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Pharmacology TL > Exam 2: Analgesics Alpha 2 Agonists > Flashcards

Exam 2: Analgesics Alpha 2 Agonists Flashcards

1
Q

When was Clonidine first developed? What as?

A

Clonidine was first developed in the 1970s as a nasal decongestant.

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2
Q

What properties does Clonidine have?

A

Clonidine has potent sympatholytic properties, but its use is somewhat limited due to sedation.

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3
Q

What significant drug was developed in the 1990s?

A

Medetomidine was developed in the 1990s.

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4
Q

What is the active enantiomer of Medetomidine?

A

The active enantiomer of Medetomidine is Dexmedetomidine.

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5
Q

How is Dexmedetomidine used in clinical practice?

A

Dexmedetomidine is a great adjunct but is not effective as a single agent; it was developed as a perioperative sedative/analgesic.

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6
Q

What is the mechanism of action for Dexmedetomidine?

A

Dexmedetomidine activates alpha2 receptors.

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7
Q

What should not be used with Dexmedetomidine and why?

A

Dopamine, norepinephrine, and epinephrine should not be used because they would worsen heart rate and blood pressure.

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8
Q

What alternatives does Dave prefer for managing low heart rate and blood pressure from precedex?

A

Dave prefers IV fluids, ephedrine, phenylephrine, and dobutamine.

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9
Q

What are the effects of Alpha2a subtype?

A

Sedation, hypnosis, analgesia, sympatholysis

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10
Q

What are the effects of Alpha2b subtype?

A

Mediates vasoconstriction, antishivering action, analgesia

Kappa receptor Activated

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11
Q

Which drugs have antishivering effects?

A

Demerol (Meperidine), Staydol (butorphanol), Precedex

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12
Q

What is the role of Alpha2c subtype?

A

Learning and startle response

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13
Q

What is the site of analgesia for Alpha 2 agonists?

A

Analgesia occurs at the spinal cord level (dorsal horn).

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14
Q

What is the mechanism of sedation caused by Alpha 2 agonists?

A

Sedation is linked to inactivation of the locus ceruleus (sleep center).

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15
Q

What are the primary hemodynamic effects of Alpha 2 agonists?

A

The primary hemodynamic effects are hypotension and bradycardia.

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16
Q

Where are the hemodynamic effects of Alpha 2 agonists mediated?

A

They are mediated at the vasomotor center of the brainstem and the nucleus tractus solitarius.

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17
Q

What medications can reverse hypotension caused by Alpha 2 agonists?

A

Hypotension responds to ephedrine, phenylephrine, and dobutamine.

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18
Q

Which medications show less reversal of hypotension from Alpha 2 agonists?

A

Less reversal is seen with norepinephrine and dopamine.

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19
Q

What occurs with peripheral stimulation of alpha2b receptors?

A

It causes a transient hypertension after rapid IV bolus.

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20
Q

What are the chemical categories of Alpha2 Adrenergic Agonists?

A

Phenylethylates, Imidazolines, oxaloazepines

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21
Q

Name an example of Phenylethylates.

A

Methyldopa, quanabenz

These are specific drugs within the Phenylethylates category of Alpha2 Adrenergic Agonists

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22
Q

Name an example of Imidazolines.

A

Clonidine, dexmedetomidine

These are specific drugs within the Imidazolines category of Alpha2 Adrenergic Agonists

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23
Q

What is the potency of Clonidine at alpha2 compared to alpha1?

A

Clonidine is 200 times more potent at alpha2 than alpha1.

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24
Q

How lipid soluble is Clonidine?

A

Clonidine is moderately lipid soluble.

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25
What is the absorption rate of Clonidine after oral administration?
Clonidine has complete absorption after oral administration.
26
What is the onset of action for Clonidine when administered intravenously?
The onset of action for intravenous Clonidine is 60-90 minutes.
27
What is the onset of action for Clonidine when administered epidurally?
The onset of action for epidural Clonidine is 15-20 minutes.
28
What is the elimination half-life of Clonidine?
The elimination half-life of Clonidine is 12-24 hours.
29
What is Dexmedetomidine's alpha2 activity compared to clonidine?
Dexmedetomidine has 8x greater alpha2 activity than clonidine.
30
What is the distribution half-life of Dexmedetomidine?
The distribution half-life of Dexmedetomidine is 6 minutes.
31
What is the elimination half-life of Dexmedetomidine?
The elimination half-life of Dexmedetomidine is 2 hours.
32
To what substances is Dexmedetomidine highly bound?
Dexmedetomidine is highly bound to albumin and alpha1 glycoprotein.
33
How does Dexmedetomidine undergo metabolism?
Dexmedetomidine undergoes extensive liver metabolism and is a weak cytochrome P450 inhibitor.
34
What is the significance of redistribution in Dexmedetomidine?
Redistribution makes the effects of Dexmedetomidine short.
35
How are the metabolites of Dexmedetomidine excreted?
Methyl and glucuronide conjugates of Dexmedetomidine are excreted via the kidneys.
36
Special populations who may show increased benefit with Alpha2 Adrenergic Agonists
– Drug addicts and alcoholics (increased sympathetic tone) – Chronic cancer/non-cancer pain (require large doses of opioids) – Hypertension – Procedures where hypotension advantageous – Ophthalmic surgery (lowers IOP) – Adjuvant to ketamine (prevents post-op delirium)
37
How do Clonidine & dexmedetomidine affect anesthetic requirements?
Clonidine can decrease the amount of anesthetics required by 20-40%, while dexmedetomidine may decrease it by up to 50%.
38
What is the sedation effect of Dexmedetomidine?
Calm and relaxed, able to breathe, but easily arousable. It can be used post extubation without causing respiratory depression.
39
What is the role of Alpha2 Adrenergic Agonists in drug withdrawal syndrome?
Prevention of drug withdrawal syndrome.
40
How do Alpha2 Adrenergic Agonists contribute to hemodynamic stability?
They blunt the release of catecholamines.
41
What is the effect of Alpha2 Adrenergic Agonists when used intrathecally? Drawbacks?
Less vasoconstriction than epinephrine, decreased cardiac output decreases clearance of local anesthetic, increased quality and duration of block, but may cause hypotension. ## Footnote No more than 1 mcg/kg when co-administered with a local anesthetic.
42
What is the dosage of Alpha2 Adrenergic Agonists for epidural use? What are the effects?
1-4 mcg/kg ## Footnote Increases quality of block, prolongs analgesia, prevents shivering, and causes less hypotension.
43
Alpha2 Adrenergic Agonists Clinical Effects
– Analgesia—more prominent after spinal or epidural administration than intravenous – Sedation—mimics normal sleep; deeply sedated, but can rouse themselves to all most full consciousness – Hypotension/bradycardia – Anti-shivering properties – Mild ventilatory depression
44
Uses for Alpha2 Adrenergic Agonists
- Pre-op medication for sedation/anxiolysis/amnesia – Anesthetic sparing - Sedation - prevention of drug withdrawal syndrome - hemodynamic stability - Enhancement of local anesthetic block -postop analgesia -Analgesia for labor -chronic pain -prevention/tx of shivering
45
How do Alpha-2 adrenergic agonists function as pre-operative medications, and what are their benefits and limitations in anesthesia management?
• Special populations who may show increased benefit • May decrease dose of anesthetics/analgesics required intra-op • Blunts sympathetic response to intubation/induction • Can cause xerostomia and decreased GI transit • May cause prolonged anesthesia and delayed emergence • Use is limited by hypotension and bradycardia
46
How do Alpha-2 adrenergic agonists enhance caudal anesthesia, and what is their optimal dosing range?
– 0.75-3 mcg/kg – Increased duration of anesthesia/analgesia
47
How do Alpha-2 adrenergic agonists enhance peripheral nerve blocks, and what are their effects on different block techniques?
– Adjuvant for brachial plexus block; duration of analgesia/anesthesia increased up to 24 hours. – Bier, retrobulbar, and intra-articular blocks also employed
48
How is Alpha2 Adrenergic Agonists Post operative analgesia given?
• Epidural infusion typically
49
What is the typical dose of epidural analgesia for labor?
10-15 mcg epidural
50
What is a benefit of using epidural analgesia during labor?
Decreased shivering
51
What are some potential side effects of epidural analgesia?
Hypotension, bradycardia, crosses placenta, and can depress fetal heart rate
52
What is the recommended limit for the dose of epidural analgesia?
The dose should be limited to 1 mcg/kg
53
What kind of pain are alpha2 agonists used to treat ?
They are used for neuropathic pain and sharp/shooting pain.
54
What is a treatment for neuropathic pain?
