Lewis
The reason most Dr's want you to have your first shot of Imitrex in office is because for many it make the ha "10 times" worse for the first 30-60 minutes. I was one of the people who went on the shots as soon as they were available to the general public many years ago. Within 20 minutes of the shot I would get a hot feeling in my head, ears and my throat felt like I had Strep or something it was so sore, hard to swallow too, nausea went through the roof :0. I also thought my head was going to split down the middle from the pain. I curled into a fetal ball on the Dr's table

. Within and hour of the shot the ha was gone. I could function but was shaky and a bit queasy. I used the shots for 3 years cause it was the only thing available that would stop a migraine.
As for the day after effects--could it have been from the severity of the ha? I feel wobbly, tired and out of sorts for 24 hours after every bad migraine. It really is called a migraine hangover in some circles.
I have found Relpax in the last year. It is better for many than Imitrex -- less (much!) side effects. Zomig did not help me. I wish you luck.
BB -- Magna