I Have Been Taking Doxycycline For 10 Days For Pneumonia

Posted on Thu, 24 Jan 2019

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Thu, 24 Jan 2019 Answered on

Last reviewed on

Question : I have been taking doxycycline for 10 days for pneumonia. dark urine. Had urinalysis today and came back saying I had traces of PCP and meth in my system! I have NEVER TOUCHED EITHER!!!! I was also having to take Nyquil and Theraflu.
Why is this showing up in my system????

Follow up: Dr. Ashok Kumar Choudhary (6 minutes later)

I also take hydrochlorothiazide 12.5 mg cp, venlafaxine hcl er 225 MG, and lots of aleve

Answered by Dr. Ashok Kumar Choudhary (22 minutes later)

Brief Answer:
It is probably false positive

Detailed Answer:
Hello,
Thanks for using Healthcaremagic.

I read your query and understand your concerns.

The dextrometharphan which is active ingredient in Nyquil can cause false positive urine test for PCP. Similarly Diphenhydramine which is active ingredient in Theraflu can cause false positive test for PCP and methadone.

Considering these facts and number of prescribed medication it is possible that you got false positive test results.
You can request your testing authority to conduct higher level tests for proving you clean and right as the false positive will not stand higher accuracy tests such as chromatography.

I hope this helps you.
Feel free to write back to me if you have more questions.
Thanks and regards.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar