Clonidine

Question 1

What is the trade name for clonidine?

Answer 1

Catapres

Question 2

What is the formal drug classification of clonidine?

Answer 2

partial central alpha-2 adrenergic agonist

Question 3

What are the clinical uses of Clonidine?

Answer 3

• 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

Question 4

What are the uses of clonidine for preanesthesia?

Answer 4

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

Question 5

What is the MOA for Clonidine?

Answer 5

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

Question 6

What is the MOA of Clonidine for analgesia purposes?

Answer 6

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

Question 7

How does Clonidine treat drug withdrawal symptoms?

Answer 7

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

Question 8

How does Clonidine stop shivering?

Answer 8

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

Question 9

What electrolyte channel dose Clonidine affect? Whats this cause?

Answer 9

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

Question 10

If given orally how is clonidine absorbed?

Answer 10

rapidly absorbed when given orally

Question 11

What is the onset of action of PO Clonidine?

Answer 11

0.5-1 hour PO

Question 12

When does Clonidine produce peak plasma concentrations when given PO?

Answer 12

60-90 minutes

Question 13

What is the DOA of PO Clonidine?

Answer 13

8 hours PO

Question 14

How is Clonidine metabolized and eliminated?

Answer 14

• 50% of the drug is metabolized in the liver

- 50% excreted unchanged in the urine

Question 15

What is the elimination 1/2 time of Clonidine?

Answer 15

9-12 hours

Question 16

What is the bioavailability of Clonidine?

Answer 16

75-95%

Question 17

What is the half-life of Clonidine?

Answer 17

12-24 hours

Question 18

What is the volume of distribution of Clonidine?

Answer 18

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

Question 19

Is clonidine protein bound?

Answer 19

20-40% protein bound

Question 20

What are the side effects of clonidine?

Answer 20

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

Question 21

What can happen with abrupt withdrawal of clonidine?

Answer 21

rebound hypertension

Question 22

What are the contraindications of Clonidine?

Answer 22

• 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

Question 23

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

Answer 23

Blunts the sympathetic nervous system activation

Question 24

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

Answer 24

Prolongs the effects of regional anesthesia

Question 25

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

Answer 25

TCAs Phenothiazines Butyrophenone

Question 26

What can happen when Clonidine is given with Fentanyl?

Answer 26

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

Question 27

What does clonidine do to anesthesia?

Answer 27

potentiates anesthetic effects of other volatile or injectable anesthetics

Question 28

What happens when clonidine and beta blockers are combined?

Answer 28

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

Question 29

What is the dosage of PO Clonidine?

Answer 29

0.2mg-0.3mg/day

Question 30

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

Answer 30

150-450mcg IV

Question 31

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

Answer 31

18 hours after discontinuation

Question 32

What are the symtpoms of rebound hypertension?

Answer 32

``` Flushing Headache Insomnia Flushing Sweating Apprehension Tremulous ```

Question 33

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

Answer 33

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

Question 34

Is clonidine Dialysis capable for excretion?

Answer 34

NO