Combination epidural lidocaine/clonidine.
55
What is a treatment for sharp or shooting pain?
Transdermal patch.
56
What are Alpha2 agonists used for in cancer patients?
Alpha2 agonists are used for cancer pain management.
57
How are Alpha2 agonists administered for cancer pain?
They are administered via epidural continuous infusion.
58
What line of treatment of Alpha2 agonists in cancer pain management?
They serve as a second line treatment as an opioid sparing agent.
59
Who utilized cocaine as a local anesthetic?
Carl Koller and Sigmund Freud ## Footnote They used it for tongue numbing and corneal anesthesia.
60
What are the significant drawbacks of cocaine?
Significant toxicity, short duration, high cost, and addiction.
61
What is differential nerve block?
Blockade of sensory information via sodium channels. Limited blockade occurs at potassium and calcium channels.
62
What is the structure of local anesthetics?
Local anesthetics have a lipophilic substituted benzene ring linked to a hydrophilic amine group (tertiary or quaternary) through either an ester or amide linkage.
63
Amides Local Anesthetics group
• Lidocaine • Prilocaine • Mepivicaine • Ropivicaine • Bupivicaine • Levobupivicaine • etidocaine **Footnote HAS TWO + “I”
64
What happens to lipophilic amides?
Lipophilic amides sit on the brain.
65
What happens to hydrophilic amides?
Hydrophilic amides sit in the plasma.
66
Esters Local Anesthetics group
• Cocaine • Procaine • 2-chloroprocaine • Tetracaine • Benzocaine **Footnote HAS ONE “I” & Super Shorter
67
What kind of bases are local anesthetics?
Local anesthetics are weak bases.
68
What is the form of local anesthetics?
They exist in a lipid soluble neutral form in equilibrium with a hydrophilic charged form.
69
What is pKa in the context of local anesthetics?
pKa (dissociation constant) is the pH at which the two forms occur equally.
70
How does pKa affect the onset of local anesthetics?
Lower pKa agents have a more rapid onset.
71
What effect does increased lipophilicity have on local anesthetics?
Increased lipophilicity slows the rate of onset and prolongs the duration of action.
72
How does increased protein binding affect local anesthetics?
Increased protein binding increases the duration of action.
73
What are the exceptions among local anesthetics racemic mixtures?
Lidocaine, ropivacaine, and levobupivacaine are exceptions.
74
What type of enantiomers are ropivacaine and levobupivacaine?
Ropivacaine and levobupivacaine are S-enantiomers.
75
What properties do ropivacaine and levobupivacaine have?
They have vasoconstrictive properties which increase their duration.
76
What is the relationship between R-enantiomers and local anesthetics?
R-enantiomers have greater efficacy but greater systemic toxicity.
77
What is tachyphylaxis in the context of local anesthetics?
Tachyphylaxis (tolerance) does not occur if re-dosing occurs before pain occurs. **Footnote If they can feel pain; your block is gone Tachyphylaxis refers to a reduced response to a drug after repeated doses, meaning it becomes less effective over time. In the case of local anesthetics: • If you re-dose before the patient starts feeling pain, the block is maintained, and the nerve fibers stay desensitized. • But if you wait until the pain returns, the body can become more reactive, and subsequent doses may not be as effective—this is tachyphylaxis in action. So the key point is: timing matters. Re-dosing proactively, before pain returns, helps maintain analgesia and prevents tachyphylaxis. This principle is especially important in continuous or repeat dosing during surgeries or for labor analgesia.
78
What technique can increase local anesthetic activity?
Epinephrine can prolong the local anesthetic block and decrease systemic absorption.
79
How does epinephrine affect local anesthetic clearance?
Epinephrine causes vasoconstriction, which slows clearance from the injection site.
80
What is the typical concentration of epinephrine used with local anesthetics?
Typically 1:200,000.
81
What technique can shorten the onset to blockade for local anesthetics?
Alkalinization can shorten the onset to blockade.
82
What is the pH range of commercial local anesthetic solutions?
The pH of commercial solutions is 3.9-6.47 (lower with epi).
83
What is the pKa range of local anesthetic agents?
The pKa of agents is 7.6-8.9.
84
What percentage of local anesthetic agents is in lipid soluble, neutral form?
Less than 3% is in lipid soluble, neutral form.
85
How much sodium bicarbonate should be added to lidocaine to hasten blockade?
1 ml of sodium bicarbonate per 10 ml of lidocaine will hasten blockade by 3-5 minutes.
86
What is the effect of opioids when given neuraxially with local anesthetics? Except for?
Opioids provide synergistic analgesia with local anesthetics when given neuraxially, except for 2-chlorprocaine.
87
What are two methods of administering local anesthetic/opioid combinations?
Intra-articular and infiltration administration.
88
What type of agonists can be used with local anesthetics?
Alpha2 agonists can be used with local anesthetics.

Pharmacology TL (7 decks)

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