Medicines that could be very useful, but which have toxic side effects, could become safer and more widely available thanks to some unexplained chemistry.
Many potential drugs are fat soluble chemicals that do not dissolve or mix well with water, blood and other body fluids. To turn them into medicines, they are usually dissolved in a “carrier” oil, and then an additive such as a detergent is used to disperse the oily solution in water.
A more sophisticated approach is to encase the drugs in microscopic water-soluble particles. But the carrier oils and additives can have unpleasant side effects, trigger allergic reactions and be painful to inject, while the soluble-particle approach requires a complicated manufacturing process.
Ric Pashley of the Australian National University in Canberra believes he has found a better way. Two years ago, he discovered that, contrary to what we are taught at school, oil and water will mix – providing all the gas dissolved in the liquids is removed first.
While chemists continue to puzzle over what exactly is going on (see “It works – but why?” – below), Pashley and Mathew Francis, also of ANU, have now shown that the technique can be used to mix fat soluble drugs with water, which could do away with additives and their adverse reactions, as well as simplifying drug production. They will publish their results in an upcoming issue of Colloids and Surfaces A.
Pashley and Francis have demonstrated their technique on two fat-soluble drugs: propofol, a widely used sedative that comes in liquid form, and a solid drug called griseofulvin, which is taken by mouth to treat jock itch and other fungal infections.
The technique also worked on soybean oil, which is commonly used to dissolve fat-soluble drugs, as well as a variety of other oils. What is more, the oil droplets are a good size – about 0.6 micrometres in diameter – for intravenous injection, says Pashley.
“You can minimise droplet size without dispersal agents,” says Laurence Mather of the University of Sydney at the Royal North Shore Hospital, Australia. The technique has the potential to “open the way to making many more drugs for injection without complicated formulations”, he says.