Washington, Jun 17 (IANS): The US is soon likely to see a shortage of antibiotics after Pfizer warned doctors that it expects to run out of its formulations for children and adults by the end of June, the media reported.

The US drug maker, in a letter sent to doctors this week, informed that its falling short of Bicillin -- a long-acting injectable form of the antibiotic penicillin.

It is one of the antibiotics used to treat common childhood infections, but the recommended treatment for the sexually transmitted infection syphilis -- a disease rising significantly in the US and other countries.

According to the US Centers for Disease Control and Prevention, the rates of syphilis have been steadily increasing, rising more than 30 per cent in 2021 in adults, putting additional pressure on limited supplies of the treatment.

"The supply interruption is the result of a complex combination of factors including significant increases in demand, due to an increase in syphilis infection rates as well as competitive shortages," Pfizer shared in the letter, posted by the US Food and Drug Administration (FDA).

"In order to meet this increased demand, Pfizer has prioritised manufacturing capacity of Bicillin," it added.

Further, Pfizer said that Bicillin is not widely used in paediatrics because of other options, such as amoxicillin, which is more preferred for kids, the report said.

But "the adult formulation of Bicillin L-A is the most important, as that is the only product available to treat pregnant patients with syphilis," Erin Fox, a pharmacist at the University of Utah who tracks drug shortages, was quoted as saying.

Syphilis can be passed from mother to baby in the womb. Up to half of babies infected this way die shortly before or after birth. Even if a baby survives, they may face lifelong consequences from their infections including blindness or deafness.

This comes after the country, earlier this year, began facing a shortage of chemotherapy drugs. To meet rising demands, the US FDA has allowed for a temporary import of the cancer drug made in China.

Pfizer said that supplies were strained over the fall and winter when the antibiotic amoxicillin went into shortage and doctors began using Bicillin as a recommended alternative.

The US FDA said in a statement that it "recognises the potential impact that lack of availability of certain products may have on health care providers and patients."

The agency said that it is working closely with numerous manufacturers and others in the supply chain to understand, mitigate and prevent or reduce the impact of intermittent or reduced availability of certain products.