For 8yrs i'm taking lexaurin as needed (1.5-3mg).i have never taken it consistently, maybe 30 pills per year.recently i took 6mg but there was no effect at all. why did it stop working like that?what does that mean for me with that class of med?

First, you have to make sure the pill has not expired yet because you did not take it often so you have not had it refilled. Second, when using this kind of medication for 8 years you may develop tolerance although 6 mg is a relatively high dose for home use. Last but not least, if your symptom is so severe you may need a very high dose as used in inpatient care, 6-12 mg, 2 to 3 times a day.