As face masks, hand sanitizers and rubber gloves fly off store shelves, pharmacists are quietly fretting over a looming shortage of vital prescription medications.

On Thursday pharmaceutical manufacturer AmeriSource Bergen sent to its pharmacists a list of respiratory medications that it’s placing on back order because they are in short supply, The Post has learned.

The $168 billion publicly traded company flagged nebulizer solutions and two types of generic respiratory medications used for asthma and other breathing disorders, sources said.

In a statement, the Valley Forge, Pa.-based company said it “has not received any formal notification from supply chain partners regarding drug shortages or disruptions in respiratory medication in light of the coronavirus.”

“As an active participant in the pharmaceutical supply chain, we are engaged with health officials and are constantly monitoring for any potential impact to the supply chain. We will continue to be highly engaged as the situation evolves on a day-to-day basis,” the company said.

Drug supplier Anda Inc., meanwhile, warned its pharmacists about low levels of respiratory drugs and inhalers, as well as antibiotics, alcohol prep pads, face masks and hand sanitizers. Privately held Adna also did not return requests for comment.

Their outreach was intended to encourage pharmacy customers to place orders now for items that may not be available in the near future, Tom D’Angelo owner of Franklin Square Pharmacy told The Post.

“They don’t tell us why it’s going on back order,” D’Angelo said, but he suspects it has to do with supply-chain issues arising from the deadly coronavirus. “Most of the items on the lists are things that would help someone suffering from coronavirus,” he noted.

The worrisome development comes on the heels of a Feb. 22 government update about shortages of “critical medical products” in the US due to the coronavirus outbreak.

In its update, the US Food & Drug Administration explained that a manufacturer contacted the agency about a shortage of a “human drug.” The agency did not identify the medication nor did it disclose the manufacturer.

The FDA also said it has been in contact with 180 manufacturers about their supply levels, and it has identified about 20 drugs that source their ingredients from China, where the coronavirus outbreak has severely crimped production, including for pharmaceuticals.

Adding to the problem, India — a big supplier of generic drugs to the US — this week said it‘s restricting exports of 26 drugs and drug ingredients, including pain relievers and antibiotics.

India, which accounts for nearly a quarter of US medicines and about a third of medicine ingredients, pulled the plug because it wants to ensure it has enough medicine for its own citizens, according to reports.

Fears of the coronavirus, which has killed more than 3,350 people globally, have escalated in the US since Sunday when the first death here was reported in Washington state. In just five short days, the death toll has climbed to 12 with new cases popping up in Rhode Island and New York.

This has resulted in panicked buying of face masks, hand sanitizer, canned goods and bottled water — as well as medications commonly used to treat the flu.

“Tamiflu is sold out from one of my wholesale sources while Tylenol with Codeine and Ibuprofin are slowly going out of stock,” said Shalom Rakhminov, owner of Shalom’s Pharmacy in Midwood Brooklyn.