Paracetamol crystals, polarised light micrograph of paracetamol (acetaminophen) crystals.

Paracetamol crystals. A desirable form of these crystals has been made by mixing carefully chosen ingredients at room temperature. Credit: Gerd Guenther/SPL


To create elusive crystals, just open the box

A simple recipe creates a valuable crystalline drug.

Crystal growing is a finicky process that can demand the use of vacuums or ice baths. A new method could be as simple as mixing two judiciously chosen solids together at room temperature and leaving them alone.

Two solids in contact will spontaneously fuse into one homogeneous liquid if the ions of one solid can form weak intermolecular forces with those of the other. Simon Hall and his colleagues at the University of Bristol, UK, discovered that if one of the solids evaporates easily, this phenomenon could help to produce drugs in crystal forms that are hard to grow by other means.

The researchers mixed a solid form of the drug paracetamol — also known as acetaminophen — in a sealed container with an evaporation-prone solid called phenol. After the duo melted together, the researchers uncapped the container and left the liquid alone for a few days. The phenol completely evaporated, leaving only crystals of paracetamol.

The team’s method yielded an elusive paracetamol crystal that is more effective than the commercially produced crystal form, which has been deemed too difficult to manufacture.