Why Is Merck Suspending This Drug?


On Friday, Merck & Co. (NYSE:MRK) reported that it was going to be suspending sales of Zilmax in the U.S. and Canada temporarily. Zilmax is a growth drug used to add weight to cattle  prior to being slaughtered. The drug can add about 2 percent to the weight of an animal, which is around 24 to 33 pounds.

Reuters reported that the company said there were no safety issues with the drug aside from what was seen in clinical trials before its 2007 introduction to the U.S. market. According to K.J. Varma, head of research for Merck’s animal division, “From everything we’ve done, we have not found any (new) safety or efficacy issues with this drug.”

However, Tyson (NYSE:TSN) started rejecting cattle that had been treated with the drug because of recent incidents where the cattle who arrived at the plants were lame or couldn’t move. It has notified suppliers that starting September 6 it is not going to purchase cattle treated with the drug.

Last year, the drug brought in $159 million in sales in North America alone. According to estimates from Merck, about 70 percent of beef cattle in the U.S. are given Zilmax or its competitor’s  Optaflexx.

During testing, many of the cattle did become acidotic, which means that there was an increase in acid in the blood and tissue of the animals, which can lead to lameness. However, Merck pointed out that this also happens in animals that have not been treated with the drug.

Furthermore, Merck also pointed out that the conditions in which animals are kept can also contribute to lameness, says Reuters. Thus, the company is also looking into these conditions as well. There was no word from Merck as to when the drug would be used again.

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