How do I Know How Long Drugs Last ?

[Chip (OP)]

2 things about drugs to be aware of:

1. find out said product's active drug half-life. You get about 5 half-life's and then you can no longer feel any of it.

2. it's LD50 (lethal dose of 50% of the population)

example:

50 mg. of d-Amphetamine has a half life of 4-6 hours ... 6+3+1.5+0.75+0.37 hours = 11-12 hours.