How rare is rare? It's a phrase beloved by our drug regulators, who use it like confetti to describe adverse reactions and side-effects. Because a reaction can be rare, the guilty drug may be spared, even if the reaction is death itself.
Take, for instance, the disease-modifying antirheumatic drug (DMARD) Arava (leflunomide) for rheumatoid arthritis. It's been on the market only since 1998, but it caught the attention of the European Agency for the Evaluation of Medicinal Products (EMEA) in 2001 and, in recent weeks, there's been intensive lobbying to have it removed from the US market.
The EMEA reported that Arava could cause severe liver reactions; at that time, they were aware of 296 cases, 129 of which were serious, including cases of liver failure.
The US health-watchdog group Public Citizen describes a similar picture, with 130 severe liver reactions, including 22 deaths, linked to the drug.
Their efforts to get the drug banned have failed, however. An advisory panel to the American Food and Drug Administration (FDA) has recommended that the benefits of the drug outweigh its 'rare' side-effects.
So, how rare is rare? The FDA discovered that one in 200 users may be at risk of serious acute liver injury, and Public Citizen reckons it is six times more likely to cause fatal liver toxicity than another DMARD, methotrexate, which remains the drug of choice in the US for treating rheumatoid arthritis.
Arava is also 13 times more likely to cause hypertension than methotrexate, and 12 cases of the life-threatening Stevens-Johnson syndrome have been linked to the drug. But none has been associated with methotrexate, even though five times more prescriptions were written for methotrexate than for Arava in the three years up to 2001.
As steak lovers know, rare is a subjective and relative term. But when it comes to our wellbeing, we need more objectivity from those supposed to protect us.