Reviving an old thread here.. having a similar scare. I just took modafinil (Alertec brand) for the first time yesterday morning. I purposely took a really small 'test dose' because I'm very cautious that way with meds, especially ones that aren't being supervised by a doctor (I wanted to try it out for it's alterness properties, I'm a university student). I must have taken no more than about 20 mg. About an hour or so later, I had a severe need to "evacuate" and had to run to the toilet many times over the next few hours. Not cool. Then once that started to go away, I started getting a headache, which was quite severe by about 6 or 7 hours after dosing. That went on for hours. By about 13 hours after taking it, that started to fade, but then I started itching all over. I tossed and turned in bed, unable to sleep, both because I felt I physically couldn't, but also I'm sure due to anxiety about the side effects. I finally dozed off a bit in the early hours. Now it's been about 26 hours since I took it and I still feel itchy all over my body. I haven't seen any signs of rash though, luckily, or fever, but I'm worried. If I can react so quickly to so little, I don't think I should be playing with this medication.
I think the thing is with this medication, like many others, is that the majority of people won't have bad effects but there will always be a minority who have bad, even severe effects, and they might have it even from one dose, or it can happen after a couple months of daily use. That's what scares me about this drug, is the danger isn't about how much you take it, it's more about your genetics and whether you're susceptible to a severe reaction or not, but you can't know until you try it. Some drugs you can start with a small amount and get an idea how you react, with this, you could be fine for a few weeks and then suddenly react.
Considering I don't have any allergies that i know of, I rarely react to things, have taken penecillin and other drugs with similar risks and was fine, I guess I'm just one of the unlucky ones. At least with stimulants I feel I have some control over how much symptoms I will get. I just hope everything goes away soon and i don't have to be itchy for weeks like the above poster, that will drive me crazy.