Morphine is a highly potent and addictive opioid that is used widely in clinical medicine and surgery for a variety of reasons. Due to the euphoria and pleasurable effects the drug exerts, it is also widely used for recreational purposes and is commonly abused by drug addicts.
Morphine is absorbed into the bloodstream via multiple routes of administration including:
Once morphine reaches the bloodstream, it is carried to the liver where a large proportion of it is broken down, a process termed first-pass metabolism. Due to this first-pass metabolism, only around 40% to 50% of morphine reaches the central nervous system.
In the case of subcutaneous injection, blood levels of morphine peak after about 20 minutes and with oral ingestion, levels peak after about 30 minutes.
During metabolism, around 60% of morphine becomes morphine-3-glucuronide and 6% to 10% becomes morphine-6-glucuronide. The morphine is glucuronidated by the phase II metabolism enzyme UDP-glucuronosyl transferase-2B7. The drug may also be metabolized into small quantities of normorphine, codeine, and hydromorphone.
Around 90% of morphine taken is excreted from the body within 24 hours, mostly in the form of urine. Morphine has an elimination half-life of around 120 minutes. The drug can be stored in fat, so remains detectable for a long time after use and even after a person has died.