Drop-in additives will not work if the U/A is an instant-type test because it takes approximately 90 min to destroy all of the drug metabolites in the sample.

Plus labs had caught on to additives and been detecting them on a frequent basis for quite some time. They get detected when the sample is flagged for excessive nitrites, high chromates, and/or an abnormal pH.

You'd be better off subbing with a clean sample or synthetic if you wont be watched. If youre brave enough to sneak in an additive, then youre brave enough to sneak in a substituted urine sample.