PCP (Phencyclidine) is an illicit substance that is commonly abused and is known for its dissociative effects. It is commonly tested for on drug screenings. In fact, PCP is one of the 8 most commonly tested for substances and is included on most standard urinalysis screenings. Other commonly tested substances include:

  • Amphetamines
  • Cocaine
  • Benzodiazepines
  • Barbiturates
  • Marijuana 
  • Opiates
  • Opioids

What Causes A False Positive PCP Test?

What has apparently happened in your situation is known as a "false positive", a mistaken positive reading on the drug test which is not accurate. Unfortauntely, false positives are relatively common on standard urinalysis drug tests.

The issue with common drugs tests is that they aren't all that accurate. Most drug screening facilities use simple "immunoassay" based tests that work by utilizing antibodies to react to specific drug compounds. When a specified drug is present in a test urine sample, an antibody binds to it, producing a reaction. When a reaction occurs, it is recorded as a 'positive' result.

These "immunoassay" based tests can have significant problems with "cross-reactivity". In other words, drugs that are NOT being tested for can occasionally react with the wrong antibody (i.e. 'cross react'), resulting in a 'false positive'. 

There are many non-illicit, legal medications which are well known to cause positive tests. In your situation, you are unfortunately taking two medications which are specifically known to cause false positive PCP tests. The following medications are known and documented as being able to produce false positive PCP tests:

  • Dextromethorphan
  • Diphenhydramine
  • Ibuprofen
  • Imipramine
  • Ketamine
  • Meperidine
  • Thioridazine
  • Tramadol
  • Venlafaxine

If you are sure that your test result is incorrect and a false positive has occurred, you could ask to retake the test. In addition, you can request another type of drug test that does not have problems with cross-reactivity. Two of these tests are:

  • Gas chromatography-mass spectrometry (GC-MS)
  • High-performance liquid chromatography (HPLC)

Both of the above tests do not use antibodies and can accurately determine the exact molecules present in a sample. If you received a 'false positive', these tests will be able confirm that a particular drug compound is not present.