The Crystal That Could Destroy All Medicine

A rare chemical phenomenon called polymorphism caused the drug ritonavir to spontaneously change into a more stable, undissolvable crystal form. This "tin pest"-like transformation spread uncontrollably, rendering the drug useless and forcing a switch to an older liquid formulation.

• 🧪 Polymorphism is when a compound can exist in multiple crystal forms with different properties, like silver cyanate and silver fulminate.
• 🍫 Chocolate's texture and melting point change based on its crystal form (polymorphs), which can be managed with careful heating and cooling.
• ⚙️ The stable ritonavir crystal form (Form II) had a much deeper energy well, making it nearly impossible to revert back to the original (Form I).
• 🦠 "Tin pest" is a similar phenomenon where tin transforms into a less dense gray form below 13°C, cracking and spreading like a disease.
• 🏭 The transformation likely began with a tiny seed crystal of Form II acting as a nucleation site, lowering the activation energy and causing all Form I to convert.

A close-up of blue gloved hands holding a vial containing white, needle-like crystals, with the word "Unstoppable?" overlaid.