Pholcodine is an opioid anti-tussive (ie. cough suppressant). It is a common component of over-the-counter cough medications. However it has a special significant to anesthesiologists in relation to anaphylaxis risk, particularly related to neuromuscular agents.
Florvaag et al's 2009 review covers this issue very comprehensively. Earlier 2006 research from Florvaag et al attempting to explain some of the regional variability in anaphylaxis rates showed that exposure to pholcodine causes an 60-105 times increase in IgE levels!
Countries where pholcodine use is common (eg Norway) seem to have experienced higher levels of anaphylaxis to neuromuscular blocking agents than countries where it is not common (eg Sweden). In fact, in Norway rocuronium anaphylaxis was such a problem that its use was restricted to modified rapid sequence inductions. A pholcodine containing cough syrup has been withdrawn from the market in Norway because of this (and levels of sensitisation seem to be dropping although it is still too early to draw conclusions). It will be interesting to see if there are other compounds that have a similar effect on IgE sensitisation and whether other countries will consider withdrawing pholcodine products.
In addition to the two articles from Florvaag that specifically look at Pholcodine and it's effects, there is also an interesting review looking at recent insights into anaphylaxis in the anaesthetic setting from Dewachter and team.summary
...and 1 more note
First described in 1909, and then used for treatment of various types of headache and facial pain, the sphenopalatine ganglion block may offer a novel, simple and less-invasive treatment for post-dural puncture headache.
Very little has been published, primarily case studies, case series and retrospective audits. This limited data does however suggest that the technique may be as effective as the traditional epidural blood patch, though with significantly fewer risks.
Larger studies are however needed to properly define the block's role in treating PDPH.
Publications describe a trans-nasal approach, either sitting or supine. First topicalising with co-phenylcaine spray, then placing 2%-4% viscous lignocaine-soaked cotton-tipped applicators for 10 minutes, and finally repeated for a further 20 minutes. Success appears to range from 30-70%.
The mechanism of action may result from parasympathetic blockade at the SPG, resulting in reversal of the cerebral vasodilation thought to be associated with post dural puncture headache.
Several videos showing how simple SPG techniques:
- Roger Browning demonstrating one method for performing a topical SPG block.
- SPG Block for chronic migraine.
- SPG demonstration in the ED setting.
- SPG demonstration for family member to perform later at home.
Oxycodone is a semi-synthetic opioid commonly used as an oral, rectal or intravenous analgesic (subcutaneous, intramuscular & intranasal also possible). Trade names include Endone™, OxyContin™ and OxyNorm™.
- Semi-synthetic opioid; thebaine derivative. First synthesised in 1916.
- Oxycodone po conversion from morphine IV 2:1 (oxycodone:morph).
- (NB: oral to IV morphine 3:1)
- 10 mg of oral oxycodone is equivalent to 20 mg of oral morphine.
- 10 mg of oral oxycodone is equivalent to 5 mg of IV/IM morphine.
- 10-15 mg of parenteral oxycodone (IV/IM) is equivalent to 10-15 mg parenteral morphine (ie. morphine up to 50% more potent)
- Absorption - orally up to 87%
- Distribution - 2.6 L/kg
- Protein binding
- Onset - within 10-15 min orally, peak 45-60 minutes; Offset ~2-3h.
- Metabolism - ß1/2 ~3-4hrs, metabolised principally to noroxycodone, noroxymorphone and oxymorphone (p450 system). Oxymorphone has some activity
- Clearance - 0.8 L/min; predominately renally excreted.
- Oxycodone is a full opioid agonist with no antagonist properties whose principal therapeutic action is analgesia.
- It has affinity for kappa, mu and delta opiate receptors in the brain and spinal cord.
- Oxycodone is similar to morphine in its action. Other pharmacological actions of oxycodone are in the central nervous system (respiratory depression, antitussive, anxiolytic, sedative and miosis), smooth muscle (constipation, reduction in gastric, biliary and pancreatic secretions, spasm of sphincter of Oddi and transient elevations in serum amylase) and cardiovascular system (release of histamine and/or peripheral vasodilation, possibly causing pruritus, flushing, red eyes, sweating and/or orthostatic hypotension).
- Strong potentially for tolerance, dependence and abuse.