Compare and contrast dexmedetomidine and ketamine
The majority of candidates were able to describe the mechanism of action, uses, dose and
some side effects of each drug. The better answers were in a table format. It is of course
possible to include much of the relevant information without using a table; however without
the visual prompt of a table it makes it likely sections will be omitted.
When comparing two drugs it would be useful to note that though they both provide sedation
with analgesia they are used in different circumstances. In ICU, dexmedetomidine is mainly
used for sedation peri-extubation and may be continued post-extubation but this was not
The pharmacodynamic effects often omitted the cardiovascular and respiratory effects of
ketamine (particularly bronchodilation).
The pharmacokinetic information required was not detailed but only minimal marks can be
awarded for ‘administered IV with 100% bioavailability, liver metabolism and renal excretion’
which was a common answer. Noting dexmedetomidine is metabolised to inactive
metabolites and ketamine is metabolised to norketamine gained marks, specific pathways
were not required. Both drugs are licenced for administration intravenously (and ketamine
may be administered IM); however other routes of administration are emerging in clinical
practice for both drugs.