Remifentanil

Question 1

What class of opioid is Remifentanil

Answer 1

Synthetic phenylpiperidine derivative

Question 2

Outline the pharmaceutical aspects

Answer 2

Presented as a white crystalline powder containing glycine (must not be used intrathecally)
1mg, 2mg and 5mg vials
Commonly reconstituted to 50mcg/mL
Once reconstituted will remain stable at room temp for 24hrs

Question 3

What is the pKa

Answer 3

7.3

Question 4

What percentage is unionised at pH 7.4

Answer 4

58%

Question 5

How much is protein bound

Answer 5

70%

Question 6

What is the volume of distribution

Answer 6

0.4L/kg

Question 7

What is the morphine analgesic equivalence

Answer 7

100x more potent (similar to Fentanyl)

100mcg Remifentanil = 10mg Morphine

Question 8

Outline the metabolism and how this relates to its structure

Answer 8

Remifentanil contains an ester linkage that is susceptible to hydrloysis by non-specific plasma and tissue esterases
Carboxylic acid metabolite (clinically inactive)
Renal excretion

Question 9

What is the elimination half time

Answer 9

10mins

Question 10

What are the unique features of Remifentanil

Answer 10

Pure mu receptor agonist
Ester linkage - rapid metabolism causing precise and titratable effect
Non-cumulative (short context sensitive half time)

Question 11

What are the major side effects

Answer 11

Bradycardia
Hypotension
Muscle rigidity
Hyperalgesia post prolonged infusion

Question 12

What is the dose of Remifentanil

Answer 12

Induction - 0.5-1mcg/kg bolus

Maintenance of anaesthesia with volatile or IV agent - 0.05-2mcg/kg/min