Terfenadine is a highly effective but dangerous antihistamine remedy for hayfever (seasonal allergic rhinitis). It is or was made by Hoechst Marion Roussel (Merrell Dow) under the brand name Seldane. Another brand is Triludan. When overdosed on, it can cause fatal cardiac arrhythmia. It is a tiny white pill, so if you take your one-a-day pill in the morning and a couple of hours later forget whether you've taken it, taking a second one is getting close to a potentially toxic overdose.

It is strongly amplified by grapefruit juice. Many common medications are highly dangerous when taken with grapefruit juice. It also reacts badly with numerous other medicines, of course, but not mixing these is common sense.

Hoechst Marion Roussel have developed an alternative, fexofenadine, under the brand names Allegra and Telfast, which has similar effect to terfenadine on hayfever but does not cause cardiac arrhythmia and does not have adverse reaction with grapefruit juice.

Terfenadine is now withdrawn in Britain, and is prescription-only in Canada. A move to withdraw it in the USA in 1997 was resisted by the manufacturer, who said the answer was education in correct use. The antihistamines astemizole and loratadine are reported to have similar problems, though not as strongly as terfenadine.

I wouldn't say resisted.

As soon as the patent on terfenadine ran out, SELDANE® terfenadine manufacturer Hoechst Marion Roussel successfully petitioned the FDA to have terfenadine pulled from the market in favor of ALLEGRA® brand fexofenadine products such as Allegra-D (fexofenadine + pseudoephedrine), apparently because fexofenadine's interactions with foods and other drugs are much milder than those of terfenadine, as the digestive system actually turns terfenadine into fexofenadine. (Source: http://www.fda.gov/bbs/topics/ANSWERS/ANS00843.html)

But the timing makes one wonder: was it a safety precaution, or was it IP abuse?

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