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