Friday, 21 October 2011

Urine Drug Screens and Buprenorphine

A drug treatment service conducts urine drug screens. Certainly, if a drug service did nothing else, it'd at least prescribe substitute medication and carry out frequent urine tests. The tests provide an easy (save for paruresis) and cost effective way of monitoring the success treatment and are generally accurate...

I say generally as no test can be 100% accurate; a fact that was born out when a patient who had recently come on to my caseload returned three consecutive buprenorphine positive urine screens (he was prescribed methadone). He denied it's usage emphatically on each occasion.

As a drug worker, it's often hard not to be cynical. I understand buprenorphine has gained popularity in prisons where it is snorted, and it's not a drug the service routinely tests for (I ordered the test specifically). It wasn't out of the question that this particular individual had found a substance that fell under the radar, so-to-speak. Nevertheless, his impassioned denial spurred me to investigate.

I contacted the lab who had conducted the test and spoke to the manager. He told me that an individual prescribed buprenorphine would return a positive result in the order of 15 000 units. My patient's sample showed around 1500 units; a weak positive? On further investigation (probably a google search?) the lab manager told me that urine tests can show up positive for buprenorphine if the individual is also taking opiates such as codeine, dihydrocodeine, tramdol, etc.

And indeed it was that this particular patient had been taking co-codamol for chronic back and neck pain.Was it this that was skewing the test? More than likely, given the weakness of the positive.

In drug treatment services, the truth can often seem difficult to come by. It's hard to question what's written in black and white on a pathology report, but it's often harder to question the seemingly genuine pleas from our patient's. Ultimately, it somewhere in the middle of laboratory tests, clinical judgement, and - perhaps most importantly - the development of a good patient/nurse relationship, that the truth can be found.