How Can a Crystal Make a Medicine Stop Working?

TL;DR

Ritonavir stopped dissolving properly because a previously unseen crystal form appeared, even though its chemical composition remained the same. The case shows that atom arrangement and crystal structure can change a compound’s behavior, allowing an effective medicine to become unusable without changes to its ingredients or documented manufacturing process.

Transcript

• For two years, this drug was a miracle. It was introduced in 1996 to treat HIV. And by 1998, 75,000 patients across the country were taking up to 20 of them every day. It's called ritonavir, and it turned a certain death into a manageable condition. This particular pill is on its way to quality control to a dissolution tester. Here, analysts moni... Read More

Key Insights

• Ritonavir was introduced in 1996 to treat HIV, and by 1998, 75,000 patients across the country were taking as many as 20 pills daily. The drug helped turn what had been described as a certain death into a manageable condition.
• Dissolution testing is essential because ritonavir capsules needed to dissolve in around 30 minutes to be absorbed properly. After 240 consecutive lots passed, one capsule unexpectedly failed, prompting an emergency shutdown, destruction of the batch, and deep cleaning of the production line.
• The cloudy ritonavir capsules contained millions of tiny needle-shaped crystals that researchers had never seen before. Laboratory attempts to create normal ritonavir also produced the same white paste, despite researchers checking ingredients, settings, temperatures, and procedures without finding any manufacturing error.
• The production failure spread rapidly across locations. An Italian factory initially produced pills that passed testing, but one tablet failed within days of the Chicago team’s visit, and within roughly five or six weeks, every place containing the product had encountered the crystals.
• The crisis was difficult to control because Abbott did not know how to detect, test for, prevent, cause, or remove the crystals. There was no gradual trend or early warning, so a working production process became unreliable over a very short period.
• Chemical composition alone does not determine a compound’s behavior. Justus von Liebig and Friedrich Wöhler produced substances containing the same numbers of silver, nitrogen, oxygen, and carbon atoms, yet one behaved quietly when heated while the other detonated with great sensitivity.
• Atomic arrangement is a crucial part of chemical identity and behavior. Liebig and Wöhler initially accused each other of analytical mistakes, but experiments performed on neutral ground showed that both results were correct, forcing a change in how compounds were understood.
• Infrared spectroscopy works by exposing molecules to a range of infrared frequencies. Different bonds stretch, squeeze, or bend most strongly at particular frequencies, producing spectral peaks that act like a fingerprint and reveal which types of bonds are present in a molecule.

Questions & Answers

Q: Why did ritonavir capsules suddenly stop dissolving?

Ritonavir capsules stopped dissolving properly after a previously unseen crystal form appeared inside them. The capsules became white and cloudy and contained millions of tiny needle-shaped crystals. Tests still indicated that the material was ritonavir, and investigators found no incorrect ingredient, temperature, setting, or procedure. The altered solid structure changed how the capsules behaved during dissolution testing.

Q: How was the ritonavir crystal problem first detected?

The problem was discovered during routine quality control when a capsule failed to dissolve properly in a dissolution tester. Ritonavir capsules were expected to dissolve in around 30 minutes so the medicine could be absorbed properly. Following protocol, analysts triggered an emergency shutdown, destroyed the affected batch, and deep-cleaned the production line, but the same failure returned the following day.

Q: What did Abbott do after ritonavir production began failing?

Abbott stopped production, destroyed a failed batch, deep-cleaned the production line, and conducted numerous experiments. Teams checked ingredients, equipment settings, temperatures, pressure, humidity, chemical weights, and procedures. They also rebuilt facilities, created new production lines, and searched for alternative manufacturing sites. An Italian factory initially succeeded, but its tablets soon developed the same dissolution failure.

Q: Why did the Italian ritonavir factory not solve the problem?

The Italian factory initially produced ritonavir capsules that passed dissolution testing, suggesting that the Chicago facility might have made an unidentified mistake. Scientists compared pressure, temperature, humidity, chemical weights, and other procedures, but found that both sites operated alike. Within days of the Chicago team’s visit, an Italian tablet failed, and the crystal problem subsequently appeared wherever the product was present.

Q: Why was the ritonavir crystal crisis so difficult to control?

The crisis offered no gradual trend or early warning. Abbott did not know what caused the crystals, how to detect or test for them, how to prevent them, or how to remove them. Within roughly five or six weeks, every place containing the product had encountered the crystals. Even laboratory production repeatedly generated cloudy white material despite apparently correct procedures.

Q: How can compounds with the same atoms behave differently?

Compounds can contain the same types and numbers of atoms yet behave differently because the arrangement of those atoms also matters. Liebig and Wöhler demonstrated this with compounds containing one silver, one nitrogen, one oxygen, and one carbon atom. One material reacted quietly when heated, while the other was highly sensitive and detonated, even though both analyses were correct.

Q: What did Liebig and Wöhler discover about chemical compounds?

Liebig and Wöhler discovered that identifying the atoms in a compound is not enough to predict its properties. After two years of publicly disputing each other’s analyses, they met in Frankfurt and reproduced each other’s work. Both compounds had the same elemental composition, but behaved very differently. Their results showed that the ordering of atoms also determines chemical behavior.

Q: How does infrared light help identify molecular bonds?

Infrared light has an electric field that pulls a molecule’s electrons and nuclei back and forth, causing bonds to stretch, squeeze, and bend. Each bond responds most strongly to a particular frequency, depending on its strength and the masses of the connected atoms. Scanning many infrared frequencies produces peaks that form a molecular fingerprint and indicate which bonds are present.

Summary & Key Takeaways

• Ritonavir transformed HIV from a certain death into a manageable condition, but after two years and 240 successful lots, capsules unexpectedly failed dissolution testing. Clear capsules became white and cloudy, with microscopic examination revealing millions of tiny needle-shaped crystals. The failures rapidly spread through both laboratory and factory production.

• Abbott halted production, destroyed failed batches, cleaned equipment, rebuilt facilities, and tested an alternative factory in Italy. Italian pills initially passed, but failures began shortly after Chicago scientists visited. Within five or six weeks, every location containing the product had encountered crystals that researchers could neither detect early nor eliminate.

• The historical dispute between Justus von Liebig and Friedrich Wöhler showed how compounds containing the same elements could behave completely differently. Their experiments established that chemical behavior depends not only on which atoms are present, but also on their arrangement. Infrared light can reveal molecular bonds by producing a characteristic spectrum.