BT_PM 1.16 Opioid dose conversion

Ok this is a bit of a weird one for the primary syllabus in my books. It could be asked in an MCQ but I don’t think it would be asked in a viva, because we all know it is virtually impossible to do mental arithmetic under pressure!

It is of practical consideration for us though and is something we do all the time, when managing patients in the post operative period.

There are various opioid conversion tables out there, including an app produced by the FPM. If you look the app, I would suggest that you look at the “practical considerations” in the information section (it is a bit hidden at the bottom of the Opioid Dose Equivalence  page)

I think this poor patient needs more of whichever opioid he has received…. Taken at the Legend of Hong Kong Toys exhibition. I hate to think what happens when you turn that toy on…..

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BT_PM 1.16 Outline the dose conversion between commonly used opioids

No change in tramadol dose is required when switching from oral to s/c dosing  TRUE/FALSE

Twice as much oral compared with intravenous morphine is required to produce the same analgesic effect   TRUE/FALSE

It is easy to calculate an equipotent dose of morphine for a patient taking methadone  TRUE/FALSE

When switching a patient between one opioid and another, equipotent doses of the two drugs tend to underestimate the amount of the new opioid that will be required  TRUE/FALSE

A buprenophine patch 20mcg/hr is equipotent to a 12.5mcg/hr fentanyl patch  TRUE/FALSE

Methoxyflurane

BT_PM 1.9

Describe the pharmacology of the following agents applicable to pain management, including:

  •   Opioids
  •   Tramadol
  •   Local anaesthetic agents (also refer to the Regional and local anaesthesia clinical fundamental)
  •   NSAIDs
  •   Paracetamol
  •   NMDA antagonists
  •   Anticonvulsants
  •   Antidepressants
  •   Corticosteroids
  •   Inhalational analgesics – nitrous oxide, methoxyflurane

Methoxyflurane has a risk of nephrotoxicity and hepatotoxicity TRUE/FALSE

Methoxyflurane can be used in paediatric practice TRUE/FALSE

Methoxyflurane is safe in patients with Malignant Hyperpyrexia. TRUE/FALSE

The “Penthrox” inhaler dispenses 2-4% methoxyflurane. TRUE/FALSE

A large proportion of the inhaled methoxyflurane that is taken up by the body is removed from the body by exhalation. TRUE/FALSE

2017.1 : SAQ 4

Outline the genetic variations in the cytochrome P450 2D6 enzyme and discuss the clinical relevance for drugs used in the perioperative period.

BT_GS 1.20

This enzyme is responsible for much of the variation in efficacy and toxicity of some commonly used drugs.

This enzyme metabolises tramadol into a more active metabolite   TRUE/FALSE

Ondansetron may be ineffective with poor metabolisers  TRUE/FALSE

Patients from the middle east are more likely to be ultrarapid metabolisers  TRUE/FALSE

Approximately 90% of caucasians are poor metabolisers  TRUE/FALSE

This enzyme metabolises codeine into a more active metabolite  TRUE/FALSE

 

BT_PM1.18

Sticking with neuraxial opioids…

Intrathecal fentanyl has fewer adverse effects than intrathecal morphine TRUE/FALSE

Intrathecal morphine produces better postoperative analgesia than intrathecal fentanyl after LSCS   TRUE/FALSE

Doses of intrathecal morphine greater than 50mcg have no greater benefits in terms of analgesia but carry a higher incidence of respiratory depression    TRUE/FALSE

100 mcg of morphine is 0.1ml of morphine 10mg/ml    TRUE/FALSE

extended-release epidural morphine is associated with less respiratory depression than IVPCA morphine    TRUE/FALSE

BT_PM1.18 : neuraxial opioids

This has been a popular topic in vivas (and the occasional SAQ) for ages. It’s an important and relevant topic that is not always well-covered in the basic texts.

BT_PM 1.18 Describe the pharmacology of opioids deposited in the epidural space or cerebrospinal fluid

With regard to epidural fentanyl (1 mcg.kg-1)

plasma concentrations of fentanyl are similar to the same dose given intramuscularly TRUE/FALSE

the duration of analgesia is 1 hour TRUE/FALSE

the CSF concentrations of fentanyl are maximal at 50 minutes  TRUE/FALSE

the incidence of pruritis is greater than following an equi-analgesic dose of epidural morphine  TRUE/FALSE

the onset of analgesia is around 2-5 minutes because fentanyl is highly lipid soluble  TRUE/FALSE

BT_PM 1.15 : Routes of opioid administration

It’s such fun being able to use so many different routes to administer drugs in our jobs. So many doctors out there don’t get our opportunities.

BT_PM 1.15  Discuss the pharmacokinetic and clinical implications of different routes of administration for commonly used opioids, including the oral, transdermal, subcutaneous, intramuscular and intravenous routes, and with particular reference to fentanyl, morphine, methadone, tramadol and codeine

Fentanyl undergoes significant first pass pulmonary uptake and metabolism.  TRUE/FALSE

The cytochrome P450 3A4 (CYP3A4) is predominantly responsible for the metabolism of Alfentanil.   TRUE/FALSE

Alfentanil undergoes extensive hepatic metabolism that demonstrates extensive interindividual variability   TRUE/FALSE

The bioavailability of sublingual buprenorphine is similar to that of parenteral buprenorphine   TRUE/FALSE

Epidural fentanyl undergoes a biphasic absorption pattern   TRUE/FALSE

 

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