###Human: My urine and blood tests are negative after taking Nucynta. Why? ###Assistant: Hi.  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.