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Pharmacology 1 > Opioid analgesics > Flashcards

Opioid analgesics Flashcards

1
Q
  • The different Opoid receptors:
A
  • µ–opioid receptor (MOR) = morphine
  • κ-opioid receptor (KOR)
  • δ-opioid receptor (DOR)
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2
Q

Mechanism of effect og µ-opioid receptor:

A

Morphine receptor

  • Specific, strong analgesic effect (brain, sc, periphery)
  • slight sedation
  • brainstem –> inhibits impulses of the respiratory centers (pCO2 sensitivity decrease) -> respiratory depression
  • antitussive
  • brainstem vasomotor center -> bradycardia
  • Plexus myentericus -> obstipation
  • Medulla oblongata CTZ -> emesis
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3
Q

Mechanism of effect of: κ-opioid receptor (KOR)

A
  • slight analgesic effect (spinal cord)
  • slight sedation
  • dysphoria
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4
Q

mechansim of effect of: δ-opioid receptor (DOR)

A
  • Analgesia
  • most important in the eye

–> only if damaged (1%morphine)

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5
Q

Give examples for Full agonist, Partial agonist and Antagonist

A
  • Full agonist: eg. morphine, fentanyl, methadone on µ-receptors
  • Full antagonist: eg. naloxone on both mahor receptors
  • Partial agonist: eg. buprenorphine on µ-receptors
  • Agonist-antagonist: eg butorphanol = agonist on κ-receptors, antagonist on µ-receptors
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6
Q

Pharmacokinetics of Opioids:

A

Absorption: Good - excellent

  • per os: first pass metabolism (heroin, morphine, buprenorphine)
  • fentanyl: very lipophilic, skin

Distribution:

  • maximum effect: 15-45 min morphine (IV, IM, SC)
  • 2-3min fentanyl
  • 45min buprenorphine

Metabolism:

  • frequent activation (liver):

–> Morphine = morphine-glucuronide (Fe!)

–> Tramadol = O-desmethyltramadol (Fe!)

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7
Q

Side effects of Opioids:

A

Respiratory depression:

  • full agonist >> partial agonist
  • buprenorphine “ceiling effect”

Emesis: CTZ

  • (Apomorphine) >> morphine, codeine > fentanyl >> buprenorfin, tramadol ACP

Bradycardia: But, CV risk patients!

  • No hypotension
  • Cats: stronger sympathetic tone –> not pronounced (first choice in CV patients)

Obstipation:

  • inhibition of plexus myentericus
  • decreased pancreas secretion (u), Pancreatitis: buprenorphine
  • Therapeutic: loperamide - not penetrating to the CNS

Histamine release:

  • morphine >> fentanyl
  • IV: carefully (Infusion, ACP)

Hyperthermia

Excitation, dysphoria: cats

  • ACP, BDZ
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8
Q

Morphine:

A
  • intermediate duration of action (2-6hr)
  • sedation, respiratory depression, bradycardia, emesis
  • IV slowly! (H), IM 100% bioavailability
  • 0.1-0.8 mg/kg IM -> at least 4 h post op. analgesia.
  • TI= 460
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9
Q

Fentanyl:

A
  • short duration of action (15-30 min)
  • sedation, respiratory depression, bradycardia
  • IV bolus or infusion pump

Transdermal patch: Ca 24hr, Fe 12hr

Sufentanyl, remifentanyl (plasma esterases)

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10
Q

Tramadol:

A
  • weak full agonist
  • intermediate duration of action (4-6 hr) <–> delayed release tablets
  • rare side effects
  • approx 65% and 90% absorption p.o
  • absence of glucuronidation -> longer duration in cats
  • analgetic + cough relief (antitussive)!
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11
Q

Buprenorphine:

A
  • long duration of action (4-8-12 hr), appears slowly
  • moderate analgesia (“ceiling effect”)
  • very slight sedation
  • respiratory depression: “ceiling effect”
  • TI: 12.300

P.O first pass effect (sublingual 50-100%)

Partial agonist –> pronounced receptor binding –> decreases analgetic effect of full agonist –> postoperative usage

  • soft tissue surgery: anytime
  • pancreatitis

(Simbadol til katt som varer i 24 timer!)

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12
Q

Butorphanol

A
  • shorter duration of action (1-2h, Fe 2-6), appears more quickly
  • slight-moderate analgesia (“ceiling effect”)
  • pronounced visceral analgesia
  • sedation (minimal in cats, rather dysphoria)
  • pronounced cough relief (antitussive)
  • slight respiratory depression (“ceiling effect”)
  • κ agonist, µ antagonist –> very safe antidote
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13
Q

Ketamine:

A

(other analgesics, not opioids)

  • NMDA receptor antagonist (central sensitization decrease)
  • dissociative anasthesia 5-20 mg/kg: catalepsia, analgesia
  • Pre- and intraoperative: 0.5-1 mg/kg
  • Part of multimodal analgesia
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14
Q

Amantadine:

A

(other analgesics, not opioids)

  • NMDA receptor antagonist (central sensitization decrease)
  • Neuropathic pain
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15
Q

Gabapentin

A

(other analgesics, not opioids)

Neurontin!

  • Tumors, neuropathic pain
  • postoperative: together with opioids (spinal cords, DS, meningitis)
  • ventral sensitization decrease
  • per os: 10mg/kg -> 10-20 mg /kg every 8 hr.
  • weak metabolism, eliminaton by kidney
  • rare side effects: slight sedation, salivation, increased appetite
  • sudden quitting –> Shouldn´t!
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16
Q

Cannabinoids

A
  • Tetrahydrocannabinol (THC) vs. Cannabidiol (CBD)
  • CB1 and CB2 receptors
  • antinociceptive (CB and opioid receptors)
  • serotonin agonist
  • several CB2 receptors on WBCs (anti-inflammatory)
  • Epilepsy!
  • f= 0-19%

Pharmacology 1 (12 decks)

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