Polymyxin B
Sulfate

The Discovery

Chapter 1: The Discovery

Hope and Wonder in the Soil

In 1947, three separate research teams made an amazing discovery. Scientists in England and America found a germ-killing substance in ordinary soil bacteria. The bacterium was named Bacillus polymyxa. The antibiotic it produced was called polymyxin B.

This was exciting stuff. World War II had just ended. Penicillin had saved millions of lives from infections. Doctors and scientists believed more miracle drugs would follow. Polymyxin B seemed to be exactly that. It killed germs that nothing else could touch, especially tough bacteria with protective outer walls called gram-negative bacteria.

Medical journals published papers about the discovery. Pharmaceutical companies began making it. For a few years, polymyxin B seemed like a real breakthrough—a new hope in the fight against dangerous infections. Patients with serious bacterial infections that had no treatment suddenly had options.

The Breakthrough

Chapter 2: The Glory Days

When Polymyxin B Saved Lives

Through the 1950s and 1960s, polymyxin B became an important medicine in hospitals. Doctors used it to treat serious gram-negative bacterial infections. It was especially valuable because many of these bacteria had no other good treatments.

The drug was given through injections into the bloodstream or muscles. Doctors used it for severe urinary tract infections, pneumonia, and blood poisoning from resistant bacteria. Scientists also discovered they could use tiny amounts topically—directly on skin wounds. This topical form became even more famous than the injected version.

Polymyxin B combined with bacitracin and neomycin became Neosporin, the common antibiotic ointment that billions of people have used on cuts and scrapes. That same formula was created in the 1950s and remains unchanged today. During these two decades, the drug was manufactured by major pharmaceutical companies and used in hospitals around the world. For doctors treating serious infections, it was reliable and often the only choice for certain deadly bacteria.

The Trials

Chapter 3: The Dark Discovery

When the Wonder Drug Showed Its Dark Side

Starting in the 1960s, doctors began noticing something troubling. Patients who received polymyxin B injections sometimes developed kidney damage. In medical language, this is called nephrotoxicity. The drug was poisoning the kidneys.

Patients would show signs of kidney failure. Some required dialysis to survive. The damage was sometimes permanent. Additionally, some patients experienced nerve damage, or neurotoxicity. These weren't rare accidents. Research showed the toxicity was real and happened fairly often with the doses being used.

By the 1970s, this problem became widely known in the medical community. Scientists published papers warning about the dangers. The reputation of polymyxin B changed dramatically. What had been a valued medicine was now seen as too dangerous for regular use. Hospitals began avoiding it when possible. Pharmaceutical companies reduced production. The golden age was over.

The Crisis

Chapter 4: The Abandonment

The Drug the Medical World Forgot

By the mid-1970s, the decision was final: stop using polymyxin B for serious infections. It was simply too dangerous. Even though it killed germs nothing else could touch, the risk to kidneys and nerves was unacceptable. Better alternatives existed.

New antibiotics had been discovered. Cephalosporins, fluoroquinolones, and other modern drugs killed the same germs but didn't cause kidney damage. Hospitals removed polymyxin B from their shelves. Medical schools taught students that it was ancient history. Pharmaceutical companies quit manufacturing it for injection.

The drug became a medical footnote, a historical curiosity. For nearly 25 years, polymyxin B was essentially forgotten by mainstream medicine. It hung on in only one form: the topical ointment in Neosporin. Patients applying Neosporin to cuts had no idea they were using a drug that had been abandoned as too dangerous for internal use. Polymyxin B had gone from celebrated breakthrough to forgotten has-been.

The Legacy

Chapter 5: The Reluctant Return

When the Dangerous Old Drug Became Our Only Hope

The story takes a dramatic turn in the late 1990s and early 2000s. Terrifying bacteria began appearing in hospitals—superbugs resistant to almost all modern antibiotics. These weren't science fiction. They were real bacteria like Pseudomonas aeruginosa and Acinetobacter baumannii. Some even resisted carbapenem antibiotics, supposedly the strongest drugs available.

Doctors found themselves in a nightmare. Patients with life-threatening infections faced bacteria that no standard antibiotic could kill. As options dwindled, researchers faced an uncomfortable truth. One drug still worked against these superbugs: polymyxin B. The same drug abandoned for its kidney damage. The same drug doctors had been taught was too toxic.

Starting in the early 2000s, polymyxin B came back from the dead. Hospitals began manufacturing it again. Pharmaceutical companies resumed production. Doctors learned to use it carefully—lower doses, modified schedules—to minimize kidney damage while killing the superbugs. Research showed modern approaches were safer than the old way. Today, polymyxin B is FDA approved and considered essential for treating hospital superbugs. It remains one of the few drugs that work against carbapenem-resistant gram-negative bacteria. For patients with untreatable infections, it's the difference between life and death.