2017.1 : SAQ 3

Propofol and remifentanil target controlled infusions are often given together as a total intravenous anaesthesia technique. Discuss pharmacological reasons why this is a useful combination.

BT_GS 1.59    BT_GS 1.53    BT_GS 1.41

A practical pharmacology question on a common drug combination. Before setting out to write a model answer try asking yourself first what are the clinical reasons you use this combination.

There are significant pharmacokinetic interactions between these drugs  TRUE/FALSE

There are significant pharmacodynamic interactions between these drugs  TRUE/FALSE

Both drugs have a rapid offset  TRUE/FALSE

Adding remifentanil to propofol can lead to more stable haemodynamics  TRUE/FALSE

Can be used in patients susceptible to malignant hyperthermia  TRUE/FALSE




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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BT_RA 1.16 Neuraxial Opiates

Candidates are often a bit vague on neuraxial opiates in the vivas. These are used very commonly in clinical practice, so it is unwise to overlook this topic.

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

BT_RA 1.16 Describe the drugs which may be injected into the intrathecal or epidural space as adjuvant agents to a central neuraxial block and discuss their risks and benefits

TRUE/FALSE The analgaesic effect from continuous epidural infusion of hydroPHILIC opioids is primarily from systemic absorption

TRUE/FALSE Intrathecal morphine provides analgaesia to more spinal levels than intrathecal fentanyl

TRUE/FALSE Significant amounts of epidural morphine are sequestered in epidural fat

TRUE/FALSE Epidural infusion of fentanyl may lead to systemic concentrations high enough to produce pharmacological effects

TRUE/FALSE The peak period for respiratory depression with intrathecal morphine is from 18-24 hours after injection