A national shortage of three first line antibiotics is forcing hospitals to stockpile, ration and use back-up treatments that expose patients battling serious infection to more toxic drugs, and embolden superbugs.

The drugs Vancomycin, Aciclovir and metronidazole are the latest in a long list of antibiotic shortages over the past few years which are the most effective, least expensive, least toxic and least likely to cause resistance, infectious diseases doctors say.

When hospitals are out of stock or have to ration these antibiotics, doctors are driven to use back-up treatments including giving patients broader spectrum antibiotics which can cause potentially catastrophic complications such as bowel inflammation, and potentially put the community at greater risk of superbugs. .

"These are decisions that will lead to the deaths of people if they can't get an effective antibiotic," said Professor of infectious diseases at Australian National University, Peter Collignon.