Opren killed 61 elderly patients in the UK — Eli Lilly's arthritis drug disaster

Benoxaprofen, marketed as Opren in the UK and Europe and Oraflex in the United States, was a non-steroidal anti-inflammatory drug developed by Eli Lilly for arthritis. It was launched in the UK in 1980 and in the US in May 1982. The drug was promoted as a once-daily treatment with fewer gastrointestinal side effects than older NSAIDs, making it an instant blockbuster. But benoxaprofen had a long half-life that increased significantly in elderly patients, causing the drug to accumulate to toxic levels.

In May 1982, the British Medical Journal reported at least 12 deaths linked to Opren. The drug caused liver and kidney failure, particularly in patients over 65. By August 1982, the British government had identified 61 deaths associated with the drug. The US FDA reported 11 additional deaths among Oraflex users. On 4 August 1982, the British government suspended Opren sales, and Eli Lilly withdrew the drug worldwide that same afternoon. The drug had been on the US market for only three months.

Eli Lilly faced approximately 1,000 lawsuits in the US and UK. The company settled many of them out of court, with total costs estimated at over $200 million. The disaster was a major factor in the UK's decision to strengthen its post-market drug surveillance system. Benoxaprofen became a textbook case of how a drug that is safe in young adults can be lethal in the elderly, and how the standard dosing regimen failed to account for age-related changes in drug metabolism.