Oxycodone
Chemical
Semi-synthetic opium alkaloid derivative
Use
Analgesia
Presentation
PO → immediate & controlled release
→ 5/10/20mg tablets/capsules
IV → 10mg/mL
Dose
(IV) 2.5 – 5mg
(PO) 5 – 10mg
NB: PO oxycodone 10mg = PO morphine 20mg
PO oxycodone 10mg = IV oxycodone 5mg
ORAL bioavailability is high ~70% of IV dose
Recall M OBA is 30% due to high 1st pass metabolism
∴ oral endone is more potent than oral morphine
Onset
Peak Plasma
IR – 1.5hrs
CR – 3hrs
Offset
IR – 3hrs
CR – 4.5hrs
MoA
µOP, kOP, δOP agonist
PD
CNS – analgesia, miosis
CVS – ↓BP 2° histamine
GI – N&V, constipation
GU – ↑smooth m. tone → urinary retention
MSK – pruritus
PK
A
Good OBA 70%
pKa 8.5
= 10% UNIONISED
D
VD 2.6L/kg
Crosses placenta + breast milk
Low lipid solubility
M
Hepatic
- CYP3A4 (74%) → noroxycodone
- CYP2D6 (<3%) → oxymorphine
E
Renally excreted metabolites
20% unchanged
NB: oxymorphine is v potent
CYP2D6 has 2 phenotypes
- Extensive metabolites → ↑dose
- Poor metabolisers → ↓dose
Needs to be given with caution in hepatic & renal impairment
Although metabolites have less adverse effects cf. M
Adverse Effects
Resp D
Hypotension
N&V
Hallucinations
Dependence
Drug Interactions
Incompatible with prochlorperazine