ImClone Systems and Bristol Myers Squibb informed health care providers on September 13, 2005 about two new warnings added to the label for Erbitux© (cetuximab):
* **Longer observation times after infusion** Because some patients have experienced allergic reactions during and after Erbitux infusion, the following was added to the label: *A 1-hour observation period is recommended following the ERBITUX infusion. Longer observation periods may be required for patients who experience infusion reactions.*
* **Laboratory tests for low magnesium levels** Patients should be monitored for low magnesium levels and accompanying low calcium and potassium levels during treatment with Erbitux and for approximately 8 weeks after treatment ends.
About half of patients in clinical trials experienced low magnesium levels, 10 to 15% had severely depleted levels. Onset of low magenesium levels occured within days to months after beginning treatment and can be a risk after for several weeks after treatment ends.
[Dear Health Professional Letter from ImClone and Bristol Myers Squibb](http://www.fda.gov/medwatch/safety/2005/Erbitux_91405_dearhcp.pdf)
[FDA Medwatch changes to the Erbitux label](http://www.fda.gov/medwatch/safety/2005/Cetuximab_91405_PI.pdf)
[Associated Press story about the changes](http://news.yahoo.com/s/ap/20050915/ap_on_he_me/cancer_drugs)