Iodinated contrast agents (for use in CT-scans) are on the list of drugs myasthenics shouldn't use. Here's a new study that shows that they raise the risk of thyroid problems significantly. Since MG patients are prone to Graves' disease anyway, it's something to keep in mind.

http://www.medscape.com/viewarticle/757345

When I went to have my thymus scanned, the neurologist and the radiologist couldn't agree whether the contrast agent was necessary, had never heard that iodinated contrast agents are dangerous for MG patients, and didn't know if a Graves' patient could tolerate the iodine anyway. So, now we can add a fourth thing they didn't know to the list. I spent three hours at the radiologist's that day, and all I got out of it was a huge caffeine-withdrawal migraine because I was fasting in my johnnie the whole time they were inconclusively arguing. Not my favorite patient memory. In the end I announced I was going home, and they could call me when they figured it all out.

Abby