how much cross tolerance is there between clen and ephedrine. i work at night and on those sleepless days i may take say 10mg ephedine and 100mg caffine or strong coffee rather than mega dosed caffine. i find it less jittery . and how bout caffine. i think you can use caffine in an emergency for asthma attacks because of beta receptor stimulation. clen doesnt seem to have as much cns stimulation and in larger doses gives me the shakes. would taking an antihistime before bed quell my worries.