antibiotics without the need for them, Mathers said, is antibiotics can remove more than one type of bacteria, and not all of them are infected. 

“Other organisms take the places of the bacteria that was wiped out that are more likely to be resistant to antibiotics,” Mathers said. “Emerging science showing that says you’re more likely to harbor more resistant bacteria the longer you’re on the antibiotics.” 

Mathers mentions that despite this danger with certain infections, others do still require a longer course of antibiotics in most cases.  These include bladder infections, prostate infections, bone infections, and heart valve infections. 

The factor that usually determines the necessary prescription, Mathers said, is the type of bacteria and how fast it grows.  If the bacteria grow quickly, then a shorter course is called for, but for slowing growing bacteria, such as tuberculosis, a longer course will be employed. 

The burden of the patient is to not quit the antibiotic early. 

“The antibiotics go where the blood flow goes,” Mathers said. “You may kill off the ones on the outer edge, decrease the amount, and start feeling better, but if there’s any bacteria left, it may come back and cause another infection.” 

The key is to trust your physician, ask for full context and do what is required. 

“The best bet is to listen to your physician, take the full course of antibiotics, but it is good to ask your physician to ask why you need the longer course?” Mathers said.