All topical things get to the blood stream.

The topical Flector patch is causing liver problems in some patients!

When I first started Lidoderm, I had some rapid heart beats.
That only lasted for the first couple of days or so. That is why I
cut them now in half for some uses. I even found that 1/2 patch is quite effective when placed properly.

But I will caution you....doctors DO NOT KNOW how to use them.
We used to get endless calls at my last job (nursing home provider) from nurses who could not figure out what to do with them. Doctors don't know. Everyone would eventually come me for advice. I even met a drug saleswoman at a pain conference and asked HER about the drug company's advice...and she told me...They don't know either and don't recommend placement!

Kind of spooky isn't it? So start with 1/2 patch, keep the other half in its foil pack fold over tightly and put in a ziploc. They do dry out if exposed to air. Using 1/2 successfully will save you mega bucks too.