Stimulants such as MDxx will make your pupils huge immediately. Mephedrone tends to cause immediate pupil dilation as well.
However, most uppers, such as amphetamines, methcathinone, cocaine etc, won't affect your pupils untill later on, usually when you start coming down, that's when you will notice that your pupils are bigger.
Everyone and everyones body chem is VERY different. Not many of my mates get gurny, saucer messed like I still do yet I act fairly normal. Usually
Mephedrone, Cocaine, Amphetamine might not but might on some might do 1/3rd size.
trips and md** always tends to give you biggins.
Opites make them small.
I slammed Ritalin-analoge, ethylphenadate today in smallest bits 5-10mg and noticed dialation also even large dialation can be "in your head" with stims
When IVing Cocaine and Heroin: i seen them blow right up then over 10-20seconds shink back down (h)