- Antihypertensive:
- Clonidine
(Catapres) acts in the brain, inhibiting
adrenergic outflow from the brainstem.
Inhibition of sympathetic outflow results
in a decrease in blood pressure.
- Mechanism
of action: centrally acting selective a2
adrenergic agonist.
- Especially effective in
- management of
severe hypertension or
- in renin-dependent
hypertension
- Transdermal clonidine
(Catapres) patch: useful for surgical
patients unable to take oral formulation
- Clonidine (Catapres) reduces
cardiac output (by reducing both stroke
volume and heart rate) and peripheral
resistance.
- Reduction in stoke volume
occurs due to increased venous pooling
(decreased preload).
- Clonidine (Catapres) does
not interfere with cardiovascular
responses to exercise.
- Renal blood flow and function
is maintained during clonidine treatment.
- Clonidine (Catapres) has
minimal or no effect on plasma lipids.
Other Clinical Uses
- Analgesia--
- Preservative-free clonidine
administered into epidural/subarachnoid
space (150-450 micrograms)--
dose-dependent analgesia
- No respiratory depression,
nausea, vomiting, delayed gastric
emptying or pruritus -- effects
associated with opioids
- Probable Mechanism:
activation postsynaptic a2 receptors
in the spinal cord substantia gelatinosa
- Clonidine
(Catapres) & morphine: no
cross-tolerance when used
concurrently in neuraxial
analgesia
- Side effects of neuraxial
clonidine (Catapres)
- hypotension, sedation, dry mouth
- Preanesthetic Medication:
- Oral clonidine (Catapres) (preanesthetic medication):
- Enhances
intrathecal morphine + tetracaine
(pontocaine) for postoperative
analgesia (no increase in
morphine-related side effects)
- Preanesthetic
clonidine (Catapres) also:
- Reduces
reflex tachycardia that
may be caused by direct
laryngoscopy for tracheal
intubation
- Reduces
intraoperative
blood-pressure heart rate
lability
- Reduces
plasma catecholamines
levels
- Significantly
decreases anesthetic
requirements for inhaled
(MAC) and injected
agents.
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