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Flashcards in Clonidine Deck (34):
1

What is the trade name for clonidine?

Catapres

2

What is the formal drug classification of clonidine?

partial central alpha-2 adrenergic agonist

3

What are the clinical uses of Clonidine?

-hypertension
-drug withdrawal symptoms
-analgesia in acute and chronic pain states (use limited due the adverse effects of postural hypotension and sedation)
-Preanesthetic drug
-used to decrease myocardial ischemia, infarction, and mortality following CV surgery
-used in diagnosis of pheochromocytoma
-controls shivering
-used as a neuroaxial analgesic, which prolongs the anesthesia effect when mixed with local anesthetics

4

What are the uses of clonidine for preanesthesia?

1) Blunts the SNS response to direct laryngoscopy for intubation
2) Decreases intraoperative lability of blood pressure and heart rate
3) Decreases plasma catecholamine concentrations
4) Dramatically decreases anesthetic requirements for inhaled and injected drugs

5

What is the MOA for Clonidine?

Selectively avtivates alpha-2 adrenergic receptors and thereby inhibits sympathetic outflow from the medulla, which then causes a decrease in heart rate, contractility, and vasomotor tone

6

What is the MOA of Clonidine for analgesia purposes?

the alpha-2 adrenergic receptors found in the dorsal horn of the spinal cord produces an anti-nocioceptive state by inhibiting the release of spinal substance P and nocioceptive neuron firing produced by painful stimuli

7

How does Clonidine treat drug withdrawal symptoms?

by blocking the sympathetic hyperactivity and to a certain extent the GI hyperactivity seen in withdrawal
The alpha-2 receptors inhibit the stimulation of noradrenergic neurons in the brain and cholinergic neurons in the gut associated with opioid withdrawal, and alpha-2 agonists partially block opioid withdrawal symptoms

8

How does Clonidine stop shivering?

Alpha2B receptors stop shivering by inhibiting central thermoregulatory control, which decrease the vasoconstriction and shivering thresholds

9

What electrolyte channel dose Clonidine affect? Whats this cause?

Affects the function of the potassium channel in the CNS, making the cell hyperpolarized, which leads to the decrease anesthetic requirement

10

If given orally how is clonidine absorbed?

rapidly absorbed when given orally

11

What is the onset of action of PO Clonidine?

0.5-1 hour PO

12

When does Clonidine produce peak plasma concentrations when given PO?

60-90 minutes

13

What is the DOA of PO Clonidine?

8 hours PO

14

How is Clonidine metabolized and eliminated?

-50% of the drug is metabolized in the liver
-50% excreted unchanged in the urine

15

What is the elimination 1/2 time of Clonidine?

9-12 hours

16

What is the bioavailability of Clonidine?

75-95%

17

What is the half-life of Clonidine?

12-24 hours

18

What is the volume of distribution of Clonidine?

Adults 2.1L/kg; highly lipid soluble; distributes readily into extra-vascular sites

19

Is clonidine protein bound?

20-40% protein bound

20

What are the side effects of clonidine?

-bradycardia
-heart failure
-hepatotoxicity
-dry mouth
-sedation
-postural hypotension
-skin rashes
-impotence
-rebound hypertension with abrupt withdrawal of clonidine
-sodium and water retention

21

What can happen with abrupt withdrawal of clonidine?

rebound hypertension

22

What are the contraindications of Clonidine?

-Holding clonidine prior to surgery is not recommended
-contraindicated in pregnant women and nursing mothers, excreted in breast milk
-Hypersensitivity to clonidine or any component of formulation

23

What are the drug interactions with Clonidine with Desflurane or Ketamine?

Blunts the sympathetic nervous system activation

24

What happens to regional anesthesia when Clonidine is combined with a solution containing Tetracaine or Bupivacaine?

Prolongs the effects of regional anesthesia

25

What 3 drugs can exacerbate rebound hypertension when clonidine is abruptly withheld?

TCAs
Phenothiazines
Butyrophenone

26

What can happen when Clonidine is given with Fentanyl?

Increased risk of respiratory depression due to accumulation of fentanyl can occur when clonidine and fentanyl are simultaneously given IV

27

What does clonidine do to anesthesia?

potentiates anesthetic effects of other volatile or injectable anesthetics

28

What happens when clonidine and beta blockers are combined?

Non selective beta blockers may increase the symptoms of rebound hypertension when used to treat patients with abrupt discontinuation of clonidine
-these effects of non selective beta blockers are due to the unopposed alpha vasoconstriction factors

29

What is the dosage of PO Clonidine?

0.2mg-0.3mg/day

30

What is the Epidural/ subarachnoid space dosage of clonidine for analgesia?

150-450mcg IV

31

When do symptoms of rebound hypertension occur with abrupt termination of clonidine?

18 hours after discontinuation

32

What are the symtpoms of rebound hypertension?

Flushing
Headache
Insomnia
Flushing
Sweating
Apprehension
Tremulous

33

How long do the symptoms of rebound hypertension last? and what is the dose usually associated with this?

24-72 hours and usually occurs with patients taking more than 1.2mg/day

34

Is clonidine Dialysis capable for excretion?

NO