stuffed: dont call names. theyre right; ketamine is not supposed to cause positives for pcp, or any other substance. i didnt just check erowid for this, i looked up the elimination products of the two and while they are similar, they are not identical by any means.
i had a friend that tested positive for pcp once, we think because of dxm, even though its much more chemically different to pcp than ketamine. k and pcp have similar dual ring structures, but arent identical, nor are the elimination products.
a gc/ms test would be able to tell the difference *I GARENTEE IT*, i donno about the cheapie tests they employ in most cases, though. but if they suspected ket, the gc/ms would show its presence, obviously.
im not sure pure mdma would cause the amphetamine false positive, they also dont have identical elimination products, and a gc/ms would show this, although if they were looking, they could see the presence of the mdma elimination products. remember, lots of things cause false amphetamine positives, namely pseudophedrine, sudafed.
all my studies on this thanks to this topic turned up one verrry comforting piece of news: zolpidem (ambien) will not interfere or cause false positives on any drug tests.
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I pity the fool