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Q. My urine and blood tests are negative after taking Nucynta. Why?

Answered by
Dr. Arul Amuthan
and medically reviewed by Dr. Divya Banu M
This is a premium question & answer published on Jun 05, 2019

Hello doctor,

I am a 28-year-old female. I have been on Nucynta for over a year. I take Nucynta ER 50 mg BID and Nucynta IR 50 mg once a day. For the last two months, my urine tests (immunoassay and lab testing) have come back negative. Two weeks ago a blood test was done and it was also negative. I religiously take these medicines as prescribed by my pain management doctor. Due to these negatives he is now refusing to prescribe any oral medications (including my Flexeril, Gabapentin, and oral Ketamine). I understand his need to be able to prove to Nucynta in my system but he is also refusing to try anything else.

I am a walking genetic defect. I also have known pharmacogenetic and pharmacokinetic issues. I also have EDS, CRPS, POTS, MCAS, gastroparesis (severe enough that EGD showed food in my stomach 18 hours after last eating), endometriosis. Could any of this be causing the problem? Could any of the medicines I take be causing the problem? My medicines are Lopressor, Trazadone, Fetzima, Zyrtec, Ketamine, Magnesium Citrate pills, Melatonin, Gabapentin, Flexeril, Nucynta, Junel Fe. What suggestions do you have? Is there any research to help me?

Dr. Arul Amuthan

Ayurveda Specialist Naturopathy Pharmacology Siddha Medicine Toxicology


Welcome to

Nucynta is an opioid analgesic, that has high first-pass metabolism when administered orally. It means only 32 % of orally administered dose reaches blood. After it produces its effect, 97 % gets metabolized in gastrointestine and liver and gets excreted out from body through urine.

In your case, you have delayed (slow) intestinal movements, hence the drug may get faster metabolism and faster excretion than a normal individual. Hence, I think it is not detectable in blood or urine.

Another possibility is very less amount of drug reaches your blood (less than 32 %) due to intestinal absorption issues. The half-life of this drug is four hours in healthy individual. It means, after oral administration, 32 % drug reaches the blood within 3 to 4 hours. If I draw the blood after four hours of oral administration, the amount showing in blood is expected to be 16 % (50 % of drug gets excreted by four hours). It is in a normal person. In your case, when to draw blood is the question. So, individualistic reasearch could be done for you with special care.

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