L2i / 18B13: Compare and contrast rocuronium and cisatracurium

18B13: Exam Report

Compare and contrast rocuronium and cisatracurium.

32% of candidates passed this question.

This question was best answered using a tabular format outlining class of drug, pharmaceutics, pharmacokinetics, reversibility and side effects. Better answers commented on the significance of the differences between the two agents and its relevance to ICU practice. Many candidates confused these muscle relaxants with each other and with depolarising muscle relaxants.

L2i / 18B13: Compare and contrast rocuronium and cisatracurium

Rocuronium

Cisatracurium

Comparisons

Chemical

Rocuronium

Aminosteroid non-depolarising neuromuscular blocker

Cisatracurium

Benzylisoquinolinium

Cis-cis isomer of atracurium

Comparisons

Use

Rocuronium

  1. RSI
  2. Skeletal muscle paralysis for mechanical ventilation

Cisatracurium

Paralysis

Comparisons

Rocuronium is used for RSI in ICU due to its favourable side effect profile cf SUX and also as it confers some paralysis post intubation

Cisatracurium cannot be used for RSI

Presentation

Rocuronium

Clear, colourless, 10mg/ml

Fridge 4C

Cisatracurium

Clear, colourless,

5mg/ml

Refridgerated

Comparisons

Both require refridgeration

Dose

Rocuronium

0.6mg/kg

1.2mg/kg RSI

Cisatracurium

0.15mg/kg

Comparisons

SUX has a more favourable dose calculation in an emergency

Route

Rocuronium

IV

Cisatracurium

IV

Comparisons

SUX can be given IM but the onset is slower and less predictable

Onset

Rocuronium

60 sec RSI

Cisatracurium

2 mins

Comparisons

Intubation

DoA

Rocuronium

Intermediate

Cisatracurium

Intermediate

Comparisons

SUX is used for intubation wherease Cis is used to maintain paralysis longterm

MoA

Rocuronium

Competitive antagonism of pre & post junctional nAChR

Prevents Ach binding receptors on motor end plate

Therefore prevents depolarisation

Cisatracurium

Post-junctional competitive inhibition nAChR

Relaxation requires

> 75% receptor occupancy

Comparisons

Different MoA

PD

Rocuronium

MSK: paralysis

CVS: mild vagolysis

Cisatracurium

Comparisons

PK

Rocuronium

A

IV

D

30% PPB

Vd 0.27L/kg

M

No metabolites

E

40% unchanged bile

35% unchanged urine

Cisatracurium

A

 

D

Small

Large MW

V polar

M

Hoffman degradation

E

Metabolites in urine & feces

t1/2b 30 mins

Comparisons

Cisatracurium has organ independent elimination making it attractive for muscle paralysis in ICU (but requires favourable pH conditions)

A/E

Rocuronium

Anaphylaxis

Cisatracurium

Hypotension, bradycardia

Bronchospasm

Anaphylactoid reactions

Critical illness myopathy (IV infusions)

Comparisons

Both have unwanted side effects, anaphylaxis is more common in Rocuronium probably due to its more common use