ALTHESIN REBIRTH Drawbridge Pharmaceuticals says Phaxan has a much higher safety profile than propofol.

A SAFER ANESTHETIC Will Phaxan Challenge Propofol's Dominance?

Could an alternative to propofol be on its way? Drawbridge Pharmaceuticals, an Australian company, hopes to bring an anesthetic called Phaxan to market in the next few years. The brand is new, but the fundamental science behind the new drug isn't. Phaxan is a reformulation of a once-popular, but long-gone, anesthetic called Althesin.

"Althesin was a very well-loved drug that was marketed by Glaxo everywhere except the United States between 1972 and 1984," says anesthesiologist and surgeon Colin Goodchild, PhD, Drawbridge's co-director and chief medical officer. "It still has the highest safety profile of any anesthetic that's ever been synthesized."

It was taken off the market, he says, because to make it suitable for injection, it was dissolved in an excipient called cremophor EL. The excipient caused severe allergic reactions in a small percentage of patients. That happened to be just when the boom in outpatient surgery was beginning, and the withdrawal created a huge need for another fast-onset, short-duration anesthetic — a vacuum that was quickly filled by propofol.

Althesin was gone, but not forgotten. Fast forward to 2010, when Dr. Goodchild's wife, neuroscientist and anesthesiologist Juliet Serrao, PhD, recalling the sadness senior anesthesia providers had expressed over the loss of Althesin, suggested to her husband that a reformulation with modern excipients might solve the allergy problem.

"She's the primary inventor (of Phaxan)," says Dr. Goodchild. "She said, look, propofol is getting really bad press, it's outlived its usefulness. You should look at Althesin and try other ways to dissolve it." It wasn't long before a new formulation was born, one that uses a water-based excipient, sulfobutyl ether-beta-cyclodextrin, which, says Dr. Goodchild, has long been recognized as safe by the FDA.

Dr. Goodchild says not only won't Phaxan impair cognitive ability, it may actually help protect it. "Because it's an allopregnanolone analogue," says Dr. Goodchild, "chances are, Phaxan will be able to replace allopregnanolone levels that are falling (during surgery) and will protect the aging brain from the inflammation that the surgical onslaught causes." Dr. Goodchild says Phaxan is still years away from hitting the market.

— Jim Burger