A potent opioid analgesic.
The "gold standard" of pain relief.
High potential for tolerance and addiction.
Mimics natural 'pain relief' chemicals - endorphins and cephalins
Blocks calcium and potassium flux via GPCRs and protein kinase cascade.
Binds very strongly.
Blocks peristalsis - therefore anti-diarrhoea
Can be taken orally, rectally, subcutaneously, intravenously, intrathecally or epidurally.
Extensive first-pass metabolism by liver (only 40 - 50 % of an oral dose reaches CNS).
Elimination half-life 120 mins.