Asprin has been proven to sometimes cause false negatives on a urine drug screen.
I recommend taking two asprin 2 hours before the test, one asprin 1 hour before the test, and two more asprin 30 minutes before the test. This is to be sure that the asprin stays in your system as you urinate. Make sure to drink lots of fluids during this time period, also (2-4 quarts)
Eyedrops and bleach are for theoretically "neutralizing" all of the chemicals in a home piss test. Those methods should not be used in laboratory tests because the labs can see if the chemicals have been neutralized. Since asprin only triggers a false negative for THC and is not added to the urine sample after it has left the body, it doesn't show up on lab drug screen. Ever.