Cialis is not so contraindicated with amphetamines. That's because it's mode of action is more specific to the 5-phosphodiesterase enzyme involved with the physiology of getting an erection. If you used Viagra before Cialis became available, you may notice (probably but not necessarily) that there is less facial and body flushing from Cialis due to it being more specific in it's action.
As mentioned these drugs work by inhibiting the di-esterase enzyme, resulting in more blood flow to the area/s affected. With Viagra, different forms of the enzyme are affected so greater arterial dilation occurs and more flushing is usually noticed.
I suppose you will be aware that nitrites and nitrates are ABSOLUTELY not to be taken with viagra , Cialis or Levatra or any of these compounds. Again it's because of the enzyme involved which also metabolises nitrites etc.
Cialis and amphetamines AFAIK are not contraindicated, although exuberance could up the risk of a heart attack while on BP raising drugs. I've used Cialis with MDMA on a couple of occasions, and felt none of the noted effects with MDMA and viagra. Be careful though, cialis is relatively new so stage 3-4 trials no-doubt continue somewhere.
I've never noticed any headaches with Cialis, but apart from dehydration or reading related tension, I don't very often get headaches at all.
[Ed: fixed grammar and comprehension; p_d]
