Buprenorphine

Chemical

Synthetic PARTIAL AGONIST opioid from the PHENANTHRENE OPIUM ALKALOID TUEBAINE

Use

Chronic pain

Presentation

Clear colourless solution 300mcg/mL

Patches 5, 10, 20mcg/hr

Dose

300 – 600mcg TDS (25 x more potent cf. morphine; 400mcg = 10mg morphine (IM doses))

Route

IV/IM/Epidural & topical

Onset

30 mins (this is for IM data – not sure about PATCH).  Recall Fentanyl patch takes 72hrs to work

DoA

8hrs

MoA

  • Partial µOP agonism
    • High affinity for µOP
    • Slow dissociation from receptors
    • ∴ prolonged DoA & resistance to Naloxone
  • NB: this means it could displace full agonists at certain doses & act as a competitive antagonist

PD

Similar to morphine:

  • Analgesia
  • Drowsiness
  • Resp depression
  • N&V

PK

A

Significant 1st pass metabolism oral admin

Bioav IM 40-90%

Bioav SL 44-94%

D

96%PPB

Vd 3.2L/kg

M

2/3 unchanged in bile → rest dealkylation in liver → inactive metabolites

E

inactive metabolites → urine

Adverse Effects

As a partial agonist it antagonizes effects of M & other opioid agonists, may precipitate abstinence syndromes in opioid dependant subjects

 

Respiratory depression may not be reversed even w large doses of Naloxone.  Severe resp depression when co-administered w midaz

 

  • Drowsiness
  • Dizzyness
  • Headache
  • Confusion
  • Dysphoria
  • N&V

NB less liable to produce dependence cf pure mu-agonists