Question 5(p.2)

List the potential clinical uses of an alpha 2 adrenoceptor agonist. Outline the limitations of clonidine for each use.

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College Answer

Producing a list that included the following was required:
To treat hypertension and substance withdrawal.
To provide anxiolysis, sedation, analgesia, and sympatholysis.
A brief discussion of the abilities of clonidine in each of these areas would have rounded off
a good answer.
Many candidates listed only a couple of uses of these agents, and then followed this with a
comparison of clonidine and dexmedetomidine. Most answers did not include sufficient
information to achieve a pass mark.

Discussion

Where something is asked, and then something is again asked "for each", one could easily offer an answer in the form of a table. Thus:

Uses Limitations
Sedation
  • Too long acting for procedural sedation
  • Too slow in onset
Analgesia
  • Too sedating for routine use, in addition to the side effects listed below
ADHD
  • Prohibitive side effects:
    • Dry mouth
    • Dry eyes
    • Slowed gastric emptying
    • Slowed peristalsis, constipation
    • Erectile dysfunction
    • Miosis
Hypertension
  • Too short acting to be convenient for outpatient use (qid dosing)
  • Rebound phenomenon on withdrawal
  • Causes bradycardia, which may not be desirable
Vasoconstriction
  • Like other α2 agonists, eg. oxymetazoline and zylometazoline, clonidine can act as a regional vasoconstrictor, but it penetrates the CNS and has an undesirable sedating effect
Clonidine suppression test
  • An obsolete test for phaeochromocytoma

References

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