Post consumption, heroin is quickly broken down into 6-monoacetylmorphine and finally into morphine. Morphine is further converted into morphine-3-glucuronide and morphine-6-glucuronide. These metabolites are mainly excreted via urine and to a lesser extent via bile.
After injecting heroin, about 70% of its metabolites are excreted through urine. Apart from conjugated morphines, a number of other metabolites such as normorphine, codeine, morphine-3-6-diglucuronide, and morphine-3-ethersulphate are also excreted.
Usually, the half life of heroin ranges between 2-8 minutes. Almost 100% of it is broken down to metabolites that are excreted via urine. However, in long term and heavy users, some of the heroin may remain unchanged that is also excreted through urine.
The concentration of metabolite 6-monoacetylmorphine peaks within a few minutes of heroin ingestion. This metabolite tends to have a longer half life that is estimated to be 5-52 minutes. After an intravenous injection, 6-monoacetylmorphine remains detectable in plasma for up to 1-3 hours while in urine for up to 1-5 hours.
Only a small amount of heroin appears as 6-monoacetylmorphine in the urine while the remaining amount appears as morphine and morphine glucuronides. These can be detected within minutes of heroin ingestion. The half life of morphine ranges between 2-7 hours while that of morphine guluronides ranges between 2-6.5 hours.