Strange side effect?

I don't know whether this is a side effect per se of imitrex or part of the normal migraine cycle, but I thought I'd see if this happens to anyone else.

I've noticed lately after I've taken an imitrex that when it starts to work, my breathing rate slows down tremendously. It's actually kind-of relaxing.. but I didn't know whether this is a side effect or just some way my body is attempting to heal itself? It would make sense that it is helping to dissipate the migraine as slower breathing probably helps to calm nerves and reduce inflammation. On the other hand it's sort-of scary too to be breathing slower than normal.

I had this majorly with the imitrex injection. I had to remind myself to breath and was only having about 3-4 breaths a minute, very shallow, without doing it. Along with the searing pain of the injection site and the headrush that felt awful, I decided after 3 tries not to have it again. Plus it barely helped the migraine and I got my usual worse migraine about 24 hours after using it. But I didn't get the slow breathing with any other triptan, just sumatriptan. Maybe you'd have better luck with a differrent one?

Amy