TUESDAY, June 13, 2017 (HealthDay News) -- States that let doctors prescribe drugs to treat chlamydia or gonorrhea in both partners when only one makes an office visit have lower rates of the sexually transmitted infections, according to a study published online May 17 in Sexually Transmitted Infections.

The approach, called expedited partner therapy (EPT), is allowed in 38 states. University of Michigan researchers analyzed reported chlamydia cases from 2000 to 2013. In states where EPT is barred, the average increase in chlamydia infections was 17.5 cases per 100,000 people per year. This compared with 14.1 cases per 100,000 in states where EPT is allowed, the researchers found.

"We know that to most effectively treat and prevent sexually transmitted diseases, we have to consider both the infected patient and his or her partners," lead author Okeoma Mmeje, M.D., an assistant professor of obstetrics and gynecology at the University of Michigan in Ann Arbor, said in a university news release. "Allowing doctors to treat both patients and their partners in this way has proven to be effective at preventing reinfection and the spread of infections such as chlamydia and gonorrhea. Long term, there are many societal benefits both in health and cost."

Several national agencies and organizations -- including the U.S. Centers for Disease Control and Prevention and the American Congress of Obstetricians and Gynecologists -- have endorsed expedited partner therapy. But, Mmeje said, it remains underused. Many insurers don't cover medication costs for sexual partners, and some doctors are reluctant to treat patients without an exam due to liability concerns, according to Mmeje.