(Tribune News Service) — A common type of penicillin used to treat syphilis is in short supply in the U.S. as cases of the sexually transmitted disease continue to rise.

Penicillin G benzathine, an antibiotic sold in the U.S. by Pfizer Inc., was added to the Food and Drug Administration's shortage list this week. Pfizer has limited supply of the drug because of increased demand, according to the agency, and the situation may persist into September.

This type of penicillin is also used to treat strep throat, which is spreading more than usual in the U.S., the CDC has said.

"The FDA believes the demand increase of this drug is related to increased cases of Strep throat and syphilis in the U.S.," the agency said in an emailed statement.

There are other drugs that are commonly used to treat strep throat, like amoxicillin, but penicillin G benzathine is the standard treatment for syphilis. The CDC said on April 14 that some STD programs weren't able to get enough of the medicine.

The rate of syphilis in the U.S. is the highest it's been since 1990, according to data from the Centers for Disease Control and Prevention released earlier this month. In 2021, there were 176,713 cases of syphilis, a 32% increase from the year before. Other STDs have also become more common.

Several common, essential medicines are in short supply, including other antibiotics, as well as cancer drugs and ADHD medicines. Last month, a congressional committee held a hearing about drug shortages, pointing to a broken market for medicines as well as a lack of transparency in the supply chain. Other types of penicillin are also in shortage in other countries.

Shortages of penicillin are frequent around the world, which makes it difficult to treat and prevent syphilis, according to the World Health Organization. This is especially dangerous for fetuses, who can contract syphilis in the womb. Penicillin can pass through the placenta and treat the disease, while other antibiotics cannot, according to WHO treatment recommendations.

In 2021, congenital syphilis caused at least 220 stillbirths and infant deaths in the U.S., 45% higher than the prior year, according to CDC data.

"If you're pregnant and you have syphilis, this is the treatment of choice," said Erin Fox, who runs the University of Utah's drug information service, which tracks shortages. "There's nothing else you can use."

Pfizer is the only company that sells the drug in the U.S., the FDA said, and Fox's center has been monitoring the supply constraints since January. There have been previous supply issues with the drug in the U.S. from 2005 to 2007, in 2010, and from 2016 to 2017, she said. The FDA said the most recent shortage in the U.S. was from 2016 to 2018.

Another Pfizer penicillin product, which is a combination of penicillin G benzathine and penicillin G procaine, is also in short supply because of increased demand, according to the University of Utah service. That medicine can be used to treat some bacterial infections, but is not used for syphilis.

The CDC and Pfizer did not immediately provide comment.

©2023 Bloomberg L.P.

Visit bloomberg.com.

Distributed by Tribune Content Agency, LLC.