Buprenorphine and metabolites

Buprenorphine is an opiate analgesic derived from thebaine, an alkaloid found in the opium poppy Papaver somniferum. Buprenorphine is licensed for use in the treatment of opiate addiction and for pain relief in the operating theatre environment. Its use in opiate dependence is relatively new in the UK, although in France it has mostly replaced methadone, as overdose and death are far less common for clients treated with buprenorphine. This can be partly attributed to buprenorphine’s mixed agonist and antagonist effects on opiate receptors, which also partly precipitate withdrawal and make dose reduction less traumatic. Buprenorphine is supplied in tablet form (Subutex®, Temgesic®, or Suboxone®) and must be taken sublingually, and its effects are more prolonged than for other opioids. This means that its potential for abuse is less than methadone, and coupled with its better safety record in other countries, this makes its use in the UK more common. There is some evidence of buprenorphine being available on the street and being injected, although its properties and formulation makes this less attractive to heroin users than methadone or other opiates.

Following buprenorphine administration (sublingual or intravenous), urinary concentrations of unconjugated buprenorphine are very often ‘negative’ (< 5 µg/L), and only metabolites can be detected. The detection of parent drug without metabolites suggests addition of buprenorphine directly to the sample.