Nancy-
I hope by now that you have gotten an answer to your question. However, I would like to tell you some good news.
Naproxen, as well as,
Ibuprofen and ketoprofen are known to cause false positives for THC tests. I am sure you can find plenty of web sites that will tell you this and here is the reason why:
Naproxen is in a class of drugs known as propionic acid type non-steroidal anti-inflammatory. these medications are metabolized in the body by various routes, at least one at which involves a process known as carboxylation.
with
Marijuana, the active agent, delta-9-tetra-hydrocannabiol (THC)is carboxylated and excreted in the urine as delta-9-tetrahydrocannibol-9-carboxylic acid.
Therefore, chemical similarities in the form of carboxylic acid groups will cause false positives. This is well documented and will occur most often in cheap drug tests.